GEOS 2 electric field observations during a sudden commencement and subsequent substorms

Abstract

This paper presents and discusses electric field and plasma density data obtained by the GEOS 2 double probe experiment on March 22, 1979. The observation period encompasses a sudden storm commencement and two consecutive substorms. The E field data are compared with magnetic field recordings both at GEOS and on the ground. The influence of the solar wind on magnetospheric dynamics is studied with the help of additional data from IMP 8 and ISEE 3. The E field data, which were obtained when GEOS was in the dayside (front) of the magnetosphere, are grouped in transients, pulsations and underlying dc electric fields. We find that solar wind discontinuities cause strong electric field transients in the dayside magnetosphere. These transients are followed by Pc 4 oscillations of considerable amplitude. The data also show the existence of dc electric fields during buildup, onset and expansion phase of the two substorms. The combined observations by GEOS 2, ISEE 3, IMP 8 and ground‐based magnetometers provide information on propagation of transients in the magnetosphere, on the nature of large scale oscillations and on the overall convection pattern during periods when the interplanetary magnetic field has a negative Bz component.

Long-period geomagnetic pulsations caused by the solar wind negative pressure impulse on 22 March 1979 (CDAW-6)

“…At station 3, sinusoidal oscillations are recorded with a period of 240 s, the maximum amplitude is clearly seen further south of this, e.g. at v 5X9X The period and form of the oscillations is in good agreement with electric ®eld oscillations i Dcomponent) observed by GEOS-2 (Knott et al, 1985).…”

“…To identify with con®dence these oscillations requires: (1) simultaneous observations by a series of satellites in the outer magnetosphere and at an extended meridional chain of stations, and (2) studying time intervals not coincident with the active phase of a substorm which produces a number of disturbances, distorts the eigen-oscillations and makes their identi®cation dicult. These requirements were not fully met in Knott et al (1985) and Warnecke et al (1990) which probably did not permit the global oscillations to be observed unambiguously.…”

“…Oscillations at all stations of the chain were recorded over 25 min, which corresponds to duration of the oscillations recorded by the geostationary satellite GEOS-2 (Knott et al, 1985).…”

Electrodynamics in the duskside inner magnetosphere and plasmasphere during a super magnetic storm on March 13–15, 1989

“…The feature of the magnetic and electric field perturbations and high energy particle modulations during SCs in the inner magnetosphere has been well known (e.g., Knott et al, 1985;Laakso and Schmidt, 1989;Cahill et al, 1990;Blake et al, 1992;Li et al, 1993;Wygant et al, 1994;Wilson et al, 2001;Shinbori et al, 2004aShinbori et al, , 2004b. A case study of an SC event which occurred on March 24, 1991 observed by the CRRES satellite was reported by Wygant et al (1994), who showed that the electric and magnetic field perturbation with the bipolar waveform in the inner magnetosphere (L = 2.6) at the nightside (02:40 MLT) have large amplitude of about 80 mV/m and 140 nT, respectively.…”

Magnetospheric ULF Wave Phenomena Stimulated by SSC.

“…Actually, this picture of the magnetospheric PI generation and its transmission to low latitudes is the extrapolation of the Nishida-Tamao mechanism to the inner magnetosphere. The comparison of ssc electric transient in the magnetosphere with conjugated ground magnetic variations demonstrated ir/2 rotation of the signal in the ionosphere, typical for Alfven mode (Nishida, 1964;Knott et al, 1985). So, the observation at the geostationary satellite and on the ground indicate the possibility of the excitation of an Alfven pulse at the front of a compressional wave.…”