CRRES Plasma Wave Observations during Quiet Times, during Geomagnetic Disturbances, and during Chemical Releases

Abstract

The Combined Release and Radiation Effects Satellite (CRRES) was launched July 25, 1990, into an 18 degree inclination orbit with a 350 km perigee altitude, a 6.3 Re geocentric apogee distance, and an orbital period of 9.9 hours. During the nearly 15 months period that CRRES operated, the Plasma Wave Experiment (PWE) collected much valuable data on the plasma wave environment in the plasmasphere and inner magnetosphere during quiet times, during geomagnetica1ly disturbed periods, and during the high altitude chemical releases.The detection of upper hybrid resonance (UHR) frequency emissions provided measurements of the electron number density from which the structure and dynamics of the plasmasphere and plasmapause could be determined as well as the in situ density profiles during the high altitude chemical releases. Frequently the number density profiles showed rapid variations and these were observed simultaneously with enhanced very low frequency electric field fluctuations. Plasmaspheric hiss was usually contained within the plasmasphere and chorus usually resided outside the plasmapause. Enhancements in the plasmaspheric hiss intensity above the lower hybrid resonance frequency occurred for passes well away from the geomagnetic equator. Increased plasmaspheric hiss intensities also occurred for local increases in plasma density within the plasmasphere. Occasionally ELF hiss bands were observed both inside and outside the plasmapause. Both electromagnetic whistler-mode chorus and electrostatic electron cyclotron harmonic (ECH) wave intensities increased dramatically during geomagnetically disturbed periods. Strong enhancements in the ECH wave intensities also occurred near the geomagnetic equator for both quiet and disturbed periods. A narrow band of low frequency electromagnetic waves frequently was observed associated with either plasmapause crossings or with the onsets of strong ECH waves.Many plasma wave instabilities were detected during the CRRES high altitude chemical releases carried out in January and February 1991. A low-frequency burst of electromagnetic radiation was observed as the leading edge of the expanding ion cloud moved over the spacecraft for all of the releases. Strong low-frequency whistler-mode emissions were observed inside the clouds for the releases done closest to earth. For all 73 of the releases, strong low-frequency electrostatic emissions were observed which usually continued until well after the magnetic field had returned to its pre-release value. Strong broadband electrostatic emissions were observed when the electron density in the cloud returned to ambient levels for many of the releases. Enhanced emission lines at the electron cyclotron frequency, the upper hybrid resonance frequency, or the ion plasma frequency could be observed at times in the various releases.

Substorm dependence of chorus amplitudes: Implications for the acceleration of electrons to relativistic energies

“…The longdashed line represents the local lower hybrid resonance frequency fLHR, the dashed lines represent 0.1fce and 0.5fce, and the dotted lines represent harmonics of the electron gyrofrequency 2000 UT at frequencies near 10 kHz. These emissions could be the result of magnetospherically reflected whistlers [e.g.,Thorne and Horne, 1994] or could be due to chorus waves leaking into the plasmasphere[Anderson, 1994].Enhanced electron cyclotron harmonic (ECH) waves are seen between 2025 UT and 2115 UT. These waves, which propagate between the harmonics of the electron gyrofrequency, are substorm-dependent and tend to be confined to the equatorial region [Meredith et al, 2000].…”

CLUSTER and IMAGE: New Ways to Study the Earth’s Plasmasphere

“…Launched in 1996, this spacecraft followed CRRES, ISEE 1, and others (Anderson 1994), by providing excellent surveys of wave activity over a wide range of frequencies. At this stage, radio instruments as well as the corresponding data interpretation had evolved into true remote sensing techniques.…”

“…It also contributed to the study of waves in the plasmasphere by detecting many different kinds of waves over a wide frequency range (see Fig. 11 and, e.g., Anderson 1994). Yet all these missions, however sophisticated their instruments, suffered from the fact that the measurements were made locally.…”