A modeling study of ionospheric F2-region storm effects at low geomagnetic latitudes during 17-22 March 1990
We have presented a comparison between the modeled <I>Nm</I>F2 and <I>hm</I>F2, and <I>Nm</I>F2 and <I>hm</I>F2, which were observed in the low-latitude ionosphere simultaneously by the Kokubunji, Yamagawa, Okinawa, Manila, Vanimo, and Darwin ionosp...
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2006-05-01
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| Series: | Annales Geophysicae |
| Online Access: | https://www.ann-geophys.net/24/915/2006/angeo-24-915-2006.pdf |
| _version_ | 1828475169453113344 |
|---|---|
| author | A. V. Pavlov S. Fukao S. Kawamura |
| author_facet | A. V. Pavlov S. Fukao S. Kawamura |
| author_sort | A. V. Pavlov |
| collection | DOAJ |
| description | We have presented a comparison between the modeled <I>Nm</I>F2
and <I>hm</I>F2, and <I>Nm</I>F2 and <I>hm</I>F2, 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 <I>Nm</I>F2 observed over Manila during 17-22 March 1990. As a
result, the new physical mechanism of the nighttime <I>Nm</I>F2 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 <B><I>E</I></B>×<B><I>B</I></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 N<sub>2</sub> and O<sub>2</sub> promote
the equatorial anomaly enhancement during the predominant part of the
studied time period, however, the role of vibrationally excited N<sub>2</sub> and
O<sub>2</sub> 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 <I>Nm</I>F2 and <I>hm</I>F2, 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. |
| first_indexed | 2024-12-11T06:08:55Z |
| format | Article |
| id | doaj.art-85cd0c28f29f4008ba49281463d3e1ca |
| institution | Directory Open Access Journal |
| issn | 0992-7689 1432-0576 |
| language | English |
| last_indexed | 2024-12-11T06:08:55Z |
| publishDate | 2006-05-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Annales Geophysicae |
| spelling | doaj.art-85cd0c28f29f4008ba49281463d3e1ca2022-12-22T01:18:11ZengCopernicus PublicationsAnnales Geophysicae0992-76891432-05762006-05-012491594010.5194/angeo-24-915-2006A modeling study of ionospheric F2-region storm effects at low geomagnetic latitudes during 17-22 March 1990A. V. Pavlov0S. Fukao1S. Kawamura2Pushkov Institute of Terrestrial Magnetism, Ionosphere and Radio-Wave Propagation, Russian Academy of Science (IZMIRAN), Troitsk, Moscow Region, 142190, RussiaResearch Institute for Sustainable Humanosphere (RISH), Kyoto University, Kyoto, 611-0011, JapanNational Institute of Information and Communications Technology, 4-2-1, Nukui-kita, Koganei, Tokyo 184-8795, JapanWe have presented a comparison between the modeled <I>Nm</I>F2 and <I>hm</I>F2, and <I>Nm</I>F2 and <I>hm</I>F2, 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 <I>Nm</I>F2 observed over Manila during 17-22 March 1990. As a result, the new physical mechanism of the nighttime <I>Nm</I>F2 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 <B><I>E</I></B>×<B><I>B</I></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 N<sub>2</sub> and O<sub>2</sub> promote the equatorial anomaly enhancement during the predominant part of the studied time period, however, the role of vibrationally excited N<sub>2</sub> and O<sub>2</sub> 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 <I>Nm</I>F2 and <I>hm</I>F2, 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.https://www.ann-geophys.net/24/915/2006/angeo-24-915-2006.pdf |
| spellingShingle | A. V. Pavlov S. Fukao S. Kawamura A modeling study of ionospheric F2-region storm effects at low geomagnetic latitudes during 17-22 March 1990 Annales Geophysicae |
| title | A modeling study of ionospheric F2-region storm effects at low geomagnetic latitudes during 17-22 March 1990 |
| title_full | A modeling study of ionospheric F2-region storm effects at low geomagnetic latitudes during 17-22 March 1990 |
| title_fullStr | A modeling study of ionospheric F2-region storm effects at low geomagnetic latitudes during 17-22 March 1990 |
| title_full_unstemmed | A modeling study of ionospheric F2-region storm effects at low geomagnetic latitudes during 17-22 March 1990 |
| title_short | A modeling study of ionospheric F2-region storm effects at low geomagnetic latitudes during 17-22 March 1990 |
| title_sort | modeling study of ionospheric f2 region storm effects at low geomagnetic latitudes during 17 22 march 1990 |
| url | https://www.ann-geophys.net/24/915/2006/angeo-24-915-2006.pdf |
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