Extreme-Ultraviolet Jets and Hα Surges in Solar Microflares

Jongchul Chae, Jiong Qiu, Haimin Wang, Philip R. Goode
1999 Astrophysical Journal  
We analyzed simultaneous EUV data from the Transition Region and Coronal Explorer and Ha data from Big Bear Solar Observatory. In the active region studied, we found several EUV jets that repeatedly occurred where pre-existing magnetic flux was "canceled" by newly emerging flux of opposite polarity. The jets look like Yohkoh soft X-ray jets, but are smaller and shorter lived than X-ray jets. They have a typical size of 4000-10,000 km, a transverse velocity of 50-100 km s Ϫ1 , and a lifetime of
more » ... -4 minutes. Each of the jets was ejected from a looplike bright EUV emission patch at the moment that the patch reached its peak emission. We also found dark Ha surges that are correlated with these jets. A careful comparison, however, revealed that the Ha surges are not cospatial with the EUV jets. Instead, the EUV jets are identified with bright jetlike features in the Ha line center. Our results support a picture in which Ha surges and EUV jets represent different kinds of plasma ejection-cool and hot plasma ejections along different field lines-which must be dynamically connected to each other. We emphasize the importance of observed flux cancellation and a small erupting filament in understanding the acceleration mechanisms of EUV jets and Ha surges.
doi:10.1086/311910 fatcat:owynjzug35ghzpzvabzbet6ege