Giant Meterwave Radio Telescope observations of an M2.8 flare: insights into the initiation of a flare-coronal mass ejection event

We present the first observations of a solar flare with the GMRT. An M2.8 flare observed at 1060 MHz with the GMRT on Nov 17 2001 was associated with a prominence eruption observed at 17 GHz by the Nobeyama radioheliograph and the initiation of a fast partial halo CME observed with the LASCO C2 coronograph. Towards the start of the eruption, we find evidence for reconnection above the prominence. Subsequently, we find evidence for rapid growth of a vertical current sheet below the erupting arcade, which is accompanied by the flare and prominence eruption.Comment: Accepted for publication in Solar Physic

Distinctive Spatial Configuration of a Class Microwave Flaring Sources

We discuss a particular spatial configuration of a class of microwave flaring regions in which the primary energy release results from the interaction between emerging magnetic flux and an existing overlying region. Such events typically exhibit radio and X-ray emission at the main flare site (the site of interaction) and in addition radio emission at a remote site up to 10 (exp 05) km away in another active region. We have identified and studied more than a dozen microwave flares in this class, in order to arrive at some general conclusions on reconnection and energy release in such solar flares

May 15, 2002 The Physical Properties of a Flaring Loop

We use high-resolution radio observations to study the physical parameters of a flaring loop. The loop is visible at radio wavelengths due to gyrosynchrotron emission by nonthermal electrons (energies typically above several hundred keV) accelerated by the flare. We are able to measure the loop thickness and length with a precision of order 1 . We find that the loop length increases from about 60 initially to about in the decay phase of the event. The loop (averaged along its length) initially is no more than 3 wide. The soft and hard X-ray data obtained with the SXT and HXT telescopes on the Yohkoh satellite are consistent with the same loop as observed at radio wavelengths (although the soft X-ray morphology has some small differences early in the event). This event was accompanied by a coronal mass ejection and a coronal dimming visible in SOHO/EIT images, so it involved a very large volume of the corona, yet the radio observations clearly indicate that much of the energy release in the low corona was restricted to a region apparently no more than 2000 km across

Radio imaging observations of hard x-ray microflares observed by RHESSI

International audienc

Radio imaging observations of hard x-ray microflares observed by RHESSI

International audienc

Radio imaging observations of hard x-ray microflares observed by RHESSI

International audienc

NoRH and RHESSI observations of the X 1.5 flare of April 21,

We present an overview of the radio observations of the X1.5 flare of April 21, 2002, and complementary data from other wavelengths. This flare was fairly well observed by the Ramaty High Energy Spectroscopic Imager (RHESSI) spacecraft and fully observed by the Nobeyama Radioheliograph (NoRH) at 17 and 34 GHz. This long-duration event lasted more than 2 hours and features a beautful arcade of rising loops on the limb visible at X–ray, EUV and radio wavelengths. The main flare was preceded by a small event 90 minutes earlier showing a long EUV loop connecting well-separated radio and hard X-ray sources. The main flare itself starts with a compact radio and hard X-ray source at the eastern end of the region that develops into emission close to the solar surface (and well inside the solar limb) over a large region to the northwest. As the flare proceeds a large set of loops is seen to rise well above the solar limb. Distinct regions of radio emission with very different time behaviour can be identified in the radio images, and in particular a peculiar nonthermal source seen in radio and hard X–ray

Nobeyama Radio Heliograph and RHESSI Observations of the X 1.5 Flare of April 21, 2002

We present an overview of the microwave (17 and 34 GHz) observations of the X1.5 flare of April 21,2002, along with RHESSI hard X-ray observations. The event lasted more than 2 hours and features a beautiful arcade of rising loops on the limb visible at X-ray, EUV and radio wavelengths. The main flare was preceded by a small event 90 minutes earlier showing a long loop ,connecting well-separated radio and hard X-ray sources. The main flare itself starts with a compact radio and hard X-ray source well inside the solar limb. As the flare proceeds a large set of loops is seen to rise well above the solar limb. Distinct regions of radio emission with very different time behavior can be identified in the radio images, and in particular a peculiar nonthermal source seen in radio and hard X-rays low in the corona at the base of the arcade is seen to turn on 30 minutes after the start of the impulsive phase. At about the same time an extremely intense burst of coherent radio emission is seen from 500 to 2000 MHz: we speculate that this lower-frequency burst is produced by electrons that are accelerated in the nonthermal source at the base of the arcade and injected into the loop system where they radiate plasma emission in the 10(exp 10)/cm(exp 3) density plasma at the top of the arcade of loops