Abstract.This paper extends a recent study of eleclric field penetration into the inner magnetosphere observed by the Colnbined Release and Radiation Effects
The low-energy plasma analyzer on CRRES has detected significant fluxes of 10-eV to 30-keV electrons trapped on plasmaspheric field lines. On energyversus-time spectrograms these electrons appear as banded structures that can span the 2 < L < 6 range of magnetic shells. We present an example of banded electron structures, encountered in the nightside plasmasphere during the magnetically quiet January 30, 1991. Empirical analysis suggests that two clouds of low-energy electrons were injected from the plasma sheet to L < 4 on January 26 and 27 while the convective electric field was elevated. The energies of electrons in the first cloud were greater than those in the second. DMSP F8 measurements show that after the second injection, the polar cap potential rapidly decreased from >50 to <20 kV. Subsequent encounters with the lower-energy cloud on alternating CRRES orbits over the next 2 days showed a progressive, earthward movement of the electrons' inner boundary. Whistler and electron cyclotron harmonic emissions accompanied the most intense manifestations of cloud electrons. The simplest explanation of these measurements is that after initial injection, the Alfv•n boundary moved outward, leaving the cloud electrons on dosed drift paths. Subsequent fluctuations of the convective electric field penetrated the plasmasphere, transporting cloud elements inward. The magnetic shell distribution of electron temperatures in one of the banded structures suggests that radiative energy losses may be comparable in magnitude to gains due to adiabatic compression. Introduction This paper presents an example of "banded structures" of trapped electrons with energies of <30 keV encountered by the low-energy plasma analyzer (LEPA) aboard the Combined Release Radiation Effects Satellite (CRKES) on plasmaspheric magnetic shells (L < 4) during magnetically quiet intervals. We refer to these electron stmctUr es as "banded" because of their appearance on energy-versus-time spectrograms. Although other satellites, such as Explorer 45, Dynamics Explorer 1 (DE 1), and ISEE ! and 2, carried sensors capable of detecting electrons inn the appropriate energy range and passed through this region of space, we believe that this is the first report 0f observing low-keV electrons inside the plasmaspheke. When DE 1 passed through the ß plasmasphere, it Wa s generally traveling along rather than across magneti c shells. Because of their high apogees, the ISEE sateIIit 'es passed very quickly across the 2 < L _< 4 region; often at off-equatorial magnetic latitudes. Explorer 45, also known as the Small Scientific Satellite A (Sa-A), flew in a low-inclination orbit with apogee at a geocentric distance of 5.24 RE [Longanecker and Hoffman, 1973] . The main objective of the S3-A mission was to understand the relationship of ring current acceleration and transport to the dynamics of geomagnetic storms and substorms. Smith and Hoffman [1974] identified a class of 1-to 100-keV protons whose trajectories carry them well inside of the plasmapause during the mai...
An analytical model of the satellite photosheath is obtained in the presence of spacecraft charging. The combined potential is described by a combination of monopole and dipole contributions. This simple monopole-dipole model predicts the saddle point behavior found in computer simulations. Applications to daylight charging and sheath effects on particle measurements are described.
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