Abstract
We analyzed simultaneous data from Huairou Solar Observing Station (HSOS) and the Transition Region and Coronal Explorer (TRACE) of November 4, 1998 in the active region NOAA 8375. The magnetic fields in this region had the following properties: a main positive polarity line-of-sight field was surrounded by relatively weak negative polarity fields; many moving magnetic features emerged from the positive magnetic field, and cancelled (merged) with the opposite (the same) polarity fields. There was a filament on the neutral line between the main positive polarity field and its surrounding negative polarity fields. The filament was cut off at a magnetic cancellation site and separated into two segments. One segment erupted and disappeared; the other segment rose from one end, but another end was fixed at an interface of a pair of opposite magnetic polarities, finally the morphology of this segment appeared as an Hα surge. Comparing Hα filtergrams with EUV images, we noticed that the Hα surge was co-spatial with an EUV surge. The EUV surge was whiplike in shape, then sidewards moved. We suggest that the evolution of the EUV surge represent the process of EUV loop opening.
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