Wave intensifications near the electron cyclotron frequency within the polar cusp

Journal Article · Tue May 01 00:00:00 EDT 1990 · Journal of Geophysical Research; (United States)

DOI:https://doi.org/10.1029/JA095iA05p06493· OSTI ID:5048056

Farrell, W M; Gurnett, D A ^[1]; Menietti, J D; Wong, H K; Lin, C S; Burch, J L ^[2]

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1. Univ. of Iowa, Iowa City (United States)
2. Southwest Research Inst., San Antonio, TX (United States)

As DE 1 flew through the polar cusp, enhanced narrowband electrostatic waves were sometimes observed just above the electron cyclotron frequency, f{sub ce}. In this report, the authors present wave and particle measurements from three representative cusp transits in order to characterize these signals and understand the conditions that favor their generation. In these representative cases, narrowband emission intensifications occurred at frequencies between 1.1 to 1.3 f{sub ce}. The emission intensities ranged between 5 {times} 10{sup {minus}14} to 10{sup {minus}12} V{sup 2}/(m{sup 2} Hz), such waves being 50 to 1,000 times greater than the narrowbanded cyclotron-related signal levels detected in adjacent regions. Simultaneously occurring with the wave enhancements were energetic cusp electrons with energies extending up to about 500 eV. It was found that the form of the local cusp electron velocity distribution had a direct influence on the wave spectral character. A preliminary study indicates that electron beams in the cusp can generate the enhanced signals, although generation by an anisotropic warm component cannot be ruled out. Based on an examination of many cusp transits, the occurrence of these enhanced signals appeared to have some dependency on Kp index, indicating that increased particle flows seem to affect their generation. Although the exact wave/particle coupling mechanism resonsible for these enhancements is difficult to identify, it is evident that the generation is directly related to the energetic cusp electrons.

• OSTI ID: 5048056
• Journal Information: Journal of Geophysical Research; (United States), Vol. 95:A5; ISSN 0148-0227
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
POLAR CUSP
PLASMA WAVES
CYCLOTRON FREQUENCY
EARTH MAGNETOSPHERE
ELECTRON BEAMS
ELECTRONS
EXPLORER SATELLITES
MAGNETOSHEATH
MASS TRANSFER
BEAMS
EARTH ATMOSPHERE
ELEMENTARY PARTICLES
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LEPTON BEAMS
LEPTONS
PARTICLE BEAMS
SATELLITES
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