bluuebunny/crossref_metadata_2025_split huggingface dataset:
Simultaneous Double Star and Cluster FTEs observations on the dawnside flank of the magnetosphere
Authors: Marchaudon A. , Owen C. J. , Bosqued J.-M. , Fear R. C. , Fazakerley A. N. , Dunlop M. W. , Lahiff A. D. , Carr C. , Balogh A. , Lindqvist P.-A. , Rème H. 
Published: June 2010

Abstract. We present Cluster and Double Star-1 (TC-1) observations from a close magnetic conjunction on 8 May 2004. The five spacecraft were on the dawnside flank of the magnetosphere, with TC-1 located near the equatorial plane and Cluster at higher geographic latitudes in the Southern Hemisphere. TC-1, at its apogee, skimmed the magnetopause for almost 8h (between 08:00-16:00 UT). Flux Transfer Events (FTEs), moving southward/tailward from the reconnection site, were observed by TC-1 throughout almost all of the period. Cluster, travelling on a mainly dawn-dusk trajectory, crossed the magnetopause at around 10:30 UT in the same Magnetic Local Time (MLT) sector as TC-1 and remained close to the magnetopause boundary layer in the Southern Hemisphere. The four Cluster spacecraft observed FTEs for a period of 6.5h between 07:30 and 14:00 UT. The very clear signatures and the finite transverse sizes of the FTEs observed by TC-1 and Cluster imply that, during this event, sporadic reconnection occurred. From the properties of these FTEs, the reconnection site was located northward of both TC-1 and Cluster on the dawn flank of the magnetosphere. Reconnection occurred between draped magnetosheath and closed magnetospheric field lines. Despite variable interplanetary magnetic field (IMF) conditions and IMF-Bz turnings, the IMF clock angle remained greater than 70° and the location site appeared to remain relatively stable in position during the whole period. This result is in agreement with previous studies which reported that the dayside reconnection remained active for an IMF clock angle greater than 70°. The simultaneous observation of FTEs at both Cluster and TC-1, separated by 2h in MLT, implies that the reconnection site on the magnetopause must have been extended over several hours in MLT.
Multiple flux rope events at the magnetopause observations by TC-1 on 18 March 2004
Authors: Xiao C. J. , Pu Z. Y. , Wei Y. , Liu Z. X. , Carr C. M. , Zhang T. L. , Glassmeier K.-H. , Rème H. , Dandouras I. , Daly P. 
Published: June 2010

Abstract. From 23:10 to 23:50 UT on 18 March 2004, the Double Star TC-1 spacecraft detected eight flux ropes at the outbound crossing of the southern dawnside magnetopause. A notable guide field existed inside all ropes. In the mean time the Cluster spacecraft were staying in the magnetosheath and found that the events occurred under the condition of southward IMF Bz and dominant negative IMF By. There are six ropes that appeared quasi-periodically, with a repeated period being approximately 1-4 min. The last flux rope lasts for a longer time interval with a larger peak in the BN variations; it can thus be referred to as a typical FTE. The 18 March 2004 event is quite similar to the multiple flux rope event observed by Cluster on 26 January 2001 at the northern duskside high-latitude magnetopause. A detailed comparison of these two events is made in the paper. Preliminary studies imply that both of these multiple flux ropes events seem to be produced by component reconnection at the dayside low-latitude magnetopause.
Cluster and Double Star observations of dipolarization
Authors: Nakamura R. , Baumjohann W. , Zhang T. L. , Carr C. M. , Balogh A. , Fornacon K-H. , Georgescu E. , Rème H. , Dandouras I. , Takada T. , Volwerk M. , Asano Y. , Runov A. , Eichelberger H. , Klecker B. , Mouikis C. , Kistler L. M. , Amm O. 
Published: June 2010

Abstract. We studied two types of dipolarization events with different IMF conditions when Cluster and Double Star (TC-1) were located in the same local time sector: 7 August 2004, 18:00-24:00 UT, during a disturbed southward/northward IMF interval, and 14 August 2004, 21:00-24:00 UT, when the IMF was stably northward. Cluster observed dipolarization as well as fast flows during both intervals, but this was not the case for TC-1. For both events the satellites crossed near the conjugate location of the MIRACLE stations. By using multi-point analysis techniques, the direction/speed of the propagation is determined using Cluster and is then compared with the disturbances at TC-1 to discuss its spatial/temporal scale. The propagation direction of the BZ disturbance at Cluster was mainly dawnward with a tailward component for 7 August and with a significant Earthward component for 14 August associated with fast flows. We suggest that the role of the midtail fast flows can be quite different in the dissipation process depending on the condition of the IMF and resultant configuration of the tail.
Pitch angle distribution of trapped energetic protons and helium isotope nuclei measured along the Resurs-01 No. 4 LEO satellite
Authors: Leonov A. , Cyamukungu M. , Cabrera J. , Leleux P. , Lemaire J. , Gregorie G. , Benck S. , Mikhailov V. , Bakaldin A. , Galper A. , Koldashov S. , Voronov S. , Casolino M. , De Pascale M. , Picozza P. , Sparvolli R. , Ricci M. 
Published: June 2010

Abstract. The NINA detector on board the Resurs-01 No. 4 satellite (835 km, 98° inclination) is equipped with particle trackers based on silicon strip detectors. From the energy deposited in each of its silicon layers the mass, the momentum direction and energy of incident particles have been determined. The resolutions in mass and energy allow identification of H and He isotopes over the 10-50 MeV/n energy range. The angular resolution is about 2.5°. We present the direct measurements of proton and helium isotopes pitch angle distributions derived from Resurs-01 No.4/NINA observations and their variations as functions of (B, L) coordinates and energy. The measurements of trapped helium isotopes spectrum are also presented.
Mesoscale ionospheric electrodynamics of omega bands determined from ground-based electromagnetic and satellite optical observations
Authors: Amm O. , Aksnes A. , Stadsnes J. , Østgaard N. , Vondrak R.R. , Germany G.A. , Lu G. , Viljanen A. 
Published: June 2010

Abstract. We present ground-based electromagnetic data from the MIRACLE and BEAR networks and satellite optical observations from the UVI and PIXIE instruments on the Polar satellite of an omega band event over Northern Scandinavia on 26 June 1998, which occured close to the morning side edge of a substorm auroral bulge. Our analysis of the data concentrates on one omega band period from 03:18-03:27 UT, for which we use the method of characteristics combined with an analysis of the UVI and PIXIE data to derive a time series of instantaneous, solely data-based distributions of the mesoscale ionospheric electrodynamic parameters with a 1-min time resolution. In addition, the AMIE method is used to derive global Hall conductance patterns. Our results show that zonally alternating regions of enhanced ionospheric conductances ("tongues") up to ~60S and low conductance regions are associated with the omega bands. The tongues have a poleward extension of ~400km from their base and a zonal extension of ~380km. While they are moving coherently eastward with a velocity of ~770ms-1, the structures are not strictly stationary. The current system of the omega band can be described as a superposition of two parts: one consists of anticlockwise rotating Hall currents around the tongues, along with Pedersen currents, with a negative divergence in their centers. The sign of this system is reversing in the low conductance areas. It causes the characteristic ground magnetic signature. The second part consists of zonally aligned current wedges of westward flowing Hall currents and is mostly magnetically invisible below the ionosphere. This system dominates the field-aligned current (FAC) pattern and causes alternating upward and downward FAC at the flanks of the tongues with maximum upward FAC of ~25µA m-2. The total FAC of ~2MA are comparable to the ones diverted inside a westward traveling surge. Throughout the event, the overwhelming part of the FAC are associated with gradients of the ionospheric conductances, and 66-84% of the FAC are connected with ionospheric Hall currents.
Is there a plasma density gradient role on the generation of short-scale Farley-Buneman waves?
Authors: Haldoupis C. , Ogawa T. , Schlegel K. , Koehler J. A. , Ono T. 
Published: June 2010

Abstract. The physics of the unstable E-region plasma is based on the modified two stream, or Farley-Buneman, and the gradient drift instabilities. The theory combines both mechanisms into a single dispersion relation which applies for the directly generated short-scale plasma waves, known as type 1 irregularities. In the absence of a plasma gradient it is only the two stream mechanism acting which favors wave excitation if E×B electron drifts relative to the ions exceed a threshold slightly above the ion acoustic speed. On the other hand, the theory also predicts that a destabilizing (stabilizing) electron density gradient acts to decrease (increase) the ion acoustic threshold, and hence the wave phase velocities at threshold, depending on the gradient strength and the wavelength. Given a destabilizing plasma gradient, the threshold reduction is larger at longer than shorter wavelengths and thus the best way to test the gradient role is by simultaneous observations of type 1 waves at two or more radio backscatter frequencies. The present paper relies on dual frequency backscatter observations of 1.1 m and 3.1 m type 1 irregularities made simultaneously at 144 MHz and 50 MHz, respectively, in mid-latitude sporadic E-layers. Using as typical plasma gradient scale lengths for destabilized sporadic E-layers those that are obtained from rocket electron density profiles, the radar observations are compared with the predictions of kinetic theory. The results suggest that the plasma density gradient effect on meter scale Farley-Buneman waves is not important. This is reinforced further by the analysis of backscatter from destabilized meteor trail plasma when very steep gradients are expected in electron density. The present findings, and more from past studies, question the electron density gradient role in the generation of short-scale plasma waves as predicted by the linear instability theory. This deserves attention and more study.
A statistical comparison of SuperDARN spectral width boundaries and DMSP particle precipitation boundaries in the afternoon sector ionosphere
Authors: Chisham G. , Freeman M. P. , Lam M. M. , Abel G. A. , Sotirelis T. , Greenwald R. A. , Lester M. 
Published: June 2010

Abstract. The open-closed magnetic field line boundary (OCB) is best measured at the foot points of the boundary in the Earth's ionosphere where continuous and extensive spatiotemporal measurements can be made. The ability to make routine observations of this type is crucial if accurate global measurements of energy transfer processes occurring at the boundary, such as magnetic reconnection, are to become a reality. The spectral width boundary (SWB) measured by the Super Dual Auroral Radar Network (SuperDARN) has been shown to be a reliable ionospheric proxy for the OCB at certain magnetic local times (MLTs). However, the reliability of the SWB proxy in the afternoon sector ionosphere (12:00-18:00 MLT) has been questionable. In this paper we undertake a statistical comparison of the latitudinal locations of SWBs measured by SuperDARN and particle precipitation boundaries (PPBs) measured by the Defense Meteorological Satellite Program (DMSP) spacecraft, concentrating on the PPB which best approximates the location of the OCB. The latitudes of SWBs and PPBs were identified using automated algorithms applied to 5 years (1997-2001) of data measured in the 12:00-18:00 MLT range. A latitudinal difference was measured between each PPB and the nearest SWB within a ±10 min universal time (UT) window and within a ±1 h MLT window. The results show that when the SWB is identified at higher geomagnetic latitudes (poleward of ~74), it is a good proxy for the OCB, with 76% of SWBs lying within 3 of the OCB. At lower geomagnetic latitudes (equatorward of ~74), the correlation is poor and the results suggest that most of the SWBs being identified represent ionospheric variations unassociated with the OCB, with only 32% of SWBs lying within 3 of the OCB. We propose that the low level of precipitating electron energy flux, typical of latitudes well equatorward of the OCB in the afternoon sector, may be a factor in enhancing spectral width values at these lower latitudes. A consequence of this would be low latitude SWBs unrelated to the OCB.
Cluster magnetotail observations of a tailward-travelling plasmoid at substorm expansion phase onset and field aligned currents in the plasma sheet boundary layer
Authors: Draper N. C. , Lester M. , Cowley S. W. H. , Wild J.A. , Milan S. E. , Provan G. , Grocott A. , Fazakerley A. N. , Lahiff A. , Davies J. A. , Bosqued J.-M. , Dewhurst J. P. , Nakamura R. , Owen C. J. , Waterman J. , Henderson M. G. , Singer H. J. , Donovan E. 
Published: June 2010

Abstract. We present data from both ground- and space-based instruments for a substorm event which occurred on 5 October 2002, with an expansion phase onset time of 02:50 UT determined from the ground magnetometer data. During this substorm, the Cluster spacecraft were located around 15 RE downtail, 8 RE from midnight in the pre-midnight sector and just 2 RE above the equatorial plane (in GSM coordinates). At expansion phase onset the Cluster spacecraft were located in the plasma sheet, tailward of a near-Earth neutral line and detected a significant time delay of 6 min between the tail field Bz component becoming negative and the subsequent detection of Earthward flows. This is explained by the formation of a tailward-directed travelling compression region initially Earthward of the spacecraft; 7 min later the Cluster spacecraft entered the plasma sheet boundary layer; they remained in and close to the plasma sheet boundary layer for around 15 min before exiting to the lobe. The spacecraft then re-entered the plasma sheet 30 min after onset. Earthward then tailward directed currents detected in the plasma sheet boundary layer after onset indicate that the Cluster spacecraft encountered the dawnward and duskward portions of the reconnection flow associated current system with Region 1 sense, respectively. The reconnection site and current system were initially skewed towards the pre-midnight sector, consistent with previous observations that found the majority of substorm onsets located in this sector. At later times the reconnection site and current system had moved towards dawn, to be located more centrally in the midnight sector.
On the motion of dayside auroras caused by a solar wind pressure pulse
Authors: Kozlovsky A. , Safargaleev V. , Østgaard N. , Turunen T. , Koustov A. , Jussila J. , Roldugin A. 
Published: June 2010

Abstract. Global ultraviolet auroral images from the IMAGE satellite were used to investigate the dynamics of the dayside auroral oval responding to a sudden impulse (SI) in the solar wind pressure. At the same time, the TV all-sky camera and the EISCAT radar on Svalbard (in the pre-noon sector) allowed for detailed investigation of the auroral forms and the ionospheric plasma flow. After the SI, new discrete auroral forms appeared in the poleward part of the auroral oval so that the middle of the dayside oval moved poleward from about 70° to about 73° of the AACGM latitude. This poleward shift first occurred in the 15 MLT sector, then similar shifts were observed in the MLT sectors located more westerly, and eventually the shift was seen in the 6 MLT sector. Thus, the auroral disturbance "propagated" westward (from 15 MLT to 6 MLT) at an apparent speed of the order of 7km/s. This motion of the middle of the auroral oval was caused by the redistribution of the luminosity within the oval and was not associated with the corresponding motion of the poleward boundary of the oval. The SI was followed by an increase in the northward plasma convection velocity. Individual auroral forms showed poleward progressions with velocities close to the velocity of the northward plasma convection. The observations indicate firstly a pressure disturbance propagation through the magnetosphere at a velocity of the order of 200km/s which is essentially slower than the velocity of the fast Alfvén (magnetosonic) wave, and secondly a potential (curl-free) electric field generation behind the front of the propagating disturbance, causing the motion of the auroras. We suggest a physical explanation for the slow propagation of the disturbance through the magnetosphere and a model for the electric field generation. Predictions of the model are supported by the global convection maps produced by the SuperDARN HF radars. Finally, the interchange instability and the eigenmode toroidal Alfvén oscillations are discussed as possible generation mechanisms for the dayside auroral forms launched by the SI.
Relation between the ring current and the tail current during magnetic storms
Authors: Kalegaev V. V. , Ganushkina N. Y. , Pulkkinen T. I. , Kubyshkina M. V. , Singer H. J. , Russell C. T. 
Published: June 2010

Abstract. We study the dynamics of the magnetospheric large-scale current systems during storms by using three different magnetospheric magnetic field models: the paraboloid, event-oriented, and Tsyganenko T01 models. We have modelled two storm events, one moderate storm on 25-26 June 1998, when Dst reached -120nT and one intense storm on 21-23 October 1999, when Dst dropped to -250nT. We compare the observed magnetic field from GOES 8, GOES 9, and GOES 10, Polar and Geotail satellites with the magnetic field given by the three models to estimate their reliability. All models demonstrated quite good agreement with observations. Since it is difficult to measure exactly the relative contributions from different current systems to the Dst index, we compute the contributions from ring, tail and magnetopause currents given by the three magnetic field models. We discuss the dependence of the obtained contributions to the Dst index in relation to the methods used in constructing the models. All models show a significant tail current contribution to the Dst index, comparable to the ring current contribution during moderate storms. The ring current becomes the major Dst source during intense storms.
The ionospheric heating beneath the magnetospheric cleft revisited
Authors: Prölss G. W. 
Published: June 2010

Abstract. A prominent peak in the electron temperature of the topside ionosphere is observed beneath the magnetospheric cleft. The present study uses DE-2 data obtained in the Northern Winter Hemisphere to investigate this phenomenon. First, the dependence of the location and magnitude of the temperature peak on the magnetic activity is determined. Next, using a superposed epoch analysis, the mean latitudinal profile of the temperature enhancement is derived. The results of the present study are compared primarily with those obtained by Titheridge (1976), but also with more recent observations and theoretical predictions.
Cluster observations of a structured magnetospheric cusp
Authors: Balan N. , Alleyne H. , Walker S. , Réme H. , Décréau P. M. E. , Balogh A. , André M. , Fazakerley A. N. , Cornilleau-Wehrlin N. , Gurnett D. , Fraenz M. 
Published: June 2010

Abstract. On 18 April 2002 the Cluster spacecraft crossed through the northern outer magnetospheric cusp region during 16:25-17:55 UT when the solar wind dynamic pressure was rather low (<2 nPa) and IMF Bz was more negative than IMF By. The Cluster data from the FGM, CIS, PEACE, EFW, WHISPER and STAFF instruments reveal that the cusp is structured with three anti-sunward ion flow events of durations ≈1.5, 17.5 and 19.0 min, with bulk plasma flow roughly parallel to the magnetopause toward north. The ion and electron densities within the events are much greater than those outside. The zonal electric field in the ion flow events turns eastward as expected from V×B effect. The sharp inward boundaries of the ion flow events cross the four spacecraft in one time sequence, and the outward boundaries of the events cross the spacecraft in the reverse time sequence. The observations studied using magnetosphere and magnetopause models suggest that the structured cusp is a temporal feature that arises due to three inward and outward movements of the magnetopause by about 1.5RE so that Cluster, while crossing through the cusp, happened to be in the magnetosheath (ion flow event) and cusp alternately. The magnetopause moved due to the changes in the solar wind dynamic pressure by up to 100%.
Polar mesosphere winter echoes during MaCWAVE
Authors: Kirkwood S. , Belova E. , Blum U. , Croskey C. , Dalin P. , Fricke K.-H. , Goldberg R. A. , Manninen J. , Mitchell J. D. , Schmidlin F. 
Published: June 2010

Abstract. During the MaCWAVE winter campaign in January 2003, layers of enhanced echo power known as PMWE (Polar Mesosphere Winter Echoes) were detected by the ESRAD 52 MHz radar on several occasions. The cause of these echoes is unclear and here we use observations by meteorological and sounding rockets and by lidar to test whether neutral turbulence or aerosol layers might be responsible. PMWE were detected within 30 min of meteorological rocket soundings (falling spheres) on 5 separate days. The observations from the meteorological rockets show that, in most cases, conditions likely to be associated with neutral atmospheric turbulence are not observed at the heights of the PMWE. Observations by instrumented sounding rockets confirm low levels of turbulence and indicate considerable small-scale structure in charge density profiles. Comparison of falling sphere and lidar data, on the other hand, show that any contribution of aerosol scatter to the lidar signal at PMWE heights is less than the detection threshold of about 10%.
From the Sun to the Earth: impact of the 27-28 May 2003 solar events on the magnetosphere, ionosphere and thermosphere
Authors: Hanuise C. , Cerisier J. C. , Auchère F. , Bocchialini K. , Bruinsma S. , Cornilleau-Wehrlin N. , Jakowski N. , Lathuillère C. , Menvielle M. , Valette J.-J. , Vilmer N. , Watermann J. , Yaya P. 
Published: June 2010

Abstract. During the last week of May 2003, the solar active region AR 10365 produced a large number of flares, several of which were accompanied by Coronal Mass Ejections (CME). Specifically on 27 and 28 May three halo CMEs were observed which had a significant impact on geospace. On 29 May, upon their arrival at the L1 point, in front of the Earth's magnetosphere, two interplanetary shocks and two additional solar wind pressure pulses were recorded by the ACE spacecraft. The interplanetary magnetic field data showed the clear signature of a magnetic cloud passing ACE. In the wake of the successive increases in solar wind pressure, the magnetosphere became strongly compressed and the sub-solar magnetopause moved inside five Earth radii. At low altitudes the increased energy input to the magnetosphere was responsible for a substantial enhancement of Region-1 field-aligned currents. The ionospheric Hall currents also intensified and the entire high-latitude current system moved equatorward by about 10°. Several substorms occurred during this period, some of them - but not all - apparently triggered by the solar wind pressure pulses. The storm's most notable consequences on geospace, including space weather effects, were (1) the expansion of the auroral oval, and aurorae seen at mid latitudes, (2) the significant modification of the total electron content in the sunlight high-latitude ionosphere, (3) the perturbation of radio-wave propagation manifested by HF blackouts and increased GPS signal scintillation, and (4) the heating of the thermosphere, causing increased satellite drag. We discuss the reasons why the May 2003 storm is less intense than the October-November 2003 storms, although several indicators reach similar intensities.