Propagation of Shear Alfven Wave Packets Near the Ion Cyclotron Frequency.
Abstract
Alfven waves in the auroral ionosphere are the subject of renewed interest. Recent measurements by both the Freja and FAST satellites indicate an association between localized field-aligned current structures and low-frequency electromagnetic field perturbations. These current structures are observed to have perpendicular widths comparable to the electron inertial length, δ=c/ω_pe. A localized perturbation of such a current channel on a time scale less than the ion cyclotron period will result in the excitation of a shear Alfven wave packet comprising a spectrum of k_⊥ values. To model this process in a laboratory plasma, we draw a field-aligned electron current to a wire mesh disk with radius, r_disk=δ, and modulate this current with an RF tone burst. The center frequency of the burst is less than the ion cyclotron frequency. We report here on the temporal and spatial evolution of such a wave packet. This study is carried out at UCLA in the LArge Plasma Device (LAPD.)
- Publication:
-
APS Division of Plasma Physics Meeting Abstracts
- Pub Date:
- November 1997
- Bibcode:
- 1997APS..DPPbMP117V