We have developed a new type of cellular automaton (CA) model, the extended CA (X-CA), for the study of solar flares. The X-CA model is consistent with the MHD approach, in contrast to the previously proposed CA models (classical CAs), it consistently yields all the relevant physical variables, and it successfully reproduces the observed distributions of total energy, peak flux, and duration of...

In previous works we have developed a method to convert solar X-ray data, collected with the Yohkoh/SXT, into templates of stellar coronal observations. Here we apply the method to several solar flares, for comparison with stellar X-ray flares. Eight flares, from weak (GOES class C5.8) to very intense ones (X9) are selected as representative of the flaring Sun. The emission measure distribution...

Giant flares can release large amounts of energy within a few days 1−7 : X-ray emission alone can be up to ten percent of the star's bolometric luminosity. These flares exceed the luminosities of the largest solar flares by many orders of magnitude, which suggests that the underlying physical mechanisms supplying the energy are different from those on the Sun. Magnetic coupling between the comp...

The study of the statistical distribution of short quiescent times (≤ 30 minutes) between solar flares has been investigated on a 1D MHD model. A power law behaviour is found which indicates the existence of sympathetic flaring. This prediction is supported by recent observations. Solar flares are the most violent phenomena observed in the solar system. It is believed that they play a fundament...

We report on the spatial relationship between solar flares and coronal mass ejections (CMEs) observed during 1996-2005 inclusive. We identified 496 flare-CME pairs considering limb flares (distance from central meridian ≥ 45◦) with soft X-ray flare size ≥ C3 level. The CMEs were detected by the Large Angle and Spectrometric Coronagraph (LASCO) on board the Solar and Heliospheric Observatory (SO...

Commission 10 aims at the study of various forms of solar activity, including networks, plages, pores, spots, fibrils, surges, jets, filaments/prominences, coronal loops, flares, coronal mass ejections (CMEs), solar cycle, microflares, nanoflares, coronal heating etc., which are all manifestation of the interplay of magnetic fields and solar plasma. Increasingly important is the study of solar ...

Particle acceleration by direct-current electric field in the current sheet has been extensively studied, in which an electric and a magnetic field are generally prescribed, and a power law distribution of the electron energy is obtained. Based on MHD numerical simulations of flares, this paper aims at investigating the time evolution of the electron energy spectrum during solar flares. It turn...

STUDIES OF SOLAR WHITE-LIGHT FLARES AND SMALL-SCALE MAGNETIC STRUCTURES OBSERVED IN THE NEAR INFRARED

We present simultaneous ultraviolet and optical observations of five flares on the very late type M dwarf Gl 866 (dM5.5e). A procedure to estimate the physical parameters of the flaring plasma has been developed using a simplified model of the flare and a comparison of observed and computed Balmer decrements. With this procedure we have determined the optical thickness, electron temperature and...