Abstract
Abstract We picked up five solar flares larger than GOES X-ray class M/Hα importance 1, and studied the magnetic evolution of the corresponding active regions. In particular, we investigated the spatial relationships among Hα flare ribbons, soft X-ray (SXR) flare loops, and magnetic configurations. Our results show that all of these flares are not associated with high magnetic shear, but with emerging flux, indicating that flux emergence is a common phenomenon in this kind of solar flare with low magnetic shear. The maximum values of the transverse magnetic fields on the neutral lines responsible for these flares are 300-800 G. All of these flares but one have multiple (more than two) Hα ribbons, and almost all of these ribbons are located at the footpoints of SXR flare loops. The flare-related shear changes, which can be both positive and negative, may be determined by the balance of the energy carried by the emerging flux and that required to power the flare.
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