sources of magnetic susceptibility in a slate abstract magnetic susceptibility and its anisotropy in the borrowdale volcanic slates at kentmere in the english lake district are attributed largely to preferred orientation of a paramagnetic chlorite of diabantite ripidolite composition in units of 10 6 cgs g the principal susceptibilities for the slates are 9 61 9 42 8 69 and for the chlorite grains the minimum anisotropy is represented by principal susceptibilities of 11 57 11 22 and 9 15 because the magnetic susceptibility is carried by a tightly packed matrix forming mineral that has recrystallised during the deformation it is not possible to imagine simple grain rotation as being responsible for the anisotropy of susceptibility

marine isotope stage 3 paleotemperature inferred from reconstructing the die shan ice cap northeastern tibetan plateau glacial extent mapping and dating indicate that the local last glacial maximum llgm of the northeastern tibetan plateau occurred during mid marine isotope stage mis 3 this is asynchronous with the global last glacial maximum lgm that occurred during mis 2 the causes underlying this asynchronicity are the subject of ongoing debate and paleoclimatic reconstructions are a key to advancing understanding of the climatic influence on the spatial and temporal patterns of paleoglaciation we used multiple methods to reconstruct the equilibrium line altitude ela of the die shan paleo ice cap on the northeastern tibetan plateau and to infer past temperature for ice maximum positions believed to be mid mis 3 in age based on regional correlation geomorphic ela reconstructions combined with an energy and mass balance model yield a paleo ela of 4117 31 m asl 786 m lower than present with temperature depressions of 3 8 to similar to 4 6 degrees c compared to the present this is less than the lgm reconstruction of temperature depression inferred from other climatic proxy records on the tibetan plateau and suggests that the llgm glacial advance was a product of lower temperatures and slightly reduced precipitation compared to present whereas the lgm was a more restricted advance in which much colder conditions were combined with much lower precipitation

magnetic susceptibility of the rock matrix related to magnetic fabric studies non ferromagnetic minerals constitute what is called the rock matrix whose susceptibility k1 is directly accessible using only high magnetic fields measurements on minerals and a wide range of rock types show that k1 is mainly due to paramagnetism and hardly exceeds 10 3 si with an anisotropy degree p less than 1 35 different methods to estimate the role of the matrix component in low field susceptibility k and its anisotropy include petrological and chemical analysis evolution of p vs k low temperature studies and comparison of k with remanent magnetizations

enhancing weak magnetic fabrics using field impressed anisotropy application to the chinese loess summary the anisotropy of the low field magnetic susceptibility ams alternating field treated ams af ams and anisotropy of anhysteretic remanent magnetization aarm have been systematically examined for a sandwich sequence of loess palaeosols crossing the upper loess unit l2 marine oxygen isotope stage 6 mis6 to the last interglacial maximum palaeosol unit s1s3 mis5e from the yuanbao section northwestern china results show that a weak but detectable magnetic lineation is controlled by coarse grained aeolian fe3o4 magnetite because the long axes of the coarse grained magnetites are statistically parallel to the palaeowind directions the declination of the maximum susceptibility principal axis of ams can be used as an indicator of palaeowind direction in contrast fine grained pedogenic magnetic particles are responsible for the magnetic foliation we found that af ams can indicate the domain state of the magnetic particles which is consistent with potter stephenson s earlier model we also found that af demagnetization can significantly alter the ams in conclusion the angular dependence of af ams can enhance the weak ams fabrics

spatial relationship of equatorial plasma bubbles and field aligned irregularities observed with an all sky airglow imager and the equatorial atmosphere radar 1 we report for the first time simultaneous two dimensional observations of 630 nm airglow depletions and radar backscatter from field aligned irregularities fai associated with equatorial plasma bubbles spatial distributions of backscatter were obtained by performing east west scans with the 47 mhz equatorial atmosphere radar ear in west sumatra indonesia a 630 nm airglow depletion caused by a plasma bubble was simultaneously observed with an all sky airglow imager both the airglow depletion and backscatter region appeared as band like structure elongated in the meridional direction with a zonal width of about 100 km to compare the spatial structures of backscatter with that of airglow depletion the backscatter was projected onto a horizontal plane at 250 km altitude backscatter was found to occur within the entire airglow depleted region

a study of colour changes in purple green slate by petrological and rock magnetic methods abstract the purple cambrian slates of north wales show colour changes to green in bedding parallel patches and ellipsoidal spots these are referred to as reduction spots but the process is more complex the colour change is not simply associated with the reduction of iron the green discoloration is accompanied by diffusion of fe 3 away from and possibly by mg and ca towards the green material the actual colour change is brought about by the replacement of the fine metamorphic hematite pigment with magnetite however coarser clastic hematite persists in the green slate the green slate has twice as much chlorite and traces of magnetite despite having less total fe the additional chlorite is chiefly responsible for the doubling of the magnetic susceptibility of the green slate with respect to the purple slate chlorite and epidote have the same compositions in both green and purple slates despite the difference in whole rock fe content both purple and green slates behave predominantly as paramagnets between 194 c and 700 c the anisotropy of low field susceptibility magnetic fabric is increased by heating and therefore made easier to measure and the principal directions of anisotropy are preserved heating to 700 c increases the saturation isothermal remanence dramatically and increases its anisotropy due to the growth of single domain magnetite however heating is not universally recommended as a means of enhancing otherwise feeble magnetic fabrics some other slates and schists show regressive changes in magnetic fabric on heating with erratic changes in principal directions

paleomagnetism carried by crystal inclusions the effect of preferred crystallographic orientation abstract randomly oriented phlogopite crystals from a pegmatite contain submicroscopic inclusions of magnetite the inclusions have oblate magnetic fabrics subparallel to the ab crystal plane alternating field demagnetization of individual crystals shows that the remanence is influenced by the crystal symmetry of the phlogopite host the magnetizations isolated by alternating field demagnetization either cluster close to the a axis or scatter in the ab plane coarse grained igneous and metamorphic rocks can only record a paleofield direction accurately if there is a suitable orientation distribution of the rock forming minerals that host the ferromagnets an isotropic distribution of rock forming minerals is preferable but it is not obligatory rock forming minerals that have l fabrics or s fabrics with a strong l component are also suitable if they contain oblate inclusion fabrics of ferromagnets

interpretation of magnetic fabrics in the early proterozoic diabase dykes of keuruu central finland abstract magnetic fabrics petrophysics petrography and chemical compositions are described for 14 diabase dykes located in the keuruu area central finland these early proterozoic 1880 ma dykes sharply cut both low density granodiorites and high density diorites and gabbros the diabase dykes with a nw se strike and an almost vertical dip have a maximum length of a few kilometers and widths of about 1 m strongly developed magnetic fabrics of deformation type anisotropy degree up to 1 4 were observed in six of the dykes and weakly developed fabrics of flow type anisotropy degree below 1 1 in eight dykes no systematic differences in the dyke widths mean densities palaeomagnetic poles mineral compositions degrees of alteration or chemical characteristics were observed between the two types of dykes suggesting that the dykes had a common magma source all the fabrics of deformation type are dominantly ferrimagnetic with tightly aligned horizontal foliations and well grouped lineations which in most cases are parallel to the dyke trends it is suggested that the deformation fabrics were generated as tholeiitic magma was forced to intrude laterally along its level of neutral buoyancy lnb which may have been close to the present erosion level pel in the low density granodiorite environment ferri and paramagnetic fabrics of flow type characterize the dykes located in the denser mafic parts of the crust in these parts the lnb was possibly somewhat higher in the crust so that magma flow passed the pel and formed weakly developed flow fabrics with gently plunging lineations and vertical or variable magnetic foliations

field impressed anisotropies of magnetic susceptibility and remanence in minerals the application of alternating af or direct df magnetic fields to samples containing dispersed particles of magnetite titanomagnetite or maghemite has been found to alter significantly the measured low field susceptibility anisotropy even though the particle orientation is unchanged the acquisition of isothermal remanent magnetization irm is also strongly dependent on the previous af treatment given to the samples a method of quantifying the changes brought about by application of the fields is described the samples studied were intrinsically isotropic or only weakly anisotropic and the computed impressed susceptibility or irm ellipsoids produced by the applied fields were ellipsoids of revolution with the unique axis aligned with the applied field axis the size and shape of the field impressed ellipsoids were strongly dependent upon particle size these effects might thus form the basis of a rapid nondestructive means of estimating particle size in rocks the results also have important implications for magnetic fabric analysis and the static af demagnetization of rocks in particular to ensure that the intrinsic magnetic fabric is measured without any field impressed component of anisotropy samples should not be subjected to static af demagnetization prior to the determination of either low field susceptibility anisotropy or irm anisotropy samples should also not carry a significant remanence such as an irm acquired in a field greater than about 5 mt prior to low field susceptibility anisotropy analysis

diagenetic magnetic enhancement of sapropels from the eastern mediterranean sea diagenetic dissolution of magnetic minerals has been widely observed in organic rich sediments from many environments organic rich sediments from the eastern mediterranean sea sapropels recovered during leg 160 of the ocean drilling program reveal a surprising catalogue of magnetic properties sapropels from all sites studied across the eastern mediterranean sea are strongly magnetic and the magnetization is directly proportional to the organic carbon content the magnetization of the sapropels is dominated by a low coercivity probably single domain magnetic mineral with an inverse magnetic fabric that exhibits a clear decay in magnetic properties when exposed to air during heating the magnetic particles irreversibly break down between 360 and 400 c the contrast between the magnetic properties of sapropels and surrounding sediments is marked with remanence intensities of sapropels often being more than three orders of magnitude higher than those of underlying sediments the contrast between the magnetic properties of sapropels and the surrounding sediments is apparently controlled by non steady state diagenesis sulphate reducing conditions dominated during sapropel deposition while overlying sediments were deposited under oxic conditions the mineral responsible for the magnetic properties of sapropels is most likely to have formed under sulphate reducing conditions that existed during times of sapropel formation attempts to identify this mineral have been unsuccessful but several lines of evidence point toward an unknown ferrimagnetic iron sulphide phase the influence of diagenesis on the magnetic properties of cyclically deposited eastern mediterranean sedimentary sequences suggests that magnetic parameters may be a useful proxy for diagenesis in these sediments

development of intermediate scale structure at different altitudes within an equatorial plasma bubble implications for l band scintillations an important aspect of the development of intermediate scale length 100 m few km irregularities in an equatorial plasma bubble epb that has not been considered in the schemes to predict the occurrence pattern of l band scintillations in low latitude regions is how these structures develop at different heights within an epb as it rises in the post sunset equatorial ionosphere due to the growth of the rayleigh taylor r t instability irregularities at different heights over the dip equator map to different latitudes and their spectrum as well as the background electron density determine the strength of l band scintillations at different latitudes in this paper vhf and l band scintillations recorded at different latitudes together with theoretical modelling of the scintillations are used to study the implications of this structuring of epbs on the occurrence and strength of l band scintillations at different latitudes theoretical modelling shows that while s4 index for scintillations on a vhf signal recorded at an equatorial station may be 1 s4 index for scintillations on a vhf signal recorded near the crest of the equatorial ionization anomaly eia generally does not exceed the value of 1 because the intermediate scale irregularity spectrum at f layer peak near the eia crest is shallower than that found in the equatorial f layer peak this also explains the latitudinal distribution of l band scintillations thus it is concluded that there is greater structuring of an epb on the top side of the equatorial f region than near the equatorial f layer peak

energy and mass balance comparison between zhadang and parlung no 4 glaciers on the tibetan plateau tibetan glaciers experience spatially heterogeneous changes which call for further investigation of the mechanisms responsible from an energy and mass perspective in this study 2 year parallel observations august 2010 july 2012 at 5665 m a s l on zhadang glacier a subcontinental glacier and 5202 m a s l on parlung no 4 glacier a maritime glacier were used to reveal the drivers of surface energy and mass balance at these sites glacio meteorological data show that air temperature and specific humidity were 1 7 c and 0 5 g kg 1 lower on zhadang glacier than on parlung no 4 glacier the mass accumulation occurred primarily before the indian summer monsoon onset on parlung no 4 glacier and after its onset on zhadang glacier point net mass loss was 2 5 times larger on parlung no 4 glacier than on zhadang glacier mainly due to the difference in melt energy overall the physical mechanisms controlling the mass and energy difference can be attributed to both the feedback role of surface albedo through different snow accumulation characteristics and longwave radiation emission of the atmosphere due to different meteorological backgrounds finally a review of the few studies dealing with energy balance on the tibetan glaciers describes the possible spatial characteristics requiring further investigation in the future on larger spatial and temporal scales

permanent el nino and the onset of northern hemisphere glaciations mechanism and comparison with other hypotheses 1 the tropical pacific transitioned from a permanent el nino state that is without the current equatorial zonal gradient of sea surface temperatures to one with an equatorial cold tongue in a process that started 4 ma during the early pliocene the latter stages of this transition around 2 75 ma marked the onset of northern hemisphere glaciations we explore the hypothesis that this onset of glaciation is causally linked to the development of the cold tongue guided by atmosphere general circulation model agcm simulations forced by various hypothesized climate influences a unique feature of our simulations is imposing permanent el nino conditions not by imposing sea surface temperatures anomalies directly but rather through changing the implied ocean heat transport in the slab ocean component of the agcm done in such a way as to maintain global ocean heat balance similar to previous studies we find increased near surface temperature conditions occur during simulated permanent el nino conditions at the locations of known ice sheet growth during glacial periods we establish that this tropical extratropical connection is mediated through atmospheric stationary waves a well known atmospheric pathway for today s el nino influence on north america the influence of the permanent el nino condition is compared through model simulations to other mechanisms proposed to date to explain the onset of glaciations at 2 75 ma changes in atmospheric carbon dioxide co2 concentrations closure of the panama seaway and changes in north pacific seasonality the exact comparison is done by calculating differences in the equilibrium line altitude at the known locations of ice sheet growth an approach that permits the translation of climate anomalies into a measurement of glaciation trends in terms of glacier mass balance we find that permanent el nino and atmospheric co2 are the leading influences in this comparison leading us to conjecture that the two influences combined determined the long term background conditions governing ice sheet growth within this long term background evolution however we additionally find that the exact timing of northern hemisphere glaciations is likely to have come from favorable orbital conditions our results regarding permanent el nino on northern hemisphere glaciations is however conditioned on a strong sensitivity of northern hemisphere climate changes to how the oceanic heat compensation to the permanent el nino is achieved

sem and magnetic fabric study of a compacting sediment scanning electron microscopy sem anisotropy of magnetic susceptibility ams and anisotropy of anhysteretic remanence aar studies were conducted on kaolinite magnetite samples compacted to pressures between o and 0 2 mpa to determine if clay and magnetic fabric development mimic a change in compaction behavior marked by a break in slope in the compaction curve this break in slope indicates that the rate of void ratio decrease with increasing pressure abruptly slows down at pressures of about 0 04 mpa about one half of a compaction caused inclination decrease occurs at pressures less than 0 04 mpa sem photomicrographs show that horizontal clay fabric develops inhomogeneousiy within a sample at pressures below the break in slope since pore spaces are larger than magnetite grains at low pressures below the break in slope the observed pattern of inclination decrease during compaction may be due to magnetite grains being attached to clay particles and constrained to follow clay fabric development this interpretation is supported by the observation that aar minimum axes become vertical at pressures above the break in slope this may indicate that magnetic fabric is developing at low pressures and that most of the magnetite particles are constrained to lie subhorizontally the ams maximum axes tend to lie 90 from a strong remanence in these samples suggesting single domain magnetic behavior measurement of ams after alternating field demagnetization yields maximum axes which cluster near to the aar maximum axes suggesting multidomain behavior this apparent contradiction aay be due to magnetic conditions prior to ams aeasurement controlling domain wall nucleation

the magnetic fabric of metasediments in a detachment shear zone the example of tinos island greece abstract we present a magnetic fabric study 12 sites in strongly deformed metasediments micaschists and calcschists from a well exposed detachment shear zone at tinos island cyclades greece a gradient of deformation is observed from the southwest side to the northeast side of tinos the detachment shear zone is contemporaneous with a greenschist retrogression episode ca 25 20 ma high pressure hp 45 ma metasediments are preserved in the southwest side of tinos we compared the anisotropy of magnetic susceptibility ams 158 samples to the anisotropy of isothermal remanent magnetization airm 40 samples ams is primarily dominated by phyllosilicates whilst airm reflects the contribution of mixture of ferromagnetic grains magnetite hematite goethite and pyrrhotite interestingly we observe the appearance of goethite feo oh is observed when approaching the detachment area the orientation of the ams and airm axes shows a general consistency on the other hand airm is more prolate and anisotropic than ams we document a close agreement between the ams magnetic foliation and the structural cleavage that has been measured from the core sample the magnetic lineation is generally parallel to the stretching lineation observed on the field however composite magnetic lineations suggest well preserved petrofabrics contemporaneous to the 45 ma hp episode an increase in the ams foliation anisotropy parameter is observed in micaschists when deformation increases unfortunately no quantitative estimate of finite deformation is possible using ams due to the dominant role of phyllosilicates and the complex ferromagnetic mineralogy

meltwater runoff in a changing climate 1951 2099 at chhota shigri glacier western himalaya northern india meltwater runoff in the catchment area containing chhota shigri glacier western himalaya is simulated for the period 1951 2099 the applied mass balance model is forced by downscaled products from four regional climate models with different horizontal resolution for the future climate scenarios we use high resolution time series of 5 km grid spacing generated using the newly developed intermediate complexity atmospheric research model the meteorological input is downscaled to 300 m horizontal resolution the use of an ice flow model provides annually updated glacier area for the mass balance calculations the mass balance model calculates daily snow accumulation melt runoff as well as the individual runoff components glacial melt snowmelt and rain the resulting glacier area decreases by 35 representative concentration pathway rcp 4 5 scenario to 70 rcp 8 5 scenario by 2099 relative to 2000 the average annual mass balance over the whole model period 1951 2099 was 0 4 0 3 m w e a 1 average annual runoff does not differ substantially between the two climate scenarios however for the years after 2040 our results show a shift towards earlier snowmelt onset that increases runoff in may and june and reduced glacier melt that decreases runoff in august and september this shift is much stronger pronounced in the rcp 8 5 scenario

effects of clouds on surface melting of laohugou glacier no 12 western qilian mountains china we analyzed a 2 year time series of meteorological data january 2011 december 2012 from three automatic weather stations on laohugou glacier no 12 western qilian mountains china air temperature humidity and incoming radiation were significantly correlated between the three sites while wind speed and direction were not in this work we focus on the effects of clouds on other meteorological parameters and on glacier melt on an average 18 of top of atmosphere shortwave radiation was attenuated by the clear sky atmosphere and clouds attenuated a further 12 most of the time the monthly average increases in net longwave radiation caused by clouds were larger than decreases in net shortwave radiation but there was a tendency to lose energy during the daytime when melting was most intense air temperature and wind speed related to turbulent heat flux were found to suppress glacier melt during cloudy periods while increased water vapor pressure during cloudy days could enhance glacier melt by reducing energy loss by latent heat from these results we have increased the physical understanding of the significance of cloud effects on continental glaciers

magnetic fabric studies of the nipissing sill province and senneterre dykes canadian shield and implications for emplacement the 2 21 ga nipissing diabase sills intrude the huronian supergroup of the southern province coeval senneterre dykes in the adjacent portion of the superior province are potential feeders for the sills anisotropy of magnetic susceptibility ams data were obtained from both of these units to study flow patterns and test emplacement models the sills exhibit three distinct paleomagnetic directions that are likely primary and represent a time correlation tool within the magmatic event two of the three directions are also found in senneterre dykes sites in the northern cobalt embayment carry an n1 reverse paleomagnetic signature they possess maximum ams axes that trend north northwest south southeast interpreted as the direction of magma emplacement in one area the data rule out a cone sheet emplacement mechanism the n3 paleomagnetic signature is restricted to a sill and or dyke like bodies near lake timiskaming where the ams axes are dominantly north northwest south southeast similar to that of the nearby n1 reverse sites sites in a geographically restricted area farther south carry an n1 normal paleomagnetic direction the ams patterns in these sites exhibit very poor within and between site consistency compatible with the magma having crystallized statically in this volumetrically minor magmatic pulse in the sudbury elliot lake area the nipissing diabase is deformed and outcrops exhibit east west elongation parallel to the fold axes of the enclosing huronian sedimentary rocks ams fabrics are interpreted as reflecting this deformation rather than primary magmatic flow three of eight senneterre dyke sites show horizontal flow patterns whereas the remainder have more complicated ams patterns

anisotropy of magnetic susceptibility in the ponta grossa dyke swarm brazil and its relationship with magma flow direction abstract measurements of anisotropy of magnetic susceptibility ams in 95 mafic dykes mainly tholeiites 10 200 m in width from the mesozoic ponta grossa swarm southern brazil revealed two main types of magnetic fabric type i fabric plane k 1 k 2 parallel to the dyke plane represents magma flow within the dykes whereas type ii plane k 1 k 3 parallel to the dyke plane is compatible with a fabric pattern reflecting vertical compaction of the magma column fabric type i dominates 51 of the dykes within the swarm whereas type ii 38 of the dykes concentrates mainly in the western region where the dykes intrude sediments considering the dykes with type i fabrics it is concluded that 58 of the dykes were fed by horizontal or sub horizontal k 1 inclinations less than 30 magmatic flow and 42 were fed by inclined to vertical k 1 inclinations more than 30 magma flow the latter are more frequent in the southeastern part of the swarm suggesting a magma source close to this area although there may have been other sources in other regions where dykes with inclined flow and distinct chemical characteristics are also found

on seeding large scale wave structure equatorial spread f and scintillations over vietnam 1 understanding the day to day variability in occurrence of equatorial spread f esf remains as a high priority objective in space weather research a major difficulty has been an inability to resolve the roles being played by large scale wave structure lsws and the post sunset rise pssr of the equatorial f layer in the production of esf in this paper we show conclusively that total electron content tec measured as a function of latitude and longitude provides clear routine descriptions of lsws then together with ionosonde data we show for the first time that while a seed for lsws can occur in the late afternoon its amplification takes place mostly during the pssr implications of these findings are discussed in light of existing theories

differences in paleomagnetic interpretations due to the choice of statistical demagnetization and correction techniques kapuskasing structural zone northern ontario canada abstract the kapuskasing structural zone ksz reveals a section through the archean lower crustal granoblastic gneisses our new paleomagnetic data largely agree with previous work but we show that interpretations vary according to the choices of statistical demagnetization and field correction techniques first where the orientation distribution of characteristic remanence directions on the sphere is not symmetrically circular the commonly used statistical model is invalid fisher r a proc r soc a217 1953 295 any tendency to form an elliptical distribution indicates that the sample is drawn from a bingham type population bingham c 1964 distributions on the sphere and on the projective plane phd thesis yale university fisher and bingham statistics produce different confidence estimates from the same data and the traditionally defined mean vector may differ from the maximum eigenvector of an orthorhombic bingham distribution it seems prudent to apply both models wherever a non fisher population is suspected and that may be appropriate in any tectonized rocks non fisher populations require larger sample sizes so that focussing on individual sites may not be the most effective policy in tectonized rocks more dispersed sampling across tectonic structures may be more productive second from the same specimens mean vectors isolated by thermal and alternating field af demagnetization differ which treatment gives more meaningful results is difficult to decipher especially in metamorphic rocks where the history of the magnetic minerals is not easily related to the ages of tectonic and petrological events in this study thermal demagnetization gave lower inclinations for paleomagnetic vectors and thus more distant paleopoles third of more parochial significance tilt corrections may be unnecessary in the ksz because magnetic fabrics and thrust ramp are constant in orientation to the depth at which they level off at approximately 15 km depth with archean geothermal gradients primary remanences were blocked after the foliation was tilted to rise on the thrust ramp therefore the rocks were probably magnetized in their present orientation tilting largely or entirely predates magnetization

equilibrium line altitudes along the andes during the last millennium paleoclimatic implications deciphering the climate changes that influenced the glacial fluctuations of the last millennium requires documenting the spatial and temporal patterns of these glacial events here we estimate the

application of a mass balance model to a himalayan glacier a mass balance model based on the energy balance at the snow or ice surface is formulated with particular attention paid to processes affecting absorption of radiation the model is applied to a small glacier glacier ax010 in the nepalese himalaya and tests of its mass balance sensitivity to input and climatic parameters are carried out calculated and observed area averaged mass balances of the glacier during summer 1978 june september show good agreement namely 0 44 and 0 46 m w e respectively results show the mass balance is strongly sensitive to snow or ice albedo to the effects of screening by surrounding mountain walls to areal variations in multiple reflection between clouds and the glacier surface and to thin snow covers which alter the surface albedo in tests of the sensitivity of the mass balance to seasonal values of climatic parameters the mass balance is found to be strongly sensitive to summer air temperature and precipitation but only weakly sensitive to relative humidity

geomagnetic conjugate observations of equatorial airglow depletions 1 we report for the first time large scale equatorial f region airglow depletions extending to low midlatitudes in both hemispheres the observational sites were located at low midlatitude geomagnetic conjugate points clear depletions of 630 0 nm airglow intensity due to equatorial plasma bubbles were simultaneously observed with two all sky imagers at sata japan magnetic latitude 24 n and its geomagnetic conjugate point darwin australia magnetic latitude 22 s on the night of november 12 2001 airglow depletion regions with east west scale sizes of 40 100 km extend poleward the maximum apex altitude of the plasma bubbles is about 1 700 km over the geomagnetic equator the depletions move eastward at about 100 m s without changing their structures the darwin depletion structures mapped onto the northern hemisphere along the geomagnetic field coincide closely with structures in the sata images even for the 40 km structure these observations indicate that plasma depletions in the equatorial ionosphere elongate along the geomagnetic field lines

monitoring and prediction of shrinkage of a small glacier in the nepal himalaya in 1978 the first detailed glaciological studies were carried out on the small glacier ax010 in a glacier inventory of dudh kosi region in the nepal himalaya its length area and highest and lowest elevations in 1978 were 1 7 km 0 57 km2 5360 and 4950 m a s l respectively two resurveys of its terminus position and or surface elevations were carried out in 1989 and 1991 the glacier retreated by about 30 and 28 m during the periods 1978 89 and 1989 91 respectively in 1995 annual monitoring of this glacier by means of ground survey stake method and topographical mapping began in order to obtain its mass balance surface flow velocity and extent and link them with climatic conditions the results obtained in 1995 are summarized as follows 1 during the period 1991 95 the glacier retreated by 12 m 2 associated with the ice thickness loss in the lower part of the glacier the horizontal surface velocities along the center line in 1995 june october showed a remarkable decrease on the glacier tongue to about 50 of those in 1978 shrinkage of the glacier in the near future is predicted from a simple model calculation for the case that climatic conditions remain unchanged from 1995 the results show that the present shrinkage should continue and accelerate

energy and mass balance of zhadang glacier surface central tibetan plateau climate variables that control the annual cycle of the surface energy and mass balance on zhadang glacier in the central tibetan plateau were examined over a 2 year period using a physically based energy balance model forced by routine meteorological data the modelled results agree with measured values of albedo incoming longwave radiation surface temperature and surface level of the glacier for the whole observation period the radiation component dominated 82 the total surface energy heat fluxes this was followed by turbulent sensible 10 and latent heat 6 fluxes subsurface heat flux represented a very minor proportion 2 of the total heat flux the sensitivity of specific mass balance was examined by perturbations of temperature 1 k relative humidity 20 and precipitation 20 the results indicate that the specific mass balance is more sensitive to changes in precipitation than to other variables the main seasonal variations in the energy balance were in the two radiation components net shortwave radiation and net longwave radiation and these controlled whether surface melting occurred a dramatic difference in summer mass balance between 2010 and 2011 indicates that the glacier surface mass balance was closely related to precipitation seasonality and form proportion of snowfall and rainfall

a simple energy balance model to calculate ice ablation at the margin of the greenland ice sheet apres avoir etabli les relations donnees climatiques taux d enlevement de la glace dans 2 glaciers du groenland un modele simple de bilan energetique est effectue pour calculer le taux d enlevement de la glace aux bordures du glacier

low temperature demagnetization isolates stable magnetic vector components in magnetite bearing diabase summary it may be difficult to isolate stable palaeomagnetic vectors of different ages if they lie in grain assemblages with overlapping ranges of coercivity or of unblocking temperature this is because some moments associated with either vector may demagnetize at the same stage of experimental demagnetization the sharp transition between vector components may be obscured and stable components may appear less linear on the demagnetization plot thermal and alternating field af demagnetization techniques remove vector components on a quantitative basis according to a discrete limiting unblocking temperature or coercivity low temperature demagnetization ltd differs in that it removes vector components discretely wherever there are mobile domain walls experiments tested the ability of ltd to improve the effectiveness of af demagnetization on isothermal and anhysteretic remanent magnetizations irm arm in diabase multicomponent nrms were simulated irms or arms in different non overlapping coercivity ranges along three orthogonal axes or along two non orthogonal directions the known directions of the experimentally applied vector components were always more successfully verified by af demagnetization if ltd was first applied for the same specimens ltd reduced the same artificial remanences by 50 per cent for the coercivity range 0 15 mt by 25 per cent for the range 15 30 mt and negligibly for higher coercivity fractions ltd demagnetizes polydomain magnetite as domain walls rearrange on passing through a low temperature transition near 120 k

matrix deformation in a basement involved fold and thrust belt a case study in the central andes malargue argentina abstract an analysis of the anisotropy of magnetic susceptibility ams is used to investigate the matrix strain record of weakly deformed clastic rocks including sandstones and shales along a cross section of the malargue fold and thrust belt mftb argentina we collected 339 oriented cores from the tres esquinas sandstones the red beds of the tordillo and neuquen formations as well as from shales silts of the mendoza group overall 90 of the magnetic fabrics are well defined and are related to the strain imprint of the layer parallel shortening among the tectonic related fabrics 40 show the development of a magnetic lineation at right angle of the shortening type ii 38 display an apparent loss of magnetic foliation type iii and 21 develops a magnetic foliation at right angle of the shortening type iv there is no lithological control on magnetic fabric typology despite contrasting ferromagnetic mineralogy between the red sandstones and dark shales thin section observations highlight the good match between the orientation of both the susceptibility ellipsoid and microstructure orientation which enables us to infer the preferred orientations of the petrofabric i e finite strain directions in this way two trends can be recognized in the study area shortening directions trending n110 in the north and trending n80 in the south in addition the spatial distribution of magnetic fabric typology and burial data suggests an atypical pattern of deformation from the foreland to hinterland such a pattern contrasts with previous studies in fold thrust belt settings suggesting that at the matrix scale the deformation even in a pre folding setting is compartmentalized and controlled by the occurrence of deep seated thrusts localized along inherited structures from the analysis of cross sections we can distinguish several domains each of them reflecting distinct states of matrix deformation

archean uplift of a subprovince boundary in the canadian shield revealed by magnetic fabrics abstract a high strain zone reported elsewhere as a subprovince or tectonic terrane boundary shows evidence of uplift during a penetrative d 1 event some outcrops reveal this by conventional l s petrofabric observations however all outcrops permit measurements of the anisotropy of low field magnetic susceptibility ams which here records the preferred crystallographic orientation of chlorite biotite and amphibole furthermore anisotropy of anhysteretic magnetic remanence aarm reflects the preferred orientation of ferromagnetic grains magnetite and pyrrhotite all three types of fabric show that the rocks were shortened in a north south direction perpendicular to the terrane boundary and stretched upwards in a nearly coaxial strain history a few anomalous magnetic fabrics may indicate some late d 1 subhorizontal e w extension compatible with transpression along the boundary we conclude that this boundary is a zone of high strain associated with the uplift of the high grade plutonic rocks of the winnipeg river subprovince with only slight evidence of minor components of late transpression during the penetrative d 1 fabrics

explicit characteristics of evolutionary type plasma bubbles observed from equatorial atmosphere radar during the low to moderate solar activity years 2010 2012 using the fan sector backscatter maps of 47 mhz equatorial atmosphere radar ear at kototabang 0 2 s geographic latitude 100 3 e geographic longitude and 10 4 s geomagnetic latitude indonesia the spatial and temporal evolution of equatorial plasma bubbles epbs were examined to classify the evolutionary type epbs from those which formed elsewhere and drifted into the field of view of radar a total of 535 epbs were observed during the low to moderate solar activity years 2010 2012 out of which about 210 39 are of evolving type and the remaining 325 61 are drifting in epbs in general both the evolving type and drifting in epbs exhibit predominance during the postsunset hours of equinoxes and december solstices interestingly a large number of epbs were found to develop even a few minutes prior to the apex sunset during equinoxes further the occurrence of evolving type epbs exhibits a clear secondary peak around midnight 2300 0100 lt primarily due to higher rate of occurrence during the postmidnight hours of june solstices a significant number 33 of postmidnight epbs generated during june solstices did not exhibited any clear zonal drift while about 14 of epbs drifted westward also the westward drifting epbs are confined only to june solstices the responsible mechanisms for the genesis of fresh epbs during postmidnight hours were discussed in light of equatorward meridional winds in the presence of weak westward electric fields

influence of static alternating field demagnetization on anisotropy of magnetic susceptibility experiments and implications anisotropy of magnetic susceptibility ams indicates the preferred orientation of a rock s constituent minerals however other factors can influence the ams e g domain wall pinning or domain alignment in ferromagnetic minerals therefore it is controversial whether samples should be alternating field af demagnetized prior to ams characterization this may remove the influence of natural remanent magnetization nrm or domain wall pinning on ams however it may also result in field induced anisotropy this study investigates the influence of stepwise af and low temperature demagnetization on mean susceptibility principal susceptibility directions ams degree and shape for sedimentary metamorphic and igneous rocks alternating fields up to 200 mt were applied along the sample x y and z axes rotating the order for each step to characterize the relationship between ams principal directions and the last af orientation the changes in anisotropy defined by the mean deviatoric susceptibility of the difference tensors are between 2 and 270 of the ams in nrm state variations in ams parameters range from small changes in shape to complete reorientation of principal susceptibility axes with the maximum susceptibility becoming parallel to the last af direction this is most prevalent in samples with low degrees of anisotropy in the nrm state no clear correlations were found between field induced anisotropy and hysteresis properties therefore we propose that future studies check any samples whose ams is carried by ferromagnetic minerals and low anisotropy degrees for af induced artifacts these results highlight the need for understanding the ams sources and carriers prior to any structural interpretation

a comparative study of magnetic anisotropy measurement techniques in relation to rock magnetic properties abstract magnetic anisotropy measurements are becoming increasingly common to many studies within the different disciplines of geology involving sedimentary igneous and metamorphic rocks a plethora of techniques exists for measuring magnetic anisotropy of rocks some are rapid and non destructive while others are more labor intensive or may result in alteration of the magnetic minerals all however have the potential of revealing a wealth of information when measured and interpreted correctly in broad terms anisotropy techniques subdivide into measurements of susceptibility remanence and torque here we consider the first two of these anisotropy of magnetic susceptibility ams is by far the most utilized and measures composite fabrics magnetic susceptibilities in high fields and low temperatures however are being increasingly used to isolate the paramagnetic contribution to the fabrics when distinguishing between fabrics carried by different ferromagnetic phases or to separate these from the diamagnetic and paramagnetic contributions to the fabric then remanence anisotropy techniques become necessary anisotropies of thermal remanence atrms of anhysteretic remanence aarm and of isothermal remanence airm are the most common examples remanence anisotropy may be measured over the full spectrum of magnetic coercivities or over a targeted range e g partial or aparm moreover anisotropies may be calculated using only the resolved field parallel component of the vector in which case a minimum of six different orientations is necessary to obtain a complete symmetric tensor or using the three components full vector of the measured magnetic vectors e g avarm in which case three orthogonal applied magnetizations are the minimum requirement in this study we utilize a variety of magnetic remanence room temperature techniques to measure remanence anisotropy of selected coarse and finer grained gneiss granulitic specimens with well pronounced fabrics results are compared to room temperature ams and are interpreted in terms of the applicability of instrumentation technique to specific rock magnetic properties

numerical modelling of historical front variations and dynamic response of sofiyskiy glacier altai mountains russia the recent fluctuation of the central asian climate and its effect on the region s glaciers is poorly known largely because of a lack of knowledge of the dynamic behaviour of so called summer accumulation type glaciers in this study a one dimen sional numericalglaciermodelisusedtosimulatethedynamicresponseof sofiyskiyglacier altai mountains russia to climate forcing a successful simulation of the observed histor ical front variations was accomplished by dynamic calibration this resulted in a recon struction of the recent mass balance history of the glacier showing a distinct decline in surface massbalance in the second half of the19th century a slightly higher massbalance at the beginning of the 20th century followed by a steady decline towards present condi tions the future response of sofiyskiy glacier was projected for six 21st century climate scenarios undera no change scenario the glacier will retreat 42kmby 2100 if airtem perature gradually risesby 45 c during this century the glacier will vanish around 2100 basic response characteristics of sofiyskiy glacier were determined these indicate rather low mass balance sensitivity to temperature change but a strong front reaction due to geo metric conditions

rotational remanent magnetization rrm and its high temporal and thermal stability summary the time and temperature stability of various types of magnetic remanence has been measured in pottery samples containing magnetite and in a clay sample containing manganese ferrite the time decay of rotational remanent magnetization rrm anhysteretic remanent magnetization arm and a low field isothermal remanent magnetization irm has been measured while the decay of the last two remanences is easily measurable at about 2 and 19 per cent per decade of time respectively the decay of rrm is too small to be measured being less than about 0 1 per cent per decade of time thermal demagnetization of thermoremanent magnetization trm arm and rrm indicates that rrm is also the most thermally stable the implications of these experiments are that rocks which exhibit gyromagnetic effects such as rrm contain highly stable particles and therefore are likely to be most suitable for palaeomagnetism

magnetic anisotropy of some phyllosilicates magnetic susceptibility anisotropy of susceptibility and hysteresis of single microcrystals of chlorite biotite phlogopite muscovite zinnwaldite and fuchsite were measured in low and high magnetic fields with an alternating gradient force magnetometer micromag their properties are sufficient to account for the low field susceptibility ams of most micaceous rocks nearly all samples show some ferromagnetic contribution at low fields due to inclusions of pseudosingle domain and multidomain magnetite the paramagnetic contribution isolated at high fields usually exceeds the ferromagnetic contribution the paramagnetic susceptibility is intrinsic to the silicate lattice and agrees with values predicted from chemical composition within the limits of error the minimum susceptibility is nearly parallel to c another axis is parallel to b and the third susceptibility usually the maximum is close to a the paramagnetic susceptibility has a disk shaped magnitude ellipsoid with strong anisotropy p 2 the ferromagnetic contributions at low fields have more variably shaped ellipsoids with greater eccentricity p 5 the silicate lattice does not constrain their orientation our technique cannot determine the principal axes of the ferromagnetic component however its principal values usually correspond with the paramagnetic principal susceptibilities in order of magnitude thus the combined paramagnetic ferromagnetic anisotropy recognised in routine studies of ams should faithfully represent the petrofabric of most micaceous rocks nevertheless nearly 10 of our samples have incompatible anisotropy ellipsoids for the silicate host and magnetite inclusions these yield a net inverse ams that does not correctly represent the orientation of the silicate lattice therefore some caution is necessary in petrofabric ams studies of micaceous rocks

estimation of atmospheric transmissivity of solar radiation from precipitation in the himalaya and the tibetan plateau though solar radiation is important for glacier mass balance simulation solar radiation data are not always available as a result of analyzing meteorological data measured in the himalaya and the tibetan plateau a favorable correlation between precipitation and atmospheric transmissivity of solar radiation is found in terms of monthly values monthly mean solar radiation is derived from the relationship between atmospheric transmissivity of solar radiation and precipitation with input of monthly precipitation latitude skyline and time the differences between estimated and observed monthly mean solar radiation are 40 w m 2 in most cases however the differences at some sites are significantly large the error in the estimated solar radiation during the monsoon season can be large when the monthly mean precipitation rate is about 5 mm d 1 though the error in the estimated solar radiation during the non monsoon season is generally small due to low precipitation in the himalaya and the tibetan plateau during this season it can exceed 100 w m 2

is this magnetic fabric normal a review and case studies in volcanic formations abstract when studying weakly anisotropic rocks non standard relationships between magnetic and expected petrofabric axes are sometimes observed in particular the so called inverse or intermediate fabrics a review of possible explanations for these effects is presented and leads to the conclusion that a majority of abnormal magnetic fabrics often encountered in magnetite rich volcanic rocks are due to abnormal preferred orientations or distributions of magnetite grains through case studies in dikes from skye island yemen and the iberian peninsula and magma and ash flows from the ethiopian traps and southern corsica the various possible origins of such fabrics are examined it is possible to retrieve reliable magma flow directions from these sites provided proper data selection is performed leading to non unique interpretations

on the generation and growth of equatorial backscatter plumes 1 wave structure in the bottomside f layer we examine the initial conditions that lead to backscatter plume development in the equatorial f region ionosphere by analyzing altair radar data we obtained the following principal results 1 prior to plume development an altitude modulation of electron density contours exists in the bottomside f layer these quasi periodic variations were mapped spatially over a 1200 km east west distance by using incoherent scatter measurements and found to consist of three cycles with an average spatial wavelength of 400 km 2 the wave structure observed in the bottomside electron density contours grew in amplitude at a rate consistent with that predicted by the generalized gradient drift instability 3 bottomside backscatter developed on the west walls of all three altitude modulated regions followed by plume development from near the crests of these regions

the magnetic fabric of weakly deformed late jurassic shales from the southern subalpines chains french alps evidence for sw directed tectonic transport direction abstract extensive magnetic fabric investigations have been conducted on the late jurassic sedimentary black shales 37 sites 362 samples the so called terres noires formation from the southern subalpine chains western alps this study completes a previous study done in the northern subalpine chains which demonstrated that the terres noires formation preserves a subtle magnetic lineation related to tectonic transport direction in the southern subalpine chains diois devoluy embrunais digne nappe similar magnetic fabrics have been found the shape of the magnetic fabric is oblate and locally mirrors the gradient of deformation in the embrunais footwall the magnetic foliation is parallel to the bedding or to the slaty cleavage about 50 of the magnetic lineations have down dip magnetic directions while the other magnetic lineations are sub horizontal or parallel to the intersection bedding cleavage the tectonic magnetic fabrics recorded in the embrunais confirm the ability of the terres noires to record tectonic transport direction the magnetic fabric geometry suggests sw directed tectonic transport in the southern subalpine chains the diois appears as a tip zone where transport directions are abruptly clockwise rotated from nw directed in the northern subsalpine chains to sw directed the magnetic fabric from the digne nappe exhibits a fan pattern of transport directions in close agreement with the arcuate shape of the thrust

quantification of illite content in sedimentary rocks using magnetic susceptibility a rapid complement or alternative to x ray diffraction abstract the paramagnetic clay mineral illite can have important controls on fluid permeability and microporosity in sedimentary rocks increases in illite content of a few percent can reduce permeability by several orders of magnitude traditional x ray diffraction xrd techniques for quantifying illite content can be very time consuming requiring significant sample preparation and generally examine only a relatively small sample volume in contrast a technique based on magnetic susceptibility described here is very rapid cheap sensitive nondestructive and requires no extra preparation of the sample it is representative of a much larger sample volume and in the present paper utilizes standard 1 inch diameter cylindrical core plugs but it can be applied to other sample shapes and volumes the magnetic susceptibility derived estimates of illite content from core plugs correspond well with xrd results from small powdered samples of the same material in terms of both absolute values and overall trends with depth however neither the magnetic method nor xrd should be regarded as definitive each technique has merits and limitations and these help to explain some observed differences in the illite determinations by each method xrd may underestimate the illite content particularly in muddy rocks whereas the magnetic method theoretically provides an upper limit for the illite content the magnetic method is also capable of simultaneously estimating the quartz content in the present samples changes in the concentration and distribution of illite during core cleaning or core flooding experiments can also be potentially quantified by the magnetic technique the development of portable field sensors potentially allows the magnetic method to provide high resolution illite profiles on slabbed cores outcrops and unconsolidated samples without the need to cut core plugs the method could also be applied to whole core measurements and to downhole magnetic susceptibility data the processing of the magnetic susceptibility signal can also be extended to quantify other minerals in simple systems

numerical modelling of historical front variations and the 21st century evolution of glacier ax010 nepal himalaya due to the lack of measurements of ice velocity mass balance glacier geometry and other baseline data model based studies of glacial systems in the nepal himalaya are very limited here a numerical ice flow model has been developed for glacier ax010 in order to study its relation to local climate and investigate the possible causes of its general retreat since the end of the little ice age first an attempt is made to simulate the historical front variations considering each climatic parameter separately good agreement between the observations and model projections can be obtained under the assumption that variations in glacier front position are a response to changes in temperature alone the same assumption is made about future changes to explore the 21st century evolution of the glacier under a no change scenario the glacier will retreat by another 600 m by ad 2100 whereas it is projected to vanish completely during this century for all trends with a temperature rise larger than 2 58 cb yad 2100 with respect to the 1980 99 mean with constant precipitation at the 1980 99 mean the model predicts that the glacier will cease to exist at ad 2083 2056 or 2049 if the temperature rises linearly by 38c 4 58 co r 68c respectively by the end of this century with an additional range of precipitation changes between 30 and 30 the life expectancy of glacier ax010 varies by 18 6 and 2 years for the respective temperature rises thus the role of precipitation becomes minimal for the higher trends of temperature rise

a distributed surface energy balance model for a small valley glacier i development and testing for haut glacier d arolla valais switzerland this paper describes the development and testing of a distributed surface energy balance model used to calculate rates of surface melting at haut glacier d arolla valais switzerland the model uses a digital elevation model dem of the glacier surface and surrounding topography together with meteorological data collected at a site in front of the glacier to determine hourly or daily totals of the energy balance components and hence of melting over the entire surface of the glacier with a spatial resolutio of 20 m the model can also be used to determine temporal and spatial variations in snow depth snow line position and glacier surface albedo calculations from the model are compared with observations made along the glacier centre line in 1990 and in general the model performs very well the correlation coefficients between calculated and measured snow line elevation albedo and ablation are 0 99 0 85 and 0 81 respectively the main source of error between modelled and measured values of these variables is probably inadequacies in the parameterization of albedo used in the model

changes in mean magnetic susceptibility and its anisotropy of rock samples as a result of alternating field demagnetization measurements of low field magnetic susceptibility k and its anisotropy ams on different rock types during stepwise alternating field af demagnetization in increasing fields revealed not only significant changes of the ams principal susceptibilities but also an increase of the mean magnetic susceptibility km studied collections of loess paleosol samples from different sections in belgium bulgaria china siberia and tadjikistan and diorites granites and gneisses from antarctica show systematic km increase between 2 and 27 as compared to the initial values after af demagnetization up to 100 or 200 mt maximum amplitude the relationships between magnetic susceptibility increase and magnetic hysteresis parameters and their ratios indicate that the km increase is due to changes in magnetic domain configuration of the initial natural remanent magnetization nrm state of the remanence carriers during af treatment the obtained linear relationship between k increase and the degree of anisotropy p for strongly anisotropic gneiss samples suggests that magnetostatic interactions also play a role in the observed af effect on km

rock magnetism of remagnetized paleozoic carbonates low temperature behavior and susceptibility characteristics we have conducted a new set of rock magnetic experiments on samples of remagnetized paleozoic carbonates of eastern north america these experiments were designed to investigate the origin of the unusual hysteresis behavior of these rocks by evaluating 1 the importance of ferrimagnetic pyrrhotite as a remanence carrier and 2 the sources of low field susceptibility low temperature measurements of saturation isothermal remanent magnetization sirm indicate that the pyrrhotite magnetic transition at 32 k is absent in the trenton and onondaga limestones of new york this transition is observed but poorly expressed in the knox group of east tennessee room temperature sirms cooled to 10 k in zero field lose a small fraction of their intensity between 30 and 35 k samples from all three formations show a broad peak in irm intensity at about 200 k which is typical of pyrrhotite in the trenton and onondaga samples the ferrimagnetic component of low field susceptibility is significantly larger than the ratio mrs hcr and is thus probably due dominantly to magnetite in some of the knox samples the reverse is true suggesting an important pyrrhotite contribution for all of the samples the ferrimagnetic susceptibility normalized by the saturation magnetization is anomalously high about a factor of 5 or 10 higher than the typical value for magnetite we believe that this indicates a very substantial contribution from superparamagnetic particles strong frequency dependence of susceptibility and very high ratios of anhysteretic to saturation remanence confirm the importance of ultrafine particles spanning the superparamagnetic single domain boundary all three of these chemically remagnetized carbonates units exhibit the following properties which have not previously been found together for any rock or synthetic analog and which therefore appear to constitute a diagnostic set of rockmagnetic criteria for recognizing chemically remagnetized rocks mrs ms 0 89 hcr hc 0 6 k ms 50 m a arm sirm 20 ka mrs hcr 50

proterozoic paleomagnetism in the nipigon embayment of northern ontario pillar lake lava waweig troctolite and gunflint formation tuffs abstract by using unusual combinations of demagnetization techniques proterozoic paleomagnetic vectors and paleopoles are provided for two recently discovered post tectonic proterozoic units near armstrong northern ontario and also for well dated gunflint formation which by previous techniques yielded problematical paleomagnetic data the first paleomagnetic data are provided also for the seagull pluton and inspiration sills characteristic remanent magnetizations chrm for the pillar lake lavas indicate a keweenawan age more specifically 1000 1040 ma by comparison with the well established apwp for the late proterozoic superior craton four combinations of demagnetization techniques yield declinations in the range 108 133 and inclinations in the range 65 to 70 n 100 which define paleopoles near 200 w 48 n corresponding to a location on the keweenawan apwp near 1040 ma in the underlying basement a recently discovered proterozoic igneous complex the waweig troctolitic complex yields new paleomagnetic data with declination and inclination 42 54 n 14 defining a paleopole at 238 w 09 n its ages may be 1400 1600 or 2000 ma by comparison with the presently available ambiguous and sparsely populated apwp the first paleomagnetic results for the seagull pluton u pb age 1113 ma yield a mean declination of 87 4 75 7 n 32 corresponding to a keweenawan paleopole near 233 42 n consistent with other paleopoles near 1200 ma tuffs of the oft studied but problematical gunflint formation u pb age1878 ma yielded stable and presumably primary vectors using several different demagnetization techniques on the same specimens their mean primary declination and inclination 303 48 8 n 17 yields a paleopole now located near 178 w 42 n comparable with the published locations of paleopoles of 2000 ma of broader interest we recognized that low temperature demagnetization preceding conventional demagnetization techniques enhanced the isolation of characteristic vectors combining the conventional techniques thermal and af demagnetization also improved the resolution of characteristic vectors not achieved by other means low grade metamorphism affected the non tectonized proterozoic cover to the canadian shield due to burial or hydrothermal effects obfuscating or erasing primary vectors in some lithologies and especially at certain sites

ams nrm interferences in the deccan basalts toward an improved understanding of magnetic fabrics in flood basalts the evaluation of flow direction in volcanic rocks is among the most important applications of magnetic fabrics studies a statistically significant sample set of titanomagnetite bearing lava flows from the malwa plateau the northern part of the deccan traps in india has been investigated for a possible interference of induced and natural remanent magnetization nrm the nrm alters the scalar anisotropy of magnetic susceptibility ams parameter and the orientations of the ams principal magnetic axes which are crucial for the evaluation of the flow direction for cleaning of the nrm component the lava samples have been demagnetized by use of an alternating field af tumbling demagnetizer peak fields of 100 mt as previous studies have shown that static af demagnetization can bias the results samples with normal magnetic fabrics demonstrate a redistribution of their principal axes after the demagnetization the evaluated flow directions show a more differentiated flow pattern of the malwa area which seems to fit better into the regional geological setting in samples with inverse magnetic fabrics carrying a higher portion of single domain particles ams principal axes remain unchanged after the demagnetization indicating that these samples with high coercivity of magnetic carriers are not suitable for geological interpretations according to these results we propose that the ams measurements after tumbling demagnetization give a better reflection of the intrinsic anisotropy of magnetic carriers at least for samples with normal magnetic fabrics and therefore a more precise and better reflection of the actual mineral fabric

characteristics of large scale wave structure observed from african and southeast asian longitudinal sectors the spatial large scale wave structure lsws at the base of f layer is the earliest manifestation of seed perturbation for rayleigh taylor instability hence found to play a deterministic role in the development of equatorial plasma bubbles epbs except for a few case studies a comprehensive investigation has not been conducted on the characteristics of lsws because of the complexity involved in detecting the lsws particularly in spatial domain in this scenario a comprehensive study is carried out for the first time on the spatial and temporal characteristics of lsws observed in spatial domain over african and southeast asian longitudinal sectors during the year 2011 the observations indicate that these wave structures can be detected a few degrees west of e region sunset terminator and found to grow significantly at longitudes past the sunset terminator the phase fronts of these spatial structures are found to align with the geomagnetic field b lines over a latitudinal belt for at least 5 6 500 600 km centered on dip equator the zonal wavelengths of these structures are found to vary from 100 to 700 km which is consistent with the earlier reports and the epbs were consistently observed when the amplitudes of lsws were grown to sufficient strengths these results would provide better insights on the underlying physical processes involved in excitation of lsws in terms of important roles being played by e region electrical loading and polarization electric fields induced via spatially varying dynamo current due to neutral wind perturbations associated with atmospheric gravity waves

the prereversal enhancement of the zonal electric field in the equatorial ionosphere the electric fields in the ionospheric e and f regions near the magnetic equator often show a strong eastward enhancement shortly after sunset and before the eastward normally daytime field reverses to westward several theoretical models of the low latitude fields suggest that this enhancement is caused mainly or entirely by f region winds the f region dynamo but some authors have suggested that it could be produced solely by e region tidal winds we give here additional calculations and arguments in support of the f region source the enhancement of the eastward field for an eastward f region wind turns out to be a simple direct consequence of the fact that after sunset the ionospheric conductivity decreases far more rapidly in the e region than in the f region

composite magnetic fabric in weakly deformed black shales abstract the anisotropy of magnetic susceptibility ams of weakly deformed sediments of the subalpine terres noires french alps is due to phyllosilicates matrix contribution and detrital titanomagnetites ferromagnetic contribution of variable grain size various rock magnetic and anisotropy techniques have been carried out to understand the origin of the scattering of maximum and minimum susceptibility axes we demonstrate the major contribution of the matrix both to susceptibility and ams anisotropy even when mean matrix susceptibility is weak this suggests that phyllosilicates are better oriented within the foliation plane and that intrinsic anisotropy of the detrital titanomagnetite grains is probably weaker than expected also the separation of the two magnetic subfabrics of three selected sites by coupling together low field ams hfa high field ams and aas anisotropy of anhysteretic remanence demonstrates the existence of a competition between two magnetic lineations and an interchange of the intermediate and minimum ams axes as a result of fine titanomagnetite this is the first evidence of the so called intermediate fabric as predicted by theory

thirty year history of glacier melting in the nepal himalayas 1 two net balance records of neighboring glaciers under different conditions are analyzed to extract temporal variations in glacier melting in the himalayas significant melt was observed every year at one site wet site whereas no melt occurred at the second site because of its high elevation dry site accumulation at the wet site of a glacier is estimated from the dry site neighboring another glacier through a measured precipitation record for a short time period the difference between the estimated accumulation and the net balances at the wet site is obtained as the melt index which represents the glacier melting conditions the melt index with an interannual timescale is significant as a climatic proxy at high elevation since no relationship between stable isotopes and temperature is established and few long term temperature records are available at high elevations in the himalayas the melt index showed a decadal fluctuation with a major amplitude never reported in previous studies with respect to temperature and ice cores analyses in the himalayas ice cores from a site where significant melt occurs every year have not been considered available in reconstructing past climates since climatic signals in ice were disturbed by meltwater infiltration however we suggest a new approach to glean temperature information by a combination of wet and dry cores not obtainable from a good quality ice core alone

magnetic fabrics in archean granitoids northwestern ontario isolation of accessory and matrix contributions by inspection of ams data abstract pre tectonic and post tectonic granitoid plutons in the same area share similar orientations for their ams anisotropy of magnetic susceptibility foliation and lineation and these are similar in orientation to the l s fabrics of the country rock which bears a vertical ene wsw foliation the ams fabrics in the granitoids are composite blending contributions from accessory but highly susceptible magnetite with those from paramagnetic matrix silicates we isolate magnetic sub fabrics in the granitoids by a simple numerical approach that standardizes the mean tensor for susceptibility of specimens thereby suppressing the skewing effect of high susceptibility accessories i e magnetite this approach approximately separates the contributions of ferro magnetic and of paramagnetic minerals to ams though not as completely as technical laboratory experiments

magnetic fabric in the umvimeela dyke satellite of the great dyke zimbabwe abstract anisotropy of magnetic susceptibility ams has been determined for 22 locations from the 500 km long gabbroic umvimeela dyke of zimbabwe ams is controlled by the presence of multi domain magnetite grains which appear to have preserved a variety of magnetic fabrics related to magma movement at the time of dike emplacement three locations along the umvimeela dyke have been identified as feeder points at which magma flowed into the dike from below lateral flow away from these points supplied the rest of the dike system the presence of several foci of igneous activity along the umvimeela dyke parallels the development of the neighbouring contemporaneous great dyke layered complex which consists of a line of contiguous subchambers individual feeder points to the umvimeela dyke may be directly related to activity in adjacent subchambers

interpreting anomalous magnetic fabrics in ophiolite dikes abstract anisotropy of magnetic susceptibility ams may reveal mineral orientation distributions defining magmatic flow axes in igneous dikes the mafic silicates are the best indication of magmatic flow but fe ti accessories may contribute more to the bulk susceptibility if the orientation distributions of the two subfabrics are incongruent anomalous fabrics will occur that do not reflect magma flow axes for ophiolite dikes ocean floor metamorphism changes the mineralogy producing new fe oxides by retrogression and exsolution from mafic silicates and by the oxidation of primary oxides incompatibly oriented ferro magnetic subfabrics may be isolated by anisotropy of anhysteretic remanence aarm anomalous ams fabrics in ophiolites elsewhere have been attributed to inverse fabric contributions from single domain magnetite in varying combinations however in ophiolite dikes from the troodos ophiolite of cyprus anomalous fabrics arise from ocean floor metamorphism extensively or completely replacing the original magnetite and titanomagnetite accessory phases with titanomagnetite fe 2 4 ti 0 6 o 4 tm60 and its oxidised versions titanomaghemite to varying degrees according to depth beneath the ocean floor distance from spreading axis and proximity to transform faults at best the oxide orientation distribution defined by aarm could only be indirectly related to magma flow if its nucleation orientation controlled by a host lattice however more commonly the topotactic lattice reorganization produces weaker arm fabric anisotropies although recrystallized oxidised tm60 dominates the bulk low field susceptibility its anisotropy is generally too feeble to compete with the flow fabric defined by the ams contribution from paramagnetic mafic silicates

the palaeomagnetism of lesbos ne aegean and the eastern mediterranean inclination anomaly summary palaeomagnetic results for 44 sites in 16 22 ma volcanic rocks from lesbos ne aegean yield a mean pole at 81 8 n 178 1 e k 9 0 a95 7 6 the mean direction for these sites d 4 3 i 48 5 k 10 8 95 6 9 is 5 9 6 1 shallower than the reference direction for miocene lesbos calculated from besse courtillot 1991 combining these new data with previous work yields a mean inclination that is 5 6 4 7 too shallow experimental problems magnetic anisotropy the magnetic terrain effect geomagnetic anomalies and problems with the reference path all seem unable to account for this observation shallow inclinations are a common feature of the aegean region 17 of 18 palaeomagnetic studies on cenozoic igneous rocks have returned an inclination that is shallower than expected northward motion of the aegean block by 500 km with respect to northern europe would account for this observation

first observations of the spatial structure of f region 3 m scale field aligned irregularities with the equatorial atmosphere radar in indonesia 1 this paper presents first results of spatial structure associated with 47 mhz coherent backscatter from the low latitude f region in the indonesian thai longitude sector the measurements were made with the equatorial atmosphere radar ear located on the geographic equator in west sumatra indonesia 0 20 s 100 32 e dip latitude 10 36 s the active phased array of the ear was used to perform rapid scans over a wide azimuth sector with a temporal resolution that has heretofore been unachievable application of this unique capability is demonstrated herein to be effective in investigations of spatial structure of plasma bubbles and associated backscatter plumes most notably tiny plumes are shown to grow rapidly while traversing from west to east across the scanned azimuth sector within an initial 20 min period backscatter intensity increased by more than 40 db and the area of the plume increased by a factor of about 20 occasionally plumes reached altitudes as high as 800 to 860 km in the scanned sector these backscatter regions were traced along the magnetic field line to altitudes of 1200 to 1300 km over the geomagnetic equator however these tall structures are not so common over the ear the ear observes fairly conspicuous patchy backscatter from the bottomside of a backscatter plume the backscatter generated at the bottom of the plume appears to descend and eventually merge into the e region backscatter the ear has also observed a downward moving plume that continues for more than 4 hours beginning at an altitude well into the topside of the ionosphere and descending below 300 km the backscatter sometimes observed with the ear at dip latitude of 10 36 s resembles that observed with the mu radar at mid latitudes investigation of these properties with the fast beam steerability of the ear is expected to provide further insight into the nature of the source mechanism for plasma bubbles and plumes

a theoretical and experimental comparison of the anisotropies of magnetic susceptibility and remanence in rocks and minerals summary susceptibility thermo remanent magnetization trm and isothermal remanent magnetization irm anisotropy ellipsoids have been determined for several rock samples the results indicate that the ellipsoid of initial susceptibility is less anisotropic than the trm and low field irm ellipsoids which are found experimentally to be of identical shape this suggests that palaeomagnetic data for anisotropic rocks may be corrected by using the anisotropy ellipsoid determined from magnetically non destructive low field irm measurements such irm measurements can also be used to obtain anisotropy axes of samples which are inherently anisotropic but which have a susceptibility which is too weak to be accurately measured the results for a series of artificial anisotropic samples containing magnetite particles of different sizes in the range 0 2 90 m were very similar to those for the rocks in contrast a comparison of the susceptibility and irm ellipsoids for anisotropic samples containing particles from a magnetic tape gave very different results in accordance with theory such results imply that susceptibility and irm ellipsoids could be used to determine whether anisotropic rocks contain uniaxial single domain particles magnetization confined to the easy axis or whether the particles are essentially multidomain

modelling 60 years of glacier mass balance and runoff for chhota shigri glacier western himalaya northern india glacier mass balance and runoff are simulated from 1955 to 2014 for the catchment 46 glacier cover containing chhota shigri glacier western himalaya using gridded data from three regional climate models 1 the rossby centre regional atmospheric climate model v 4 rca4 2 the regional atmosphere model remo and 3 the weather research and forecasting model wrf the input data are downscaled to the simulation grid 300 m and calibrated with point measurements of temperature and precipitation additional input is daily potential global radiation calculated using a dem at a resolution of 30 m the mass balance model calculates daily snow accumulation melt and runoff the model parameters are calibrated with available mass balance measurements and results are validated with geodetic measurements other mass balance model results and run off measurements simulated annual mass balances slightly decreased from 0 3 m w e a 1 1955 99 to 0 6 m w e a 1 for 2000 14 for the same periods mean runoff increased from 2 0 m 3 s 1 1955 99 to 2 4 m 3 s 1 2000 14 with glacier melt contributing about one third to the runoff monthly runoff increases are greatest in july due to both increased snow and glacier melt whereas slightly decreased snowmelt in august and september was more than compensated by increased glacier melt

effects of the vertical plasma drift velocity on the generation and evolution of equatorial spread f we use radar observations from the jicamarca observatory from 1968 to 1992 to study the effects of the f region vertical plasma drift velocity on the generation and evolution of equatorial spread f the dependence of these irregularities on season solar cycle and magnetic activity can be explained as resulting from the corresponding effects on the evening and nighttime vertical drifts in the early night sector the bottomside of the f layer is almost always unstable the evolution of the unstable layer is controlled by the history of the vertical drift velocity when the drift velocities are large enough the necessary seeding mechanisms for the generation of strong spread f always appear to be present the threshold drift velocity for the generation of strong early night irregularities increases linearly with solar flux the geomagnetic control on the generation of spread f is season solar cycle and longitude dependent these effects can be explained by the response of the equatorial vertical drift velocities to magnetospheric and ionospheric disturbance dynamo electric fields the occurrence of early night spread f decreases significantly during equinox solar maximum magnetically disturbed conditions due to disturbance dynamo electric fields which decrease the upward drift velocities near sunset the generation of late night spread f requires the reversal of the vertical velocity from downward to upward for periods longer than about half an hour these irregularities occur most often at 0400 local time when the prompt penetration and disturbance dynamo vertical drifts have largest amplitudes the occurrence of late night spread f is highest near solar minimum and decreases with increasing solar activity probably due to the large increase of the nighttime downward drifts with increasing solar flux

anisotropy of magnetic susceptibility sedimentological igneous and structural tectonic applications as was noted by graham 1954 anisotropy of magnetic susceptibility ams data has many applications to the study of geological processes this type of anisotropy expresses directional variation in the magnetization induced in a rock most notably in its iron oxides and especially in its magnetite and hematite the ams is commonly expressed by an ellipsoid of which the principal axes are k1 k2 and k3 from greatest to least this ellipsoid is generally interpreted in terms of the distribution and shape of grains of magnetic minerals in a rock although the ellipsoid determined depends also on magnetocrystalline anisotropy and on factors of instrumental technique ellwood et al in press 1987 the challenge for the geoscientist in analyzing ams data is first to identify the origin of the ams geometry then second to relate that geometry to the natural processes which produced the inferred or measured distribution of magnetic materials

current challenges and future developments in magnetic fabric research abstract magnetic fabrics are used extensively as proxies for mineral fabrics and to correct paleomagnetic data and have been proposed to quantify pore fabrics today s understanding and interpretation of magnetic anisotropy benefits from decades of carefully observing anisotropic mineral and rock properties establishing and testing empirical relationships between magnetic and mineral fabrics and developing models to quantify aspects of anisotropy each advance was preceded by some puzzling observations i e data that could not be explained based on the models available at the time e g oblique or inverse fabrics or lithology dependent anisotropy strain relationships these observations led to numerous experimental and numerical techniques designed to characterize magnetic fabrics and determine their origin despite the successful application of magnetic fabrics in many structural and tectonic problems there are still phenomena and measurements that cannot be explained based on today s magnetic fabric theory with the purpose of fostering future development i will touch on three main areas where i see challenges in magnetic fabric research 1 experimental characterization of magnetic anisotropy including the non uniqueness of reported tensors and non linearity 2 anisotropy modelling and defining the carrier minerals and origin of the magnetic fabric 3 selection of adequate sets of anisotropy tensors to correct paleomagnetic data the description of the challenges presented here will hopefully help define directions for future research inform those that are new to anisotropy and advance our field

can remanence anisotropy detect paleomagnetic inclination shallowing due to compaction a case study using cretaceous deep sea limestones we studied 35 cretaceous limestone specimens from five pacific plate deep sea drilling project sites inclination in of the natural remanence is on average 17 shallower than the average 44 expected paleofield inclination i anhysteretic remanence arm applied identically to various axes was found to be weakest armmin perpendicular to bedding and strongest armmax parallel to bedding the average armmin armmax of 0 87 as well as the inclination shallowing of 17 likely originated from sediment compaction rotating the long axes of magnetite grains toward the bedding plane this origin is theoretically and experimentally consistent with the average fractional compaction of 0 6 experienced by our sediments estimated from their porosity a compaction origin is also supported by the significant correlation found between tan in tan i and armmin armmax the correlation line s slope of 2 3 0 7 agrees with theory taking into account our observation that arm given perpendicular to the long axes of magnetite grains has on average 0 37 times the intensity of arm given axially these results suggest that compaction induced inclination shallowing may be detected in a suite of fine grained magnetite bearing sediments by looking for a correlation between tan in and armmin armmax having shown that arm anisotropy is foliated in the bedding plane this correlation line s prediction of in when armmin armmax 1 should estimate i corrected for inclination shallowing

mass balance gradients and climatic change it is generally assumed that the mass balance gradient on glaciers is more or less conserved under climatic change in studies of the dynamic response of glaciers to climatic change one of the following assumptions is normally made i the mass balance perturbation is independent of altitude or ii the mass balance profile does not change it simply shifts up and down observational evidence for such an approach is not convincing on some glaciers the inter annual changes in mass balance seem to be independent of altitude on others not at all moreover it is questionable whether inter annual variation can be projected on different climatic states to see what a physical approach might contribute we developed an altitude dependent mass balance model it is based on the energy balance of the ice snow surface where precipitation is included in a parameterized form and numerical integrations are done through an entire balance year with a 30 min time step atmospheric temperature snowfall and atmospheric transmissivity for solar radiation are all dependent on altitude so a mass balance profile can be calculated slope and exposure of the ice snow surface are taken into account and the effects of these parameters studied in general the calculations were done for 100 m elevation intervals climatological data from the sonnblick observatory austria 3106 m a s l and from vent 2000 m a s l oetztal alps austria served as input for a number of runs simulation of the mass balance profiles for hinterseisferner north easterly exposure and kesselwandferner southeasterly exposure yields reasonable results the larger balance gradient on kesselwandferner is produced by the model so exposure appears to be an important factor here sensitivity of mass balance profiles to shading effects different slope and exposure are systematically studied another section deals with the sensitivity to climatic change perturbations of air temperature cloudiness albedo and precipitation are imposed to see their effects on the mass balance profiles the results clearly show that in general mass balance perturbations depend strongly on altitude they generally increase down glacier and are not always symmetric about the reference state for typical climatic conditions in the alps we found that a 1 k temperature change leads to a change in equilibrium line altitude of 130 m three factors contribute to this large value turbulent heat flux longwave radiation from the atmosphere and fraction of precipitation falling as snow here the albedo feed back increases the sensitivity in a significant way

anisotropy of magnetic susceptibility of magnetically oriented rock powders to estimate the maximum magnetic anisotropy of the ensemble of magnetic carriers present in a rock we measured the anisotropy of magnetic low field susceptibility ams of magnetically oriented rock powder we studied basaltic rock chaine des puys massif central france and metasediments coffs harbour australia in the basaltic powder psd titanomagnetites show maximum anisotropy of l 1 16 in the metasediments the foliation anisotropy is constant f 1 3 controlled by iron bearing phyllosilicates the linear anisotropy goes up to l 2 in pyrrhotite bearing rocks in contrast magnetite bearing samples show low linear anisotropy l 1 1

single domain particles in rocks and magnetic fabric analysis magnetic susceptibility anisotropy is commonly used as a guide for determining stress and flow axes in rocks and for assessing the suitability of anisotropic rocks for palaeomagnetic purposes we have recently demonstrated however in laboratory produced samples that as theoretically expected susceptibility anisotropy is dependent on particle size multidomain particles of magnetite or similar strongly magnetic particles with shape anisotropy exhibit a maximum susceptibility parallel to their easy remanent magnetization axes whereas uniaxial single domain particles exhibit a maximum susceptibility perpendicular to their easy magnetization axes hence susceptibility anisotropy does not yield an unambiguous determination of particle alignment in rocks independent of domain state by demonstrating uniaxial single domain anisotropy characteristics for the first time in a rock specimen we show here that susceptibility measurements by themselves may not correctly identify the degree or type of alignment of ferro or ferrimagnetic particles in rocks in particular apparently foliated rocks can actually be lineated and vice versa moreover rocks with low anisotropy of susceptibility can have a much higher anisotropy of remanence remanence anisotropy methods are shown to give unambiguous determinations of the degree and type of alignment

spatial patterns of holocene glacier advance and retreat in central asia glaciers in the southern himalayas advanced in the early holocene despite an increase in incoming summer solar insolation at the top of the atmosphere these glacier advances are in contrast to the smaller alpine glaciers in the western and northern regions of central asia two different glacier mass balance models are used to reconcile this holocene glacier history with climate by quantifying the change in equilibrium line altitudes ela for simulated changes in holocene climate both ela models clearly show that the lowering of elas in the southern himalayas is largely due to a decrease in summer temperatures and that an increase in monsoonal precipitation accounts for less than 30 of the total ela changes the decrease in summer temperatures is a dynamic response to the changes in solar insolation resulting in both a decrease in incoming shortwave radiation at the surface due to an increase in cloudiness and an increase in evaporative cooling in the western and northern zones of central asia both ela models show a rise in elas in response to a general increase in summer temperatures this increase in temperatures in the more northern regions is a direct radiative response to the increase in summer solar insolation

magnetic fabric and its significance in the 1400 ma mealy diabase dykes of labrador canada an anistropy of magnetic susceptibility ams study of the relatively fresh mealy diabase dyke swarm indicates a correlation between the ams and the deformational effects in the rocks several ams components were revealed during experimental work on 211 samples that had been heated to 640 c during a paleomagnetic study and 22 fresh samples progressively treated in alternating fields seventeen sites with slight or no deformation have a magnetic fabric composed of two major components the stable component attributed to a primary shape anisotropy has minimum and maximum principal susceptibility directions preferentially oriented vertically and along dyke strike n 60 e respectively this configuration is consistent with an origin due to a post emplacement stress field whereby horizontal extension acted on a vertical sheet of partially crystallized magma the orientation of this component with respect to the present horizontal suggests that the dykes have not been tilted since their emplacement the unstable component removed by fields up to 250 mt is attributed to induced domain anisotropy produced by mild tectonic stress during the grenville orogeny the approximate orientation of its principal components as found by the method of substitutional ellipsoids suggests an east west directed maximum stress four other sites with noticeable deformation have magnetic fabric that could not be reliably analyzed but which may be largely composed of domain and stress induced anisotropies developed during the grenville orogeny

sensitivities of the equilibrium line altitude to temperature and precipitation changes along the andes abstract equilibrium line altitudes elas of alpine glaciers are sensitive indicators of climate change and have been commonly used to reconstruct paleoclimates at different temporal and spatial scales however accurate interpretations of ela fluctuations rely on a quantitative understanding of the sensitivity of elas to changes in climate we applied a full surface energy and mass balance model to quantify ela sensitivity to temperature and precipitation changes across the range of climate conditions found in the andes model results show that ela response has a strong spatial variability across the glaciated regions of south america this spatial variability correlates with the distribution of the present day mean climate conditions observed along the andes we find that elas respond linearly to changes in temperature with the magnitude of the response being prescribed by the local lapse rates ela sensitivities to precipitation changes are nearly linear and are inversely correlated with the emissivity of the atmosphere temperature sensitivities are greatest in the inner tropics precipitation becomes more important in the subtropics and northernmost mid latitudes these results can be considered an important step towards developing a framework for understanding past episodes of glacial fluctuations and ultimately for predicting glacier response to future climate changes

on the enigma of day to day variability in equatorial spread f 1 we show that large scale wave structure lsws in plasma density in the bottomside f layer is a hitherto unheralded contributor to the long standing enigma of day to day variability in equatorial spread f esf little is known about lsws it seems to appear in altitude near a vertical shear in zonal plasma drift during the post sunset rise of the f layer and its growth via an interchange instability appears to predispose quasi periodically spaced regions to development of plasma bubbles first indications are that lsws development is necessary and sufficient for esf occurrence we suggest that variability in lsws development perhaps together with the shear in zonal drift may contribute to day to day esf variability a need revealed by this study is that a cluster of distributed sensors not isolated ones is necessary to pursue the problem of day to day variability