Evidence for Oscillating Two Stream Instability and Spatial Collapse of Langmuir waves in a Solar Type II Radio Burst Source Region
Abstract
We present the high time resolution, in situ wave observations of Langmuir waves, obtained by the STEREO spacecraft in the source region of a solar type II radio burst. We show that these waves, excited probably by an electron beam accelerated by the coronal mass ejection (CME) driven super-critical quasi-perpendicular interplanetary shock into its upstream solar wind, occur as coherent localized magnetic field aligned, one dimensional wave packets with durations of a few milliseconds and peak intensities well in excess of the threshold for strong turbulence processes. We also show that these wave packets provide what is believed to be the first evidence for a type II burst for: (a) the four-wave interaction called the oscillating two stream instability (OTSI) involving the Langmuir wave, the counter streaming up- and down-shifted sidebands, and an ion sound wave, (b) collapsing Langmuir solitons formed as a result of OTSI, and (c) a three wave interaction, which results in the excitation of the electromagnetic waves at the second harmonic of the electron plasma frequency, as a result of the merging of counter-streaming up- and down-shifted sidebands. The implication of these observations is that the OTSI and related strong turbulence processes probably play very important roles in excitation of electromagnetic waves at the fundamental and higher harmonics of the electron plasma frequency, as well as in stabilization of electron beams so that they can survive over large distances in the upstream regions of the interplanetary shocks.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMSH23B3386G
- Keywords:
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- 7829 Kinetic waves and instabilities;
- SPACE PLASMA PHYSICS;
- 7845 Particle acceleration;
- SPACE PLASMA PHYSICS;
- 7846 Plasma energization;
- SPACE PLASMA PHYSICS;
- 7851 Shock waves;
- SPACE PLASMA PHYSICS