Multi-spectral observations of flickering auroral chirps
Abstract
Flickering aurora is observed in the magnetic zenith as rapid oscillations (typically 2-20Hz) in auroral luminosity. We present observations of several examples of flickering auroral chirps, in which the flickering frequency decreases or increases over short time-scales. We have found that on these short time-scales there is a strong anti-correlation between flickering frequency and electron precipitation energy. This result supports the theory that flickering aurora and field-aligned bursts (FABs) are caused by resonant acceleration and deceleration of electrons by electromagnetic ion cyclotron (EMIC) waves. We have also found that the flickering electron precipitation was at a higher energy than the steady, non-flickering precipitation during these events. Our observations were made with the ASK (Auroral Structure and Kinetics) instrument, consisting of three highly-sensitive Electron-Multiplying CCD imagers and two photometers co-aligned on the magnetic zenith. The three cameras and two photometers are each equipped with a different narrow passband spectral filter. Ionospheric modelling combined with analysis of the ratios between observed emission brightnesses allows the energy of auroral electron precipitation to be determined. To the authors' knowledge these are the first multi-spectral observations of flickering aurora analysed in this way.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2009
- Bibcode:
- 2009AGUFMSM41B1714W
- Keywords:
-
- 2407 IONOSPHERE / Auroral ionosphere;
- 2451 IONOSPHERE / Particle acceleration;
- 2704 MAGNETOSPHERIC PHYSICS / Auroral phenomena;
- 2772 MAGNETOSPHERIC PHYSICS / Plasma waves and instabilities