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Titolo:
Preliminary impulse of the geomagnetic storm sudden commencement of November 18, 1993
Autore:
Sastri, JH; Takeuchi, T; Araki, T; Yumoto, K; Tsunomura, S; Tachihara, H; Luehr, H; Watermann, J;
Indirizzi:
Kyoto Univ, Grad Sch Sci, Dept Geophys, Kyoto 6068502, Japan Kyoto Univ Kyoto Japan 6068502 h Sci, Dept Geophys, Kyoto 6068502, Japan Indian Inst Astrophys, Bangalore 560034, Karnataka, India Indian Inst Astrophys Bangalore Karnataka India 560034 , Karnataka, India Kyushu Univ, Dept Earth & Planetary Sci, Fukuoka 8128581, Japan Kyushu Univ Fukuoka Japan 8128581 Planetary Sci, Fukuoka 8128581, Japan Kakioka Magnet Observ, Ibaraki, Osaka 3150116, Japan Kakioka Magnet Observ Ibaraki Osaka Japan 3150116 i, Osaka 3150116, Japan Geoforschungszentrum Potsdam, D-14473 Potsdam, Germany Geoforschungszentrum Potsdam Potsdam Germany D-14473 73 Potsdam, Germany Danish Meteorol Inst, Solar Terr Phys Div, DK-2100 Copenhagen, Denmark Danish Meteorol Inst Copenhagen Denmark DK-2100 2100 Copenhagen, Denmark
Titolo Testata:
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
fascicolo: A3, volume: 106, anno: 2001,
pagine: 3905 - 3918
SICI:
0148-0227(20010301)106:A3<3905:PIOTGS>2.0.ZU;2-Z
Fonte:
ISI
Lingua:
ENG
Soggetto:
POLAR ELECTRIC-FIELDS; LOW-LATITUDE; F-REGION; EQUATORIAL ENHANCEMENT; IONOSPHERIC CURRENT; NUMERICAL-ANALYSIS; MAGNETIC EQUATOR; PLASMA; DRIFTS; MIDDLE;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
35
Recensione:
Indirizzi per estratti:
Indirizzo: Sastri, JH Kyoto Univ, Grad Sch Sci, Dept Geophys, Kyoto 6068502, Japan Kyoto Univ Kyoto Japan 6068502 Geophys, Kyoto 6068502, Japan
Citazione:
J.H. Sastri et al., "Preliminary impulse of the geomagnetic storm sudden commencement of November 18, 1993", J GEO R-S P, 106(A3), 2001, pp. 3905-3918

Abstract

The characteristics of the geomagnetic sudden commencement (SC) that occurred at 1211:30 UT on November 18, 1993, following an interval of prolonged geomagnetic quietness are! studied using high time resolution data of several magnetometer networks. We present the first results concerning the behavior of the preliminary reverse impulse (PRI) of the H component of the SC near the dip equator from simultaneous observations in different longitude (local time) sectors. It is found that the preliminary reverse impulse appeared only in the prenoon (0912 LT) sector very close to the magnetic equator(dip 0.6 degrees). At locations farther away (dip 6.0 degrees -7.2 degrees) but on the same meridian, the preliminary reverse impulse diminished in amplitude and led to a delayed onset of the main impulse BMI) of the SC. Thepreliminary reverse impulse is not apparent at locations close to the magnetic equator (dip 1.2 degrees -2.7 degrees) in either the afternoon (1300 LT) or the near-dusk (1740 LT) sectors. What is seen instead here is an unambiguous reduction in the rate of increase of H component coincident with the preliminary reverse impulse in the forenoon sector. HF Doppler radar measurements of F layer vertical plasma drift close to the magnetic equator (dip 4.9 degrees) near the dusk sector showed the SC-related disturbance to bea decrease in ambient upward drift with considerable temporal structure, which indicates the imposition of a westward electric field. The preliminaryreverse impulse is seen in the subauroral to polar region (MLAT 56.8 degrees -76 degrees) on the afternoon side simultaneous with that near the prenoon dip equator and with a conspicuous increase in amplitude and duration with latitude over MLAT range 66 degrees -76 degrees. Theoretical calculations suggest that the global current system set up by a pair of field-aligned currents at 80 degrees latitude and shifted to morningside (centers at 1300and 0300 LT) could, in general, account for the observed behavior of the preliminary reverse impulse, except in the dip equatorial region near dusk.

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Documento generato il 30/03/20 alle ore 13:12:57