Previous abstract Next abstract

Session 1 - Chromosphere, Corona, Flares.
Display session, Friday, June 27
Ballroom B, Chair: Charles Kankelborg

[1.75] Preflare Event and Flare: Successive Stages of a Single Physical Process in a System of Intercommunicating Current Sheets

A. I. Verneta (ZAO Comp. and Astron. Inst. MSU, Russia)

A part of solar flares is accompanied by preflare events (PFEs). Typically a preflare event is not at a flare site and does not reach a flare brightness. Various schemes of a connection between PFEs and flares were discussed by different authors. I suggest the following scenario. In a complex magnetic configuration several current sheets form and exist in different places. At an appropriate moment a process of a quasistationary magnetic reconnection in one of these sheets becomes strong enough (a preflare event). Flows of heat, plasma and may be a plasmoid (and other perturbations) propagate from this current sheet. Throughout a system of magnetic tubes or by other appropriate ways they reach a site of another current sheet(s) and destroy the quasistationary state of this sheet. The sheet develops in an explosive manner with a fast energy release and is responsible for a flare. In other words, a magnetic reconnection in one current sheet triggers an explosive phase of reconnection in other sheet(s). N.B.: Beginning from an appropriate moment a probability of a destabilization of a current sheet is determined rather by physical states of other current sheets than by outer actions such as a new magnetic flux, photospheric motions etc. So we have to tell about a single system of interacting current sheets. To express my idea more exactly I suggest to name such current sheets as intercommunicating current sheets. A simplest variant of the proposed model is the following. Let us consider two current sheets with different temperatures. They are located at different places. Fluxes of heat and plasma from the first sheet reach throughout magnetic tubes an environment of the second sheet and vice versa. One can see that due to this intercommunicating, the sheet with the lower temperature becomes to be surrounded by a plasma with a temperature higher than the inside sheet temperature. This sheet will be explosively destabilized. Thus in the system of two intercommunicating sheets with different temperatures, the sheet with the higher temperature (that corresponds to the preflare event) destabilizes the sheet with the lower temperature and induces its explosion with a fast energy release. It is the flare. Described concept of intercommunicating current sheets explains observed features of preflare events and flares. A detail check of the described model can be made by an analysis of profiles and intensities of XUV lines emitted from sites of preflare events and flares. This research can be carried out in a framework of Yohkoh SXT data with an invoke to SOHO UVCS and CDS observations.


Late Abstract Listing