Rapid Submillimeter Brightenings Associated with a Large Solar Flare

Abstract

We present high time resolution observations of Active Region 8910 obtained simultaneously at 212 and 405 GHz during a large Ha flare, which produced a soft X-ray class X1.1 event. Data were obtained with the new solar submillimeter telescope recently installed at the El Leoncito Observatory to explore this poorly known part of the solar emission spectrum. A small slow submillimeter enhancement (≤300 sfu) was associated to bulk emissions at X-rays, Ha, and microwaves. The event exhibited numerous submillimeter-wave 100-300 ms duration spikes, the larger ones with fluxes on the order of 220 and 500 sfu ‫)%02ע(‬ at 212 and 405 GHz, respectively. A dramatic increase in the incidence rate of submillimeter spikes sets in as a new large loop system appears in AR 8910, and X-ray emission increases nearly 1 hr before the large flare. The brightening incidence rate (∼20 per minute) correlates well with the large flare light curves at X-rays and Ha. The submillimeter spikes may be associated to microflares, waves, or quakes in flaring active regions.

First detection of the impulsive and extended phases of a solar radio burst above 200 GHz

“…2, bottom). This is in agreement with the suggestion by Kaufmann et al (2001) that the SXR and 212 GHz emission arise from different regions. Kaufmann et al also proposed that the short mm-wave emission might be produced deep in the chromosphere.…”

“…This is achieved by the Solar Sub-millimeter Telescope (SST) installed at the El Leoncito Astronomical Complex in the argentinean Andes which started solar observations at 212 and 405 GHz mid-1999 (Kaufmann et al 2000a). First SST observations of a solar flare that occured on 2000 March 22 at ∼1834 UT have been described in Kaufmann et al (2001). This study emphasizes the detection of numerous 100-300 ms duration spikes at both observing frequencies but did not provide clear evidence that the time evolution of 212 and 405 GHz emission exhibits a counterpart to the gyrosynchrotron microwave burst observed up to 18 GHz.…”

“…During the 2000 March 22 flare observations, the projection on the sky of beam 5 is centered on and tracks AR 8910, while those of beams 2-4 vary with time but always cover the active region, and those of beams 1 and 6 are away from AR 8910 (see Fig. 1 in Kaufmann et al 2001). The half power beamwidths were 7.5 for beams 2, 3, 4, 5 and 10 for beams 1 and 6.…”

“…Since then, the latter have been improved by a factor of ∼10, and so too, the sensitivity (e.g. Kaufmann et al 2001). We thus consider that, at 405 GHz, the flux density increase from the flare was lower than 90 sfu, the estimated noise level from beam 5.…”

On the Temporal and Spatial Properties of Elementary Bursts

“…It was first discovered in high-resolution hard X-ray and microwave observations that flare bursts consist of fine structures on time scales from tens of milli-seconds to a few seconds de Jager, 1974, 1976;Hoyng, van Beek, and Brown, 1976;Kiplinger et al, 1983Kiplinger et al, , 1988Kaufmann et al, 1980Kaufmann et al, , 1984Kaufmann et al, , 2001Aschwanden, Benz, and Schwartz, 1993;Aschwanden, Schwartz, and Alt, 1995;Aschwanden et al, , 1998. These are called "elementary bursts" (de Jager and de Jonge, 1978).…”