Study of bright points in the off‐band Hα filtergrams of active regions

Abstract

Hα filtergrams of selected active regions are obtained by the six inch refractor telescope at Udaipur Solar Observatory through a birefringent filter of 0.5 Å full width at half maximum. The field of view is ∼4 × 5 arcmin with a spatial resolution of better than one arc sec. The filtergrams are obtained in the wavelength range of ‐1 to +1 Å centered at 6563 Å at steps of 0.1 ° A. A complete scan takes about 5 seconds (occasionally longer). The images are recorded with a cooled CCD camera and corrected for dark current and flat field. We observe the bright points in the filtergrams beyond 0.5 Å off line center. In general, these features are located away from the strong field regions. We study their property with respect to the co‐temporal photospheric magnetograms obtained with the GONG instrument at Udaipur. This might help in understanding their relation with the magnetic flux emergence and annihilation.