Characteristics of Thermal and Suprathermal Ions Associated with the Dayside Plasma Trough as Measured by the Dynamics Explorer Retarding Ion Mass Spectrometer

Authors

Jan Josef Sojka, Utah State UniversityFollow
Robert W. Schunk, Utah State UniversityFollow
J.F. E. Johnson
J. H. Waite
C. R. Chappell

Document Type

Article

Journal/Book Title/Conference

Journal of Geophysical Research: Space Physics

Volume

88

Issue

A10

Publisher

American Geophysical Union

Publication Date

1983

First Page

7895

Last Page

7911

Abstract

The retarding ion mass spectrometer (RIMS) instrument on Dynamics Explorer 1 has carried out high-altitude measurements of the polar wind. During an outbound pass through the outer plasmasphere and plasma trough at 0900 LT the RIMS instrument measured the detailed characteristics of the thermal and suprathermal ions. Three distinct populations were observed: (1) thermal ions (H⁺ and He⁺) with densities ranging from > 500 ions/cm³ to < 1 ion/cm³, temperatures around 2 eV (20,000° K), and H⁺/He⁺ density ratios of 2 to 4, (2) warm anisotropic plasma with densities ranging from 2 to 12 ions/cm³, temperatures between 10 and 15 eV, and H⁺/He⁺ density ratios of 0.1 to 6, and (3) thermal field-aligned H⁺ and He⁺ ion streams displaying both single stream and counterstreaming flow characteristics—the polar wind. These streaming ions display temperatures ≤ 1.5 eV and ≤ 2.0 eV for H⁺ and He⁺, respectively, and respective parallel drift velocities of < 30 km/s and < 15 km/s with an H⁺/He⁺ flux ratio of 3 to 10. Best-fitting techniques for the H⁺ and He⁺ streaming distributions indicate a supersonic flow, although the data cannot be interpreted unambiguously. These comprehensive measurements of thermal and suprathermal plasma characteristics are interpreted in terms of plasmasphere refilling processes.

Comments

Originally published by the American Geophysical Union. Abstract available online through the Journal of Geophysical Research: Space Physics.