An Alternative Interpretation of Ion Ring Distribution Observed by the S3-3 Satellite.
Abstract
Recently, theoretical interest has grown in possible plasma wave instabilities arising from free energy in auroral ion distributions, and a number of ion-mode instabilities have been identified. These instabilities typically rely on positive slopes in the ion's velocity distribution parallel (del f/del v(sub par) > 0) or perpendicular (del f/del v(sub perp) > 0) to the magnetic field. Upflowing ion beams generated by electrical potential drops along auroral field lines are obvious candidates for the parallel (beam) instability, while ion conics have been treated in the limit of the flute mode instability, assuming that a positive perpendicular gradient exists. However, ion conics are not responsible for the condition del f/del v(sub perp) > 0. Downflowing ion beam distributions can have del f/del v(sub perp) > 0 and therefore might lead to flute mode instability. Examples of both conics and downflowing beams are presented, showing that only the downflowing component leads to significant del f/del v(sub perp) > 0, while ion conics generally have del f/del v(sub perp) < 0 and are themselves stable to the flute mode.
Document Details
- Document Type
- Technical Report
- Publication Date
- May 15, 1985
- Accession Number
- ADA157655
Entities
People
- D. J. Gorney
Organizations
- The Aerospace Corporation