Plasma waves in the distant magnetotail

Abstract

In this study we identify the principal types of plasma waves which occur in the distant magnetotail, and we investigate the relationship of these waves to simultaneous plasma and magnetic field measurements made on the same spacecraft. The observations used in this study are from the Imp 8 spacecraft, which passes through the magnetotail at radial distances ranging from about 23.1 to 46.3 Re. Three principal types of plasma waves are detected by Imp 8 in the distant magnetotail: broad band electrostatic noise, whistler mode magnetic noise bursts, and electrostatic electron cyclotron waves. The electrostatic noise is a broad band emission which occurs in the frequency range from about 10 Hz to a few kilohertz and is the most intense and frequently occurring type of plasma wave detected in the distant magnetotail. This noise is found in regions with large gradients in the magnetic field near the outer boundaries of the plasma sheet and in regions with large plasma flow speeds, 11Y km s -1, directed either toward or away from the earth. The whistler mode magnetic bursts observed by Imp 8 consist of nearly monochromatic tones which last from a few seconds to a few tens of seconds. These noise bursts occur in the same region as the broad band electrostatic noise, although much less frequently, and are thought to be associated with regions carrying substantial field-aligned currents. Electrostatic electron cyclotron waves are seldom detected by Imp 8 in the distant magnetotail. Although these waves occur very infrequently, they may be of considerable importance, since they have been observed in regions near the neutral sheet when the plasma is extremely hot.

Plasma Wave Observations with GEOTAIL Spacecraft.

“…The BEN are the most intense and most frequently detected electrostatic waves in the magnetotail as first reported by Gurnett et al (1976) from IMP-8 observations. The GEOTAIL-PWI measurement of BEN will provide additional information to that already obtained by previous spacecraft such as IMP-8 (Gurnett et al, 1976), ISEE-3 and ISEE-1 (Catell et al, 1986).…”

“…Intense broadband electrostatic noise (BEN) has been observed.not only in the near-Earth regions of the magnetosphere (Rodriguez and Gurnett, 1975;Anderson, 1984;Frank, 1977, 1978;Scarf et al, 1972;Gurnett et al, 1979;Catell et al, 1986) but also in the tail regions (Gurnett et al, 1976;Scarf et al, 1974Scarf et al, , 1984aNishida et al, 1985). The ISEE-3 spacecraft observed BEN in the magnetosheath, the lobe and the lowlatitude boundary layer (Scarf et al, 1984a), as well as in conjunction with sheath flux ropes (Kennel et al, 1986) and slow shocks .…”

A region of intense plasma wave turbulence on auroral field lines

“…in the distant magnetotail. Recently Gurnett et al [1976], using data from the IMP--8 spacecraft at geocentric radial distances from about 23.1 to 46.3 Re, have reported observations of broad-band electrostatic noise and.…”

“…Since the plasma at these altitudes is nearly collisionless some mechanism is needed to transfer the energy and momentum from the electrons to the protons. The [see Gurnett et al, 1976]. Since the anomalous resistivity varies as the square of the electric field strength (Sagdeev and Galeev, 19661 the field-aligned potential differences in the regions surveyed by The normalized frequency of occurrence of the broad-band.…”

Generation of the narrowband electrostatic noise in the geomagnetic tail: Geotail observations

“…The frequency spectra of these waves fell within the frequency range of 100 Hz to I kHz, which is completely different from that of broadband electrostatic noise (BEN) [Gurnett et al, 1976]. In light of the spectral feature of these emissions, Coroniti and …”