Blue-wing enhancement of the chromospheric Mg ii h and k lines in a solar flare

Abstract

We performed coordinated observations of AR 12205, which produced a C-class flare on 2014 November 11, with the Interface Region Imaging Spectrograph (IRIS) and the Domeless Solar Telescope (DST) at Hida Observatory. Using spectral data in the Si IV 1403Å, C II 1335Å, and Mg II h and k lines from IRIS and the Ca II K, Ca II 8542Å, and Hα lines from DST, we investigated a moving flare kernel during the flare. In the Mg II h line, the leading edge of the flare kernel showed the intensity enhancement in the blue wing, and the smaller intensity of the blue-side peak (h2v) than that of the red-side one (h2r). The blueshift lasted for 9-48 s with a typical speed of 10.1 ± 2.6 km s −1 and it was followed by the high intensity and the large redshift with a speed of up to 51 km s −1 detected in the Mg II h line. The large redshift was a common property for all six lines but the blueshift prior to it was found only in the Mg II lines. A cloud modeling of the Mg II h line suggests that the blue wing enhancement with such peak difference can be caused by a chromospheric-temperature (cool) upflow. We discuss a scenario in which an upflow of cool plasma is lifted up by expanding hot plasma owing to the deep penetration of non-thermal electrons into the chromosphere. Furthermore, we found that the blueshift persisted without any subsequent redshift in the leading edge of the flare kernel during its decaying phase. The cause of such long-lasting blueshift is also discussed.

The expansion of the Universe may be an illusion created by Compton scattering of free electrons

“…The distance between the spectral line forming region and the core of the flare increases and the influence of the flare decreases. These are consistent with the spectral line width 24 .…”

“…In flare AR 12205 24 . The formation temperature of Si IV 1403 Å, C II 1335 Å, Mg II h 2803 Å, H α 6563, CA II K 3934 Å, CA II 8542 Å in log T [k] is 4.8, 4.3, 4.0, 4.0, 4.0 and 4.0, from the highest to the lowest.…”

The expansion of the Universe may be an illusion created by Compton scattering of free electrons

“…The radiation at 1-8 Å is caused by the free thermal electrons 24 . When the first burst of feimi 29-31 keV (T = 150-200 s) occurred, there were no significant corresponding bursts at 1-8 Å, due to the lack of free electrons in the chromosphere at the beginning of the flare.…”

“…After the flare occurs, the thermal expansion (the Balmer and Ca II H lines showed blue asymmetry Doppler effect 24 ), and the number of free electrons gradually increases. The FEC effect also gradually increases, and the spectral linewidth gradually broadens 24,25 . When the FEC effect is larger than the Doppler effect, the blue asymmetry changes to a red asymmetry.…”

Free electron Compton scattering produces the illusion of the universe expansion

“…The surface temperature of the sun is 5700K in the quiet sun and almost all solar atmospheric spectral lines do not show any redshift 24,25 .The gravitational redshift of the sun is known to be less than 1 km S −1 26 . When solar flares occur, their spectral profile has a redshift asymmetry 27,28,29 that is difficult to explain with the Doppler effect, and the redshift asymmetry rules out the Stark effect because Stark-induced shift occurs in dense plasma (plasma with electron concentration about and above 16 -3 10 cm 30 ). The electron density of solar flares is generally in the range of 12 14 -3 10 10 cm : 31,32 .…”