Astronomy and Astrophysics – Astronomy
Scientific paper
Sep 1998
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1998apj...504l.123c&link_type=abstract
Astrophysical Journal Letters v.504, p.L123
Astronomy and Astrophysics
Astronomy
34
Sun: Uv Radiation, Sun: Transition Region, Sun: Chromosphere, Sun: Magnetic Fields
Scientific paper
Transition region explosive events are considered to be a manifestation of small-scale magnetic reconnection ubiquitously occurring--even in the quiet Sun. In this paper, we report a close association between transition region explosive events and chromospheric upflow events seen in H alpha . From a comparison of the Big Bear Solar Observatory (BBSO) H alpha spectrograph data and the Solar and Heliospheric Observatory (SOHO) / Solar Ultraviolet Measurements of Emitted Radiation (SUMER) data, we found a succession of chromospheric upflow events at sites where repeated explosive events occurred. Individual chromospheric events appear as compact dark features that are best visible in H alpha -0.5 A and that have a size of 2"-3" and a lifetime of 1-2 minutes. They are characterized by an upward motion of 15-30 km s-1, a temperature of 104 K, a mass density of 1x10^{-13} g, and a nonthermal velocity less than 10 km s-1. Unlike spicules, which display descending motion following their ascending phase, these upflow events are not followed by noticeable redshifts. "H alpha jets" at -1.0 A studied by Wang et al. appear to be a special case of this kind of chromospheric upflow event. The physical characteristics of chromospheric upflow events and their close association with transition region explosive events suggest that chromospheric upflow events may be the manifestation of cool plasma material flowing into magnetically diffusive regions, while explosive events represent hot plasma material flowing out of the same regions.
Chae Jonchul
Goode Philip. R.
Lee Chik-Yin
Schühle Udo
Wang Haimin
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