[P-EM14] Frontiers in solar physics

[PEM14-07] Comparison of Spectra of Solar Magnetic Active Phenomena Using Multiple Chromospheric Lines Taken by DST at Hida Observatory

*Junya Natsume¹, Ayumi Asai¹, Satoru Ueno¹, Takato Otsu¹, Kiyoshi Ichimoto^1,2 (1.Graduate School of Science, Kyoto University, 2.Ritsumeikan University)

Keywords:solar flare, stellar flare, solar active phenomenon, chromosphere

Solar active phenomena can be observed as spatially resolved images while stellar ones cannot be. Recently, so-called "Sun-as-a-star analysis" has been conducted on solar active phenomena by spatial integration of solar observation data into data mimicking stellar observations. H-alpha (6563 angstroms) line has been often used for this analysis and analysis including other chromospheric lines will provide more detailed information on dynamics of stellar active phenomena than single line. For example, the simulated He I (10830 angstroms) line in flaring atmosphere with an electron beam produces much stronger emission and absorption than that without an electron beam (Ding et al. 2005). The absorption sensitivity of the He I line increases due to EUV radiation (Fontenla et al. 1993). Ca II K (3934 angstroms) line consists of three components, K₁, K₂ and K_3, ordered from lower to higher formation heights, which exhibit profiles with wide absorption outside, emission inside of K₁ and absorption inside of K₂, respectively. We observed solar flare and filament activation which occurred at active region NOAA 13078 on 2022 August 19, taken by Domeless Solar Telescope (DST) at Hida Observatory of Kyoto Univesity. Using Horizontal Spectrometer in DST, we obtained imaging spectroscopic data in four chromospheric lines, H-alpha, Ca II K, Ca II IR (8542 angstroms) and He I, simultaneously. The flare ribbons were confirmed in both wings of Ca II K and the line centers of H-alpha, Ca II K and Ca II IR lines while they were weak in He I line. The darkening of the filament activation was confirmed in both wings of H-alpha and He I lines and line centers of all the four lines. We performed Sun-as-a-star analyses on the data and compared spatially integrated spectra in the four lines. The H-alpha line showed brightening near the line center and darkenings in the red and blue wings, whereas the He I line only showed darkenings in both core and wings. On the other hand, the Ca II K line exhibited the darkening coming from the filament activation in the line center and the brightening coming from the flare ribbon in both wings. We also integrated the spectra in wavelength into equivalent width (EW). The EWs around flare peak time had brightening coming from flare ribbon in H-alpha, Ca II K and Ca II IR lines and started darkening 5-10 min after the peak in H-alpha and Ca II K lines coming from the filament activation. The time developments of EWs of H-alpha and Ca II K lines are similar. The EW of He I line started darkening around flare peak time without brightening. The difference between H-alpha and He I lines is caused by the weakness of flare brightening in He I line, which is considered to be contributed to EUV radiation or electron beam. The difference between H-alpha and Ca II K lines is explained by the broad width of K_1,2 emission by the flare ribbon at lower altitude and the narrow width of K₃ absorption by the filament at higher altitude. Even though the EWs of H-alpha and Ca II K lines are similar, the wavelength from line center of H-alpha and Ca II K had information of line-of-sight velocity and formation heights in this event, respectively.