Main Objective: Investigating spicule dynamics and prominence structures by multi-line spectroscopy and deriving physical properties of them.
Scientific Justification: Spicules are cylindrical jet-like structures universally observed in the chromospheric network regions. The physical mechanism of spicules is not well understood yet. In addition, how spicules contribute to heating the upper atmosphere is not clear. One reason is that determinations of physical quantities of spicules from the observational data have not been completed.
Prominences or filaments represent another type of chromospheric-like gas, surrounded by the hot corona and supported by magnetic fields. Modeling of them has been conducted in the optical spectral lines mainly observed from ground and, recently, in the UV range in Mg II lines observed by IRIS.
We will observe off-limb spicules, network regions, prominences, or filaments simultaneously at multiple spectral lines. In addition, we will conduct the non-LTE modeling of those lines. By comparing the observations and modeling, we will derive various physical quantities of these structures such as kinetic temperatures, densities, turbulent velocities, and 3D velocities and we will investigate their properties and temporal evolution. Spectroscopic observations of such plasmas will be conducted by the Interface Region Imaging Spectrograph (IRIS) in space and by the Domeless Solar Telescope (DST) at the Hida Observatory of Kyoto University, Japan.
To obtain a set of off-limb spicule or on-disk network data at the same location with high cadence by both IRIS and DST, DST will conduct slit-scan observation while IRIS will be operated in a sit- and-stare mode. The temporal cadence of 10 sec by IRIS is necessary to follow the dynamics of the targets.
To obtain a set of off-limb prominence or on-disk filament data and to investigate their structures, both IRIS and DST will conduct slit-scan observations. In this case, the spatial coverage (95" x 175" by IRIS) is more important for us than the temporal cadence. For all targets, we will obtain spectroheliograph data by DST in the four spectral lines: Ca II K 3933 A, H-beta 4861 A, H-alpha 6563 A, and Ca II IR 8542 A and obtain IRIS data in the Mg II window around Mg II h 2803 A and k 2796 A and utilize the two lines. IRIS slit-jaw images in the Mg II 2796 A and 2832 A passbands are also necessary for alignments between different instruments. To support these spectroscopic co-observations, we ask for the spectroscopy by EIS and filter observations by XRT to see the connection between the chromospheric plasma and higher temperature plasma. SOT/SP scan is also preferable for on-disk observations (networks and filaments) to obtain the photospheric information. |
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