Multi-Band Observation of Solar Activity--Purple Mountain Observatory

Multi-Band Observation of Solar Activity

Solar spectral database has been public for the astronomy researcher from worldwide since 2014 October. People can search and download our solar spectral data freely. The spectral data here is observed by the Multi-wavelength Infrared Solar Spectral telescope (MISS) in Purple Mountain Observatory, China. It works at three lines, such as Ha 6563 A, CaII 8542 A and HeI 10830 A, whose profiles are used to detect the intensity, line width and Doppler velocity. Meanwhile, it can also get the full-disk solar image at Ha. Therefore, solar spectral database is helpful for the generalization of our solar data to the researchers.

The Multi-channel Solar Spectrograph (MSS) at Purple Mountain Observatory (PMO) was initially established in 1976. Since 1986, we have made some improvements to the MSS step by step, and now we have developed a Multi-channel Infrared Solar Spectrograph (MISS) that works at HeI 10830？ and CaII 8542？ and Ha (6563？). The original spectrograph can be used to observe simultaneously solar activity at 9 wave bands including CaII H and K line, MgI b line, HeI D₃ line and Ha through H-infinity. The newly developed MISS works in three wavelengths, i.e. HeI 10830, CaII 8542 and Ha.

In 1998, we replaced plates in the original system with Pulnix TM-860 CCDs and placed an image reducer before each CCD in order to match the CCD pixel size. The dispersions for HeI 10830, CaII 8542 and Ha of the new imaging solar spectrograph are 0.0693, 0.0767 and 0.0754 per CCD pixel respectively, and each vertical CCD pixel represents 0.34" on the solar disk (Li et al., 1999).

We replaced the TM-860 CCDs with Apogee AP7p grade 1 scientific CCDs and removed the image reducers. In the latest system, the dispersions for HeI 10830, CaII 8542 and Ha are 0.04776, 0.05113 and 0.05453 per CCD pixel respectively, and each vertical CCD pixel represents 0.375" on the solar disk (Li et al., 2002). The slit-jaw photographic system has also been updated to a CCD system, which takes image of the Sun at Ha and has a field of view of 192" x 144" . The observation data are all digitized.

We can obtain the line center and off-band intensities of the three lines and the intensities of continua adjacent to these lines through the new instrument. We can also acquire velocity maps and line profiles. Therefore, it is specially suitable for two-dimensional (2D) spectroscopic observations of solar flares and active regions. We carry out scanning observation by rotating the second mirror of the coelostat system.