Velocity Structure and Temperature Dependence of an Extreme-Ultraviolet Jet Observed by Hinode

Abstract

The acceleration mechanism of EUV and X-ray jets is still unclear. In general, there are two candidates for the mechanism. One is magnetic reconnection, and the other is chromospheric evaporation. We observed a relatively compact X-ray jet that occurred between 10:50\u2009–\u200911:10\xa0UT on 18 February 2011 by using the Solar Dynamics Observatory/Atmospheric Imaging Assembly, and the X-ray Telescope, Solar Optical Telescope, and EUV Imaging Spectrometer onboard Hinode. Our results are as follows:\xa0i) The EUV and X-ray observations show the general characteristics of X-ray jets, such as an arcade straddling a polarity inversion line, a jet bright point shown at one leg of the arcade, and a spire above the arcade. ii) The multi-wavelength observations and Ca\u2009ii H line image show the existence of a low-temperature (≈\u200910\u2009000\xa0K) plasma (i.e., filament) at the center of the jet. iii) In the magnetogram and Ca\u2009ii H line image, the filament exists over the polarity inversion line and arcade is also straddling it. In addition, magnetic cancellation occurs around the jet a few hours before and after the jet is observed. iv) The temperature distribution of the accelerated plasma, which was estimated from Doppler velocity maps, the calculated differential emission measure, and synthetic spectra show that there is no clear dependence between the plasma velocity and its temperature. For our third result, observations indicate that magnetic cancellation is probably related to the occurrence of the jet and filament formation. This suggests that the trigger of the jet is magnetic cancellation rather than flux emergence. The fourth result indicates that plasma acceleration accompanied by an X-ray jet seems to be caused by magnetic reconnection rather than chromospheric evaporation.