Short-wavelength electrostatic waves in the earth's magnetosheath

Journal Article · Fri Feb 01 04:00:00 EST 1985 · J. Geophys. Res.; (United States)

DOI:https://doi.org/10.1029/JA090iA02p01435· OSTI ID:5819194

Gallagher, D L

Recent observations with the ISEE 1 spacecraft have found electric field emissions in the dayside magnetosheath whose frequency spectrum is modulated at twice the spacecraft spin period. The upper frequency cutoff in the frequency-time spectrum of the emission has a characteristic parabola shape or ''festoon'' shape. The low-frequency cutoff ranges from 100 to 400 Hz, while the high-frequency limit ranges from about 1 to 4 kHz. The bandwidth is found to minimize for antenna orientations parallel to the wave vectors. The wave vector does not appear to be related to the local magnetic field, the plasma flow velocity, or the spacecraft-sun directions. The spacecraft observed frequency spectrum results from the spacecraft antenna response to the Doppler-shifted wave vector spectrum which exists in the plasma. Imposed constraints on the plasma rest frame wave vectors and frequencies indicate that emissions occur within the frequency range from about 150 Hz to 1 kHz, with wavelengths between about 40 and 600 m. These constraints strongly suggest that the festoon-shaped emissions are ion-acoustic waves. The small group velocity and k direction of the ion-acoustic mode are consistent with wave generation upstream at the bow shock and convection downstream to locations within the outer dayside magnetosheath.

• Research Organization: Physics Department, University of Alabama in Huntsville
• OSTI ID: 5819194
• Journal Information: J. Geophys. Res.; (United States), Journal Name: J. Geophys. Res.; (United States) Vol. 90:A2; ISSN JGREA
• Country of Publication: United States
• Language: English

Related Subjects

640203* -- Atmospheric Physics-- Magnetospheric Phenomena-- (-1987)
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
DISPERSION RELATIONS
EXPLORER SATELLITES
FREQUENCY DEPENDENCE
ION ACOUSTIC WAVES
ION WAVES
MAGNETOSHEATH
PLASMA WAVES
SATELLITES