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 04:00:00 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), Journal Name: Journal of Geophysical Research; (United States) Vol. 98:A2; ISSN JGREA2; ISSN 0148-0227
• Country of Publication: United States
• Language: English

Related Subjects

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