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Session 35 - Solar Magnetic Fields.
Display session, Tuesday, June 11
The Solar plasma like many plasma systems exhibits large scale explosive events. Solar flares and prominence eruptions are examples of large scale explosive events. Since the rate at which the stability boundary is crossed is usually slow, systems rarely achieve a large linear growth rate. Thus explosive events almost always require nonlinear destabilization to achieve the fast time-scales that are observed. A new mechanism for explosive behavior is demonstrated in a nonlinear MHD line tied Rayleigh-Taylor-Parker instability. In this mechanism the system crosses the instability threshold in a small region of space. The nonlinearity is destabilizing and broadening causing the linear instability to develop fingers and broaden into the linearly stable region. Shocks form separating the disturbed and undisturbed regions. Because the nonlinearity is destabilizing the linearly stable region is in fact meta-stable. The energy in the fingers is large enough to destabilize the meta-stable region a process we call detonation. In the simple system analyzed a finite time singularity occurs where the displacement becomes singular like (t_0 - t)^-2.1, the energy like (t_0 - t)^-6.4 and the destabilized region width like (t_0 - t)^-0.4. This is generic nonlinear behavior of MHD Ballooning type instabilities driven by gravity or curvature. It is shown that this scenario is expected to occur in prominences and perhaps at the base of the convection zone. Observational signatures will be discussed.
Program listing for Tuesday