Solar flare is one of the most energetic phenomena in the solar atmosphere. Its spectrum provides us valuable information to study the heating process. In particular, line emission from the chromosphere can provide critical diagnostics of plasma heating processes. The hydrogen Hα and Ca lines which represent typical chromospheric lines are the most observed and studied spectral lines. Although the He I 10830 Å line is much weaker than the Hα, it is still an important line in the spectroscopy of solar active phenomena. The hot iron lines reflect the hot plasma in the transition region and corona. Many authors have studied the formation of these lines. Energy release in solar flares in general results in particle acceleration, plasma heating, and plasma wave generation. Most of the released energy is transported by the accelerated particles downward along magnetic field lines and deposited in the dense chromosphere by Coulomb collisions with ambient plasma in the so-called thick target model (e.g., Brown 1971; Petrosian 1973; Lin & Hudson 1976). Some energy may be transported by thermal conduction from directly heated coronal plasma (e.g., Zarro & Lemen 1988; Battaglia et al. 2009), and possibly by plasma waves. Spectroscopic observations can provide useful diagnostics and help constrain mechanisms of energy release and particle acceleration, a fundamental question for solar flares. We plan to observe with NST, IRIS and Hinode cooperatively to get a comprehensive view ranging from the chromosphere to the corona. Our observation proposal for BBSO/NST during August 27-31 has been accepted. We will also propose for IRIS observation.
Battaglia, M. et al. 2009, A&A, 498, 891
Brown, J. C. 1971, Sol. Phys., 18, 489
Lin, R. P. & Hudson, H. S. 1976, Sol. Phys., 50, 153
Petrosian, V. 1973, ApJ, 186, 291
Zarro, D. M. & Lemen, J. R. 1988, ApJ, 329, 456