Physical conditions in the chromosphere of a solar two-ribbon flare accompanied by a surge. I
|1Baranovskii, EA, 2Kondrashova, NN, 2Pasechnik, MN, 1Tarashchuk, VP |
1Crimean Astrophysical Observatory, Nauchny, Ukraine
2Main Astronomical Observatory of the National Academy of Sciences of Ukraine, Kyiv, Ukraine
|Kinemat. fiz. nebesnyh tel (Online) 2013, 29(4):18-30|
|Start Page: Solar Physics|
We study some variations of chromospheric thermodynamic parameters at the initial stage of the two-ribbon flare occurred on 4 September 1990 and accompanied by a surge. Nonhomogeneous semiempirical models of the flare chromosphere and surge were built for four moments of the flare observations. The spectra were obtained with the solar horizontal telescope ATsU-26 at the Terskol Peak Observatory. Two bright kernels of one of the ribbons and the surge were studied. Our comparison of the observed Нα line profiles with the quiet-Sun region line profile in the same position on the solar disk as the active region revealed some significant emission in the Нα line wings (up to 1...1.2 nm) at the residual intensity 0.6...0.77 in the Нα line centre. Our calculations in the framework of two-component chromospheric models point to a possible existence of some details with deep heating chromospheric layers. These details occupy 5...12 % of the total area and can not be resolved with a telescope. A strong asymmetry of the line profiles and the shift with respect to the quiet-Sun line profile can be interpreted by height distribution peculiarities of line-of-sight velocities. It is derived that for the majority of the active region outs under investigation the motion is directed to the observer in the upper chromosphere (10...30 km/s) and from the observer in the lower chromosphere (5...20 km/s). The models calculated for the surge give the value of line-of-sight velocities up to 70 km/s.
|Keywords: chromosphere, solar flares, Sun|
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