Understanding solar flares from optical observations
Abstract
During the impulsive phase of solar flares, both hard X-ray (HXR) and optical emissions exhibit fast temporal fluctuations detectable down to sub-second scales. This is usually ascribed to the propagation of beams of accelerated particles and to the dissipation of their energy in lower layers of the solar atmosphere. Although it is rather difficult to prove a temporal correlation between HXR and optical intensity variations, we discuss here some previous results and recent attempts. Namely in coordination with RHESSI observations, several GBO's started to detect fast optical variations in the H-alpha line. In addition to this, we also explore a possibility of using some other diagnostically relevant lines. The proper interpretation of coordinated HXR and optical observations further requires robust tools for radiation-hydrodynamical (RHD) forward modeling. We briefly describe a new 'hybrid' code which consists of RHD part and particle-simulation part. Short-duration beam heating (pulses) is modeled and we predict temporal fluctuations of HXR and selected optical and UV lines formed in chromospheric layers and in the transition region. Particularly the line asymmetries originating in a highly dynamical lower atmosphere of the flare can be used to diagnose the response of these layers to particle beams.
- Publication:
-
34th COSPAR Scientific Assembly
- Pub Date:
- 2002
- Bibcode:
- 2002cosp...34E1097H