An X5.4 class flare occurred in active region (AR) NOAA11429 on 2012 March 7. The flare was associated with very fast coronal mass ejection (CME) with its velocity of over 2500 km/s. In the images taken with STEREO-B/COR1, a dome-like disturbance was
seen to detach from expanding CME bubble and propagated further. A Type-II radio burst was also observed at the same time. On the other hand, in EUV images obtained by SDO/AIA, expanding dome-like structure and its foot print propagating to the north were observed. The foot print propagated with its average speed of about 670 km/s and hit a prominence located at the north pole and activated it. While the activation, the prominence was strongly brightened. On the basis of some observational evidence, we concluded that the foot print in AIA images and the ones in COR1 images are the same, that is MHD fast mode shock front. With the help of a linear theory, the fast mode mach number of the coronal shock is estimated to be between 1.11 and 1.29 using the initial velocity of the activated prominence. Also, the plasma compression ratio of the shock is enhanced to be between 1.18 and 2.11 in the prominence material, which we consider to be the reason of the strong brightening of the activated prominence. The applicability of linear theory to the shock problem is tested with nonlinear MHD simulation.
We studied electron spectral indices of nonthermal emissions seen in hard X-rays (HXRs) and in microwaves. We analyzed 12 flares observed by the Hard X-ray Telescope aboard {it Yohkoh}, Nobeyama Radio Polarimeters (NoRP), and the Nobeyama Radioheliog
raph (NoRH), and compared the spectral indices derived from total fluxes of hard X-rays and microwaves. Except for four events, which have very soft HXR spectra suffering from the thermal component, these flares show a gap $Deltadelta$ between the electron spectral indices derived from hard X-rays $delta_{X}$ and those from microwaves $delta_{mu}$ ($Deltadelta = delta_{X} - delta_{mu}$) of about 1.6. Furthermore, from the start to the peak times of the HXR bursts, the time profiles of the HXR spectral index $delta_{X}$ evolve synchronously with those of the microwave spectral index $delta_{mu}$, keeping the constant gap. We also examined the spatially resolved distribution of the microwave spectral index by using NoRH data. The microwave spectral index $delta_{mu}$ tends to be larger, which means a softer spectrum, at HXR footpoint sources with stronger magnetic field than that at the loop tops. These results suggest that the electron spectra are bent at around several hundreds of keV, and become harder at the higher energy range that contributes the microwave gyrosynchrotron emission.
We report on the first simultaneous observation of an H-alpha Moreton wave, the corresponding EUV fast coronal waves, and a slow and bright EUV wave (typical EIT wave). Associated with an X6.9 flare that occurred on 2011 August 9 at the active region
NOAA 11263, we observed a Moreton wave in the H-alpha images taken by the Solar Magnetic Activity Research Telescope (SMART) at Hida Observatory of Kyoto University. In the EUV images obtained by the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamic Observatory (SDO) we found not only the corresponding EUV fast bright coronal wave, but also the EUV fast faint wave that is not associated with the H-alpha Moreton wave. We also found a slow EUV wave, which corresponds to a typical EIT wave. Furthermore, we observed, for the first time, the oscillations of a prominence and a filament, simultaneously, both in the H-alpha and EUV images. To trigger the oscillations by the flare-associated coronal disturbance, we expect a coronal wave as fast as the fast-mode MHD wave with the velocity of about 570 - 800 km/s. These velocities are consistent with those of the observed Moreton wave and the EUV fast coronal wave.
We report a detailed examination of the red asymmetry of H-alpha emission line seen during the 2001 April 10 solar flare by using a narrowband filtergram. We investigated the temporal evolution and the spatial distribution of the red asymmetry by usi
ng the H-alpha data taken with the 60cm Domeless Solar Telescope at Hida Observatory, Kyoto University. We confirmed that the red asymmetry clearly appeared all over the flare ribbons, and the strong red asymmetry is located on the outer narrow edges of the flare ribbons, with the width of about 1.5 - 3.0 (1000 - 2000 km), where the strong energy releases occur. Moreover, we found that the red asymmetry, which also gives a measure of the Doppler shift of the H-alpha emission line concentrates on a certain value, not depending on the intensity of the H-alpha kernels. This implies not only that the temporal evolutions of the red asymmetry and those of the intensity are not in synchronous in each flare kernel, but also that the peak asymmetry (or velocity of the chromospheric condensation) of individual kernel is not a strong function of their peak intensity.
Coronal structure of active regions appearing in coronal holes is studied by using the data obtained with the Soft X-Ray Telescope (SXT) aboard {it Yohkoh} from 1991 November to 1993 March. The following characteristics are found; Many of active regi
ons appearing in coronal holes show a structure that looks like a ``sea-anemone. Such active regions are called {it anemone ARs}. About one-forth of all active regions that were observed with SXT from their births showed the anemone structure. For almost all the anemone ARs, the order of magnetic polarities is consistent with the Hale-Nicholsons polarity law. These anemone ARs also showed more or less east-west asymmetry in X-ray intensity distribution, such that the following (eastern) part of the ARs is brighter than its preceding (western) part. This, as well as the anemone shape itself, is consistent with the magnetic polarity distribution around the anemone ARs. These observations also suggest that an active region appearing in coronal holes has simpler (less sheared) and more preceding-spot-dominant magnetic structure than those appearing in other regions.
We present a detailed examination of strongly blueshifted emission lines observed with the EUV Imaging Spectrometer on board the {it Hinode} satellite. We found two kinds of blueshifted phenomenon associated with the X3.4 flare that occurred on 2006
December 13. One was related to a plasmoid ejection seen in soft X-rays. It was very bright in all the lines used for the observations. The other was associated with the faint arc-shaped ejection seen in soft X-rays. The soft X-ray ejection is thought to be an MHD fast-mode shock wave. This is therefore the first spectroscopic observation of an MHD fast-mode shock wave associated with a flare.
