multipoint observations of a small substorm in this paper the authors present multipoint observations of a small substorm which occurred just after 0110 ut on april 25 1985 the observations were made by spacecraft ampte cce ampte irm dmsp f6 and dmsp f7 ground auroral stations eiscat magnetometer cross syowa narssarssuaq great whale river and fort churchill and mid latitude stations furstenfeldbruck toledo and argentine island these data provide them with a broad range of observations including the latitudinal extent of the polar cap visual identification of substorm aurorae and the magnetic perturbations produced directly beneath them in situ magnetic field and energetic particle observations of the disruption of the cross tail current sheet and observations concerning the spatial expansion of the current disruption region from two radially aligned spacecraft the dmsp data indicate that the event took place during a period when the polar cap was relatively contracted yet the disruption of the current sheet was observed by cce at 8 56 r sub e they have been able to infer a considerable amount of detail concerning the structure and westward expansion of the auroral features associated with the event and they show that those auroral surges were located more than 10 degree equatorward of the boundary between open andmore closed field lines moreover they present evidence that the current sheet disruption observed by cce in the neutral sheet was located on field lines which mapped to the westward traveling surge observed directly overhead of the ground station at syowa furthermore the observations strongly imply that disruption of the cross tail current began in the near earth region and that it had a component of expansion which was radially antisunward less

simultaneous observation of the poleward expansion of substorm electrojet activity and the tailward expansion of current sheet disruption in the near earth magnetotail in this paper we present observations of a substorm that occurred on june 7 1985 the data consist of energetic ion and magnetic field data from ampte cce magnetometer data from the ground stations of the eiscat magnetometer cross stare radar data and pi 1 data from sodankyla cce was in the finnish local time sector and the model field line threading cce came down near the center of the eiscat magnetometer cross furthermore cce was located near the neutral sheet and observed the disruption of the cross tail current in situ at 2209 ut sodankyla registered a pi 1 burst and the eiscat stations recorded the onset of a negative bay simultaneously cce observed the onset of current sheet disruption and ion energization the energetic ions observed during this initial burst had gyrocenters earthward of cce an intensification of activity occurred at 2212 ut and it was observed essentially simultaneously on the ground and in space it consisted of an intensification of pi 1 activity an intensification of the westward electrojet poleward of the initial breakup latitude as determined from magnetometer and radar data and magnetic turbulence and a burst of energetic ions at cce in the magnetotail significantly this second burst was composed only of ions with gyrocenters tailward of the satellite and the magnetic turbulence was considerably weaker than that observed during the initial current disruption this strongly suggests that the current disruption region had moved tailward of cce the event provides a direct observational link between the tailward expansion of active regions in the near earth magnetotail and the poleward expansion of ionospheric electrojet activity during substorms

eastward propagating undular bores over cape york peninsula abstract the existence of eastward propagating bores over cape york peninsula is shown from data obtained during the gulf lines experiment glex conducted during september and october 2002 and from numerical modeling experiments the disturbances were detected regularly at two stations observable on 24 days during the 40 day experiment the passage of a typical disturbance exhibits a sudden increase in pressure of around 1 hpa often accompanied by undulations and a change in the wind speed and direction from an easterly to a westerly flow disturbances were not observed during days of strong easterly flow a two dimensional nonhydrostatic mesoscale model is used to examine the formation of these disturbances it is shown that the west coast sea breeze is shallow and does not penetrate far inland because of the opposing low level easterly flow in contrast the east coast sea breeze is deeper and is less stable because it is modified by daytime convective mixing as it crosses the peninsula as the east

ground based observations coordinated with viking satellite measurements the instrumentation and the orbit of the viking satellite made this first swedish satellite mission ideally suited for coordinated observations with the dense network of ground based stations in northern scandinavia several arrays of complementing instruments such as magnetometers all sky cameras riometers and doppler radars monitored on a routine basis the ionosphere under the magnetospheric region passed by viking for a large number of orbits the viking passages close to scandinavia were covered by the operation of specially designed programmes at the european incoherent scatter facility eiscat first results of coordinated observations on the ground and aboard viking have shed new light on the most spectacular feature of substorm expansion the westward travelling surge the end of a substorm and the associated decay of a westward travelling surge have been analysed eiscat measurements of high spatial and temporal resolution indicate that the conductivities and electric fields associated with westward travelling surges are not represented correctly by the existing models

substorms fundamental observational features distinction from other disturbances and external triggering fundamental observational signatures of substorms and other auroral zone disturbances are summarized in this review it is shown that at least three distinct types of major geomagnetic disturbance have been identified in the auroral zones and it is suggested that care should be taken in distinguishing substorms from the other types of disturbance when reaching observational conclusions concerning substorms substorms can be uniquely identified by the formation of the current wedge and by the associated westward electrojet and region of active aurora that move poleward within the ionosphere during the expansion phase periods of enhanced convection have been observed to continue without substorms for as long as the interplanetary magnetic field imf remains stably southward they can have al signatures that look very much like intense substorms but these signatures result from strong dp 2 ionospheric currents driven by enhanced convection rather than from a nightside westward electrojet a third type of disturbance is characterized by short intervals of enhanced equatorward flow within the ionosphere and enhanced auroral emissions these enhancements move equatorward from near the polar cap boundary and they may be associated with several minute long enhancements of earthward flow within the plasma sheet studies that have examined the triggering of substorm expansions by imf changes are also reviewed when considered together and substorms are distinguished from the other disturbances these studies imply that most and perhaps all expansions are triggered by imf changes these changes include both northward turnings and reductions in the magnitude of the y component if most substorms are indeed externally triggered as suggested here then substorms must generally not be the result of an internal magnetospheric instability

evaluation of low latitude pi2 pulsations as indicators of substorm onset using polar ultraviolet imagery impulsive pi2 pulsations have long been recognized as one of the key signatures of magnetic activity during substorm periods due to their wide observable range both in latitudes and longitudes it is well documented that there is usually more than one pi2 wave burst associated with a substorm and only one of them corresponds to the onset of the substorm this observational fact poses obstacles to determining substorm onsets with pi2 signals although the pi2 have become one of the most popular indicators for substorm onsets the reliability of using the pi2 in this fashion has not been seriously investigated in this paper we address this question with a statistical approach by using 650 auroral substorm onsets identified with polar ultraviolet images for a time interval from april 1996 to may 1997 a comparison of the low latitude pi2 pulsation onsets from kakioka l 1 07 with the auroral breakups indicates that identifying substorm onset with the pi2 alone is often ambiguous of a total of 119 isolated defined as 10 min of quiet time preceding the onset pi2 bursts seen within 10 min from a magnetic positive bay there were 65 events 55 taking place within 3 min from breakups and 34 events 29 indicating no sign of an auroral breakup within 10 min of the pi2 burst this result suggests that pi2 may not be as a good indicator of the substorm onset as it was thought to be interestingly it is always possible to associate pi2 pulsations with some forms of auroral intensification when compared to auroral breakups pi2 onsets are subject to a small delay of 1 3 min with a peak around l min delays of pi2 onsets are revealed to be a function of location relative to auroral breakup this dependence is found to be consistent with the time of flight for a fast mode wave in a plasmapause cavity mode model propagating in the magnetosphere

satellite measurements through the center of a substorm surge measurements have been made of electric and magnetic fields plasma drifts and electron precipitation within a surge at the westward leading edge of the auroral bulge at the peak of the substorm expansion phase the trajectory of the de 2 satellite over the auroral emissions is determined from nearly simultaneous observations with the imager on the de 1 satellite at a higher altitude the electric field and plasma drift measurements have enabled us to deduce the basic configuration of the ionospheric electric potential or plasma convection around the surge the electric potential shows that the bulge is associated with a protrusion of the dawn convection cell into the dusk cell poleward of the harang discontinuity this protrusion contains a westward electric field that strongly enhances the westward electrojet current by the creation of a cowling channel this westward electric field and the associated cowling current appear to terminate within the surge which contains an intense upward field aligned current the magnetic field measurements show that the region containing this field aligned current is shaped more like a cylinder rather than a long sheet the total current is found to exceed one half million amperes

identification of substorm expansive phase onsets 1 over the years many different particle and electromagnetic signatures have been invoked to identify the onset of what is called a substorm in this paper i shall first clarify what is generally meant by the term substorm onset and i shall show that some disturbances identified as substorm onsets should be treated with care i shall review the substorm in terms of its two recognized characteristic components directly driven and storage release i shall then discuss the importance of pseudobreakups in deciding what constitutes a legitimate substorm onset and in doing so will illustrate the subjective nature of present substorm onset identification techniques i shall stress that substorm like disturbances can take place both near the equatorward edge of the midnight sector oval mapping to the near earth magnetotail inside 12 re and near the poleward edge of the evening sector oval mapping to regions much farther downtail i shall present case studies that illustrate that some poleward edge disturbances have magnetic and auroral signatures that may be incorrectly interpreted as legitimate expansive phase onsets on the basis of this study i suggest that what may appear to be a lengthy series of closely spaced expansive phases may in fact be a single expansive phase followed by an arbitrarily long period of poleward border activity

travelling waves and bores in the lower atmosphere the morning glory and related phenomena abstract observations of solitary wave and travelling bore like disturbances in the lower atmosphere are reviewed together with relevant theoretical laboratory and numerical studies concerning the structure propagation and genesis of such disturbances primary emphasis is given to a discussion of the morning glory phenomenon in northern australia the example par excellence of these types of disturbance and the best documented observationally to date observations of related phenomena elsewhere are reviewed briefly while such occurrences appear to be less frequent in any single location than in the southern gulf of carpentaria region of northern australia reported occurrences are widespread and there is mounting evidence that such disturbances are more common than is generally supposed the evidence suggests that whenever a suitable wave guide exists for the propagation of disturbances the latter can be generated as the natural response of quite general forcing mechanisms examples being the collision of two sea breezes from opposite directions on a peninsula the interaction between a thunderstorm outflow and a sea breeze front or simply the transformation of a thunderstorm or squall line outflow as it moves into a low level stable layer because of the large vertical displacements they produce the larger amplitude disturbances typically with surface pressure jumps of 1 mb or more must be considered as potential triggers for deep convection if the atmosphere is sufficiently conditionally unstable and the large low altitude wind shears associated with them present a serious hazard to low flying aircraft

electrodynamic parameters in the nighttime sector during auroral substorms the characteristics of the large scale electrodynamic parameters field aligned currents facs electric fields and electron precipitation which are associated with auroral substorm events in the nighttime sector have been obtained through a unique analysis which places the ionospheric measurements of these parameters into the context of a generic substorm determined from global auroral images a generic bulge type auroral emission region has been deduced from auroral images taken by the dynamics explorer 1 de 1 satellite during a number of isolated substorms and the form has been divided into six sectors based on the peculiar emission characteristics in each sector west of bulge surge horn surge middle surge eastern bulge and east of bulge by comparing the location of passes of the dynamics explorer 2 de 2 satellite to the simultaneously obtained auroral images each pass is placed onto the generic aurora the organization of de 2 data in this way has systematically clarified peculiar characteristics in the electrodynamic parameters an upward net current mainly appears in the surge with little net current in the surge horn and the west of bulge the downward net current is distributed over wide longitudinal regions from the eastern bulge to the east of bulge near the poleward boundary of the expanding auroral bulge a pair of oppositely directed fac sheets is observed with the downward fac on the poleward side this downward fac and most of the upward fac in the surge and the middle surge are associated with narrow intense antisunward convection corresponding to an equatorward directed spikelike electric field this pair of currents decreases in amplitude and latitudinal width toward dusk in the surge and the west of bulge and the region 1 and 2 facs become embedded in the sunward convection region the upward fac region associated with the spikelike field on the poleward edge of the bulge coincides well with intense electron precipitation and aurora appearing in this western and poleward portion of the bulge the convection reversal is sharp in the west of bulge and surge horn sectors and near the high latitude boundary of the upward region 1 fac in the surge the convection reversal is near the low latitude boundary of the upward region 1 with a near stagnation region often extending over a large interval of latitude in the eastern bulge and east of bulge sectors the region 1 and 2 facs are located in the sunward convection region while a spikelike electric field occasionally appears poleward of the aurora but usually not associated with a pair of fac sheets in the eastern bulge magnetic field data show complicated fac distributions which correspond to current segments and filamentary currents

sondrestrom radar initial results operation of an incoherent scatter radar at sondre stromfjord greenland began in early february 1983 marking the beginning of a new effort in ground based ionospheric research in the vicinity of the polar cusp and polar cap the sondrestrom radar is located north of the arctic circle on the west coast of greenland near the sondrestrom air base at an invariant latitude of 75 the effects of the polar cusp may frequently be observed at local noon the radar measured signature in the f region is an increase of more than a factor of two in electron density additionally the daytime variations in the f1 region electron density are dramatic in contrast to auroral zone measurements enhanced electron density at 150 km altitude has been observed and a marked absence of detectable e region ionization at night has also been noticed

currents in auroral substorms 1 we present a model of the three dimensional current system in the nighttime sector during the expansion phase through early recovery phase for bulge type aurora substorms the height integrated horizontal ionospheric currents are calculated from models of the height integrated conductivity and convection electric field previously published gjerloev and hoffman 2000a 2000b 2001 that were based on a set of data from the dynamics explorer 2 satellite while the field aligned currents are deduced from the divergence of the horizontal currents these model derived field aligned currents are then compared with the field aligned currents determined from magnetometer data from the same data set used to develop the conductance and electric field models the comparison shows good agreement thereby serving as an independent verification of the entire self consistent substorm model we find that the feeding as well as the drainage of the substorm current wedge component of the westward electrojet is principally due to an imbalance of the downward region 0 and upward region 1 current sheets under which the electrojet is flowing we do not find evidence of a simple downward current postmidnight and upward current premidnight the eastward electrojet which almost entirely originates on the dayside is partly drained by a poleward current flowing across the harang region into the westward electrojet at 19 21 magnetic local time mlt and partly by net upward field aligned currents located just prior to midnight

the development of the substorm expansive phase the eye of the substorm the explosive onset and development of a clearly defined auroral substorm has been analysed using data from the ultraviolet imager aboard the viking satellite these data permit the evolution of the substorm to be traced with a time resolution as high as 40 seconds the envelope of the disturbed region the eye expands both poleward and azimuthally to the east and west reaching an azimuthal extent of almost six hours of magnetic local time after about 15 minutes the poleward expansion involves irregular poleward motion accompanying intensifications within the eye with the maximum poleward displacement being at the meridian of the center of the eye within the eye discrete regions of enhanced luminosity develop with a tendency for each newly disturbed region to be to the west of the previous ones it is however observed that a newly excited region can be to the east of the pre existing activated region each new intensification is accompanied by a brief further poleward expansion of the high latitude edge of the eye each region of enhanced luminosity within the eye remains relatively stationary and fluctuates in intensity over its lifetime we identify these regions of enhanced luminosity with westward traveling surges as defined from ground observations in the earlier literature our uv imager data demonstrate that these surges do not necessarily propagate although the overall envelope of the substorm disturbed region expands both eastward and westward during the lifetime of the event

westward traveling surges sliding along boundary arcs and distinction from onset arc brightening 1 after onset auroral brightening rapidly spreads azimuthally along the onset arc typically but not always extending substantially farther westward than eastward expansion phase auroras also expand poleward and can contact an arc along the auroral poleward boundary for such events we find that poleward expansion of the region of active aurora accelerates after contact forming a bulge region that protrudes into the preexisting polar cap and expands westward as the westward traveling surge this westward motion is slower than and initiates later than the azimuthal spreading of the onset arc brightening the poleward boundary arc remains connected to the surge as the surge slides along the equatorward moving edge of the boundary arc and this connection appears to set off the westward traveling poleward protruding activity of the surge via localized polar cap flow adjacent to the boundary arc ground magnetic signatures show a relatively weak h component depression moving westward with the onset arc brightening and a delayed substantially larger depression moving with the westward propagating surge that must be associated with a substantially larger westward ionospheric current the clear distinction between onset arc brightening and the westward traveling surge seen in auroral and magnetometer current signatures implies that their underlying processes are very different evidence suggests that flow channels adjacent to the boundary arc possibly feed surge development these results are consistent with current wedge formation being more associated with post onset activity than with onset and with flow channels from the polar cap being important for surge bulge development

analysis of substorm expansion and surge development we have used simultaneous magnetogram radar and viking imager data from evening local time to study several substorm expansion phase onsets and an expansion phase auroral surge that formed near the radar field of view at the onsets auroral brightenings developed within the region of the electric field gradient of the harang discontinuity and if not already present a westward electrojet began poleward of the eastward electrojet immediately following onsets the poleward boundary of the westward electrojet moved poleward along with the poleward boundary of the aurora however no consistent motion of the harang discontinuity was found in the ionosphere the auroral surge formed along the poleward boundary of the westward electrojet and of the aurora we argue that the distortion of the poleward boundary of the aurora associated with the surge was a manifestation of a distortion of the separatrix between open and closed magnetic field lines the distortion being caused by the field aligned currents within the head of the surge we suggest that rapid surge development may result from a tapping of the westward electrojet current at the surge head we also suggest that the separatrix distortion could lead to the escape of trapped plasma sheet particles along open field lines in the tail

electrodynamics of the westward traveling surge it is shown that the global convection pattern the ionospheric current and the field aligned current associated with the westward traveling surge in the asymptotic state can be modeled quantitatively as consequences of a blockage of the hall current from closure in the magnetosphere via field aligned currents the conductivity is allowed to increase self consistently with increasing upward field aligned current in the model this inclusion of the self consistent enhanced ionospheric conductivity due to discrete auroral precipitations is found to generate a localized intense westward electrojet on the poleward side of the harang discontinuity the westward electrojet is also found to rotate counterclockwise merging into the eastward electrojet around the leading edge of the surge thus the major features of the westward traveling surge can be reproduced reasonably well in our model

equatorward and poleward expansion of the auroras during auroral substorms using all sky tv auroral data with high spatial and temporal resolution the formation of the auroral bulge is investigated we show how the discrete auroral structures within the poleward expanding bulge develop systematically toward the west the east and also equatorward from a localized breakup region auroral structure at the western end of the bulge a surge develops with clockwise rotation as viewed along the magnetic field direction at the eastern part of the bulge thin auroral features propagate eastward from the breakup region around the central meridian of the bulge auroral features expand equatorward and become north south aligned the n s aurora the n s aurora and the eastward propagating aurora develop into diffuse and pulsating aurora after the expansion we suggest that these discrete auroral structures in the bulge develop along the plasma streamlines in a localized distorted two cell equipotential distribution the negative potential peak is concentrated at the western part of the bulge and the positive potential region is spread poleward of the eastward propagating aurora equatorward expansion of auroral structures would be attributed in this scenario to the subsequent earthward transport of plasma from the onset region energetic particles would also be injected at the n s auroral region as well as to the east of the region and would trigger the pulsating auroral activity poleward expansion on the other hand would be produced by the tailward motion of the onset region in accordance with the tailward moving current disruption region

generation of low level mesoscale convergence lines over northeastern australia thermally forced atmospheric circulations over the gulf of carpentaria region of northeastern australia are investigated using a mesoscale numerical model the region is renown for the common occurrence of long westward moving convective and wave cloud lines including the celebrated morning glory phenomenon in the model it is found that for uniform flows over the region ranging from northeasterly to southeasterly westward moving low level convergence lines develop over the gulf during the night and early morning the authors suggest that similar convergence lines in the atmosphere are responsible for the initiation and maintenance of the observed cloud lines for northeasterly and easterly flow the convergence lines show little day to day variation despite the relatively long inertial period in the region which is nearly two days the calculations which extend an earlier study by the same authors lead to a new hypothesis to account for the observed longevity of morning glory bore waves they provide also an explanation for the marked diurnal oscillation in the lowlevel easterly flow observed at weipa during a field experiment to investigate the so called north australian cloud line

southerly nocturnal bores over northeastern australia analyses of 1 min data from automatic weather stations awss in the gulf of carpentaria region are used to study southerly nocturnal bores over northeastern australia the data cover the time period 1 august to 31 december in the three years 2012 2014 a total of 12 days on which a bore passed over the region of interest were found ten of the disturbances occurred between august and mid october in the presence of synoptic scale ridging across the continent behind a frontal trough the other two occurred in early november in the presence of localized ridging behind an inland trough separate from a frontal trough six of the bores were followed some hours later by a clear air mass change four of the 12 cases are examined in detail wherein interpretations of the aws data are aided by analysis fields from the european centre for medium range weather forecasts ecmwf the results indicate that the longevity of the bore is related to the time of day that the cold front interacts with the stable maritime layer to the north of it the ecmwf analyses are able to capture the frontal troughs as well as the timing of their passage through the aws network in the analyses the troughs are seen as narrow strips of elevated cyclonic vorticity at 950 mb vertical cross sections intersecting the troughs showed structural characteristics of a shallow cold front but the horizontal resolution of the analyses is inadequate to capture the generation of bores ahead of the fronts

the behavior of the electric field within the substorm current wedge we use the goose bay hf radar to investigate the behavior of the electric field within the substorm current wedge for a small substorm 200 nt which occurred on february 15 1992 mid and high latitude magnetometer data helped to locate the radar backscatter with respect to the longitudes and latitudes of the substorm currents as well as describing the time development of the substorm itself velocities in the portion of the field of view of the goose bay hf radar closest to the frederikshab magnetometer in greenland were compared directly with the ionospheric currents inferred from the magnetometer during the early growth phase the plasma flow and current gradually increased in response to the dp2 electric field and are related by an estimated effective height integrated conductivity 1 s the plasma flow and current continued to increase in the same proportion i e was still 1 s as the electrojet intensified in stages during the late growth early expansion phase in this interval there was probably a pseudo breakup which established a longitudinally and latitudinally narrow substorm current wedge the increased plasma flow and current measured at frederikshab are attributed to the superposition of the pseudo breakup current wedge electric field on the preexisting dp2 electric field evidently the enhanced ionospheric conductivity strip usually associated with the current wedge is initially located equatorward of frederikshab since its effect is not apparent at that location during the expansion phase proper a clearly resolved current wedge expanded so that the radar backscatter lay within it the expansion led to an increased current over frederikshab but a slightly suppressed plasma flow related by an increased 4 s the effect of the precipitation induced conductivity strip now apparent it is suggested that near earth current disruption may play a significant role in the onset of this particular substorm which occurred during a nonstorm time interval

modes of orogen parallel stretching and extensional exhumation in response to microplate indentation and roll back subduction tauern window eastern alps the tauern window exposes a paleogene nappe stack consisting of highly metamorphosed oceanic alpine tethys and continental distal european margin thrust sheets in the eastern part of this window this nappe stack eastern tauern subdome etd is bounded by a neogene system of shear the katschberg shear zone system kszs that accommodated orogen parallel stretching orogen normal shortening and exhumation with respect to the structurally overlying austroalpine units adriatic margin the kszs comprises a 5 km thick belt of retrograde mylonite the central segment of which is a southeast dipping low angle extensional shear zone with a brittle overprint katschberg normal fault knf at the northern and southern ends of this central segment the kszs loses its brittle overprint and swings around both corners of the etd to become subvertical dextral and sinistral strike slip faults the latter represent stretching faults whose displacements decrease westward to near zero the kinematic continuity of top east to top southeast ductile shearing along the central low angle extensional part of the kszs with strike slip shearing along its steep ends combined with maximum tectonic omission of nappes of the etd in the footwall of the knf indicates that north south shortening orogen parallel stretching and normal faulting were coeval stratigraphic and radiometric ages constrain exhumation of the folded nappe complex in the footwall of the kszs to have begun at 23 21 ma leading to rapid cooling between 21 and 16 ma this exhumation involved a combination of tectonic unroofing by extensional shearing upright folding and erosional denudation the contribution of tectonic unroofing is greatest along the central segment of the kszs and decreases westward to the central part of the tauern window the kszs formed in response to the indentation of wedge shaped blocks of semi rigid austroalpine basement located in front of the south alpine indenter that was part of the adriatic microplate northward motion of this indenter along the sinistral giudicarie belt offsets the periadriatic fault and triggered rapid exhumation of orogenic crust within the entire tauern window exhumation involved strike slip and normal faulting that accommodated about 100 km of orogen parallel extension and was contemporaneous with about 30 km of orogen perpendicular north south shortening of the etd extension of the pannonian basin related to roll back subduction in the carpathians began at 20 ma but did not affect the eastern alps before about 17 ma the effect of this extension was to reduce the lateral resistance to eastward crustal flow away from the zone of greatest thickening in the tauern window area therefore we propose that roll back subduction temporarily enhanced rather than triggered exhumation and orogen parallel motion in the eastern alps lateral extrusion and orogen parallel extension in the eastern alps have continued from 12 to 10 ma to the present and are driven by northward push of adria

wavelet based ulf wave diagnosis of substorm expansion phase onset 1 using a discrete wavelet transform with a meyer wavelet basis we present a new quantitative algorithm for determining the onset time of pi1 and pi2 ulf waves in the nightside ionosphere with 20 to 40 s resolution at substorm expansion phase onset we validate the algorithm by comparing both the ulf wave onset time and location to the optical onset determined by the imager for magnetopause to aurora global exploration image far ultraviolet imager fuv instrument in each of the six events analyzed five substorm onsets and one pseudobreakup the ulf onset is observed prior to the global optical onset observed by image at a station closely conjugate to the optical onset the observed ulf onset times expand both latitudinally and longitudinally away from an epicenter of ulf wave power in the ionosphere we further discuss the utility of the algorithm for diagnosing pseudobreakups and the relationship of the ulf onset epicenter to the meridians of elements of the substorm current wedge the importance of the technique for establishing the causal sequence of events at substorm onset especially in support of the multisatellite time history of events and macroscale interactions during substorms themis mission is also described

a comparison of magnetic signatures and dmsp auroral images at substorm onset three case studies the authors explore the relationship between mid latitude and synchronous orbit magnetic signatures and the location of the auroral surge at the onset of three isolated magnetospheric substorms mid latitude data come from the air force geophysics laboratory magnetometer network synchronous orbit data form the satellites goes 2 and 3 and auroral data from defense meteorological satellite program auroral images and auroral magnetograms they find that the surge forms with its western edge approximately 1 hour west of the longitude where the major axis of the mid latitude pi 2 polarization ellipse is along magnetic north and where the d component perturbation of the magnetic bay is near zero these observations are in qualitative agreement with a current wedge consisting of a localized upward current in the west and a longitudinally distributed current in the east at synchronous orbit the longitude of the surge head appears to separate a region to the west where the magnetic field becomes more taillike from one to the east where the magnetic field becomes more dipolar

separation of cowling channel and local closure currents in the vicinity of a substorm breakup spiral 1 the substorm breakup spiral demarcates the westernmost terminator of the substorm current wedge a long standing debate has been devoted to the question of to what extent the strong upward field aligned currents fac in that spiral are either closed by downward fac through pedersen currents flowing radially to the center of the spiral local closure or by currents that flow westward though a cowling channel which extends in the region eastward of the spiral cowling closure in particular studies using ground based and space based instrumentation came to systematically different results in order to address this question we reanalyze a pseudobreakup spiral event on 3 february 1999 2204 ut that has been observed with the miracle network of ground based instruments in fennoscandia and for which spatial results of electric fields conductances and currents have been calculated by amm et al 2001 we apply a new technique that allows under certain geometrical assumptions the current systems to separate in the vicinity of the breakup spiral into their local closure and cowling closure parts the result shows that for the event analyzed 68 of the upward fac in the spiral is closed via the local closure current system and the remaining 32 via the cowling closure current system therefore the local closure mechanism is the dominating provider of the upward fac in the breakup spiral overall however a localized area at the western flank of the spiral where conductance gradients are largest exists in which the cowling closure dominates and feeds more than 80 of the upward fac in that area further studies are required in order to examine the generality of the results obtained for our specific event

magnetic dipolarization with substorm expansion onset 1 we compare the timing and spatial extent of dipolarization with auroral breakup by using magnetic field data 1 min time resolution from goes 8 and goes 9 and global auroral images 37 s frame rate from the polar ultraviolet imager we survey the entire year of 1997 data and obtain 32 unambiguous dipolarization events that had ionospheric footprints within 2 hours in magnetic local time mlt from their associated auroral breakups it is found that the auroral breakup preceded the arrival of dipolarization at goes by an average of 1 7 2 7 min 1 0 2 1 min for events 1 hour from the auroral breakup the delay of geosynchronous dipolarization represents a propagation time as the substorms rarely initiated at the goes location propagation velocities derived from the propagation time are 60 km s 1 eastward 75 km s 1 westward and 270 km s 1 earthward at geosynchronous orbit we also show for the first time that auroral bulge and dipolarization region closely map the bulge is the region of currents out of the ionosphere the eastern edge of the dipolarization region where field aligned currents are flowing into the ionosphere is based on the t89 magnetic field model located at 0 5 hour in mlt eastward of the eastern edge of the auroral bulge within the initiation site meridian the dipolarization onset was observed 1 min prior to the auroral breakup at the goes altitude this time is associated with alfven transit time and therefore depends on the radial location of the onset the azimuthal scale of the initiation site is found to be 0 5 hour in mlt in the ionosphere or less than 1 earth s radius at 6 6 re these results support current diversion into the ionosphere as a critical part of substorms finally a simple timing analysis of specific substorm onset time features suggests that near earth reconnection cannot occur before current disruption and therefore cannot be the cause of substorm

substorm changes of the electrodynamic quantities in the polar ionosphere cdaw 9 on the basis of ground magnetometer data from 75 northern hemisphere stations and the ionospheric conductivity distribution estimated from viking satellite observations of auroral images various electrodynamic quantities in the polar ionosphere are calculated for the april 1 1986 coordinated data analysis workshop cdaw 9 substorm since the scandinavia and russia chains of magnetometers were located in the premidnight midnight sector during this interval and the estimated conductivity distribution is instantaneous our data set provides us with a unique opportunity to examine some long standing problems associated with the substorm expansion onset several important findings of this study are summarized as follows 1 before the expansion onset of the substorm intensifications of ionospheric currents or the cross polar cap potential are very weak in this particular example both quantities begin to increase notably only with the initiation of the substorm expansion onset 2 the intensified westward electrojet flows along the poleward half of the enhanced ionospheric conductivity belt in the midnight sector during the expansion phase while its equatorward half is occupied by a weak eastward electrojet 3 the joule heating rate and the energy input rate of auroral particles are quite comparable preceding the expansion onset during the expansion phase of the substorm however joule heating shows a marked intensification but the latter increases only moderately indicating that the joule dissipation is more effective than auroral particle energy input during substorm times 4 the hall currents are not completely divergence free the corresponding field aligned currents show highly localized structures during the maximum epoch of the substorm with the upward current being located in the region of the steepest conductivity gradient on the poleward side of the westward electrojet in the midnight sector this is indirect evidence that the so called imperfect cowling channel is effective behind the westward traveling surge

north australian cloud lines abstract a satellite classification and climatology of propagating mesoscale cloud fines in northern australia is presented these cloud fines range from long narrow lines of shallow convection to extensive deep convective squall lines with mesoscale stratiform rain areas these lines are the predominant weather feature during periods of easterly flow over the australian tropics

low level convergence lines over northeastern australia part i the north australian cloud line observations of dry season north australian cloud lines nacls that form in the gulf of carpentaria region of northern australia and the sea breeze circulations that initiate them are described the observations were made during the 2002 gulf lines experiment glex and include measurements made by an instrumented research aircraft the observations are compared with numerical simulations made from a two dimensional cloud scale model particular emphasis is placed on the interaction between the east coast and west coast sea breezes near the west coast of cape york peninsula the sea breezes are highly asymmetric due to the low level easterly synoptic flow over the peninsula the west coast sea breeze is well defined with a sharp leading edge since the opposing flow limits its inland penetration keeping it close to its source of cold air in contrast the east coast sea breeze is poorly defined since it is aided by the easterly flow and becomes highly modified by daytime convective mixing as it crosses over the peninsula both the observations and the numerical model show that in the early morning hours the mature nacl forms at the leading edge of a gravity current the numerical model simulations show that this gravity current arises as a westward moving land breeze from cape york peninsula convergence at the leading edge of this land breeze is accompanied by ascent which when strong enough produces cloud observations show that the decay of the nacl is associated with a decline in the low level convergence and a weakening of the ascent

nighttime thermospheric winds over sondre stromfjord greenland observations of nighttime thermospheric neutral winds made at sondre stromfjord greenland with optical and radar instrumentation showed an occasional abatement in the equatorward meridional wind at a magnetic local time corresponding to the nighttime division between the evening and morning convection cells this abatement appeared primarily in the poleward observations in contrast however the characteristic midnight surge was usually seen in the equatorward set of observations the apparent acceleration of about 250 m s or greater within 4 6 latitude we attribute in part to a merging of neutral jet streams generated by polar cap ion drag adjacent to the auroral zone boundary and in part to the higher electron densities and plasma convection speeds adjacent to the auroral zone comparison of these results with those from ncar tgcm computations that assumed an analytical plasma convection model showed reasonable agreement except for the abatement feature

characteristics of eastward drifting omega bands in the morning sector of the auroral oval the stare radars and the scandinavian networks of magnetometers all sky cameras and riometers recorded during the night of october 21 22 1979 the occurrence of a fairly regular sequence of auroral omega bands and associated magnetic and electric field variations the combined two dimensional data are used to derive a realistic model for the three dimensional current flow associated with the auroral forms in the model calculations the observed structure in the particle precipitation is accounted for by an inhomogeneous ionospheric conductivity distribution the main resulting feature of the model current system is a sequence of east west orientated pairs of upward and downward directed field aligned currents associated with the bright and dark areas of the visual aurora respectively the major source of magnetic disturbances on the ground is a meandering ionospheric hall current composed of a westward background electrojet and circular hall current vortices around the locations of the localized field aligned currents the total magnetic disturbance observed on the ground during different events appears however to be strongly dependent on the hall to pedersen conductivity ratio and the degree of inhomogeneity in the conductivity distribution the three dimensional current system associated with the auroral omega bands drifts eastward with a velocity comparable to an e b drift within the general southward directed electric background field however complete agreement was not found at all times

relationship between birkeland current regions particle precipitation and electric fields data from eight dmsp f7 satellite passes coincident with sondrestrom radar observations have been examined to determine how the large scale dayside birkeland currents are related to the particle precipitation regions and to the convection pattern the classification schemes recently developed from dmsp particle data were adopted the observations were limited to the prenoon local time hours and led to the following conclusions 1 the local time of the mantle currents which were traditionally called cusp currents is not limited to the longitude of the cusp proper but covers a larger local time extent 2 the mantle currents flow entirely on open field lines where open field lines is defined as a region where the ion precipitation and electron precipitation have the characteristics of plasma mantle cusp or polar rain this confirms and extends to all local times similar results obtained from other observations 3 about half of region 1 currents flow on open field lines this is consistent with the assumption that the region 1 currents are generated by the solar wind dynamo and flow within the surface that separates open and closed field lines 4 more than 80 of the birkeland current boundaries do not correspond to particle precipitation boundaries region 2 currents extend beyond the plasma sheet poleward boundary region 1 currents flow in part on open field lines mantle currents and mantle particles are not coincident 5 on most passes when a triple current sheet is observed region 2 region 1 and mantle currents the convection reversal is located on closed field lines when only two current sheets are observed either region 2 region 1 or region 1 mantle currents the convection reversal is on open field lines 6 the data appear to be more consistent with a topology such that mantle currents are an extension of region 1 currents rather than a separate system located poleward of the region 1 current system

the convection electric field in auroral substorms dynamics explorer 2 de 2 electric field and ion drift data are used in a statistical study of the ionospheric convection electric field in bulge type auroral substorms thirty one individual de 2 substorm crossings were carefully selected and organized by the use of global auroral images obtained by de 1 the selected passes which occurred during substorm expansion phase maximum or early recovery phase cover the entire nighttime substorm the organization of the data used the method developed by fujii et al 1994 which divided the data into six local time sectors covering the nighttime substorm region following the procedures employed in the paper by gjerloev and hoffman 2000b the latitudinal width and location of each auroral oval crossing was then adjusted to fit the sector average in addition to the detailed study of the characteristics of the field within each sector this database enabled us to compile a model of the ionospheric convection electric field the characteristics of the premidnight convection reversal show a pronounced local time dependency far west of the surge it is a fairly well defined point reversal or convection shear approaching the surge and within the surge it is a region of weak electric fields increasing in width toward midnight that separates regions of equatorward and poleward electric fields therefore we adopt the term harang region rather than the harang discontinuity for the premidnight convection reversal a relatively narrow convection channel is coincident with the highest conductances located just poleward of the harang region this channel drives the substorm current wedge component of the westward electrojet in the surge and middle surge sectors it is present in all premidnight passes and consequently is an integral part of the three dimensional substorm current wedge system

prograde retrograde p t t deformation path of austroalpine micaschists during variscan continental collision eastern alps a complete prograde p t path defined by 10 calculated p t fields in succession is recognized from metapelites by using geothermobarometry on garnet bearing assemblages with microstructural control overstacking of several tectonic units during an early variscan continental collision explains the complex prograde p t history isostatic uplift and deformation controlled the retrograde p t path deformation with changing character acted continuously during all stages of the evolution of the austroalpine basement complex after the intrusion of caledonian granitoids metapelites and magmatic rocks suffered a shearing deformation d1 d2 which produced sheath folds as well as the main foliation s2 spessartine rich first generation garnets situated in microlithons enclosed by s2 record the onset of shearing under increasing high pressure low temperature conditions 7 kbar 380 c geothermobarometry on second generation garnets which have been rotated during growth indicates isothermal decompression from 9 kbar to 5 kbar 500 c and subsequent recompression heating during continuing shearing this is explained by overthrusting of a tectonic unit unit 2 from ne to sw upon the micaschist unit unit 1 followed by isostatic uplift and further overstocking of a third unit unit 3 the resulting pmax of 12 kbar at 650 c and further increasing temperatures up to 680 c accompanied by decompression have been calculated using a third generation of garnets these high pressure high temperature conditions may explain the occurrence of eclogitic metabasites in adjacent regions staurolite and kyanite first appeared under decreasing pressures at the last stage of prograde p t evolution shortening deformation d3 and simultaneous growth of typical amphibolite facies minerals staurolite 2 kyanite 2 sillimanite andalusite occurred during the retrograde path a final step of variscan evolution was marked by an oppositely directed shearing d4 at t 300 c and p 3 kbar possibly indicating backthrusting or extension apart from acid intrusions no signs of a previous caledonian thermotectonic history were found in the area to the south of the defereggen antholz vals line

scientific results from the viking ultraviolet imager an introduction the ultraviolet imager on the viking spacecraft provides global images of aurora in both night and day hemispheres at rates of up to three per minute first results summarized in this and a set of eight companion papers reveal new aspects of the patterns and dynamics of the aurora including eastward as well as westward expanding substorm intensifications but very little evidence of bulk westward motion of auroral surges rapid poleward and equatorward expansions during some substorms resulting in the formation of an intense eye shaped bulge containing diffuse aurora and north south aligned arc segments substorm like intensifications at the point where transpolar arcs join the nightside oval rapid small scale auroral brightenings or hot spots over a wide range of local times and very rapid changes in auroral forms in the noon sector

joint two dimensional observations of ground magnetic and ionospheric electric fields associated with auroral zone currents 32 auroral zone currents during the passage of a westward travelling surge

comparison of height integrated current densities derived from ground based magnetometer and rocket borne observations during the porcupine f3 and f4 flights on march 19 1979 the porcupine f3 rocket was launched from esrange sweden during a period of low magnetospheric activity while the porcupine f4 rocket launched on march 31 1979 flew during a rather disturbed interval besides other experiments the rockets took measurements of ionospheric electric fields and energetic particle spectra the electron spectra measured by the rocket were used to calculate height integrated ionospheric conductivities by using rees method together with the electric field measurements height integrated current densities could be calculated from the rocket measurements during both flights the magnetic perturbations recorded on the ground by the scandinavian magnetometer array indicated a westward electrojet since during both flights the electric field was nearly southward directed and parallel to the ground magnetic disturbance vectors the westward electrojet could be attributed to a nearly pure hall current in both cases from the magnetic data height integrated ionospheric current densities have been computed at the magnetic footprints of the rockets in the ionosphere by means of field separation and upward continuation a comparison of the current densities derived from ground based magnetometer and rocket borne observations shows a very good agreement in the quiet period during the porcupine f3 flight while there are differences during stronger magnetospheric activity porcupine f4 flight due to the different spatial and temporal resolution of rocket and ground observations

comparison of uv optical signatures with the substorm current wedge as predicted by an inversion algorithm optical images of the auroral bulge as seen by the viking uv imager were compared in several cases with the substorm current wedge scw upward and downward field aligned currents fac whose positions were determined using the inversion algorithm based on the substorm related magnetic variations observed at midlatitudes with reasonable accuracy better than 0 5 hours mlt the estimated longitudes of the upward fac generally pointed to the surge or to the brightest luminousity region in the western half of the bulge the latter feature may imply a more complicated structure of the net facs than can be described by the simple substorm current wedge scheme similarly the estimated positions of the downward fac pointed close to the eastern termination of the bulge the associated optical signatures of this current system ranged from the well defined emission depletion regions to new auroral intensifications the downward current appears to correspond in some cases at least with the division between the morning sector portion of the double oval and the nightside portion connected more directly to the substorm bulge the results in general confirm the expected association between the auroral bulge and the scw as well as showing a reasonably good results from the inversion algorithm based on midlatitude magnetic observations our results however also indicate that one must be careful in interpreting the apparent motion of scw related field aligned currents inferred from midlatitude observations in terms of a true westward or eastward expansion of the scw or of the auroral bulge the observed changes may instead sometimes be related to the redistribution of the net facs within than a shift or expansion of the simple current system

spatial and temporal variations in rainfall over darwin and its vicinity during different large scale environments this study analyses the regional variations in rainfall over darwin and its vicinity due to different large scale circulations during the australian summer by utilizing the combination of in situ and c band polarimetric radar rainfall data at hourly resolution the eight phases of the madden julian oscillation as defined by wheeler and hendon mon weather rev 132 8 1917 1932 2004 were used as indicators of different large scale environments the analysis found that the large scale forcing starts to build up from phase 4 by the reversal of low to mid level easterly winds to moist westerly winds reaching a maximum in phase 5 and weakening through phases 6 7 during phases 4 6 most of the study domain experiences widespread rainfall but with distinct spatial and temporal structures in addition during these phases coastal areas near darwin receive more rainfall in the early morning 0200 0400 lt due to the spreading or expansion of rainfall from the beagle gulf explaining the occurrence of a secondary diurnal rainfall peak over darwin in contrast local scale mechanisms sea breezes reinvigorate from phase 8 further strengthening through phases 1 3 when low level easterly winds become established over darwin producing rainfall predominately over land and island locations during the afternoon during these phases below average rainfall is observed over most of the radar domain except over the tiwi islands in phase 2

solar wind control of magnetospheric energy content substorm quenching and multiple onsets in this paper we report coordinated multispacecraft and ground based observations of a double substorm onset close to scandinavia on november 17 1996 the wind and the geotail spacecraft which were located in the solar wind and the subsolar magnetosheath respectively recorded two periods of southward directed interplanetary magnetic field imf these periods were separated by a short northward imf excursion associated with a solar wind pressure pulse which compressed the magnetosphere to such a degree that geotail for a short period was located outside the bow shock the first period of southward imf initiated a substorm growth phase which was clearly detected by an array of ground based instrumentation and by interball in the northern tail lobe a first substorm onset occurred in close relation to the solar wind pressure pulse impinging on the magnetopause and almost simultaneously with the northward turning of the imf however this substorm did not fully develop in clear association with the expansion of the magnetosphere at the end of the pressure pulse the auroral expansion was stopped and the northern sky cleared we will present evidence that the change in the solar wind dynamic pressure actively quenched the energy available for any further substorm expansion directly after this period the magnetometer network detected signatures of a renewed substorm growth phase which was initiated by the second southward turning of the imf and which finally lead to a second and this time complete substorm intensification we have used our multipoint observations in order to understand the solar wind control of the substorm onset and substorm quenching the relative timings between the observations on the various satellites and on the ground were used to infer a possible causal relationship between the solar wind pressure variations and consequent substorm development furthermore using a relatively simple algorithm to model the tail lobe field and the total tail flux we show that there indeed exists a close relationship between the relaxation of a solar wind pressure pulse the reduction of the tail lobe field and the quenching of the initial substorm

zur geologie des thurntaler quarzphyllits und des altkristallins sudlich des tauernfensters ostalpen sudtirol geologische und petrographische untersuchungen im thurntaler quarzphyllit und im angrenzenden altkristallin sudlich des tauernfensters lassen einen mehrfachen wechsel von deformation und kristallisation erkennen im gesamten untersuchungsbereich waren vor allem deformationen gefugepragend fur die gesteine

toward an observational synthesis of substorm models precipitation regions and high latitude convection reversals observed in the nightside auroral oval by dmsp satellites and hf radars a combination of simultaneous measurements from high low and ground altitude instruments has been used to infer the rapid evolution of the coupled nightside magnetosphere ionosphere during substorms reversals from an eastward zonal convection to westward zonal convection become apparent inside the volume of the substorm bulge a few minutes after the intensification of the westward electrojet these reversals persist for periods of 10 20 min and appear to have a one to one correspondence with the occurrence of dipolarizations the changes in convection are accompanied by changes in precipitation flux depletion regions fdr are measured by the dmsp satellites inside the surge near the equatorward portion of the westward electrojet intensification the poleward boundary of every fdr is collocated with a convection reversal and an arc intensification that marks a poleward transition into a region initially dominated by intense discrete electron precipitation and velocity dispersed ion structures vdis convection in the fdr constitutes an eastward electrojet channel that may produce a transient recovery signature as observed by ground magnetometers the observations of fdr s and the fast westward flows that accompany them are consistent with the scenario of a rarefaction and or a neutral line in the near earth tail that produces fast earthward flows after the breakup the arc intensification at the poleward boundary of the depletion region and the collocated transient convection reversal favor an enhancement of the magnetosphere ionosphere coupling and thus the continuation of the substorm expansion in a multiple cell convection system arguments are presented to explain how a series of pseudobreakups modify the near earth magnetic field into an increasingly dipolar geometry until a breakup is possible

morning glory disturbances and the environment in which they propagate results of a field experiment carried out in 1991 to gather upper air data on the morning glory environment are presented the data include daily early morning radiosonde soundings from burketown in north queensland australia for a 28 day period during the late dry season together with pressure wind temperature and humidity data from a number of surface stations in the region during the experiment 16 morning glories were recorded on all but one day radiosonde soundings were carried out in the pre morning glory environment on 7 days additional soundings were carried out within an hour or two of the passage of a morning glory soundings made on days on which morning glories were generated over cape york peninsula but failed to reach burketown are compared with those on days when morning glories were recorded at burketown the comparison shows that the depth and strength of the surface based inversion did not differ significantly and that the stratification of the almost neutral layer above the stable layer was similar on days with and without morning glories an examination of the wind profiles is unrevealing and leads the authors to reject the hypothesis that the trapping of wave energy is the key factor that determines the longevity of the disturbances that the leakiness of the wave guide is not the only factor in the ability of disturbances to cover large distances from their place of origin is consistent with a numerical study by noonan and smith which suggests that the morning glory bore wave system is formed and maintained by mesoscale circulations associated with the sea breezes over cape york peninsula

chatanika radar and s3 2 measurements of auroral zone electrodynamics in the midnight sector measurements made by the incoherent scatter radar at chatanika alaska have been combined with s3 2 satellite data to study the relationships between conductivities electric fields and currents near the harang discontinuity three s3 2 passes were chosen for the study based on the quality of the radar and satellite data and the availability of supplementary ground and space based observations the radar measured electric fields and conductivities as a function of latitude and local time the satellite measured the latitudinal distribution of electric field and field aligned current during the three polar passes the dominant field aligned current in the midnight sector is upward equatorward of this current a downward sheet is observed which is the eastern end of the evening sector region 2 sheet poleward of the upward current are several sheets of varying directions and magnitudes these sheets are associated with active aurora during substorms the most intense electric fields were located at the poleward and equatorward boundaries of the upward current sheet a model is presented which demonstrates the self consistency of the observed relationships between conductivities electric fields and currents

characteristics of the field aligned current system in the nighttime sector during auroral substorms fujii et al 1994 obtained characteristics of the electrodynamic parameters that is field aligned currents electric fields and electron precipitation which are associated with auroral substorm events in the nighttime sector through a unique analysis that places the ionospheric measurements of these parameters into the context of a generic substorm determined from global auroral images in this paper we investigate in considerably more detail the characteristics of the field aligned currents using data from the same set of passes as the previous study we show for the first time that the net upward field aligned currents throughout the surge and surge horn are sufficient to account for most if not all of the converging currents of the auroral electrojets current densities are largest in the surge and surge horn current region continuity does not appear to exist across the substorm bulge region much of the auroral substorm field aligned current is composed of filamentary currents and finite current segments at large angles to each other the westward electrojet may contain large gradients in intensity both in local time and latitude due to sets of localized field aligned currents the net downward current for several hours to the west of the surge is insufficient to account for the eastward electrojet consistent with the concept that this electrojet originates primarily on the dayside our pattern of field aligned currents associated with the surge has common features and also differs significantly from the patterns previously derived from data from radars and ground based magnetometer arrays our pattern is considerably more complex probably due to the much higher resolution in latitude of the satellite data it is also larger in area since our average substorm is much larger than those pertaining to the previous patterns giving a substorm wedge considerably wider than that obtained from the radar and array data

neoproterozoic to early palaeozoic magmatic evolution in the gondwana derived austroalpine basement to the south of the tauern window eastern alps in the austroalpine basement to the south of the tauern window distinct suites of metabasites occur with orthogneisses in pre early ordovician units tholeiitic and alkaline within plate basalt type metabasites are associated with acid meta porphyroids in the post early ordovician thurntaler phyllite group according to their correlated trace element abundances metabasite zircons crystallized with their host rocks protolith pb pb zircon ages whole rock ta yb th yb and oxygen sr nd isotope data define two principal evolution lines an older evolution at elevated th yb typical of subduction related magmatism started by 590 ma n morb type and 550 530 ma volcanic arc basalt type basic suites which mainly involved depleted mantle sources it finished with mainly crustal source 470 450 ma acid magmatites an other evolution line by tholeiitic and 430 ma alkaline within plate basalt type suites in both pre and post early ordovician units is characterized by an intraplate mantle metasomatism and enrichment trend along multicomponent sources these magmatic evolution lines can be related to a plate tectonic scenario that involved terranes in a progressively mature neoproterozoic to ordovician active margin and a subsequent palaeo tethys passive margin along the north gondwanan periphery

observations of the electric field fine structure associated with the westward traveling surge and large scale auroral spirals the characteristics of the fine scale electric field associated with the westward traveling surge and large scale auroral spirals and surges are investigated using high resolution electric field magnetic field particle and uv imager observations from four eveningside auroral oval crossings by the freja satellite three of the crossings were associated with signatures of auroral substorms and one crossing went directly through the head of a surge close in time and space to substorm onset three passes were adjacent to auroral spiral formations one poleward of and one equatorward of such forms and one through the multiple arc region near the front of an extended region of auroral activity the ambient electric field was found to intensify in the direction toward the spiral head or the center of the auroral activity region over a region comparable to the size of the visible auroral forms these results confirm previous findings that the spiral or surge head is associated with negative space charge and an intense upward field aligned current the fourth pass directly through the surge head reveals a very complicated structure of the surge region narrowly structured intense up to 700 mv m and mostly converging electric fields associated with intense electron precipitation of both high and medium energies and balanced field aligned currents up to 30 a m2 are seen near the edge of the surge head and adjacent to auroral structures in the wake these narrow regions are embedded within more extended regions of intense high energy electron precipitation but very weak electric fields and field aligned currents according to some existing models of the surge a pronounced westward electric field component and a southward polarisation electric field is expected within the entire high conductivity region but evidence in support of this was not found in the data rather these suggest that a significant part of the upward surge current is closed by distributed downward field aligned currents from the near surroundings the freja electric field is typically seen to intensify at the edges of or in between bright auroral structures and to decrease within the arcs similar to what is observed in the ionosphere the surge electric field is however much more intense than previously observed or anticipated at these altitudes with characteristics rather similar to those observed in the auroral acceleration region since the particle data indicate that most of the acceleration takes place above freja altitudes it seems as if freja traversed the lower part of the auroral acceleration region associated with the surge

nightside ionospheric electrodynamics associated with substorms pfisr and themis asi observations 1 observations from the newly available poker flat incoherent scatter radar have been used to study the ionospheric electrodynamics during the substorm expansion phase substorm events selected have been divided into three categories based on onset location relative to the radar and repeatable features have been identified west of onset westward flows increased in response to the passage of the westward traveling surge wts poleward of them the enhanced flows occurred within the sub auroral polarization streams region of downward region 2 currents which extend equatorward from near the equatorward boundary of electron precipitation strong e region ionization increase associated with the wts occurred poleward of the enhanced westward flows suggesting that poleward pedersen currents fed by the downward region 2 field aligned current fac further equatorward contribute at least partially to closure of the upward fac of the wts an enhanced eastward flow channel developed east of onset e region ionization decreased poleward of this flow peak implying formation of downward fac and further increased equatorward of the flow peak suggesting strengthening of preexisting region 2 upward fac these observations indicate that the downward fac formed at onset at least partially closes via the upward region 2 currents the enhanced eastward flows decreased after passage of the auroral bulge and the reduced e region ionization increased again when onset occurred within the radar fov the thin breakup arc of onset occurred at the center of the harang reversal while if the optical onset was poleward of the radar fov the harang reversal was observed after the onset a 2 d picture of the evolution of ionospheric electrodynamics was generated by synthesizing observations from the three categories which provides a schematic description of the relationship between region 2 and substorm expansion electrodynamics

characterization of the dynamic variations of the dayside high latitude ionospheric convection reversal boundary and relationship to interplanetary magnetic field orientation we present initial results from observations of the northern summer polar ionospheric convection reversal boundary using ground and satellite based instrumentation ionospheric convection measurements obtained using the sondrestrom radar are used to locate and observe the boundary the flow around the reversal is compared to three different modeled flow patterns the first is a shear reversal oppositely directed flows with no flow across the boundary the second is a shear reversal combined with uniform poleward flow the final flow pattern observed is a rotational reversal where flows gradually turn from one direction to the opposite over distances on the order of 200 400 km the convection reversals observed were categorized into three different classes 1 stationary and steady 2 nonstationary and 3 oscillating a stationary and steady boundary remains at the same invariant latitude for long periods of time and demonstrates no observable motion a nonstationary boundary will propagate northward or southward generally remaining parallel to a line of invariant latitude the oscillating reversal boundary orb will have wave like motions of the local boundary location a number of different reversals were classified and then studied further using other instrumentation which include the greenland coastal and magic chains of magnetometers the drift meter and particle precipitation instruments from the dmsp f9 f10 and f11 satellites and interplanetary magnetic field imf measurements from the imp 8 satellite a stationary and steady reversal has been observed during a time of magnitude variations in the by and bz components of the imf but no sign changes in either of the components the nonstationary reversals have been observed to be a response to both sign changes and magnitude changes with no sign changes in imf components of the two orbs reported here one has been determined to be a ulf wave propagating along the convection reversal boundary which maps to the magnetospheric low latitude boundary layer the other orb has little coherence between longitudinally spaced magnetometer stations implying that the propagating waves are changing form between the stations

mesoscale ionospheric electrodynamics observed with the miracle network 1 analysis of a pseudobreakup spiral a short lived auroral spiral is observed on february 3 1999 around 2204 ut using the multi instrument array for ionosphere magnetosphere coupling studies miracle network of ground based instruments in fennoscandia which consists of magnetometers coherent scatter radars and all sky cameras four minutes later after this spiral has subsided the auroral bulge of a fully developed substorm that has set on earlier over russia intrudes into the miracle field of view from the east hence the auroral spiral precedes the substorm spatially i e it is located westward of the substorm bulge rather than temporarily since this spiral is associated with a localized and short lived substorm type auroral development we interpret it as a pseudobreakup spiral which is subsequently covered by the intruding auroral bulge during the decaying phase of the pseudobreakup activity in contrast to growth phase pseudobreakups that occur temporally before a full breakup this pseudobreakup is observed spatially ahead westward of an already evolving substorm bulge our instantaneous spatial analysis of the distributions of ionospheric electrodynamic parameters associated with this spiral shows that all key features are similar to the ionospheric electrodynamics of the westward traveling surge sharp decrease of conductance toward the west from hall conductance values up to 30 s in the spiral to less than 2 s west of it a cluster of upward field aligned currents facs in the spiral area with magnitudes up to 5 a km 2 and anticlockwise spiraling horizontal currents around it the upward facs diverging at least 100 ka of current in total are fed to a large extent by a pseudosubstorm electrojet carried by westward flowing hall currents no signs of local current closure by downward facs from the immediate vicinity of the spiral are found our results are inconsistent with the earlier conjecture that insufficient ionospheric conductance would prevent the pseudobreakup to evolve to a full breakup since the solar wind data do not provide clear evidence for being a driver of the pseudobreakup breakup sequence the driver has to be an internal magnetospheric one