Plasma structuring by the gradient drift instability at high latitudes and comparison with velocity shear driven processes

Journal Article · Fri Jun 01 04:00:00 EDT 1990 · Journal of Geophysical Research; (United States)

DOI:https://doi.org/10.1029/JA095iA06p07799· OSTI ID:5223515

Basu, Sunanda; MacKenzie, E ^[1]; Basu, S ^[2]; Coley, W R ^[3]; Sharber, J R ^[4]; Hoegy, W R ^[5]

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1. Emmanuel College, Boston, MA (USA)
2. Air Force Geophysics Lab., Hanscom AFB, MA (USA)
3. Univ. of Texas, Richardson (USA)
4. Southwest Research Inst., San Antonio, TX (USA)
5. NASA Goddard Space Flight Center, Greenbelt, MD (USA)

Specifically, by using noon-midnight and dawn-dusk orbits of the DE-2 satellite it was found possible to study the simultaneous density and electric field spectra of convecting large-scale plasma density enhancements in the polar cap known as patches in directions parallel and perpendicular to their antisunward convection. Distinct differences were noted in the behavior of the ac and dc electric field structure and short-scale (<125 m) density irregularities in these two mutually orthogonal directions perpendicular to the geomagnetic field. Structured plasma density enhancements in the auroral oval were found to have considerable power spectral density at these short scales in the presence of significant Pedersen and Hall conductances in the 10- to 20-mho range. While density irregularity amplitudes ({Delta}N/N){sub rms} were found to be as large as 15-20% using 8-s samples of the DE 2 data, the corresponding dc electric field fluctuation {Delta}E was found to be less than a few millivolts per meter for both patches and blobs. This ({Delta}N/N){sub RMS} vis-a-vis {Delta}E behavior for the gradient drift process provided a fairly dramatic contrast with velocity shear driven processes where the {Delta}E magnitudes were found to be at least an order of magnitude larger for the same levels of density irregularities. The results of this paper together with those of Basu et al. (1988a) provide fairly conclusive evidence for the existence of at least two generic classes of instabilities operating in the high-latitude ionosphere: one driven by large-scale density gradients in a homogeneous convection field with respect to the neutrals and the other driven by the structured convection field itself in an ambient ionosphere where density fluctuations are ubiquitous.

• OSTI ID: 5223515
• Journal Information: Journal of Geophysical Research; (United States), Journal Name: Journal of Geophysical Research; (United States) Vol. 95:A6; ISSN 0148-0227; ISSN JGREA
• Country of Publication: United States
• Language: English

Related Subjects

640201* -- Atmospheric Physics-- Auroral
Ionospheric
&amp; Magetospheric Phenomena
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
AURORAL OVAL
DRIFT INSTABILITY
EARTH ATMOSPHERE
ELECTRIC FIELDS
EXPLORER SATELLITES
F REGION
GEOGRAPHICAL VARIATIONS
GEOMAGNETIC FIELD
INSTABILITY
IONOSPHERE
LATITUDE EFFECT
MAGNETIC FIELDS
PLANETARY IONOSPHERES
PLASMA DENSITY
PLASMA INSTABILITY
PLASMA MICROINSTABILITIES
POLAR REGIONS
SATELLITES
SHEAR
VARIATIONS