Document Type : Original Article
Authors
1 Ph.D Student, Department of Astrophysics, Faculty of Physics, University of Tabriz, Tabriz, Iran.
2 Assistant Professor, Department of Physics, University of Zanjan, Zanjan, Iran.
3 Assistant Professor, Department of Astrophysics, Faculty of Physics, University of Tabriz, Tabriz, Iran.
Abstract
We present, observational signatures of fast and slow MHD modes over an off-limb coronal X-point in AIA 171 Å passband on 2014 April 3. The X-point structure is outlined by the coronal loops. The height of the X-point is obtained to be 52 ± 2 Mm above the limb. Slow waves with speeds in the range of 2.5 to 7.2 km/s are observed to propagate in the X-point neighboring loops (close to the fan surface) from the footpoints toward the loop apex, symmetrically. It looks that the slow modes over the slit 1 getting acceleration as they are moving toward the loop apex. Since, coronal β=0 condition breaks as getting closer to the X-point, slow modes should speed up, naturally. Over the slits f, g, h, i, L, m, n, o, signatures of the fast waves and their reflections from the loop apex are visible (or the outflows getting away from the X-point) with speeds in the range of ±3.0 to 18 km/s. On the other side, the fast MHD mode with period of 5 min is observed on the slit locating close to the loop top (slits e). A Filament Eruption (FE) happens around the time step of 350 in the nearby prominence area and triggers the fast kink modes with periods of 3 to 4 minutes at a position close to the spine axis over the slits d, e, and k.
)