Abstract
We analyze the temporal variations of the sizes and emission intensities of thirtyone flaring kernels in various parts of the H{\alpha} line profile. We have found that the areas of all kernels decrease systematically when observed in consecutive wavelengths toward the wings of the H{\alpha} line, but their areas and emission intensity vary in time. Our results are in agreement with the commonly accepted model of the glass-shaped lower parts of the magnetic flaring loops channelling high energy variable particle beams toward the chromospheric plasma. High time resolution spectral-imaging data used in our work were collected using the Large Coronagraph and Horizontal Telescope equipped with the Multi-channel Subtractive Double Pass Spectrograph and the Solar Eclipse Coronal Imaging System (MSDP-SECIS) at the Bia{\l}k\'ow Observatory of the University of Wroc{\l}aw, Poland.
Highlights
Satellite-based observations of solar flares collected in the hard X-ray domain usually reveal some hard X-ray sources located near the feet of flaring loops, while co-temporal ground-based observations recorded in visible wavelengths reveal bright compact and/or extended emission sources located in the closest vicinity of the X-ray sources
While various parts of the Hα line are formed at different depths in the chromosphere (Vernazza, Avrett, and Loeser, 1973, 1981; Kašparová and Heinzel, 2002; Berlicki and Heinzel, 2004), taking into account all obvious factors like a heterogeneous vertical stratification of the plasma, strong bulk and turbulent plasma motions inside the flaring loops and many more, an emission recorded in a particular part of the Hα line profile enables a crude determination of the precipitation depths of the non-thermal electrons, as well as an evaluation of sizes of the emitting flaring kernels at various levels
Long sets of so-called spectra-images of the flaring kernels were collected with the Large Coronagraph (LC) and the Horizontal Telescope (HT) equipped with the Multi-channel Double Pass (MSDP) imaging spectrograph and the Solar Eclipse Coronal Imaging System (SECIS) at the Białków Observatory of the University of Wrocław, Poland
Summary
Satellite-based observations of solar flares collected in the hard X-ray domain usually reveal some hard X-ray sources located near the feet of flaring loops (they form the so-called “foot-point HXR sources”), while co-temporal ground-based observations recorded in visible wavelengths (for example in strong chromospheric hydrogen Hα line, 656.3 nm) reveal bright compact and/or extended emission sources located in the closest vicinity of the X-ray sources. In our previous work (Radziszewski and Rudawy, 2008) we presented results of spectrophotometric investigations of instantaneous sizes of seven Hα flaring kernels, when measured in various parts of the Hα line profile at selected moments. We have observed that the areas of the investigated individual kernels decreased systematically when observed simultaneously at consecutive wavelengths toward the wings of the Hα line, in agreement with the theoretical models of magnetic fields and chromospheric emission mentioned before. In the present paper we describe extended investigations of the temporal variations of the sizes of the 31 individual flaring kernels, observed between 2003 and 2005, using for each kernel up to 10 thousand measurements with high-time resolution (up to 40 ms).
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