Strong electron bidirectional anisotropies in the distant tail: ISEE 3 observations of polar rain

Journal Article · Thu May 01 04:00:00 EDT 1986 · J. Geophys. Res.; (United States)

DOI:https://doi.org/10.1029/JA091iA05p05637· OSTI ID:5648448

Baker, D N; Bame, S J; Feldman, W C; Gosling, J T; Zwickl, R D; Slavin, J A; Smith, E J

A detailed observational treatment of bidirectional electrons (--50 to 50 eV)in the distant magnetotail (r-italicapprox. >100 R-italic/sub E-italic/) is presented. It is found that electrons in this energy range commonly exhibit strong, field-aligned anisotropies in the tail lobes. Because of large tail motions, the ISEE 3 data provide extensive sampling of both the north and south lobes in rapid succession. These data demonstrate directly the strong asymmetries that exist between the north and south lobes at any one time. The bidirectional fluxes are found to occur predominantly in the lobe directly connected to the sunward interplanetary magnetic field in the open magnetosphere model (north lobe for away sectors and south lobe for toward sectors). Electron anisotropy and magnetic field data are presented which show the transition from unidirectional (sheath) electron populations to bidirectional (lobe) populations. Thus we demonstrate the open nature of the distant magnetopause and show that the source of the higher-energy, bidirectional lobe electrons is the tailward directed electron heat flux population in the distant magnetosheath. Taken together, the present evidence suggests that the bidirectional electrons that we observe in the distant tail are closely related to the polar rain electrons observed previously at lower altitudes. Furthermore, these data provide strong evidence that the distant tail is composed largely of open magnetic field lines in contradistinction to some recently advanced models.

• Research Organization: Los Alamos National Laboratory, Los Alamos, New Mexico
• OSTI ID: 5648448
• Journal Information: J. Geophys. Res.; (United States), Journal Name: J. Geophys. Res.; (United States) Vol. 91:A5; ISSN JGREA
• Country of Publication: United States
• Language: English

Related Subjects

640203* -- Atmospheric Physics-- Magnetospheric Phenomena-- (-1987)
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
EARTH ATMOSPHERE
EARTH MAGNETOSPHERE
ELECTRON DRIFT
EXPLORER SATELLITES
HEAT FLUX
INTERPLANETARY MAGNETIC FIELDS
MAGNETIC FIELDS
MAGNETOSHEATH
MAGNETOTAIL
SATELLITES
SOLAR ACTIVITY
SOLAR WIND