The size of the auroral belt during magnetic storms
Using the auroral boundary index derived from DMSP electron precipitation data and the <i>Dst</i> index, changes in the size of the auroral belt during magnetic storms are studied. It is found that the equatorward boundary of the belt at midnight expands equatorward, reaching its low...
| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
1998-05-01
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| Series: | Annales Geophysicae |
| Online Access: | https://www.ann-geophys.net/16/566/1998/angeo-16-566-1998.pdf |
| _version_ | 1811196544096927744 |
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| author | N. Yokoyama Y. Kamide H. Miyaoka |
| author_facet | N. Yokoyama Y. Kamide H. Miyaoka |
| author_sort | N. Yokoyama |
| collection | DOAJ |
| description | Using the auroral boundary index derived from
DMSP electron precipitation data and the <i>Dst</i> index, changes in the size
of the auroral belt during magnetic storms are studied. It is found that the
equatorward boundary of the belt at midnight expands equatorward, reaching its
lowest latitude about one hour before <i>Dst</i> peaks. This time lag depends
very little on storm intensity. It is also shown that during magnetic storms,
the energy of the ring current quantified with <i>Dst</i> increases in
proportion to <i>L<sub>e</sub></i><sup>–3</sup>, where <i>L<sub>e</sub></i> is
the <i>L</i>-value corresponding to the equatorward boundary of the auroral belt
designated by the auroral boundary index. This means that the ring current
energy is proportional to the ion energy obtained from the earthward shift of
the plasma sheet under the conservation of the first adiabatic invariant. The
ring current energy is also proportional to <i>E<sub>mag</sub></i>, the total
magnetic field energy contained in the spherical shell bounded by <i>L<sub>e</sub></i>
and <i>L<sub>eq</sub></i>, where <i>L<sub>eq</sub></i> corresponds to the
quiet-time location of the auroral precipitation boundary. The ratio of the ring
current energy <i>E<sub>R</sub></i> to the dipole energy <i>E<sub>mag</sub></i>
is typically 10%. The ring current leads to magnetosphere inflation as a result
of an increase in the equivalent dipole moment.<br><br><b>Key words.</b> Ionosphere (Auroral ionosphere) ·
Magnetospheric physics (Auroral phenomena; storms and substorms)</p> |
| first_indexed | 2024-04-12T01:00:42Z |
| format | Article |
| id | doaj.art-f0724eb0e83644cb95879b637b6f9d6c |
| institution | Directory Open Access Journal |
| issn | 0992-7689 1432-0576 |
| language | English |
| last_indexed | 2024-04-12T01:00:42Z |
| publishDate | 1998-05-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Annales Geophysicae |
| spelling | doaj.art-f0724eb0e83644cb95879b637b6f9d6c2022-12-22T03:54:29ZengCopernicus PublicationsAnnales Geophysicae0992-76891432-05761998-05-011656657310.1007/s00585-998-0566-zThe size of the auroral belt during magnetic stormsN. Yokoyama0Y. Kamide1H. Miyaoka2Solar-Terrestrial Environment Laboratory, Nagoya University, Toyokawa 442, JapanSolar-Terrestrial Environment Laboratory, Nagoya University, Toyokawa 442, JapanNational Institute of Polar Research, Tokyo 173, JapanUsing the auroral boundary index derived from DMSP electron precipitation data and the <i>Dst</i> index, changes in the size of the auroral belt during magnetic storms are studied. It is found that the equatorward boundary of the belt at midnight expands equatorward, reaching its lowest latitude about one hour before <i>Dst</i> peaks. This time lag depends very little on storm intensity. It is also shown that during magnetic storms, the energy of the ring current quantified with <i>Dst</i> increases in proportion to <i>L<sub>e</sub></i><sup>–3</sup>, where <i>L<sub>e</sub></i> is the <i>L</i>-value corresponding to the equatorward boundary of the auroral belt designated by the auroral boundary index. This means that the ring current energy is proportional to the ion energy obtained from the earthward shift of the plasma sheet under the conservation of the first adiabatic invariant. The ring current energy is also proportional to <i>E<sub>mag</sub></i>, the total magnetic field energy contained in the spherical shell bounded by <i>L<sub>e</sub></i> and <i>L<sub>eq</sub></i>, where <i>L<sub>eq</sub></i> corresponds to the quiet-time location of the auroral precipitation boundary. The ratio of the ring current energy <i>E<sub>R</sub></i> to the dipole energy <i>E<sub>mag</sub></i> is typically 10%. The ring current leads to magnetosphere inflation as a result of an increase in the equivalent dipole moment.<br><br><b>Key words.</b> Ionosphere (Auroral ionosphere) · Magnetospheric physics (Auroral phenomena; storms and substorms)</p>https://www.ann-geophys.net/16/566/1998/angeo-16-566-1998.pdf |
| spellingShingle | N. Yokoyama Y. Kamide H. Miyaoka The size of the auroral belt during magnetic storms Annales Geophysicae |
| title | The size of the auroral belt during magnetic storms |
| title_full | The size of the auroral belt during magnetic storms |
| title_fullStr | The size of the auroral belt during magnetic storms |
| title_full_unstemmed | The size of the auroral belt during magnetic storms |
| title_short | The size of the auroral belt during magnetic storms |
| title_sort | size of the auroral belt during magnetic storms |
| url | https://www.ann-geophys.net/16/566/1998/angeo-16-566-1998.pdf |
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