eiscat svalbard radar observations of ionospheric plasma dynamics in relation to dayside auroral transients the first eiscat svalbard radar esr and ground optical campaign was carried out in january 1998 to cover a variety of dayside auroral activities in the 1000 1400 magnetic local time sector the current paper focuses on 1 hour of combined radar meridian scanning photometer and ground magnetometer observations near the cusp convection throat on january 23 1998 the radar was pointing north at a fixed elevation of 45 in the scan plane of the photometer several plasma dynamical features were revealed by this simplest possible convection mode of the esr such as spontaneous movement of the cusp inflow region and cusp related ionization blobs pushing through the ambient incompressible plasma multiple morning discrete arcs were found to be aligned with convection streamlines equatorward of the flow reversal while plasma in the polar cap inflow region streamed perpendicularly across the optical cusp boundary as earlier anticipated

ionospheric signatures of dayside magnetopause transients a case study using satellite and ground measurements a case study is presented of coordinated ground and space measurements featuring a set of transient auroral fragments located on the poleward side of a stable cusp cleft arc optical ground data from ny alesund svalbard and heiss island franz josef land were combined with dmsp f9 satellite measurements to examine the characteristics of these auroral features a stable red arc stretched across most of the dayside auroral zone in a region dominated by westward convection in accordance with the orientation of the imf poleward of the red arc were several westward moving auroral jets having characteristics similar to midday auroral breakup events such events may be ground signatures of transitory magnetic merging at the dayside magnetopause if so the driven convective motion of these structures should contribute to the polar cap potential within this limited data set we find that although the transitory structures have an inherent potential associated with the motion of the optical signatures the structures on the whole contribute a small fraction of the total polar cap potential

on the entry and transit of high density plasma across the polar cap 1 observations are presented from superdarn and the eiscat svalbard radar of two intense polar cap patch events on 6 february 2001 the interplanetary magnetic field imf was dominated by a large positive by component and for both events the electron density exceeded 1012 m 3 in the f region with superdarn we tracked the events all the way across the polar cap from the dayside svalbard sector to the nightside alaska sector the flow speed was highly dynamic and pulsed and both patches underwent substantial rotation in the polar cap on the nightside the leading edge had become the trailing edge it suggests that the first patch to enter the polar cap on the dayside may not always be the first patch to reach the nightside plasma might be stagnant in the polar cap or even overtaken the study also provides evidence that momentum transfer in the dayside polar cap can last significantly longer than 10 min after reconnection especially for extremely long field lines where imf by is dominating i e on old open field lines knowledge of the solar wind driver and the coupling processes is therefore extremely important for predicting the motion of a polar cap patch event across the polar cap gradients in the plasma flow associated with the rotation of the extreme density may in itself lead to a stronger growth of ionospheric irregularities these irregularities may continue to grow all the way across the polar cap the result is more efficient creation of ionospheric irregularities

the inqua dunes atlas chronologic database the inqua dunes atlas project has developed a global digital database of chronological information for periods of inland or continental sand dune accumulation and stabilization the database comprises information on the site location including coordinates dune type and stratigraphic context pertinent analytical information e g luminescence procedures and literature citations to the original data source this paper discusses the background to the project the concept and structure of the chronologic database that forms its core and gives some examples of the scope of the database and ways in which it can contribute to greater understanding of the spatial and temporal variability in dune development

large scale convection patterns observed by dmsp the authors present a comprehensive compilation of the average distribution of the electrostatic potential across the high latitude ionosphere the averages are compiled from potentials along the satellite path calculated from thermal ion drift data from instrumentation on the defense meterological satellite program dmsp flights 8 and 9 satellites data were collected from the dmsp f8 satellite during the period september 1987 to december 1990 and from the dmsp f9 satellite during the period march 1988 to december 1990 the potential distributions are separated by geomagnetic position season and orientation of the interplanetary magnetic field imf and then averages of the distributions are calculated the average potential distributions clearly show the displacement of polar cap convection contours to the dusk or dawk flanks under the influence of the imf b sub y component the cross cap potential decreases as imf b sub z changes from southward to northward the average distributions indicate that the development of more than two convection cells for northward imf is either uncommon or nonexistent for imf b sub z 0 and b sub z vert bar b sub y vert bar a distorted pattern is observed in the average potential distribution not a four cell pattern as some previous studies suggest it should be for allmore orientations of the imf the convection reversal boundary at the poleward edge of the auroral zone is observed in the average distributions to be a rotational boundary it is not a shear boundary as suggested by some previous investigations on average the harang discontinuity convection reversal in the auroral zone near midnight is observed to exist weakly or not at all when examining individual passes a strong eastward flow is present sometimes in the region of the harang discontinuity especially on the poleward boundary but not at all times as implied by the heppner maynard model 39 refs 9 figs 2 tabs less

on the symmetry of ionospheric polar cap patch exits around magnetic midnight in this paper we examine how polar cap patches which have been frozen into the antisolar flow over the polar cap are transported into the nighttime auroral oval first we present a detailed case study from 12 january 2002 with continuous observations of polar cap patches exiting into the nighttime auroral oval in the scandinavian sector satellite images of the auroral oval and all sky camera observations of 630 0 nm airglow patches are superimposed onto super dual auroral radar network convection maps these composite plots reveal that polar cap patches exit on both the dusk and on the dawn convection cells then we present statistics based on 8 years of data from the meridian scanning photometer at ny aalesund svalbard to investigate the possible interplanetary magnetic field imf by influence on the distribution of patch exits around magnetic midnight the magnetic local time distribution of patch exits is almost symmetric around magnetic midnight independent of imf by polarity synthesizing these observations with previous results we propose a three step mechanism for why patch material exits symmetrically around midnight first intake of patch material occurs on both convection cells for both imf by polarities second plasma intake by transient magnetopause reconnection stretches the newly cut polar cap patches into dawn dusk elongated forms during their transport into the polar cap and finally at exit dawn dusk elongated patches are split and diverted toward both the dawn and dusk flanks when grabbed by transient tail reconnection

the low latitude boundary layer and the boundary plasma sheet at low altitude prenoon precipitation regions and convection reversal boundaries the dayside zone of soft precipitation can be divided into four distinct types of plasma regimes each corresponding to the respective magnetospheric source region the cusp the mantle the low latitude boundary layer llbl and the dayside extension of the bps based on a detailed spectral study including comparisons with nonsimultaneous isee 1 satellite llbl data we identify regions of llbl type plasma in the dmsp data set and compare these plasma boundaries with convection reversal boundaries crbs as determined by either sondrestrom or the drift meter instrument on board the dmsp f9 spacecraft the nine cases considered are all in the prenoon local time sector we find that in eight of the nine cases the crb occurs within the llbl as expected generally near to but not coincident with the equatorward edge of the llbl type plasma in our sample set chosen for cases with latitudinally wide easily identifiable llbl signatures the average latitudinal width was 1 85 magnetic latitude the crb defined as the onset of steady antisunward convection occurred about 30 of this width beyond the equatorward onset of llbl type particles the most equatorward portion of the region with llbl type plasma usually had near zero or erratic convection and may correspond to the stagnation region reported from isee observations the potential drop observed across the low altitude llbl is roughly estimated to be typically 5 kev a summary is given on how the various high altitude sources can be identified when plasma regions are observed at low altitude in the dayside auroral oval

direct three dimensional imaging of polar ionospheric structures with the resolute bay incoherent scatter radar 1 ionospheric plasma density structures in the dayside f region of the polar cap are commonly occurring events but adequate measurements of their formation and evolution have been sparse with the advent of the advanced modular incoherent scatter radar risr n resolute bay incoherent scatter radar it is now possible for the first time to study the temporal evolution of the plasma properties in the polar cap region in three dimensions with a spatial resolution of tens of kilometers from which the plasma rest frame can be experimentally established we demonstrate the strength of the diagnostic with observations from an event of enhanced plasma density observed over resolute bay in december 2009 a colocated all sky imager showed faint 630 0 and 557 7 nm emission corresponding to the plasma enhancements and the structures could be traced back to a formation region in the open closed field line boundary this new plasma imaging technique will provide important information on the mechanisms controlling the structuring in the high latitude ionosphere

high resolution observations of the small scale flow pattern associated with a poleward moving auroral form in the cusp 1 in this paper we present high resolution observations by the eiscat svalbard radar of the localized ionospheric flow response due to one single flux transfer event and the relative location of a poleward moving auroral form in a fast scan mode the radar was tracking a 50 60 km wide channel of westward flow in the cusp region this flow channel was surrounded by flow running in the opposite direction at the poleward edge of the narrow flow channel a poleward moving auroral form was situated consistent with the auroral form being the signature of an upward birkeland current filament our observations can be interpreted in terms of the southwood 1985 1987 flux transfer model and the fte twin cell flow pattern appears to be a ripple onto the larger scale background convection

interpretations and common challenges of aeolian records from north american dune fields abstract geomorphic and chronologic data for dune fields are evaluated for three contrasting areas of north america 1 the prairie parkland and boreal ecozones of the northern great plains in canada 2 the central great plains of the usa and 3 the deserts of southwestern usa and northern mexico luminescence and radiocarbon ages for periods of dune accumulation and stability are compared with palaeoenvironment proxies to provide an assessment of the boundary conditions of dune system response to changes in sediment supply availability and mobility dune fields in the northern great plains were formed from sediment originating from glaciofluvial or glaciolacustrine sediments deposited during deglaciation 16 11 ka subsequent aeolian deposition occurred in parkland and prairie dune fields as a result of mid holocene 8 5 ka and late holocene despite spatial and temporal gaps in chronometric data as a result of sampling biases the record from north american dune fields indicates the strong influence of sediment supply on dune construction with changes in sediment availability as a result of drought episodes resulting in dune field reactivation and reworking of pre existing sediment

localized polar cap precipitation in association with nonstorm time airglow patches although airglow patches are traditionally regarded as high density plasma unrelated to local precipitation past observations were limited to disturbed conditions recent non storm time observations show patches to be associated with ionospheric flow channels and localized field aligned currents we examine whether non storm time patches are related also to polar cap precipitation using fast imager conjunctions we have identified localized precipitation that is enhanced within patches in comparison to the weak polar rain outside patches the precipitation consists of structured or diffuse soft electron fluxes while the latter resembles polar rain only with higher fluxes the former consists of discrete fluxes enhanced by 1 2 orders of magnitude from several to several hundred ev therefore patches should be regarded as part of a localized magnetosphere ionosphere coupling system along open magnetic field lines and their transpolar evolution as a reflection of mesoscale magnetotail lobe processes the precipitation is not a major contributor to patch ionization

on the importance of interplanetary magnetic field by on polar cap patch formation 1 a number of poleward moving events were observed between 1130 and 1300 ut on 11 february 2004 during periods of southward interplanetary magnetic field imf while the steerable antenna of the european incoherent scatter eiscat svalbard radar esr and the tromso vhf radar pointed nearly northward at low elevation in this interval simultaneous superdarn cutlass finland radar measurements showed poleward moving radar aurora forms pmrafs which appeared very similar to the density enhancements observed by the esr northward pointing antenna these events appeared quasiperiodically with a period of about 10 min comparing the observations from the above three radars it is inferred that there is an almost one to one correspondence between the poleward moving plasma concentration enhancements pmpces observed by the esr and the vhf radar and the pmrafs measured by the cutlass finland radar these observations are consistent with the interpretation that the polar cap patch material was generated by photoionization at subauroral latitudes and that the plasma was structured by bursts of magnetopause reconnection giving access to the polar cap there is clear evidence that plasma structuring into patches was dependent on the variability in imf by the duration of these events implies that the average evolution time of the newly opened flux tubes from the subauroral region to the polar cap was about 33 min

mapping the dayside ionosphere to the magnetosphere according to particle precipitation characteristics a long standing and vexing problem in magnetospheric physics is mapping the ionosphere to the magnetosphere to date almost all information on the topic has come from magnetic field mappings herein a complementary approach is tried regions are identified based on the plasma characteristics as observed by low altitude satellites using an automated identification scheme applied to approximately 60 000 individual satellite passes through the dayside oval probability maps are computed for observing various types of plasma precipitating into the ionosphere the synthesis of the various individual maps allows the construction of an ionospheric map into the magnetosphere based on plasma characteristics the results suggest a cusp which is about 2 5 hours in total local time extent an llbl which typically extends to about 0900 mlt and a mantle which reaches to about 0800 1600 consistent with earlier results the extension of the nightside region of discrete aurora into the dayside is far more substantial at dusk than at dawn

response of the dayside auroral and electrodynamic processes to variations in the interplanetary magnetic field the response of the dayside auroral and electrodynamic processes to variations in the interplanetary magnetic field imf is examined with multi instrument data from the viking and dmsp f7 satellites as well as ground magnetometer data the event selected which occurred on october 5 1986 was previously identified as a high latitude dayside form by murphree and elphinstone 1988 imf by was positive during most of the viking auroral uv observation whereas imf bz made a transient southward excursion followed by a sharp increase to 8 nt the results are summarized as follows 1 there were two auroral belts extending westward from the early afternoon sector the equatorward belt was persistent throughout the event and was embedded in the cps bps precipitation region whereas the poleward belt was in the open field line region and was associated with northward imf bz 2 a new auroral spot emerged in the afternoon sector just poleward of the previously active region delayed 10 min from the sudden increase in imf bz this time lag is ascribed to the travel time of the new imf orientation from the subsolar point to a solar wind magnetosphere interaction site tailward of the dayside cusp as well as to the response time of the dayside auroral acceleration process 3 the new auroral activity expanded both eastward and westward during the first few minutes and then expanded primarily westward across the noon meridian forming the poleward belt the speed of the westward extension in the second phase was comparable to the speed of the ionospheric convection 4 the dayside auroral process has a finite decay constant which is inferred to be at least 10 min 5 the response time of the midday ionospheric convection to imf variations is estimated to be a few to several minutes

the interaction of a magnetic cloud with the earth ionospheric convection in the northern and southern hemispheres for a wide range of quasi steady interplanetary magnetic field conditions this is the second of three papers which study a large interplanetary magnetic cloud and its interaction with the earth s magnetosphere here the authors study flows within the ionosphere during the passage of the magnetic cloud on jan 13 15 1988 this is the first study of ionospheric convections during prolonged periods of stable and different imf orientations which result from the stable but spatially varying field structure within the magnetic cloud data from imp 8 and dmsp f8 are analyzed for this work this observation gave information on ionospheric responses to greater than 10 hour period of northward and southward imf with a gradual change from one to the other issues studied included strengths of peak flows for north and south imf changes in cross polar cap potential with imf b sub z types and variations of convective patterns vs imf variations in size of the polar cap etc

impact of a reduced arctic sea ice cover on ocean and atmospheric properties abstractthe arctic sea ice cover declined over the last few decades and reached a record minimum in 2007 with a slight recovery thereafter inspired by this the authors investigate the response of atmospheric and oceanic properties to a 1 yr period of reduced sea ice cover two ensembles of equilibrium and transient simulations are produced with the community climate system model a sea ice change is induced through an albedo change of 1 yr the sea ice area and thickness recover in both ensembles after 3 and 5 yr respectively the sea ice anomaly leads to changes in ocean temperature and salinity to a depth of about 200 m in the arctic basin further the salinity and temperature changes in the surface layer trigger a great salinity anomaly in the north atlantic that takes roughly 8 yr to travel across the north atlantic back to high latitudes in the atmosphere the changes induced by the sea ice anomaly do not last as long as in the ocean the response in the transient and equilibrium simulations w

decay of polar cap patch 1 we report an event in which a polar cap patch was detected with an all sky imager asi at resolute bay canada 74 73 n 265 07 e aacgm latitude 82 9 on the nightside the patch stopped its antisunward motion associated with a northward turning of interplanetary magnetic field and stayed within the field of view of the asi for more than 1 h when the patch stagnated its luminosity decreased gradually which allows us to investigate how the patch plasma decayed in a quantitative manner the decay of the patch can be quantitatively explained by the loss through recombinations of o with ambient n2 and o2 molecules if we assume the altitude of the optical patch to be around 295 km the derived altitude of the patch around 295 km is much higher than the nominal value at 235 km obtained from the msis e90 and iri 2007 models indicating that climatological models such as iri are not suitable for describing the actual density profile of patches this is probably because the loss process was much faster in the lower altitude part of the patch thus the peak altitude of the patch increased as it traveled across the polar cap because of rapid recombination at the bottomside of the f region this suggests that we should employ higher emission altitude when we investigate optical patches transported deep into the nightside polar cap such information is important when we compare the optical data with other instruments such as coherent radars and gps scintillation measurements by mapping the all sky image on the geographic coordinate system with an assumption of the patch emission altitude

auroral morphology of the midday oval auroral displays in the noon sector were examined by using hundreds of defense meteorological satellite program auroral images taken over the southern polar region in austral winters in order to determine the morphology the auroral displays in the midday part of the auroral oval can be grouped into five characteristic types depending on the geomagnetic activity and the bz component of the interplanetary magnetic field an important characteristic is the clear disconnection in appearance between the noonside and the nightside discrete auroras also there is the lack of correlation between the concurrent nightside substorm activity and midday discrete auroral activity thus the occurrence of bright discrete auroras in the midday oval may be caused by the local injection of the magnetosheath plasma into the dayside boundary layer the observed discontinuity of discrete auroras between the dayside and the nightside ovals is consistent with the existence of two separated major injection regions along the auroral oval the dayside cusp and the nightside plasma sheet

a transient auroral event on the dayside on december 5 1986 high latitude magnetometer stations in greenland as well as iqaluit and the south pole showed a strong perturbation lasting for about 10 min beginning at 0930 ut in an otherwise quiet period a pair of field aligned currents separated in the east west sense and moving westward tailward at 4 5 km s is consistent with the data producing a twin vortex pattern of hall currents similar perturbations but with reduced intensity were also recorded on the afternoon side at svalbard heiss island and several locations in northern siberia the perturbation was also observed with the incoherent scatter radar at sondrestrom these data agreeing with the twin vortex pattern the perturbation was accompanied by auroral forms overhead at sondrestrom that also traveled westward meridian scanning photometer recordings at the radar site showed the cleft located about 3 degree to 5 degree poleward in latitude the cleft did not move from the far northern sky for several hours even while the disturbance was observed viking and polar bear satellites passed just before the disturbance over greenland and dmsp encountered the disturbance near baffin island a few minutes later these spacecraft observations increased our confidence in the interpretation of the data isee 1 2 andmore imp 8 recorded a magnetic disturbance in the solar wind the likely cause of this event similar observations by others have been associated with flux transfer events however since the observed event occurred on closed field lines our interpretation is quite different it is that an impulsive penetration of solar wind plasma on an interplanetary magnetic flux tube took place through the magnetopause ending up in the low latitude boundary layer some efficient mechanism is required to feed the boundary layer with the total amount observed other events reported in the literature may have a similar explanation less

empirical high latitude electric field models electric field measurements from the dynamics explorer 2 satellite have been analyzed to extend the empirical models previously developed from dawn dusk ogo 6 measurements j p heppner 1977 the analysis embraces large quantities of data from polar crossings entering and exiting the high latitudes in all magnetic local time zones paralleling the previous analysis the modeling is based on the distinctly different polar cap and dayside convective patterns that occur as a function of the sign of the y component of the interplanetary magnetic field the objective which is to represent the typical distributions of convective electric fields with a minimum number of characteristic patterns is met by deriving one pattern model bc for the northern hemisphere with a y interplanetary magnetic field imf and southern hemisphere with a y imf and two patterns models a and de for the northern hemisphere with a y imf and southern hemisphere with a y imf the most significant large scale revisions of the ogo 6 models are 1 on the dayside where the latitudinal overlap of morning and evening convection cells reverses with the sign of the imf y component 2 on the nightside where a westward flow region poleward from the harang discontinuity appears under model bc conditions and 3 magnetic local time shifts in the positions of the convection cell foci the modeling above was followed by a detailed examination of cases where the imf z component was clearly positive northward neglecting the seasonally dependent cases where irregularities obscure pattern recognition the observations range from reasonable agreement with the new bc and de models to cases where different characteristics appeared primarily at dayside high latitudes the analysis of these differences for strong bz conditions using passes through different mlt zones led to finding that the deviations from both the bc and de models could be modeled by extending the evening cell foci toward and beyond noon with a deformation that roughly resembles a rotational twist of the extended evening cell the morning cell accommodation to the model bc deformation produces a narrow tongue of eastward convection near 75 invariant latitude on the dayside the model de deformation compresses the morning cell toward the night hours such that the sunward convection in the morning cell is diverted to polar latitudes in the 0400 to 0700 mlt sector in both cases the deformations of the two cell patterns lead to sunward convection in dayside polar regions while maintaining the integrity of the nightside convection pattern thus the nightside dilemmas that plague three and four cell models designed to explain sunward convection in polar regions under bz conditions do not appear

events of enhanced convection and related dayside auroral activity in this paper we study the high latitude plasma flow variations associated with a periodic 8 min sequence of auroral forms moving along the polar cap boundary which appear to be the most regularly occuring dayside auroral phenomenon under conditions of southward directed interplanetary magnetic field satellite data on auroral particle precipitation and ionospheric plasma drifts from dmsp f10 and f11 are combined with ground based optical and ion flow measurements for january 7 1992 ionospheric flow measurements of 10 s resolution over the range of invariant latitudes from 71 to 76 were obtained by operating both the european incoherent scatter eiscat uhf and vhf radars simultaneously the optical site ny alesund svalbard and the eiscat radar field of view were located in the postnoon sector during the actual observations the west greenland magnetometers provided information about temporal variations of high latitude convection in the prenoon sector satellite observations of polar cap convection in the northern and southern hemispheres show a standard two cell pattern consistent with a prevailing negative by component of the interplanetary magnetic field the 630 0 nm auroral forms located poleward of the persistent cleft aurora and the flow reversal boundary in the 1440 1540 mlt sector were observed to coincide with magnetosheath like particle precipitation and a secondary population of higher energy ions and they propagated eastward tailward at speeds comparable with the convection velocity it is shown that these optical events were accompanied by bursts of sunward return flow at lower latitudes in both the morning and the afternoon sectors consistent with a modulation of dungey cell convection the background level of convection was low in this case kp 2 the variability of the high latitude convection may be explained as resulting from time varying reconnection at the magnetopause in that case this study indicates that time variations of the reconnection rate effectively modulates ionospheric convection