Naslov
Flare waves observed in helium i 10830 A: a link between ha moreton and EIT waves

Autori
Vršnak, Bojan ; Warmuth, A. ; Brajša, Roman ; Hanslmeier, A.

Izvornik
Astronomy and astrophysics (0004-6361) 394 (2002), 1; 299-310

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

Ključne riječi
Shock waves. Sun : flares. Sun : corona. Sun : chromosphere.

Sažetak
Three traveling disturbances recorded in the absorption line of Helium I at 10 830 Angstrom (He I), analogous to Halpha Moreton waves, are analyzed. The morphology and kinematics of the wavefronts are described in detail. The He I wave appears as an expanding arc of increased absorption roughly corresponding to the Halpha disturbance, although not as sharply defined. He I perturbations consist of a relatively uniform diffuse component and a patchy one that appears as enhanced absorption in He I mottles. It leads the Halpha front by some 20 Mm and can be followed to considerably larger distances than in Halpha observations. Behind the front stationary areas of reduced He I absorption develop, resembling EUV coronal dimming. The observed He I as well as the Halpha disturbances show a deceleration of the order of 100-1000 m s(-2). Moreover, in the event where Halpha, HeI, and EUV wavefronts are observed, all of them follow closely related kinematical curves, indicating that they are a consequence of a common disturbance. The analysis of spatial perturbation profiles indicates that He I disturbances consist of a forerunner and a main dip, the latter being cospatial with the Halpha disturbance. The properties and behavior of the wavefronts can be comprehended as a consequence of a fast-mode MHD coronal shock whose front is weakly inclined to the solar surface. The Halpha disturbance and the main He I dip are a consequence of the pressure jump in the corona behind the shock front. The He I forerunner might be caused by thermal conduction from the oblique shock segments ahead of the shock-chromosphere intersection, or by electron beams accelerated in the quasi-perpendicular section of the shock.

Izvorni jezik
Engleski

Znanstvena područja
Fizika

POVEZANOST RADA