We performed magnetohydrodynamic simulation of coronal mass ejections (CMEs) and associated giant arcade formations, and the results suggested new interpretations of observations of CMEs. We performed two cases of the simulation: with and without heat conduction. Comparing between the results of the two cases, we found that reconnection rate in the conductive case is a little higher than that in the adiabatic case and the temperature of the loop top is consistent with the theoretical value predicted by the Yokoyama-Shibata scaling law. The dynamical properties such as velocity and magnetic fields are similar in the two cases, whereas thermal properties such as temperature and density are very different. In both cases, slow shocks associated with magnetic reconnection propagate from the reconnection region along the magnetic field lines around the flux rope, and the shock fronts form spiral patterns. Just outside the slow shocks, the plasma density decreased a great deal. The soft X-ray images synthesized from the numerical results are compared with the soft X-ray images of a giant arcade observed with the Soft X-ray Telescope aboard Yohkoh, it is confirmed that the effect of heat conduction is significant for the detailed comparison between simulation and observation. The comparison between synthesized and observed soft X-ray images provides new interpretations of various features associated with CMEs and giant arcades. 1) It is likely that Y-shaped ejecting structure, observed in giant arcade 1992 January 24, corresponds to slow and fast shocks associated with magnetic reconnection. 2) Soft X-ray twin dimming -2corresponds to the rarefaction induced by reconnection. 3) The inner boundary of the dimming region corresponds to the slow shocks. 4) "Three-part structure" of a CME can be explained by our numerical results. 5) The numerical results also suggest a backbone feature of a flare/giant arcade may correspond to the fast shock formed by the collision of the downward reconnection outflow.

We present observations of the eruption of a miniature filament that occurred near NOAA Active Region 9537 on 2001 July 14. The eruption was observed by the Hida Observatory Domeless Solar Telescope, in the H line center and AE0.4 8 wings, the Solar and Heliospheric Observatory EUV Imaging Telescope (EIT) and Michelson Doppler Imager, and the Yohkoh Soft X-Ray Telescope (SXT). The miniature filament began to form and was clearly visible in H images by around 06:50 UT. It erupted about 25 minutes later, accompanied by a small tworibbon subflare (with an area of 61 arcsec 2 ). The two ribbons were also found to approach each other at a speed of 3.33 km s À1 . We found that this event was caused by the emergence of new magnetic flux in a quiet region. The emerging flux appeared as a bright region in the EIT and SXT images taken on the previous day. It moved southward into an area of preexisting opposite-polarity flux, where a cancelling magnetic flux region was formed. The miniature filament then appeared, and we suggest that it played some role in inhibiting the release of energy by delaying reconnection between the emerging and preexisting flux, as evidenced by the disappearance of the bright region between opposite polarities in the EUV and soft X-ray images. Consequently, magnetic energy was stored as a result of the slow converging motion of the two opposite-polarity flux regions (0.17 km s À1 ). Reconnection below the filament provoked the filament eruption, and the two-ribbon flare occurred. Miniature filaments are thought to be small-scale analogs of large-scale filaments. Our observations also suggest some common properties between small-scale and large-scale flares. These results support the view that a unified magnetic reconnection model may be able to explain all scales of flares.

We performed magnetohydrodynamic (MHD) simulations of a giant arcade formation with a model of magnetic reconnection coupled with heat conduction, to investigate the dynamical structure of slow and fast MHD shocks associated with reconnection. Based on the numerical results, theoretical soft X-ray images were calculated and compared with the Yohkoh soft X-ray observations of a giant arcade on 1992 January 24. The Y-shaped structure observed in the event was identified to correspond to the slow and fast shocks associated with the magnetic reconnection.

We analyze 17 arcades to study the relations between solar flares and arcades. Soft X-ray images taken with Yohkoh's soft X-ray telescope are used to derive , , and temporal variation of and , where and is indirect evidence that flares and arcades are heated by the same magnetic reconnection mechanism.

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