Oscillations and heating in chromospheric fine scale structures

Abstract

We have analyzed a 35-min-long time sequence of spectra obtained simultaneously in CaII H-line, NaI D1 and D2 lines, and in strong and weak FeI lines in a quiet region at; the center of the solar disc under high spatial, spectral, and temporal resolution using the VTT of NSO/Sac Peak. We derived the line profile at the sites of a large number of bright points and network elements, and extracted the various line profile parameters. The important results emerged from this analysis are: (i) The bright points and network elements exhibit 3-min and 5-7 min periodicity in their intensity oscillations respectively; (ii) The bright points are grouped into three classes according to their dynamical behavior, and it is surmised that the differences in their behavior are directly related to the inner network photospheric magnetic points to which they have been observed to bear a spatial correspondence; (iii) The period of intensity oscillations decreases outward from the low photosphere (5-min) to the middle chromosphere (3-min); (iv) The evidence for the existence of the constant period of oscillations in bright points with their brightness and the different period from network oscillations suggests that the mode of heating mechanism may be identical (by 3-min period waves) for all classes of bright points and it may be an entirely different mechanism (5-7 min period waves) in the case of network elements; (v) The physical process behind the cause for the bright points may be due to the interference of these 3-min period waves, and the 5-min bright points may be magnetic in origin. (vi) According to the current models, the energy transported by these 3-min period waves at the sites of the bright points can account for a substantial fraction of the radiative loss from the quiet chromosphere.