Recent Observations of Low-Energy Charged Particles in the Earth’s Magnetosphere

Abstract

-his research was supSpace Administration --of the Magnetosphere, Distribution of this document is unlimited.2 Ai3STFWTSeveral recent observations of low-energy proton and e l e c t r o n i n t e n s i t i e s within t h e energy range -100 eV to 50 keV i n t h e e a r t h ' s r a d i a t i o n zones with a s e n s i t i v e array of e l e c t r o s t a t i c analyzers borne on t h e e a r t h -s a t e l l i t e OGO 3 during mid-1966 a r e summarized. Measurements of charged p a r t i c l e s of t h e e x t r a t e r r e s t r i a l r i n g current during a moderate geomagnetic storm, of t h e low-energy proton and e l e c t r o n d i s t r i b u t i o n s i n t h e v i c i n i t y of t h e midnight 'trappingboundary' near t h e magnetic equatorial. plane, and of upper limits for proton and i o n (100 eV < -< 50 keV) energy f l u x e s deep within t h e inner r a d i a t i o n zone a r e presented together with several introductory comments concerning t h e morphology of t h e omnidirectional i n t e n s i t i e s of energetic e l e c t r o n s (E > 40 keV, > 230 keV and > 1.6 MeV) a t t h e magnetic equator i n t h e outer r a d i a t i o n zone. INTRODUCTIONA l a r g e c o l l e c t i o n of d e t a i l e d observations of energetic charged p a r t i c l e s within t h e v a s t region e n c i r c l i n g t h e e a r t h which i s dominated by t h e geomagnetic f i e l d has been acquired since t h e i n i t i a l discovery of intense fluxes of energetic protons and e l e c t r o n s i n t h e s e regions, t h e inner and outer r a d i a t i o n zones, with earths a t e l l i t e measurements i n 1958.observations of electrons E 2 10 keV and of protons E 2 100 key with instrumentation borne on earth-orbiting s a t e l l i t e s a t low and high a l t i t u d e s , -several hundred kilometers t o 30have been published over t h e p a s t several years [Van AJ-len, 1963; O'Brien, 1964a;Shabansky, 1965;Hess, 1965; Frank, 1965al. d i r e c t e d toward d e t a i l e d s t u d i e s of e l e c t r o n and proton i n t e n s i t i e s i n t h e above energy ranges within t h e e a r t h ' s r a d i a t i o n zones, lower energy charged p a r t i c l e s with energies E < 10 keV dominate t h e s e regions i n terms of energy d e n s i t i e s and number d e n s i t i e s . For example, t h e r a t i o s of t h e number d e n s i t i e s and energy d e n s i t i e s of t h e oftenobserved e l e c t r o n (E > 1 MeV) i n t e n s i t i e s i n t h e h e m t of t h e outer r a d i a t i o n zone near t h e magnetic equatorial plane a t 4.5 t o t h ecorresponding number and energy d e n s i t i e s of e l e c t r o n s (E 5 10 keV) axe frequently -3 X 10 and 2 X 10-, respectively. Although t h e s e energetic Current reviews concerning t h e (%, e a r t h r a d i u s ) ,Although t h e major f r a c t i o n of t h e l i t e r a t u r e has been Tu Tu -6 3 4 charged p a r t i c l e d i s t r i b u t i o n s have been and a r e p r e s e n t l y being thoroughly surveyed v i a i n s i t u measurements, t h e observations...

Two types of ELF hiss observed at Varanasi, India

“…In deriving this condition, the contribution of relativistic eect has been neglected which leads to a slight decrease in the frequency range of unstable waves (Sazhin, 1991). The observation of electrons with A>0 in the equatorial magnetosphere (Frank, 1968;Bahnsen et al, 1985) supports the idea of wave ampli®cation through wave particle interaction. Soloman et al (1988) have calculated the value of anisotropy A from the¯ux data and they have shown that A>A c for the reduced wave frequency x < 0.4.…”

Two-dimensional Chapman-Ferraro Problem with neutral sheet: 1. The boundary

“…As at least one large sink for electrons (the auroral arcs) is known to be in operation on the nightside, and others may exist (e.g., asymmetric ring currents), it is probable that the behavior of protons is a better indication of the nightside motion of flux tubes. Frank [1967] also reports different behavior of the two types of particles; the proton spectrum hardens with increasing depth in the magnetosphere, as might be expected from compression by inward motion of flux tubes. The electron spectrum, on the other hand, becomes softer.…”

Observations of charged particle precipitation into the auroral zone

“…For example, the event cen- A correspondingly severe decrease of average electron energy with radial distance near the magnetic equator is located in the earthward edge of the plasma sheet [cf. Frank, 1968aFrank, , b, 1971aVasyliunas, 1968;Schield and Franlc, 1970]. Since this distant gradient is a single decrease of average electron energy with decreasing geocentric radial distance, a simple mapping of this feature to auroral zone altitudes would obviously yield only one side of the inverted 'V' substructure displayed in the auroral E-t spectrograms.…”