Geometry of duskside equatorial current during magnetic storm main phase as deduced from magnetospheric and low-altitude observations
We present the results of a coordinated study of the moderate magnetic storm on 22 July 2009. The THEMIS and GOES observations of magnetic field in the inner magnetosphere were complemented by energetic particle observations at low altitude by the six NOAA POES satellites. Observations in the vi...
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2013-03-01
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| Series: | Annales Geophysicae |
| Online Access: | https://www.ann-geophys.net/31/395/2013/angeo-31-395-2013.pdf |
| _version_ | 1819102903123574784 |
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| author | S. Dubyagin N. Ganushkina N. Ganushkina S. Apatenkov M. Kubyshkina H. Singer M. Liemohn |
| author_facet | S. Dubyagin N. Ganushkina N. Ganushkina S. Apatenkov M. Kubyshkina H. Singer M. Liemohn |
| author_sort | S. Dubyagin |
| collection | DOAJ |
| description | We present the results of a coordinated study of the moderate
magnetic storm on 22 July 2009. The THEMIS and GOES observations
of magnetic field in the inner magnetosphere were complemented by
energetic particle observations at low altitude by the six NOAA
POES satellites. Observations in the vicinity of geosynchronous
orbit revealed a relatively thin (half-thickness of less than 1 <I>R</I><sub>E</sub>)
and intense current sheet in the dusk MLT sector during the
main phase of the storm. The total westward current (integrated
along the z-direction) on the duskside at <I>r</I> ~ 6.6 <I>R</I><sub>E</sub> was
comparable to that in the midnight sector. Such a configuration
cannot be adequately described by existing magnetic field models
with predefined current systems (error in <I>B</I> > 60 nT). At the same
time, low-altitude isotropic boundaries (IB) of > 80 keV protons
in the dusk sector were shifted ~ 4° equatorward relative
to the IBs in the midnight sector. Both the equatorward IB shift
and the current strength on the duskside correlate with the
Sym-H* index. These findings imply a close relation between
the current intensification and equatorward IB shift in the dusk
sector. The analysis of IB dispersion revealed that high-energy
IBs (<I>E</I> > 100 keV) always exhibit normal dispersion (i.e., that for
pitch angle scattering on curved field lines). Anomalous
dispersion is sometimes observed in the low-energy channels
(~ 30–100 keV). The maximum occurrence rate of anomalous
dispersion was observed during the main phase of the storm in the
dusk sector. |
| first_indexed | 2024-12-22T01:41:57Z |
| format | Article |
| id | doaj.art-6ef14b236f914918a73420ef8676fd1f |
| institution | Directory Open Access Journal |
| issn | 0992-7689 1432-0576 |
| language | English |
| last_indexed | 2024-12-22T01:41:57Z |
| publishDate | 2013-03-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Annales Geophysicae |
| spelling | doaj.art-6ef14b236f914918a73420ef8676fd1f2022-12-21T18:43:11ZengCopernicus PublicationsAnnales Geophysicae0992-76891432-05762013-03-013139540810.5194/angeo-31-395-2013Geometry of duskside equatorial current during magnetic storm main phase as deduced from magnetospheric and low-altitude observationsS. Dubyagin0N. Ganushkina1N. Ganushkina2S. Apatenkov3M. Kubyshkina4H. Singer5M. Liemohn6Finnish Meteorological Institute, Erik Palmenin aukio 1, Helsinki, 00101, FinlandFinnish Meteorological Institute, Erik Palmenin aukio 1, Helsinki, 00101, FinlandDepartment of Atmospheric, Oceanic and Space Sciences, University of Michigan, 2455 Hayward St., Ann Arbor, MI 48109-2143, USASt.~Petersburg State University, Earth Physics Department, Ulyanovskaya 1, Petrodvoretz, St.~Petersburg, 198504, RussiaSt.~Petersburg State University, Earth Physics Department, Ulyanovskaya 1, Petrodvoretz, St.~Petersburg, 198504, RussiaSpace Weather Prediction Center, 325 Broadway, Boulder, CO, USADepartment of Atmospheric, Oceanic and Space Sciences, University of Michigan, 2455 Hayward St., Ann Arbor, MI 48109-2143, USAWe present the results of a coordinated study of the moderate magnetic storm on 22 July 2009. The THEMIS and GOES observations of magnetic field in the inner magnetosphere were complemented by energetic particle observations at low altitude by the six NOAA POES satellites. Observations in the vicinity of geosynchronous orbit revealed a relatively thin (half-thickness of less than 1 <I>R</I><sub>E</sub>) and intense current sheet in the dusk MLT sector during the main phase of the storm. The total westward current (integrated along the z-direction) on the duskside at <I>r</I> ~ 6.6 <I>R</I><sub>E</sub> was comparable to that in the midnight sector. Such a configuration cannot be adequately described by existing magnetic field models with predefined current systems (error in <I>B</I> > 60 nT). At the same time, low-altitude isotropic boundaries (IB) of > 80 keV protons in the dusk sector were shifted ~ 4° equatorward relative to the IBs in the midnight sector. Both the equatorward IB shift and the current strength on the duskside correlate with the Sym-H* index. These findings imply a close relation between the current intensification and equatorward IB shift in the dusk sector. The analysis of IB dispersion revealed that high-energy IBs (<I>E</I> > 100 keV) always exhibit normal dispersion (i.e., that for pitch angle scattering on curved field lines). Anomalous dispersion is sometimes observed in the low-energy channels (~ 30–100 keV). The maximum occurrence rate of anomalous dispersion was observed during the main phase of the storm in the dusk sector.https://www.ann-geophys.net/31/395/2013/angeo-31-395-2013.pdf |
| spellingShingle | S. Dubyagin N. Ganushkina N. Ganushkina S. Apatenkov M. Kubyshkina H. Singer M. Liemohn Geometry of duskside equatorial current during magnetic storm main phase as deduced from magnetospheric and low-altitude observations Annales Geophysicae |
| title | Geometry of duskside equatorial current during magnetic storm main phase as deduced from magnetospheric and low-altitude observations |
| title_full | Geometry of duskside equatorial current during magnetic storm main phase as deduced from magnetospheric and low-altitude observations |
| title_fullStr | Geometry of duskside equatorial current during magnetic storm main phase as deduced from magnetospheric and low-altitude observations |
| title_full_unstemmed | Geometry of duskside equatorial current during magnetic storm main phase as deduced from magnetospheric and low-altitude observations |
| title_short | Geometry of duskside equatorial current during magnetic storm main phase as deduced from magnetospheric and low-altitude observations |
| title_sort | geometry of duskside equatorial current during magnetic storm main phase as deduced from magnetospheric and low altitude observations |
| url | https://www.ann-geophys.net/31/395/2013/angeo-31-395-2013.pdf |
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