Proton isotropy boundaries as measured on mid- and low-altitude satellites
Polar CAMMICE MICS proton pitch angle distributions with energies of 31-80 keV were analyzed to determine the locations where anisotropic pitch angle distributions (perpendicular flux dominating) change to isotropic distributions. We compared the positions of these mid-altitude isotropic distri...
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doaj-73d0b403e4c34d5cb45e0130e29625632020-11-25T02:27:14ZengCopernicus PublicationsAnnales Geophysicae0992-76891432-05762005-07-01231839184710.5194/angeo-23-1839-2005Proton isotropy boundaries as measured on mid- and low-altitude satellitesN. Yu. Ganushkina0T. I. Pulkkinen1M. V. Kubyshkina2V. A. Sergeev3E. A. Lvova4T. A. Yahnina5A. G. Yahnin6T. Fritz7Finnish Meteorological Institute, Space Research Division, FIN-00101 Helsinki, FinlandFinnish Meteorological Institute, Space Research Division, FIN-00101 Helsinki, FinlandInstitute of Physics, University of St.-Petersburg, St.-Petersburg, 198904, RussiaInstitute of Physics, University of St.-Petersburg, St.-Petersburg, 198904, RussiaInstitute of Physics, University of St.-Petersburg, St.-Petersburg, 198904, RussiaPolar Geophysical Institute, Apatity, Murmansk region, 184200, RussiaPolar Geophysical Institute, Apatity, Murmansk region, 184200, RussiaBoston University, Department of Astronomy, Boston, MA 02215, USAPolar CAMMICE MICS proton pitch angle distributions with energies of 31-80 keV were analyzed to determine the locations where anisotropic pitch angle distributions (perpendicular flux dominating) change to isotropic distributions. We compared the positions of these mid-altitude isotropic distribution boundaries (IDB) for different activity conditions with low-altitude isotropic boundaries (IB) observed by NOAA 12. Although the obtained statistical properties of IDBs were quite similar to those of IBs, a small difference in latitudes, most pronounced on the nightside and dayside, was found. We selected several events during which simultaneous observations in the same local time sector were available from Polar at mid-altitudes, and NOAA or DMSP at low-altitudes. Magnetic field mapping using the Tsyganenko T01 model with the observed solar wind input parameters showed that the low- and mid-altitude isotropization boundaries were closely located, which leads us to suggest that the Polar IDB and low-altitude IBs are related. Furthermore, we introduced a procedure to control the difference between the observed and model magnetic field to reduce the large scatter in the mapping. We showed that the isotropic distribution boundary (IDB) lies in the region where <i>R<sub>c</sub></i>/ρ~6, that is at the boundary of the region where the non-adiabatic pitch angle scattering is strong enough. We therefore conclude that the scattering in the large field line curvature regions in the nightside current sheet is the main mechanism producing isotropization for the main portion of proton population in the tail current sheet. This mechanism controls the observed positions of both IB and IDB boundaries. Thus, this tail region can be probed, in its turn, with observations of these isotropy boundaries.<p> <b>Keywords.</b> Magnetospheric physics (Energetic particles, Precipitating; Magnetospheric configuration and dynamics; Magnetotail)https://www.ann-geophys.net/23/1839/2005/angeo-23-1839-2005.pdf |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
N. Yu. Ganushkina T. I. Pulkkinen M. V. Kubyshkina V. A. Sergeev E. A. Lvova T. A. Yahnina A. G. Yahnin T. Fritz |
spellingShingle |
N. Yu. Ganushkina T. I. Pulkkinen M. V. Kubyshkina V. A. Sergeev E. A. Lvova T. A. Yahnina A. G. Yahnin T. Fritz Proton isotropy boundaries as measured on mid- and low-altitude satellites Annales Geophysicae |
author_facet |
N. Yu. Ganushkina T. I. Pulkkinen M. V. Kubyshkina V. A. Sergeev E. A. Lvova T. A. Yahnina A. G. Yahnin T. Fritz |
author_sort |
N. Yu. Ganushkina |
title |
Proton isotropy boundaries as measured on mid- and low-altitude satellites |
title_short |
Proton isotropy boundaries as measured on mid- and low-altitude satellites |
title_full |
Proton isotropy boundaries as measured on mid- and low-altitude satellites |
title_fullStr |
Proton isotropy boundaries as measured on mid- and low-altitude satellites |
title_full_unstemmed |
Proton isotropy boundaries as measured on mid- and low-altitude satellites |
title_sort |
proton isotropy boundaries as measured on mid- and low-altitude satellites |
publisher |
Copernicus Publications |
series |
Annales Geophysicae |
issn |
0992-7689 1432-0576 |
publishDate |
2005-07-01 |
description |
Polar CAMMICE MICS proton pitch angle distributions with
energies of 31-80 keV were analyzed to determine the
locations where anisotropic pitch angle distributions
(perpendicular flux dominating) change to isotropic
distributions. We compared the positions of these mid-altitude
isotropic distribution boundaries (IDB) for different activity
conditions with low-altitude isotropic boundaries (IB) observed
by NOAA 12. Although the obtained statistical properties of IDBs
were quite similar to those of IBs, a small difference in
latitudes, most pronounced on the nightside and dayside, was
found. We selected several events during which simultaneous
observations in the same local time sector were available from
Polar at mid-altitudes, and NOAA or DMSP at low-altitudes.
Magnetic field mapping using the Tsyganenko T01 model with the
observed solar wind input parameters showed that the low- and
mid-altitude isotropization boundaries were closely located,
which leads us to suggest that the Polar IDB and low-altitude
IBs are related. Furthermore, we introduced a procedure to control
the difference between the observed and model magnetic field to
reduce the large scatter in the mapping. We showed that the
isotropic distribution boundary (IDB) lies in the region where
<i>R<sub>c</sub></i>/ρ~6, that is at the boundary of the region
where the non-adiabatic pitch angle scattering is strong enough.
We therefore conclude that the scattering in the large field
line curvature regions in the nightside current sheet is the
main mechanism producing isotropization for the main portion
of proton population in the tail current sheet. This mechanism
controls the observed positions of both IB and IDB boundaries.
Thus, this tail region can be probed, in its turn, with
observations of these isotropy boundaries.<p>
<b>Keywords.</b> Magnetospheric physics (Energetic particles,
Precipitating; Magnetospheric configuration and dynamics;
Magnetotail) |
url |
https://www.ann-geophys.net/23/1839/2005/angeo-23-1839-2005.pdf |
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AT nyuganushkina protonisotropyboundariesasmeasuredonmidandlowaltitudesatellites AT tipulkkinen protonisotropyboundariesasmeasuredonmidandlowaltitudesatellites AT mvkubyshkina protonisotropyboundariesasmeasuredonmidandlowaltitudesatellites AT vasergeev protonisotropyboundariesasmeasuredonmidandlowaltitudesatellites AT ealvova protonisotropyboundariesasmeasuredonmidandlowaltitudesatellites AT tayahnina protonisotropyboundariesasmeasuredonmidandlowaltitudesatellites AT agyahnin protonisotropyboundariesasmeasuredonmidandlowaltitudesatellites AT tfritz protonisotropyboundariesasmeasuredonmidandlowaltitudesatellites |
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