The Solar Chromosphere Spectrum Observation during Annular Solar Eclipse 2010

Abstract

The solar chromosphere spectrum observations usually perform during total solar eclipses. However, total solar eclipse only happened once a year in average and the observation outside eclipses condition suffer from strong stray light from the Sun and daytime astronomical seeing which difficult to be controlled precisely. The idea of the observation during annular solar eclipse was based on the fact that: 1) The brightness of the solar chromopshere is as bright as the full moon, 2) The Moon is visible during daytime under excellent weather condition, and 3) The sky brightness observed during annular phase of an annular solar eclipse is 3 times dimmer than that of on the day without eclipses. The objective of the observation is to see how much information can be reveal, compare to those observed during total solar eclipses. Observation had been conducted on the annular solar eclipse occurred on 15th January 2010 at Bagan, Myanmar, under excellent weather condition. A spectrograph was built based on the design of long slit intermediate resolution spectrograph for astronomy. The spectral dispersion of the spectrograph is 1.39Å per pixel and covers the spectral range from 4750Å to 6750Å. Several chromospheric emission lines were observed, such as at the λ of 4861Å (Hβ), 5172Å (Mg I), 5876Å (He I D3) & 6563Å (Hα). The Helium D3 line is of special interest due to its value of total radiation at 1,100 km from solar surface exhibit intensity decreases with increasing of solar activity. The problem of the likely anti‐correlation between the Helium D3 line intensity and the solar activity required further studies.