We have observed the fine temporal and spatial structure of a filament eruption on 2002 May 27 following an M2-class flare. Our observations at Big Bear Solar Observatory were made at the wavelength of Ha 1.3 Å , with a cadence of 40 ms. The event was also observed by the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) at X-ray energies from 3 to 50 keV and by the Transition Region and Coronal Explorer (TRACE) in poFe xii 195 Å . The event appears to be a "failed eruption," as the filament material, seen in absorption by TRACE, first accelerated then decelerated as it approached its peak height of ∼ km while 4 8 # 10 the filament threads drained back to the Sun. The fact that the eruption did not lead to a coronal mass ejection indicates that the coronal magnetic field near ∼ km did not open during the flare. The height-time curve 4 8 # 10 obtained from the TRACE 195 Å images during the deceleration phase shows that the deceleration of the filament exceeded the gravitational deceleration by more than a factor of 10, which suggests that the filament material was pulled back by magnetic tension. Also of importance are three sequential but cospatial features-brightenings in EUV, a loop-top hard X-ray emission, and "rupturing" of the Ha filament-that point to a release of energy (and probably magnetic reconnection) above the initial filament's location but well below its terminal height. Reconnection above a filament does not appear in most models, with the notable exception of quadrupolar and "breakout" models. These observations provide evidence that at least two conditions are required for a successful eruption: a reconnection very low in the corona (possibly above the filament) and open or opening fields above that point.

No abstract

No abstract

No abstract

Sympathetic flares are a pair of flares that occur almost simultaneously in different active regions, not by chance, but because of some physical connection. In this paper statistical evidence for the existence of sympathetic flares is presented. From GOES X-ray flare data, we have collected 48 pairs of near simultaneous flares whose positional information and Yohkoh soft X-ray telescope images are available. To select the active regions that probably have sympathetic flares, we have estimated the ratio R of actual flaring overlap time to random-coincidence overlap time for 38 active region pairs. We have then compared the waiting-time distributions for the two different groups of active region pairs (R > 1 and R < 1) with corresponding nonstationary Poisson distributions. As a result, we find a remarkable overabundance of short waiting times for the group with R > 1. This is the first time such strong statistical evidence has been found for the existence of sympathetic flares. To examine the role of interconnecting coronal loops, we have also conducted the same analysis for two subgroups of the R > 1 group: one with interconnecting X-ray loops and the other without. We do not find any statistical evidence that the subgroup with interconnecting coronal loops is more likely to produce sympathetic flares than the subgroup without. For the subgroup with loops, we find that sympathetic flares favor active region pairs with transequatorial loops.

No abstract

No abstract

No abstract