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Session 18 - The Sun.
Display session, Monday, January 13
Metropolitan Ballroom,
Many X-ray jet-like features, i.e., transient X-ray enhancements with an apparently collimated motion are observed with soft X-ray telescope aboard Yohkoh satellite. Many of these X-ray jets are associated with flares in X-ray bright points, emerging flux regions, or active regions. Shibata et al.(1992) reported that one of the X-ray jets in NOAA7070 associated with a flaring bright point at the footpoint of the H-alpha surge. An integrated analysis of the observations of NOAA7070 by SXT, H-alpha, and vector magnetogram showed that both the X-ray jets and H-alpha surges grow in the same direction almost perpendicular to the emerging loops (okubo et al., 1996). This indicates that the pre-existing oblique filed in this region is almost perpendicular to the emerging loops.
We extended the numerical simulations of coronal X-ray jets by Yokoyama and Shibata (1995) to the case when the emerging magnetic fields cross the pre-existing oblique field (i.e., magnetic twists are injected into the oblique field as a result of magnetic reconnection). We carried out 2.5D MHD simulation including the three components of velocity and magnetic fileds. A new factor introduced in our model is the shear Alfven wave generated by the magnetic reconnection. We found that cool plasmas on emerging magnetic loops are more efficiently accelerated than those in previous 2D simulations. These cool plasmas may correspond to the H-alpha surges simultaneously ejected with the X-ray jets. The kinetic energy of jets, reconnection rate and the energy flux carried by Alfven waves increase with the angle between the emerging magnetic fields and the pre-existing field.
