 |
| Titel |
A modeling study of ionospheric F2-region storm effects at low geomagnetic latitudes during 17-22 March 1990 |
| VerfasserIn |
A. V. Pavlov, S. Fukao, S. Kawamura |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
0992-7689
|
| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 24, no. 3 ; Nr. 24, no. 3 (2006-05-19), S.915-940 |
| Datensatznummer |
250015521
|
| Publikation (Nr.) |
 copernicus.org/angeo-24-915-2006.pdf |
|
|
|
|
|
| Zusammenfassung |
| We have presented a comparison between the modeled NmF2
and hmF2, and NmF2 and hmF2, which were observed in the low-latitude
ionosphere simultaneously by the Kokubunji, Yamagawa, Okinawa, Manila,
Vanimo, and Darwin ionospheric sounders, by the middle and upper atmosphere
(MU) radar during 17-22 March 1990, and by the Arecibo radar for the time
period of 20-22 March 1990. A comparison between the electron and ion
temperatures measured by the MU and Arecibo radars and those produced by the
model of the ionosphere and plasmasphere is presented. The empirical zonal
electric field, the meridional neutral wind taken from the HWM90 wind model,
and the NRLMSISE-00 neutral temperature and densities are corrected so that
the model results agree reasonably with the ionospheric sounder observations,
and the MU and Arecibo radar data. It is proved that the nighttime
weakening of the equatorial zonal electric field (in comparison with that
produced by the empirical model of Fejer and Scherliess (1997) or Scherliess
and Fejer (1999)), in combination with the corrected wind-induced plasma
drift along magnetic field lines, provides the development of the nighttime
enhancements in NmF2 observed over Manila during 17-22 March 1990. As a
result, the new physical mechanism of the nighttime NmF2 enhancement
formation close to the geomagnetic equator includes the nighttime weakening
of the equatorial zonal electric field and equatorward nighttime plasma
drift along magnetic field lines caused by neutral wind in the both
geomagnetic hemispheres. It is found that the latitudinal positions of the
crests depend on the E×B drift velocity
and on the neutral wind velocity. The relative role of the main mechanisms
of the equatorial anomaly suppression observed during geomagnetic storms is
studied for the first time in terms of storm-time variations of the model
crest-to-trough ratios of the equatorial anomaly. During most of
the studied time period, a total contribution from meridional neutral winds
and variations in the zonal electric field to the equatorial anomaly changes
is larger than that from geomagnetic storm disturbances in the neutral
temperature and densities. Vibrationally excited N2 and O2 promote
the equatorial anomaly enhancement during the predominant part of the
studied time period, however, the role of vibrationally excited N2 and
O2 in the development of the equatorial anomaly is not significant. The
asymmetries in the neutral wind and densities relative to the geomagnetic
equator are responsible for the north-south asymmetry in NmF2 and hmF2, and
for the asymmetry between the values of the crest-to-trough ratios of the
Northern and Southern Hemispheres. The model simulations provide evidence in
favor of an asymmetry in longitude of the energy input into the auroral
region of the Northern Hemisphere on 21 March 1990. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|