Physical mechanism of strong negative storm effects in the daytime ionospheric F2 region observed with EISCAT
A self-consistent method for daytime F-region modelling was applied to EISCAT observations during two periods comprising the very disturbed days 3 April 1992 and 10 April 1990. The observed strong N<i><sub>e</sub></i> decrease at F2-layer heights originated from different...
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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/16/602/1998/angeo-16-602-1998.pdf |
| _version_ | 1818936104959606784 |
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| author | A. Mikhailov K. Schlegel |
| author_facet | A. Mikhailov K. Schlegel |
| author_sort | A. Mikhailov |
| collection | DOAJ |
| description | A self-consistent method for daytime F-region
modelling was applied to EISCAT observations during two periods comprising the
very disturbed days 3 April 1992 and 10 April 1990. The observed strong N<i><sub>e</sub></i>
decrease at F2-layer heights originated from different physical mechanisms in
the two cases. The negative F2-layer storm effect with an <i>N<sub>m</sub></i>F2
decrease by a factor of 6.4 on 3 April 1992 was produced by enhanced electric
fields (<strong>E</strong>≈85 mV/m) and strong downward plasma drifts,
but without any noticeable changes in thermospheric parameters. The increase of
the O<sup>+</sup> + N<sub>2</sub> reaction rate resulted in a strong enrichment
of the ionosphere with molecular ions even at F2-layer heights. The enhanced
electric field produced a wide mid-latitude daytime trough on 03 April 1992 not
usually observed during similar polarization jet events. The other strong
negative storm effect on 10 April 1990 with a complete disappearance of the
F2-layer maximum at the usual heights was attributed mainly to changes in
neutral composition and temperature. A small value for the shape parameter <i>S</i>
in the neutral temperature profile and a low neutral temperature at 120 km
indicate strong cooling of the lower thermosphere. We propose that this cooling
is due to increased nitric oxide concentration usually observed at these heights
during geomagnetic storms.<br><br><b>Key words.</b> Atmospheric composition and structure ·
Thermosphere · Ionosphere · Ion chemistry and composition · Atmosphere
interactions</p> |
| first_indexed | 2024-12-20T05:30:46Z |
| format | Article |
| id | doaj.art-fe1c574e78584dde8048da29806aa758 |
| institution | Directory Open Access Journal |
| issn | 0992-7689 1432-0576 |
| language | English |
| last_indexed | 2024-12-20T05:30:46Z |
| publishDate | 1998-05-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Annales Geophysicae |
| spelling | doaj.art-fe1c574e78584dde8048da29806aa7582022-12-21T19:51:45ZengCopernicus PublicationsAnnales Geophysicae0992-76891432-05761998-05-011660260810.1007/s00585-998-0602-zPhysical mechanism of strong negative storm effects in the daytime ionospheric F2 region observed with EISCATA. Mikhailov0K. Schlegel1Institute for Applied Geophysics, 129128 Rostokinskaya 9, Moscow, RussiaMax-Planck-Institut für Aeronomie, Max-Planck-Str. 2, D-37189 Katlenburg-Lindau, Germany Fax: +49 5556 979 240; e-mail: schlegel@linmpi.mpae.gwdg.deA self-consistent method for daytime F-region modelling was applied to EISCAT observations during two periods comprising the very disturbed days 3 April 1992 and 10 April 1990. The observed strong N<i><sub>e</sub></i> decrease at F2-layer heights originated from different physical mechanisms in the two cases. The negative F2-layer storm effect with an <i>N<sub>m</sub></i>F2 decrease by a factor of 6.4 on 3 April 1992 was produced by enhanced electric fields (<strong>E</strong>≈85 mV/m) and strong downward plasma drifts, but without any noticeable changes in thermospheric parameters. The increase of the O<sup>+</sup> + N<sub>2</sub> reaction rate resulted in a strong enrichment of the ionosphere with molecular ions even at F2-layer heights. The enhanced electric field produced a wide mid-latitude daytime trough on 03 April 1992 not usually observed during similar polarization jet events. The other strong negative storm effect on 10 April 1990 with a complete disappearance of the F2-layer maximum at the usual heights was attributed mainly to changes in neutral composition and temperature. A small value for the shape parameter <i>S</i> in the neutral temperature profile and a low neutral temperature at 120 km indicate strong cooling of the lower thermosphere. We propose that this cooling is due to increased nitric oxide concentration usually observed at these heights during geomagnetic storms.<br><br><b>Key words.</b> Atmospheric composition and structure · Thermosphere · Ionosphere · Ion chemistry and composition · Atmosphere interactions</p>https://www.ann-geophys.net/16/602/1998/angeo-16-602-1998.pdf |
| spellingShingle | A. Mikhailov K. Schlegel Physical mechanism of strong negative storm effects in the daytime ionospheric F2 region observed with EISCAT Annales Geophysicae |
| title | Physical mechanism of strong negative storm effects in the daytime ionospheric F2 region observed with EISCAT |
| title_full | Physical mechanism of strong negative storm effects in the daytime ionospheric F2 region observed with EISCAT |
| title_fullStr | Physical mechanism of strong negative storm effects in the daytime ionospheric F2 region observed with EISCAT |
| title_full_unstemmed | Physical mechanism of strong negative storm effects in the daytime ionospheric F2 region observed with EISCAT |
| title_short | Physical mechanism of strong negative storm effects in the daytime ionospheric F2 region observed with EISCAT |
| title_sort | physical mechanism of strong negative storm effects in the daytime ionospheric f2 region observed with eiscat |
| url | https://www.ann-geophys.net/16/602/1998/angeo-16-602-1998.pdf |
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