A Transition Region Explosive Event Observed in He II with the MOSES Sounding Rocket Authors
Fox, J. Lewis
Thomas, Roger J.
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Transition region explosive events (EEs) have been observed with slit spectrographs since at least 1975, most commonly in lines of C IV (1548 Å, 1550 Å) and Si IV (1393 Å, 1402 Å). We report what we believe to be the first observation of a transition region EE in He II 304 Å. With the MultiOrder Solar EUV Spectrograph (MOSES) sounding rocket, a novel slitless imaging spectrograph, we are able to see the spatial structure of the event. We observe a bright core expelling two jets that are distinctly noncollinear, in directions that are not antiparallel. The jets have skyplane velocities of order 75 km s1 and lineofsight velocities of +75 km s1 (blue) and 30 km s1 (red). The core is a region of high nonthermal Doppler broadening, characteristic of EEs, with maximal broadening 380 km s1 FWHM. It is possible to resolve the core broadening into red and blue lineofsight components of maximum Doppler velocities +160 km s1 and 220 km s1. The event lasts more than 150 s. Its properties correspond to the larger, longlived, and more energetic EEs observed in other wavelengths.
Fox, J. Lewis, Charles C. Kankelborg, and Roger J. Thomas. “ A TRANSITION REGION EXPLOSIVE EVENT OBSERVED IN He II WITH THE MOSES SOUNDING ROCKET .” The Astrophysical Journal 719, no. 2 (July 27, 2010): 1132–1143. doi:10.1088/0004-637x/719/2/1132.