Abstract
The most intense flares of Solar Physics history were registered during October - November 2003. Here we analyze the M6.7 flare (12:27 UT) on October 27, 2003, that occurred in the complex active region (AR) 10486 (NOAA number). We use data in different wavelengths provided by instruments observing from the photosphere to the corona. Using the Michelson Doppler Imager (SoHO/MDI) magnetogram at 12:47:03 UT as boundary condition, we compute the coronal magnetic field under the linear force-free field assumption. We compare the computed magnetic field lines with the Extreme ultraviolet Imaging Telescope (SoHO/EIT) loops to determine the free parameters of our model. From the model we find that a magnetic null point is present in the corona. We propose that magnetic reconnection at this null point is responsible for the M6.7 flare. Concerning radio wavelengths, we analyze the Solar Submillimeter Telescope (SST) data. At 12:31 UT, a short impulsive phase (∼ 1 minute) is detected followed by a gradual (∼ 1 hour) emission associated with H α radiation observed by the H-Alpha Solar Telescope for Argentina (HASTA). The radio spectrum during the impulsive peak suggests the presence of energetic electrons radiating through the synchrotron process. During the extended phase the radio spectrum is flat up to very high frequencies, indicating that the emission is due to the thermal radiation of a cool and dense plasma. The radio analysis is complemented with patrol data from the Bern Polarimeters and Kosma and Bemrak observations.