Magnetic pulsations from 0. 1 to 4. 0 Hz and associated plasma properties in the earth's subsolar magnetosheath and plasma depletion layer

Journal Article · Mon Feb 01 00:00:00 EST 1993 · Journal of Geophysical Research; (United States)

DOI:https://doi.org/10.1029/92JA02197· OSTI ID:6787746

Anderson, B J ^[1]; Fuselier, S A ^[2]

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1. Johns Hopkins Univ., Laurel, MD (United States)
2. Lockheed Palo Alto Research Lab., CA (United States)

Dynamic spectral analysis covering frequencies 0.1 to 4.0 Hz has been applied to analyze Active Magnetospheric Particle Tracer Explorers CCE magnetic field data during periods of magnetospheric compressions when the spacecraft sampled the magnetosheath. Ion (H[sup +], He[sub 2+]) and electron data are used to identify regions, to monitor the upstream shock geometry, and to evaluate moments of the proton distribution. For quasi-perpendicular shock conditions, two distinctive band limited spectral types are found to characterize the majority of magnetosheath observations: (1) purely compressional fluctuations with F < 0.2 F[sub H][sup +] which are attributed to mirror waves (F and F[sub H][sup +] denote the wave frequency and proton gyrofrequency, respectively); and (2) 0.25-1.0 F[sub H][sup +] frequency purely transverse fluctuations that are often left hand polarized from 0.5-1.0 F[sub H][sup +] and are attributed to electromagnetic ion cyclotron (EMIC) waves. Mirror waves are associated with [beta][sub p] > 5 and T[sub [perpendicular]p]/T[sub [parallel]p] of 1.5 whereas EMIC waves occur for [beta][sub p] [le] 1 and T[sub [perpendicular]p]/T[sub [parallel]p] = 2.5 [minus]- 5 (the subscript p denotes quantities evaluated for protons). EMIC waves also occur for higher field strength and lower plasma densities than mirror waves, indicative of EMIC wave occurrence in the plasma depletion layer (PDL). The increased T[sub [perpendicular]p]/T[sub [parallel]p] during EMIC waves relative to periods of mirror waves is due to a decrease in T[sub [parallel]p] suggesting that the EMIC wave region has suffered a loss of particles in the parallel direction. A compilation of the temporal sequence of spectral structures shows that EMIC waves occur next to the magnetopause while mirror waves occur outside the region of EMIC waves. We conclude that there is a close relationship between EMIC waves in the sheath and the PDL. 31 refs., 7 figs., 4 tabs.

• OSTI ID: 6787746
• Journal Information: Journal of Geophysical Research; (United States), Vol. 98:A2; ISSN 0148-0227
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
MAGNETOSHEATH
PULSATIONS
SOLAR WIND
SHOCK WAVES
ANISOTROPY
DENSITY
DISTRIBUTION
ELECTRONS
FLUCTUATIONS
GYROFREQUENCY
HELIUM IONS
HYDROGEN IONS 1 PLUS
HZ RANGE
INTERPLANETARY MAGNETIC FIELDS
MAGNETOPAUSE
MILLI HZ RANGE
PARTICLES
PLASMA
PROTONS
BARYONS
CATIONS
CHARGED PARTICLES
ELEMENTARY PARTICLES
FERMIONS
FREQUENCY RANGE
HADRONS
HYDROGEN IONS
IONS
LEPTONS
MAGNETIC FIELDS
NUCLEONS
PHYSICAL PROPERTIES
SOLAR ACTIVITY
VARIATIONS
661320* - Auroral
Ionospheric
&amp; Magnetospheric Phenomena- (1992-)