On the generation of the pulsating aurora by the loss cone driven whistler instability in the equatorial region

Journal Article · Sun Apr 01 00:00:00 EST 1990 · Journal of Geophysical Research; (United States)

DOI:https://doi.org/10.1029/JA095iA04p03893· OSTI ID:5152405

Huang, L; Hawkins, J G; Lee, L C ^[1]

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1. Univ. of Alaska, Fairbanks (United States)

Whistler waves are believed to play an important role in the generation of the pulsating aurora. Calculations in the literature show that either a loss cone or a thermal anisotropy in the hot plasma component of the magnetosphere can lead to the generation of incoherent whistler waves. In this paper, the authors have calculated the characteristics of incoherent whistler mode waves generated along the L = 5 geomagnetic field line, and considered the implications for the pulsating aurora if these waves play an important role in the pulsation mechanism. For the loss cone driven whistler instability, the growth rate along the L = 5 field line is largest just above the ionosphere where the loss cone angle is also large. However, the total amplification factor is actually much larger near the equator due to the more gradual magnetospheric variations and the smaller group velocity in this region. Thus, the largest wave growth from this process is expected in the same location where pitch angle scattering is believed to occur during auroral pulsations. The peak growth rate at the equator occurs at approximately 100 Hz, corresponding to {approximately} 1% of the local electron cyclotron frequency. This frequency is much smaller than the peak growth rate frequency at altitudes nearer to the ionosphere on the L = 5 field line. It is also in contrast to the frequently stated assumption that the whistler instability results in wave generation near the electron cyclotron frequency.

• DOE Contract Number: FG06-86ER13530
• OSTI ID: 5152405
• Journal Information: Journal of Geophysical Research; (United States), Vol. 95:A4; ISSN 0148-0227
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
AURORAE
PULSATIONS
ANISOTROPY
AURORAL OVAL
CYCLOTRON FREQUENCY
EARTH MAGNETOSPHERE
EQUATOR
FLUCTUATIONS
GEOMAGNETIC FIELD
IONOSPHERE
LOSS CONE
MAGNETIC BAYS
MORPHOLOGY
VARIATIONS
WHISTLER INSTABILITY
WHISTLERS
EARTH ATMOSPHERE
ELECTROMAGNETIC RADIATION
INSTABILITY
MAGNETIC FIELDS
NOISE
PLANETARY IONOSPHERES
PLASMA INSTABILITY
PLASMA MACROINSTABILITIES
RADIATIONS
RADIO NOISE
RADIOWAVE RADIATION
640201* - Atmospheric Physics- Auroral
Ionospheric
& Magetospheric Phenomena