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The magnetic field topology associated to two M flares  

Germ Cristiani   Submitted: 2007-06-05 11:27

On 27 October, 2003, two GOES M-class flares occurred in the lapse of three hours in active region NOAA 10486. The two flares were confined and their associated brightenings appeared at the same location, displaying a very similar shape both at the chromospheric and coronal levels. We focus on the analysis of magnetic field (SOHO/MDI), chromospheric (HASTA, Kanzelhoehe Solar Observatory, TRACE) and coronal (TRACE) observations. By combining our data analysis with a model of the coronal magnetic field, we compute the magnetic field topology associated to the two M flares. We find that both events can be explained in terms of a localized magnetic reconnection process occurring at a coronal magnetic null point. This null point is also present at the same location one day later, on 28 October, 2003. Magnetic energy release at this null point was proposed as the origin of a localized event that occurred independently with a large X17 flare on 28 October, 2003, at 11:01 UT. The three events, those on 27 October and the one on 28 October, are homologous. Our results show that coronal null points can be stable topological structures where energy release via magnetic reconnection can happen, as proposed by classical magnetic reconnection models.

Authors: M.L. Luoni, C.H. Mandrini, G. Cristiani, P. Demoulin
Projects: SoHO-MDI,TRACE

Publication Status: Advances in Space Research (in press)
Last Modified: 2007-06-06 12:39
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Observed flux density enhancement at submillimeter wavelengths during an X-class flare  

Germ Cristiani   Submitted: 2007-06-05 11:14

We analyse the 30 October, 2004, X1.2/SF solar event that occurred in AR 10691 (N13 W18) at around 11:44 UT. Observations at 212 and 405 GHz of the Solar Submillimeter Telescope (SST), with high time resolution (5 ms), show an intense impulsive burst followed by a long-lasting thermal phase. EUV images from the Extreme Ultraviolet Imaging Telescope (SOHO/EIT) are used to identify the possible emitting sources. Data from the Radio Solar Telescope Network (RSTN) complement our spectral observations below 15 GHz. During the impulsive phase the turnover frequency is above 15.4 GHz. The long-lasting phase is analysed in terms of thermal emission and compared with GOES observations. From the ratio between the two GOES soft X-ray bands, we derive the temperature and emission measure, which is used to estimate the free-free submillimeter flux density. Good temporal agreement is found between the estimated and observed profiles, however the former is larger than the latter.

Authors: G. Cristiani, C.G. Giménez de Castro, M.L. Luoni, C.H. Mandrini, M.G. Rovira, P. Kaufmann, M. Machado
Projects: SoHO-EIT,TRACE

Publication Status: Advances in Space Research (in press)
Last Modified: 2007-06-07 12:37
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The magnetic field topology associated to two M flares
Observed flux density enhancement at submillimeter wavelengths during an X-class flare

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