Reference : Solar wind control of auroral substorm onset locations observed with the IMAGE-FUV imagers
Scientific journals : Article
Physical, chemical, mathematical & earth Sciences : Space science, astronomy & astrophysics
http://hdl.handle.net/2268/31678
Solar wind control of auroral substorm onset locations observed with the IMAGE-FUV imagers
English
Gérard, Jean-Claude mailto [Université de Liège - ULg > Département d'astrophys., géophysique et océanographie (AGO) > Labo de physique atmosphérique et planétaire (LPAP) >]
Hubert, Benoît mailto [Université de Liège - ULg > Département d'astrophys., géophysique et océanographie (AGO) > Labo de physique atmosphérique et planétaire (LPAP) >]
Grard, Aline mailto [Université de Liège - ULg > > Aquapôle >]
Meurant, M. [> > > >]
Mende, S. B. [> > > >]
1-Mar-2004
Journal of Geophysical Research. Space Physics
American Geophysical Union (AGU)
109
03208
Yes (verified by ORBi)
International
0148-0227
Washington
DC
[en] Magnetospheric Physics: Storms and substorms ; Magnetospheric Physics: Energetic particles ; precipitating ; Magnetospheric Physics: Auroral phenomena (2407) ; Magnetospheric Physics: Solar wind/magnetosphere interactions ; Magnetospheric Physics: Magnetotail
[en] The FUV imagers on board the IMAGE satellite provide multispectral snapshots of the polar region every 2 min. The combination of the Wide-Angle Imaging Camera (WIC) with SI12 (Doppler shifted Lyman-alpha) and SI13 (135.6 nm) spectral imagers is used to discriminate between the electron and the proton aurora. We describe a statistical study of the location of 78 substorms observed close to the 2000-2001 winter solstice. The latitudinal distribution of the onsets observed with WIC is asymmetric with a median at 65.6° MLAT and a full width at half maximum (FWHM) of 3.5°. Their local time distribution is concentrated between 2000 and 0200 MLT with a median at 23.4 +/- 0.3 hours MLT and a FWHM of 1.8 hours. No statistically significant difference is found in the spatial distribution of the proton and electron onsets. All onsets take place within a region of preexisting proton precipitation, indicating that substorm initiation occurs in regions of stretched but dipole-like field lines that cross the equatorial plane close to the Earth. Latitudes of substorm onsets are located at a variable distance from the poleward FUV auroral boundary but remain at a nearly constant distance from the equatorward limit of both proton and electron auroral ovals. The magnetic latitudes of the onsets are correlated with some of the solar wind plasma properties measured by the ACE satellite prior to the substorm breakup. In particular, a clear anticorrelation is found between the onset MLAT and the 1-hour averaged solar wind dynamic pressure. A decrease of the onset latitude is also observed for larger B intensity values. No dependence of the onset MLT on the solar wind speed is observed, in contrast to the relationship expected from the thermal catastrophe model for substorm initiation. Our results are in agreement with models locating the initial instability in the near magnetosphere such as the near-Earth current disruption models.
Researchers ; Professionals
http://hdl.handle.net/2268/31678
10.1029/2003JA010129
http://adsabs.harvard.edu/abs/2004JGRA..10903208G

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