a shear instability seeding mechanism for quasiperiodic radar echoes the quasiperiodic echoes with periods in the range of 1 10 minutes originally discovered at the middle and upper atmosphere mu radar in japan in the early 1990s are now known to be a common feature of midlatitude sporadic e a possible role of shear instabilities and the associated kelvin helmholtz structure in seeding the plasma instabilities that produce the radar echoes is suggested in this paper the proposed mechanism has the advantage that the seed structure is generated in situ as part of the same neutral wind structure that serves to initiate the generation of the sporadic e layer in addition the range of observed periods can easily be explained since the kelvin helmholtz structure is embedded in the shear flow and moves with the mean flow in the shear layer the period observed in the ground based frame is simply a product of the horizontal wavelength and the mean flow velocity at the center of the disturbance finally a typical feature of the radar observations has been that the quasiperiodic structure often ebbs and wanes in intensity over a period of 30 to perhaps 60 min recent simulations of unstable neutral shears show that the timescale for the build up and eventual restabilization of the shear flow is 30 40 min comparable to the timescale found in the observations

major storm periods and climate forcing in the western mediterranean during the late holocene abstract big storm events represent a major risk for populations and infrastructures settled on coastal lowlands in the western mediterranean where human societies colonized and occupied the coastal areas since the ancient times the variability of storm activity for the past three millennia was investigated with a multi proxy sedimentological and geochemical study from a lagoonal sequence mappings of the geochemistry and magnetic susceptibility of detrital sources in the watershed of the lagoon and from the coastal barriers were undertaken in order to track the terrestrial or coastal marine origin of sediments deposited into the lagoon the multi proxy analysis shows that coarser material low magnetic susceptibility and high strontium content characterize the sedimentological signature of the paleostorm levels identified in the lagoonal sequence a comparison with north atlantic and western mediterranean paleoclimate proxies shows that the phases of high storm activity occurred during cold periods suggesting a climatically controlled mechanism for the occurrence of these storm periods besides an in phase storm activity pattern is found between the western mediterranean and northern europe spectral analyses performed on the sr content revealed a new 270 year solar driven pattern of storm cyclicity for the last 3000 years this 270 year cycle defines a succession of ten major storm periods sp with a mean duration of 96 54 yr periods of higher storm activity are recorded from 680 to 560 cal yr bc sp10 end of the iron age cold period from 140 to 820 cal yr ad sp7 to sp5 with a climax of storminess between 400 and 800 cal yr ad dark ages cold period and from 1230 to 1800 cal yr ad sp3 to sp1 little ice age periods of low storm activity occurred from 560 cal yr bc to 140 cal yr ad sp9 and sp8 roman warm period and from 820 to 1230 cal yr ad sp4 medieval warm period

major features and forcing of high latitude northern hemisphere atmospheric circulation using a 110 000 year long glaciochemical series the greenland ice sheet project 2 glaciochemical series sodium potassium ammonium calcium magnesium sulfate nitrate and chloride provides a unique view of the chemistry of the atmosphere and the history of atmospheric circulation over both the high latitudes and mid low latitudes of the northern hemisphere interpretation of this record reveals a diverse array of environmental signatures that include the documentation of anthropogenically derived pollutants volcanic and biomass burning events storminess over marine surfaces continental aridity and biogenic source strength plus information related to the controls on both high and low frequency climate events of the last 110 000 years climate forcings investigated include changes in insolation of the order of the major orbital cycles that control the long term behavior of atmospheric circulation patterns through changes in ice volume sea level events such as the heinrich events massive discharges of icebergs first identified in the marine record that are found to operate on a 6100 year cycle due largely to the lagged response of ice sheets to changes in insolation and consequent glacier dynamics and rapid climate change events massive reorganizations of atmospheric circulation that are demonstrated to operate on 1450 year cycles changes in insolation and associated positive feedbacks related to ice sheets may assist in explaining favorable time periods and controls on the amplitude of massive rapid climate change events explanation for the exact timing and global synchroneity of these events is however more complicated preliminary evidence points to possible solar variability climate associations for these events and perhaps others that are embedded in our ice core derived atmospheric circulation records

persistent solar influence on north atlantic climate during the holocene surface winds and surface ocean hydrography in the subpolar north atlantic appear to have been influenced by variations in solar output through the entire holocene the evidence comes from a close correlation between inferred changes in production rates of the cosmogenic nuclides carbon 14 and beryllium 10 and centennial to millennial time scale changes in proxies of drift ice measured in deep sea sediment cores a solar forcing mechanism therefore may underlie at least the holocene segment of the north atlantic9s 1500 year cycle the surface hydrographic changes may have affected production of north atlantic deep water potentially providing an additional mechanism for amplifying the solar signals and transmitting them globally

chlorine 36 fallout in the summit greenland ice core project ice core the natural cosmogenic radioisotope 36cl has been measured in the greenland ice core project ice core from summit greenland generally a good correlation between 36cl and 18o was found even in glacial periods with strong 18o oscillations the 36cl flux is calculated assuming an exponential relationship between accumulation rate and 18o a prominent excursion is detected between 35 and 40 kyr b p which coincides with a similar 10be peak measured in the same samples this sheds light on possible causes of this excursion in the lowest part of the ice core the flux decreases smoothly this can be interpreted as radioactive decay of 36cl t1 2 300 kyr

investigating the 8 2 ka event in northwestern madagascar insight from data model comparisons abstract the 8 2 ka event is a well known cooling event in the northern hemisphere but is poorly understood in madagascar here we compare paleoclimate data and outputs from paleoclimate simulations to better understand it records from madagascar suggest two distinct sub events 8 3 ka and 8 2 ka that seem to correlate with records from northern high latitude this could indicate causal relationships via changes in the atlantic meridional overturning circulation amoc with changes in moisture source s 18o and changes in the mean position of the inter tropical convergence zone itcz as climate modelling suggests these two sub events are also apparent in other terrestrial records but the climatic signals are different the prominent 8 2 ka sub event records a clear antiphase relationship between the northern and southern hemisphere monsoons whereas such relationship is less evident during the first 8 3 ka sub event data model comparison have also shown a mismatch between the paleoclimate data and the model outputs the causes of which are more or less understood and may lie in the proxies in the model or in both data and model knowing that paleoclimate proxies and climate models produce different sets of variables further research is needed to improve the data model comparison approach so that both paleoclimate data and paleoclimate models will better predict the likely climate status of a region during a specified time in the past with minimal uncertainties

large variations in holocene solar activity constraints from 10be in the greenland ice core project ice core 1 cosmogenic radionuclides extracted from ice cores hold a unique potential for reconstructing past solar activity changes beyond the direct instrumental period taking the geomagnetic modulation into account the solar activity in terms of the heliospheric modulation function can quantitatively be reconstructed in high resolution throughout the holocene for this period our results reveal changes in heliospheric modulation of galactic cosmic rays significantly larger than the variations reconstructed on the basis of neutron monitor measurements of galactic cosmic rays for the last 50 years moreover the 10be data from the greenland ice core project ice core as well as 14c support a high current solar activity however although the reconstruction of solar activity on long timescales is difficult our result suggests that the modern activity state of the sun is not that exceptional regarding the entire holocene this extended solar activity record provides the basis for further detailed investigations on solar and cosmic ray physics as well as on solar forcing of the earth s climate whose importance is suggested by increasing paleoclimatic evidences

on the common solar signal in different cosmogenic isotope data sets 1 in this article we aim to determine frequency ranges and intervals of time in which the solar signal dominates in different cosmogenic isotope data from a 14c based reconstruction of cosmic ray intensity over the last millennia we computed expected 10be variations in two antarctic sites dom fuji and south pole and two greenland sites dye 3 and gisp 2 and compared them with the actually measured 10be abundance at the sites by applying different methods of analysis such as bivariate correlation conventional fft coherence and wavelet coherence we found the following 1 the modeled series on the basis of 14c data are in good agreement with the measured 10be data sets on different timescales and at different locations confirming the existence of a common solar signal in both isotope data 2 the 10be data are driven by the solar signal on timescales from about 100 years up to 1000 years or even to multimillennial scales at the longer scales paleomagnetism plays an increasingly important role 3 the local climate dominates the 10be data mostly on short 100 years timescales but the solar signal becomes important even at short scales during periods of grand minima of solar activity 4 there is an indication of a possible systematic uncertainty in the early holocene likely due to a not perfectly stable thermohaline circulation which requires additional studies we have shown that both 14c and 10be based records are consistent with each other over a wide range of timescales and time intervals they form a robust basis for quantitative reconstructions of solar activity variations in the past

application of cosmogenic 10be to dating soils on the raised coral reef terraces of kikai island southwest japan 10be concentrations of six soils on the raised coral reef terraces of kikai island southwest japan range from 0 80 to 7 17 109 atoms g 1 the annual deposition rate of 10be from the atmosphere to kikai island from 2000 to 2002 ranges from 2 0 to 3 5 106 atoms cm 2 year 1 with a mean of 2 8 0 7 106 atoms cm 2 year 1 minimum absolute ages calculated from the inventory of meteoric 10be in the soils and the annual deposition rate of 10be are initial rendzina like soil 8 ka rendzina like soil 18 ka brown rendzina like soil 56 ka terra fusca like soil 127 ka terra rossa like soil 136 ka and intergrade between terra rossa like and red yellow soil 102 ka therefore it was concluded that soil formation during the first 60 000 years would be as rendzina like soils and more than 100 000 years would be required for red yellow soils to develop on raised coral reef terraces under subtropical humid climatic conditions

medium scale traveling ionospheric disturbances observed with the superdarn hokkaido radar all sky imager and gps network and their relation to concurrent sporadic e irregularities 1 we present midlatitude medium scale traveling ionospheric disturbances mstids observed with a super dual auroral radar network superdarn hf radar at around 10 mhz in hokkaido japan in combination with a 630 nm all sky imager and a gps network geonet that provides total electron content tec data mstids propagating southward from high latitudes are detected at first with the hf radar and then with the imager and geonet we analyze two mstid events one in winter event 1 and the other in summer event 2 to find that mstids appear simultaneously at least at 55 25 n it is shown that nighttime mstids propagate toward the southwest over a horizontal distance of about 4000 km and daytime mstids do so toward the southeast daytime radar echoes are due to ground sea surface gs scatter while nighttime echoes in event 1 return from 15 m scale f region field aligned irregularities fais and those in event 2 are due to gs scatter doppler velocities of the nighttime f region fai echoes in event 1 are negative motion away from the radar within strong echo regions and are positive motion toward the radar within weak echo regions this fact suggests that the strong weak echoes return from suppressed enhanced airglow tec areas in line with previous observations over central japan the nighttime mstids in events 1 and 2 are often accompanied by concurrent coherent echoes from fais in sporadic e es layers the es echo areas in event 2 rather coincide with suppressed airglow tec areas in the f region that are connected with the echo areas along the geomagnetic field indicating the existence of e and f region coupling at night

high latitude e and f region coupling signature a case study results from rapid run ionosonde rapid run ionosonde installed in the high latitude sodankyla geophysical observatory enables us to observe for the first time extraordinary details of e f region coupling process in high latitude ionosphere during geomagnetically quiet period we present an example on 15 august 2009 when a dense patchy sporadic e layer was detected associated with this unstable sporadic e layer exhibiting in addition an unusual enhancement with a vertical extent of about 10 km the highly structured f layer plasma was observed with apparent plasma depletions we examine this event taking into account the presence of mesoscale traveling ionospheric disturbances which can initiate coupling between these two regions and compare the data with current theories

beryllium 10 transport to antarctica results from seasonally resolved observations and modeling 1 cosmogenic 10be measured in polar ice cores has important application in the reconstruction of past solar activity however the processes controlling its atmospheric transport and deposition to the ice sheets are not fully understood here we use the seasonal changes in 10be concentrations in a 10 year monthly resolved ice core record from the law dome site east antarctica in conjunction with echam5 ham general circulation model gcm simulations of 10be and 7be deposition as tools to examine this problem maximum 10be concentrations are observed in the ice core during the austral late summer to early autumn summer autumn while minimum concentrations are observed during the austral winter the gcm simulations corroborated by earlier observations of 10be 7be ratios in antarctica from the georg von neumayer air sampling station suggest that the 10be concentration maximum is linked to direct input of stratospheric 10be from the antarctic stratosphere to the lower levels of the antarctic troposphere during the austral summer autumn this result contrasts with the modeled transport of 10be to greenland where the seasonal maximum in stratospheric input is seen in the late winter to spring synchronous with the timing of the seasonal maximum in midlatitude stratosphere to troposphere exchange our results suggest that a different combination of processes is responsible for the transport of 10be to the antarctic and greenland ice sheets

beryllium 10 in the greenland ice core project ice core at summit greenland concentrations of the cosmogenic isotope 10be have been measured in more than 1350 samples from the greenland ice core project grip ice core drilled at summit greenland although a dust associated component of 10be retained by 0 45 m filters in some of the samples complicates the interpretations the results confirm that the first order origin of 10be concentration variations is changes in precipitation rate associated with different climate regimes this effect is seen not only between glacial and interglacial periods but also during the shorter dansgaard oeschger interstadials by contrast the 10be data do not support the interpretation of rapidly varying accumulation i e climate during the last interglacial they can however be used to help place limits on the origin of the ice in these events after taking into account variable snow accumulation effects variations in the 10be flux are observed probably caused by solar and geomagnetic modulation but possibly also by primary cosmic ray variations the most dramatic is a 10be peak 40 000 years ago similar to that found in the vostok ice core thus permitting a very precise correlation between climate records from arctic and antarctic ice cores the 36cl 10be ratio considering either total or only ice associated 10be shows significant variability over the whole core depth thus confirming the difficulty in using this parameter for dating ice cores

strong coherence between solar variability and the monsoon in oman between 9 and 6 kyr ago variations in the amount of solar radiation reaching the earth are thought to influence climate but the extent of this influence on timescales of millennia to decades is unclear a number of climate records show correlations between solar cycles and climate1 but the absolute changes in solar intensity over the range of decades to millennia are small2 and the influence of solar flux on climate is not well established the formation of stalagmites in northern oman has recorded past northward shifts of the intertropical convergence zone3 whose northward migration stops near the southern shoreline of arabia in the present climate4 here we present a high resolution record of oxygen isotope variations for the period from 9 6 to 6 1 kyr before present in a th u dated stalagmite from oman the 18o record from the stalagmite which serves as a proxy for variations in the tropical circulation and monsoon rainfall allows us to make a direct comparison of the 18o record with the 14c record from tree rings5 which largely reflects changes in solar activity6 7 the excellent correlation between the two records suggests that one of the primary controls on centennial to decadal scale changes in tropical rainfall and monsoon intensity during this time are variations in solar radiation

meteor induced transient sporadic e as inferred from rapid run ionosonde observations at midlatitudes 1 observations were made with a rapid run ionosonde during a 1 month period from the end of july to the end of august 2002 that included the perseid meteor shower ionograms were obtained at 1 minute intervals all the echo traces below a virtual height of 200 km were hand scaled for detecting weak and broken traces as well as well determined sporadic e among the scaled e region traces a distinct meteor echo persisting for 40 min was observed this long duration meteor event was similar to that observed during the leonid meteor shower in 2001 however the apparent height of the echo traces in the current event first decreased and then increased after equaling the height of a persistent sporadic e layer while the apparent height of the long duration meteor echo trace observed in leonids 2001 remained nearly constant the descending rate of the meteor echo was approximately 22 m s which was considerably greater than that of the tidal ion layer trapped in a downward moving wind shear node we ascribe the long duration meteor echo to a transient and horizontally drifting sporadic e patch generated from meteor trail plasma

case studies of coupling between the e and f regions during unstable sporadic e conditions 1 simultaneous f region airglow e region coherent scatter radar and ionosonde observations were made in greece during the summer sporadic e season in 2002 in this paper we report on two case studies during which patchy sporadic e layers were accompanied by midlatitude spread f coherent vhf radar echoes including two stream echoes and traveling ionospheric disturbances registered by the airglow instrument we argue that these events give strong evidence that polarization electric fields are built up in the e region and are mapped upward to the f region creating rising and falling regions in the bottomside plasma the resulting structure creates conditions for midlatitude spread f as detected by the ionosonde this correlation between patchy sporadic e and midlatitude spread f is further supported in a companion paper upward coupling of this sort is particularly efficient in regions of f region plasma uplift and airglow depletion since the f region pedersen conductivity is low which reduces the electrical load on the e region generator

ionospheric effects of the missile destruction on 9 december 2009 we report on ionosonde and meteor radar observations made in sodankyla geophysical observatory sgo 67 22 n 26 38 e finland on 9 december 2009 during a test launch of the russian solid propellant military missile due to a technical problem the missile was self destroyed around 07 ut at an ionospheric height near 200 km altitude over the kola peninsula russia at a distance about 500 km to east from the observatory products of the explosion were spread into a large area and reached the region of sgo meteor radar observations in about 2 h around 09 ut after about 3 h around 10 ut a sporadic e layer presumably composed of the remains including long lived metallic aluminum and its oxides ions was observed near the zenith of the sgo ionosonde we discuss possible mechanisms accounting for transport of the remains 1 since the event occurred during a long lasting period of extremely low solar and magnetic activity the ionospheric electric field was unlikely to play a substantial role in the transport of the remains and sporadic e layer formation 2 the horizontal transport of the remains cannot be explained by the neutral winds based on empirical models 3 theoretical estimations suggest that the observed transport could be due to thermospheric turbulence

high resolution records of 10be in endogenic travertine from baishuitai china a new proxy record of annual solar activity abstract the accurate reconstruction of past solar activity is a prerequisite for assessing the role of solar forcing on climate variations cosmogenic 10be produced by galactic cosmic rays and stored in natural archives such as ice cores and lake sediments has been shown to be the most reliable as an indicator of past solar activity although reconstructions at a higher annual resolution have remained elusive due to dating imprecision and uncertainties concerning the effect of depositional processes here we employ a methodology that facilitates the annual reconstruction of past cosmic ray and solar activity variations an annual 10be record is assembled from an endogenic travertine in baishuitai china covering the period 2001 2016 ce we demonstrate that the effect of depositional processes when 10be is incorporated into travertine can be accounted for using the associated 9be and potassium k contents and that the resulting corrected 10be content significantly correlates with the modeled global 10be production rates with a time lag of 1 5 2 5 years our results from the baishuitai endogenic travertine suggest that the 10be record in such carbonate sediments has considerable potential as a high resolution proxy for past cosmic ray and solar activity variations

tree ring based reconstructions of north american glacier mass balance through the little ice age contemporary warming transition abstract glacier mass balance reconstructions provide a means of placing relatively short observational records into a longer term context in western north america mass balance records span four to five decades and capture a relatively narrow window of glacial behavior over an interval that was dominated by warming and ablation we use temperature and moisture sensitive tree ring series to reconstruct annual mass balance for six glaciers in the pacific northwest and alaska mass balance models rely on the climatic sensitivity of tree ring chronologies and teleconnection patterns in the north pacific the reconstructions extend through the mid to latter portions of the little ice age lia and explore the role of climate variability in forcing mass balance across multiple environmental gradients synchronous positive mass balance intervals coincide with regional moraine building and solar minima whereas differences in lia glacier behavior are related to synoptic climate forcing secular warming in the late 19th century to present corresponds with the only multi decadal intervals of negative mass balance in all glacier reconstructions this suggests that contemporary retreat in western north america is unique with respect to the last several centuries and that regional patterns of glacier variability are now dominated by global climate forcing

geomagnetic and atmospheric effects upon the cosmogenic 10be observed in polar ice analytical tools are developed that allow the 10 be measured in ice cores to be inverted to yield quantitative information about the long term time dependence of the cosmic ray flux outside the earth s magnetic field it is concluded that the historic changes in both the magnitude and direction of the geomagnetic dipole and the inter latitudinal mixing in the atmosphere produce effects that can be large compared to the standard deviation of 22 year average 10 be data and appropriate procedures are developed to compensate for them the 10 be response function is shown to have peaked near 1 8 gev nucleon since 1950 while during the maunder minimum it approximated 0 8 gev nucleon this shows that the 10 be data are approximately a factor of two more sensitive to cosmic ray modulation than are high latitude sea level neutron monitors the z 2 cosmic radiation contributes 30 to 49 of the observed 10 be introducing a substantial rigidity dependence into the temporal variations a mathematical model is developed that computes the 10 be flux arriving at points in the polar cap taking into account polar wander changes in the geomagnetic moment and various degrees of atmospheric mixing it is shown that polar wander introduces variations into the observed flux that may be approximately three times the standard deviation of 22 year average 10 be data and that there may be significant differences between the northern and southern hemispheres the mathematical model together with the temporal changes in the nitrate concentration observed in ice cores indicate that the secular changes in 10 be due to climate driven changes in atmospheric circulation were 4 during the little ice ages two methods are outlined that allow independent determinations of the characteristics of the region of the atmosphere that contributes to the 10 be observed in the polar caps for the antarctic this has approximated the region south of 40 s for the past millennium frequently 10 be measurements are made using 4 8 year ice samples and it is shown that the unresolved 11 year variations of the cosmic radiation are the dominant source of statistical variation in these data and a procedure developed to largely eliminate them failure to eliminate these unresolved 11 year variation greatly diminishes the value of the 10 be data in the study of the long term changes in the galactic cosmic radiation

continuous geomagnetic field models for the past 7 millennia 2 cals7k 1 we present two continuous global geomagnetic field models for recent millennia cals3k 2 covering the past 3000 years and cals7k 2 covering 7000 years from 5000 bc to 1950 ad the models were determined by regularized least squares inversion of archeomagnetic and paleomagnetic data using spherical harmonics in space and cubic b splines in time they are derived from a greatly increased number of paleomagnetic directional data compared to previous efforts and for the first time a significant amount of archeointensity data is used in this kind of global model allowing the determination of evolution of geomagnetic dipole strength while data accuracy and dating uncertainties remain a limitation reliable low resolution global models can be obtained the results agree well with previous results from virtual axial dipole moment vadm studies from archeomagnetic intensity data apart from a systematic offset in strength a comparison of model predictions with the previous 3000 year model cals3k 1 gives general agreement but also some significant differences particularly for the early epochs the new models suggest that the prominent two northern hemisphere flux lobes are more stationary than cals3k 1 implied extending considerably the time span of stationary flux lobes observed in historical models between 5000 bc and 2000 bc there are time intervals of weak dipole moment where dipole power is exceeded by low degree nondipole power at the core mantle boundary model coefficients and evaluation code can be obtained from the earthref digital archive erda together with animations and snapshots plots for every 100 years at http www earthref org detailed urls for the different material are listed in appendix a

changes in the carbon cycle during the last deglaciation as indicated by the comparison of 10be and 14c records the variations in atmospheric radiocarbon c 14 concentration during the last 50 000 years can be attributed to changes in the c 14 production rate due to changes in solar activity the geomagnetic field and or interstellar galactic cosmic ray flux and to changes in the global carbon cycle the relative contributions of these processes is the subject of current debate although the discrepancies between the various reconstructions of the past atmospheric radiocarbon concentration increase with age the relatively good agreement over the last 25 000 years allows a quantitative discussion of the causes of the observed c 14 variations for this period using be 10 measurements from greenland summit ice cores we show that in addition to solar and geomagnetically induced production rate changes significant changes in the carbon cycle have to be considered to explain the measured c 14 concentrations there is evidence that these changes are connected to 1 global deglaciation and 2 climate changes in the north atlantic region on centennial to millennial time scales related to changes in the ocean circulation differences between be 10 and geomagnetic field records however suggest that uncertainties of about 20 still exist in determinations of past changes in the c 14 production rate c 2004 elsevier b v all rights reserved less

interplanetary magnetic field during the past 9300 years inferred from cosmogenic radionuclides 1 we have reconstructed the interplanetary magnetic field imf its radial component and the open solar magnetic flux using the solar modulation potential derived from cosmogenic 10be radionuclide data for a period covering the past 9300 years reconstructions using the assumption of both constant and variable solar wind speeds yielded closely similar results during the maunder minimum the strength of the imf was approximately 2 nt compared to a mean value of 6 6 nt for the past 40 years corresponding to an increase of the open solar magnetic flux of about 350 we examine four cycles of the hallstatt periodicity in the imf with a mean period of 2250 years and an amplitude of 0 75 nt grand solar minima have largely occurred in clusters during the hallstatt cycle minima around the years 5300 3400 1100 and 1500 a d the last cluster includes the dalton maunder and sporer minima we predict that the next such cluster will occur in about 1500 years the long term imf has varied between 2 nt and 8 nt and does not confirm a proposed floor lower limit there is a slowly changing long term trend of amplitude 1 5 nt with a minimum around the year 4600 and a maximum around 0 a d that may be of solar origin but which also may be due to unknown long term changes in the atmospheric effects or geomagnetic field intensity

role of unstable sporadic e layers in the generation of midlatitude spread f 1 there is growing experimental evidence to suggest that mesoscale spread f is linked to the occurrence of midlatitude coherent backscatter from patchy sporadic e layers which are unstable to the gradient drift and farley buneman plasma instabilities to validate this suggestion we have compared e region backscatter and spread f ionosonde recordings from about 100 days of joint operation during summer and found a one to one relation in the occurrence of both phenomena also midlatitude backscatter studies over the last few years have shown the existence of enhanced electric fields inside patchy sporadic e these are believed to be polarization fields set up locally by neutral winds that transport the plasma patches horizontally and by the relatively large hall to pedersen conductivity ratios at e region altitudes moreover midlatitude echoes were found to be associated with mostly westward drifting sporadic e patches with typical scale lengths from 10 to more than 100 km and perturbed eastward electric fields from a few to maybe more than 10 to 15 mv m we propose that the enhanced polarization fields set up inside unstable sporadic e patches can easily map up the magnetic field lines to the f region and thus contribute to the formation of midlatitude spread f this new mechanism for spread f generation is basically an image process that can account for key observational properties of the phenomenon these include the rapid plasma upwelling and the abrupt changes in height uplifts of the f layer as well as the scale sizes involved and morphological characteristics

solar activity during the last 1000 yr inferred from radionuclide records identification of the causes of past climate change requires detailed knowledge of one of the most important natural factors solar forcing prior to the period of direct solar observations radionuclide abundances in natural archives provide the best known proxies for changes in solar activity here we present two independent reconstructions of changes in solar activity during the last 1000 yr which are inferred from be 10 and c 14 records we analyse the tree ring c 14 data shcal intca104 from 1000 to 1510 ad and annual data from 1511 to 1950 ad and four be 10 records from greenland ice cores camp century grip milcent and dye3 together with two be 10 records from antarctic ice cores dome concordia and south pole in general the be 10 and c 14 records exhibit good agreement that allows us to obtain reliable estimates of past solar magnetic modulation of the radionuclide production rates differences between be 10 records from antarctica and greenland indicate that climatic changes have influenced the deposition of be 10 during some periods of the last 1000 yr the radionuclide based reconstructions of past changes in solar activity do not always agree with the sunspot record which indicates that the coupling between those proxies is not as close as has been sometimes assumed the tree ring c 14 record and be 10 from antarctica indicate that recent solar activity is high but not exceptional with respect to the last 1000 yr c 2006 elsevier ltd all rights reserved less

ionospheric effects of the leonid meteor shower in november 2001 as observed by rapid run ionosondes 1 we operated ionosondes at four stations in a rapid run mode to obtain ionograms every minute for 102 hours during the period of the leonid meteor shower in november 2001 plenty of radio echoes that looked like echo traces produced by sporadic e reflection were seen in the ionograms and this allowed statistical analysis in a single meteor shower event including discrimination of the backscattering by meteor trails from reflection by a horizontally stratified sporadic e layer the radio echoes seen in the ionograms were categorized into three types the first were spontaneous echoes which were distributed across a wide range of virtual heights at times during the period of maximum meteor activity there was a statistically good correlation among the echoes seen at the four stations the echoes of this type appear to be produced by fresnel backscattering from meteor trails the second were also spontaneous echoes observed during the shower period but persisted for several tens of minutes at the same virtual height as the typical sporadic e layer and the top frequency of these echoes decayed with time echoes of this type are thus attributed to the reflection from a meteor induced sporadic e patch echoes of the last type appeared outside the period of maximum activity of the meteor shower in the same range of virtual heights as the conventional sporadic e layer and there was no time correlation between the events observed at the four stations these events are attributed to a periodical increase in foes which is modulated by planetary wave activity and have no relation with the meteor shower

variations in the geomagnetic dipole moment over the last 12 000 years summary an analysis has been made of archaeointensity data for the past 12 000 years there are 3243 results from diverent areas of the world covering the past 12 000 years of these 2203 are from the european region and 1040 are from the rest of the world the archaeointensity data set analysed in the present study is almost three times larger than that used by mcelhinny senanayake 1982 although there is no major diverence between our global data and the earlier data the data for the non european region have been improved and we now have a data set for asia

spatial and temporal variations in meteoric 10be inventories and long term deposition rates colorado front range abstract atmospherically derived cosmogenic nuclides such as meteoric 10 be offer great potential in quaternary science because they can be used as landform geochronometers and as sediment tracers use of meteoric 10 be inventories for determining landform age soil residence time or erosion rates requires knowing the long term rate of deposition for this cosmogenic nuclide to the earth s surface here we present meteoric 10 be inventories measured at 6 dated sites near the boulder creek critical zone observatory front range colorado each site lies on a relatively stable landform broad moraine or fluvial terrace at slopes between 10 be deposition precipitation dryfall and dust deposition calculated from measured inventories at these sites range from 0 4 to 5 0 10 6 atoms cm 2 yr 1 none of the inventories match expected primary meteoric 10 be deposition rates that global latitude based models or precipitation specific models predict for this region meteoric 10 be inventories and calculated deposition rates at the three older 90 ka sites fall below 0 3 0 7 model predictions inventories and rates at the three pinedale age sites lgm 21 15 ka are higher 1 5 4 than model predictions previous analysis of soils in the front range over the same timeframe as these sites indicate that long term dust accumulation rates are low and associated secondary meteoric 10 be deposition is unlikely to account for the deviation from model predictions at the pinedale age sites in particular long term dustfall would have to be 1 2 orders of magnitude higher to add the meteoric 10 be required to account for measured inventories low inventories at older sites are consistent with loss of meteoric 10 be through physical erosion or selective removal of near surface soil enriched in meteoric 10 be time averaged rates of total meteoric 10 be deposition for these sites are minima we speculate that higher inventories at pinedale age sites reflect the addition of meteoric 10 be due to snowdrifts and or interflow associated with landform location increasing the effective precipitation related primary meteoric 10 be deposition at the sampled sites given these constraints and the spatial variation observed around the front range we suggest that 1 5 0 2 10 6 atoms cm 2 yr 1 is an appropriate long term meteoric 10 be deposition rate to use across much of the front range region that receives 45 55 cm of precipitation a year this long term total meteoric 10 be deposition rate is 30 50 higher than that predicted by global or annual precipitation specific models emphasizing that local calibration of deposition rates is essential for geomorphic studies around the globe

volcanoes and climate the triggering of preboreal jokulhlaups in iceland the early holocene 12 8 2 cal ka deglaciation and pulsed warming was associated in iceland with two major generations of jokulhlaups around the vatna ice cap vatnajokull at ca 11 4 11 2 cal ka and ca 10 4 9 9 cal ka and major tephra emissions from the grimsvotn and bar arbunga subglacial volcanoes the earliest flood events were recorded inland during the middle younger dryas and their deposits were overlain by the early preboreal vedde ash 11 8 cal ka the first holocene flood events ca 11 4 11 2 cal ka are issued from a glacial advance the second and major set of floods was partly driven by the erdalen cold events and advances 10 1 9 7 10be ka initially issued from the bar arbunga 10 4 10 1 9 9 ka and grimsvotn volcanoes saksunarvatn tephra complex ca 10 2 9 9 cal ka these floods were also fed by the residual glacio isostatic depressions below the vatnajokull that enabled the storage of meltwaters in large subglacial lakes or aquifers until ca 9 3 cal ka this storage was enhanced by ice damming and permafrost especially during the twinned erdalen events due to the glacio isostatic rebound the general slope was nearly flat and the valley was partly filled with sediments until ca 10 8 cal ka temporary lacustrine deposits in this valley resulted from the very broad splay of waters as for the ca 11 2 cal ka and ca 10 1 9 9 cal ka flood due to regional permafrost these floods had a potential duration of several months as they were mostly fed by climate driven meltwater the maximal volume evacuated by these events did not greatly exceed 1 106 m3 s 1 from the flood affected transverse profile of the valleys that remain partly filled with sediments

the δ18o record along the greenland ice core project deep ice core and the problem of possible eemian climatic instability over 70 000 samples from the 3029 m long greenland ice core project grip ice core drilled on the top of the greenland ice sheet summit have been analyzed for 8o a highly detailed and continuous 8o profile has thus been obtained and is discussed in terms of past temperatures in greenland we also discuss a three core stacked annual 8o profile for the past 917 years the short term 50 years variability of the annual 8o signal is found to be 1 in the holocene and estimates for the coldest parts of the last glacial are 3 or higher these data also provide insights into possible disturbances of the stratigraphic layering in the core which seems to be sound down to the onset of the eemian spectral analysis of highly detailed sequences of the profile helps determine the smoothing of the 8o signal which for the holocene ice is found to be considerably stronger than expected we suggest this is due to a process involving diffusion of water molecules along crystal boundaries in the recrystallizing ice matrix deconvolution techniques were employed for restoring with great confidence the highly attenuated annual 8o signal in the holocene we confirm earlier findings of dramatic temperature changes in greenland during the last glacial cycle abrupt and strong climatic shifts are also found within the eem sangamon interglaciation which is normally recorded as a period of warm and stable climate in lower latitudes the stratigraphic continuity of the eemian layers is consequently discussed in section 3 of this paper in terms of all pertinent data which we are not able to reconcile

geomagnetic field intensity during the last 60 000 years based on 10be and 36cl from the summit ice cores and 14c abstract based on 10 be 36 cl and 14 c records we reconstruct past changes in the geomagnetic field intensity under the assumption that radionuclide records are mainly influenced by changes in their production rates subsequent comparison of these records with independent geomagnetic field reconstructions allows us to assess the reliability of our approach and to identify periods where our method or the geomagnetic field reconstructions might be problematic the geomagnetic field derived from the 10 be flux to summit in central greenland agrees well with independent geomagnetic field intensity reconstructions however compared to independent palaeomagnetic data the radionuclide record suggests increased geomagnetic field intensities especially for the period from 20 000 to 30 000 years bp 36 cl from the grip ice core agrees well with the 10 be record for the last ice age and hence also the reconstructed geomagnetic field based on the tree ring radiocarbon record it is possible to reconstruct geomagnetic field intensity changes during the holocene a comparison of radiocarbon based and independent geomagnetic field reconstructions indicates that changes in the carbon cycle significantly influenced the atmospheric radiocarbon concentration before 10 000 years bp

rapid run ionosonde observations of traveling ionospheric disturbances in the auroral ionosphere 1 since 2007 the sodankyla geophysical observatory routinely performs vertical ionosphere soundings once per minute using a frequency modulated continuous wave chirp at the rate of 500 khz s from 500 khz to 16 mhz we used these data to study traveling ionospheric disturbances tids during 10 16 local time the observations were made between april 2007 and june 2012 mostly during low solar activity the tids were studied in five bands of periods corresponding to the following infrasonic acoustic waves and the buoyancy cutoff periods from 5 to 10 min small scale gravity waves gws 10 15 min medium scale ms 15 30 min gws medium large scale ms ls 30 60 min gws and large scale ls 60 120 min gws relative contribution with respect to ls tids of the short period 5 15 min and ms 15 30 min tids shows minima in winter and maxima in summer these annual variations anticorrelate with variations of true height namely the largest relative amplitudes occur in summer when tids were observed at minimal heights we suggest that the summer increase of shorter period tids is due to lowering reflection to the height where the brunt vaisala period is smaller and hence shorter period gravity waves exist the summer maxima were most prominent during the 3 years of minimal solar activity 2008 2010 in 2011 when solar activity increased the annual variation seems less prominent annual variations of the longer period 30 120 min tids are essentially less significant for all tids no obvious dependences on the ae and ap indices of magnetic activity were found

observations of overturning in the upper mesosphere and lower thermosphere 1 a number of observations of the sodium density primarily in the mesosphere and lower thermosphere but also of the electron density structure have shown what appears to be overturning or convective roll cells near the transition from the mesosphere to the lower thermosphere the cells are found in the region between 95 and 105 km and occur near the boundary between the region of lower stability in the mesosphere and the region of higher stability in the lower thermosphere the vertical scale for the rolls is 5 6 km and the timescale is 1 3 hours the rolls occur in a region characterized by large shear in the neutral winds but the timescales are too long to be explained by simple kelvin helmholtz instability we present observations from the university of illinois lidar facility located at the starfire optical range near albuquerque new mexico from the arecibo observatory in puerto rico and from the maui malt lidar facility located on maui in hawaii that show the overturning structure possible mechanisms for generating the convective rolls are discussed including the relationship of the observed features to the characteristics expected for an inflection point instability

presence of the solar de vries cycle 205 years during the last ice age certain characteristic periodicities in the 14c record from tree rings such as the well known 11 yr schwabe cycle are known to be of solar origin the origin of longer period cycles such as the 205 yr de vries cycle in the 14c record was less certain and it was possible to attribute it either to solar or climatic variability here we demonstrate that the de vries cycle is present in 10be data from the grip ice core during the last ice age 25 to 50 kyr bp analysis of the amplitude of variation of this cycle shows it to be modulated by the geomagnetic field indicating that the de vries cycle is indeed of solar rather than climatic origin

solar modulation of cosmogenic nuclide production over the last millennium comparison between 14c and 10be records for about the last 30 years it has been recognized that the high frequency component of the tree rings 14c 12c record is dominated by the modulation of the cosmic ray flux by the solar wind in particular it has been demonstrated that the three most recent periods of low sunspot occurrence were characterized by high values of atmospheric 14c 12c during the last millennium other periods of high 14c 12c values were observed but their solar origin is still debatable in the present work we compare these fluctuations with an independent record of cosmogenic 10be measured in ice from the south pole to check the solar origin of the observed 14c 12c variations in order to compare quantitatively the results obtained on 10be and 14c it is necessary to take into account the different behaviour of these two cosmogenic isotopes and especially the damping effect of the carbon cycle in the case of 14c as an input to a 12 box numerical model we used the relative fluctuations of the 10be concentrations record measured in south pole ice and converted it into a synthetic 14c record we took into account the fact that 10be modulation is enhanced in polar regions due to the orientation of the geomagnetic field as expected the fluctuations of the modelled 14c record are much smaller a factor of 20 than those observed for the raw 10be record in addition the variations are smoother and shifted in time by a few decades the 10be based 14c variations closely resemble the 14c measurements obtained on tree rings r 0 81 in particular it is easy to identify periods of maximal 14c 12c which correspond to solar activity minima centred at about 1060 1320 wolf 1500 sporer 1690 maunder and 1820 dalton yr a d cross correlation calculations suggest that there is no significant lag between the 10be based 14c and the tree ring 14c records our study strongly suggests the dominance of the solar modulation on the cosmonuclide production variations during the last millennium

solar influences on holocene climatic changes illustrated by correlations between past lake level fluctuations and the atmospheric 14c record chronological correlations established at different time scales among the lake level fluctuations in the jura and french subalpine ranges glacier movements in the swiss and austrian alps and the atmospheric 14c record during the last 7 millennia show coincidences between lake level rises glacier advances and high 14c production and vice versa these correspondences suggest that the short term 14c variations may be an empirical indicator of holocene palaeoclimates and argue for possible origins of holocene climatic oscillations 1 the varying solar activity refers to secular climatic oscillations and to major climatic deteriorations showing a ca 2300 yr periodicity 2 a question is raised about a relationship between the earth s magnetic field and climate first the weak strength periods of the earth s dipole magnetic field between 3800 and ca 2500 b c coincide with higher climate variability and vice versa second the ca 2300 yr periods revealed by the 14c record and also by the major climatic deteriorations re corded in jurassian lakes ca 1500 a d ca 800 b c and ca 3500 b c coincide with the ca 2300 yr periods revealed by the earth s nondipole geomagnetic field the present warming induced by anthropogenic factors should be intensified during the next few centuries by natural factors of climate evolution

azimuth time intensity striations of quasiperiodic radar echoes from the midlatitude e region ionosphere the valensole high frequency hf radar in the south of france is an ionospheric doppler sounder which can perform e region coherent backscatter measurements over an azimuthal sector of 86 from 26 e to 58 w with 2 angular resolution this large azimuthal coverage is taken advantage of in order to study quasiperiodic qp echoes in the zonal direction using azimuth time intensity ati analysis ati plots show sequential sloping striations of scatter reminiscent of those detected routinely in the range time intensity rti plots of midlatitude radars which view the medium at a fixed azimuth about the meridian it was found that ati striation periods range from a few minutes to less than 30 min whereas the striation slopes are systematically negative motions westward prior to local midnight and turn positive motions eastward in the post midnight hours the zonal rates dx dt computed from the striation slopes take values between 30 and 160 m s these are due to real motions of unstable plasma structures most likely sporadic e patches that drift along with the neutral wind that have zonal scale lengths of several tens of kilometers the present observations imply that the mechanism responsible for qp echoes is independent of azimuth and can basically operate effectively in any direction in the horizontal plane

tree rings and ice cores reveal c 14 calibration uncertainties during the younger dryas the younger dryas interval during the last glacial termination was an abrupt return to glacial like conditions punctuating the transition to a warmer interglacial climate despite recent advances in the layer counting of ice core records of the termination the timing and length of the younger dryas remain controversial also a steep rise in the concentration of atmospheric radiocarbon at the onset of the interval recorded primarily in the cariaco basin has been difficult to reconcile with simulations of the younger dryas carbon cycle here we discuss a radiocarbon chronology from a tree ring record covering the late glacial period that has not been absolutely dated we correlate the chronology to ice core timescales using the common cosmic production signal in tree ring 14c and ice core 10be concentrations the results of this correlation suggest that the cariaco record may be biased by changes in the concentration of radiocarbon in the upper ocean during the early phase of the younger dryas climate reversal in the cariaco basin this bias in the marine record may also affect the accuracy of a widely used radiocarbon calibration curve over this interval our tree ring based radiocarbon record is easily reconciled with simulated production rates and carbon cycle changes associated with reduced ocean ventilation during the younger dryas attaching a floating tree ring chronology to ice core records that cover the abrupt younger dryas cold interval during the last glacial termination provides a better estimate of the onset and duration of the radiocarbon anomaly the chronology suggests that marine records may be biased by changes in the concentration of radiocarbon in the ocean which may affect the accuracy of a popular radiocarbon calibration program during this interval

holocene forcing of the indian monsoon recorded in a stalagmite from southern oman a high resolution oxygen isotope record from a thorium uranium dated stalagmite from southern oman reflects variations in the amount of monsoon precipitation for the periods from 10 3 to 2 7 and 1 4 to 0 4 thousand years before the present ky b p between 10 3 and 8 ky b p decadal to centennial variations in monsoon precipitation are in phase with temperature fluctuations recorded in greenland ice cores indicating that early holocene monsoon intensity is largely controlled by glacial boundary conditions after approximately 8 ky b p monsoon precipitation decreases gradually in response to changing northern hemisphere summer solar insolation with decadal to multidecadal variations in monsoon precipitation being linked to solar activity

solar and volcanic fingerprints in tree ring chronologies over the past 2000 years abstract the sun is the main driver of earth s climate yet the sun s role in forcing decadal to centennial climate variations has remained controversial especially in the context of understanding contributions of natural climate forcings to continuing global warming to properly address long term fingerprints of solar forcing on climate long term very high resolution globally distributed climate proxy records are necessary in this study we compile and evaluate a near global collection of annually resolved tree ring based climate proxies spanning the past two millennia we statistically assess these records in both the time and frequency domains for solar forcing i e total solar irradiance tsi and climate variability with emphasis on centennial time scales analyses in the frequency domain indicate significant periodicities in the 208 year frequency band corresponding to the devries cycle of solar activity additionally results from superposed epoch analysis sea point toward a possible solar contribution in the temperature and precipitation series however solar climate associations remain weak with for example no clear linkage distinguishable in the southwestern united states drought records at centennial time scales other forcing factors namely volcanic activity appear to mask the solar signal in space and time to investigate this hypothesis we attempted to extract volcanic signals from the temperature proxies using a statistical modelling approach wavelet analysis of the volcanic contribution reveals significant periodicities near the devries frequency during the little ice age lia this remarkable and coincidental superposition of the signals makes it very difficult to separate volcanic and solar forcing during the lia nevertheless the volcano free temperature records show significant periodicities near the devries periodicity during the entire past 1500 years further pointing to solar mechanisms and emphasising the need for solar related studies in the absence of strong multi decadal volcanic forcing

mid latitude e region field aligned irregularities observed with the mu radar fine structures e region field aligned irregularities were observed on june 24 25 1989 with the mu radar at shigaraki japan 34 9 n 136 1 e geomagnetic latitude 25 0 n the 3 2 m scale irregularities were observed with the mu radar in five main beam directions each of which was nearly perpendicular to the geomagnetic field at 100 km altitude doppler spectra were obtained every 20 s with a range resolution of 600 m field perpendicular echoes appeared from 2130 to 2330 lt and from 0400 to 1100 lt times that correspond to postsunset and postsunrise period in the e region a preliminary examination of the doppler spectra indicates spectral widths of 50 120 m s 1 and the mean doppler velocities are well below the ion acoustic speed these spectral characteristics are consistent with those obtained in the equatorial and auroral electrojets and have been attributed to the gradient drift instability the echoes observed during the postsunset and postsunrise periods showed quite different morphologies in the time height distribution for this reason they are classified into two types continuous and quasi periodic the appearance of the continuous echoes was mainly continuous in time and situated between 90 and 100 km altitude during the postsunrise period the appearance of the quasi periodic echoes was intermittent with periods of 5 10 min and situated above 100 km altitude during the postsunset period the quasi periodic echoes showed phase propagation toward the radar while the averaged mean doppler velocity was away from the radar by measuring the time delays in echo regions from five directions an apparent westward motion approximately 120 m s 1 of the irregularity regions was estimated

earth surface erosion and weathering from the 10be meteoric 9be ratio abstract the isotope ratio of the meteoric cosmogenic nuclide 10 be to the mineral derived stable isotope 9 be discloses both the earth surface denudation rate and its weathering intensity we develop a set of steady state mass balance equations that describes this system from a soil column over the hillslope scale to an entire river basin the prerequisites making this new approach possible are 1 the 9 be concentration of parent rock typically 2 5 0 5 ppm in granitic and clastic sedimentary lithologies is known 2 both be isotopes equilibrate between the fluids decomposing rock and reactive solids formed during weathering and 3 a critical spatial scale is exceeded at which the fluxes of both isotopes into and out of the weathering zone are at steady state over the time scale of weathering typically 10 kyr for these cases the isotope ratios can be determined in bulk sediment or soil on leachates from the reactive adsorbed and pedogenic mineral bound phase in sediment or soil and even on the dissolved phase in river water the 10 be 9 be ratio offers substantial advantages over the single isotope system of meteoric 10 be the latter system allows to directly determine erosion rates only in the case that 10 be is fully retentive in the weathering zone and that riverine sorting has not introduced grain size dependent 10 be concentration gradients in sediments we show the feasibility of the 10 be 9 be tracer approach at the river scale for sediment and water samples in the amazon basin where independent estimates of denudation rates from in situ produced 10 be exist we furthermore calculate meaningful denudation rates from a set of published 10 be 9 be ratios measured in the dissolved load of globally distributed rivers we conclude that this isotope ratio can be used to reconstruct global paleo denudation from sedimentary records