Solar Flare Statistics with a One-Dimensional Mhd Model     

S. Galtier  A. Pouquet 《Solar physics》1998,179(1):141-165

The dynamics of dissipative events in coronal loops is modeled with the compressible MHD equations in one space dimension in slab geometry, with a forcing that mimics the footpoint motions. Using a set of numerical simulations, the statistics of strong velocity and magnetic field gradients that develop, leading to a bursty dissipation, are analyzed. Agreement with existing observations of X-ray solar flares obtains concerning the power-law distribution of the luminosity histogram, including when the dynamics are simplified to that of the Burgers equation; in that latter case, this allows for recasting the analysis in terms of avalanche-type models.  相似文献   

Intermittent heating in a model of solar coronal loops     

Walsh  R.W.  Galtier  S. 《Solar physics》2000,197(1):57-73

X-ray and EUV observations of the solar corona reveal a very complex and dynamic environment where there are many examples of structures that are believed to outline the Sun's magnetic field. In this present study, the authors investigate the temporal response of the temperature, density and pressure of a solar coronal plasma contained within a magnetic loop to an intermittent heating source generated by Ohmic dissipation. The energy input is produced by a one-dimensional MHD flare model. This model is able to reproduce some of the statistical properties derived from X-ray flare observations. In particular the heat deposition consists of both a sub-flaring background and much larger, singular dissipative events. Two different heating profiles are investigated: (a) the spatial average of the square of the current along the loop and (b) the maximum of the square of the current along the loop. For case (a), the plasma parameters appear to respond more to the global variations in the heat deposition about its average value rather than to each specific event. For case (b), the plasma quantities are more intermittent in their evolution. In both cases the density response is the least bursty signal. It is found that the time-dependent energy input can maintain the plasma at typical coronal temperatures. Implications of these results upon the latest coronal observations are discussed.  相似文献   

Statistical Study of Short Quiescent Times between Solar Flares in a 1D MHD Model     

Sébastien Galtier 《Solar physics》2001,201(1):133-136

The statistical distribution of short quiescent times 30 min) between solar flares has been investigated with a 1D MHD model. A power-law behaviour is found which indicates the existence of sympathetic flaring. This prediction is supported by recent observations.  相似文献