Naslov
Characteristics of flares with H-alpha emission protruding over major sunspot umbrae

Autori
Vršnak, Bojan ; Ruždjak, Vladimir ; Brajša, Roman ; Zlobec, Paolo ; Altas, Levent ; Ozguc, Atila ; Aurass, Henry ; Schroll, Alfred

Izvornik
Solar Physics (0038-0938) 194 (2000), 2; 285-304

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Sažetak
A sample of 47 imp>(=) 1 flares whose H-alpha emission occured or protruded over umbrae of major sunspots (so called Z-flares) was studied to investigate characteristics of the associated dm/m radio, microwave and soft X-ray emission as the energy release site permeats into regions of strong magnetic fields. A close relation was found between the time of the microwave burst peak and the time of the "contact" (the time when the H-alpha emission protruded over or appeared in the sunspot umbra). The microwave bursts most often started several minutes before the contact and peaked at the time of the contact, or few minutes later. The H-alpha flares attained maximum close to, or few minutes after the contact and the microwave burst peak. The soft X-ray bursts were delayed more, attaining maximum 0-10 min after the contact. The onset of bursts in the dm/m wavelength range was associated with the period of growth or the peak of the microwave burst. Two categories of type III and IV bursts could be recognized: the ones starting some ten minutes before the microwave peak, and those that begin close to the microwave burst peak. It was found that type III bursts occur preferably in the events in which the microwave peak and the contact coincide. Type III bursts were not recorded in the cases when the microwave burst peaked before the contact. A possible relation between flares and noise storms was found in one third of the studied cases. The results are explained presuming that the contact reveals a permeation of the energy release process into a region of strong magnetic fields, where the process intensifies, and where from the accelerated particles have an access to magnetic field lines protruding to large coronal heights. Different manifestations of the energy release process occuring in various magnetic field topologies are considered to explain various time sequences of the events which have been observed during the studied flares.

Izvorni jezik
Engleski

Znanstvena područja
Fizika

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