The calibration and initial results of the HeI D3 line flash spectrum obtained during the 2008 total solar eclipse

Abstract

The flash spectra in the HeI D3 line were obtained during the 2008 total solar eclipse. This paper describes the instrument and the calibration of the obtained flash spectrum, and presents our initial results. The average integrated intensity is Eave = 8.13×10 13 erg·cm −1 · s −1 ·ster −1 at h = 1100 km, which confirms that the HeI D3 emission is negatively correlated with the solar activity. The surface brightness reaches a maximum of F ave = 8.25×10 5 erg·cm −2 ·s −1 ·ster −1 at about h ≈ (1290 ± 75) km and then decreases exponentially with height when h >1800 km with an exponential index β = 1.63×10 −8 cm −1 .total solar eclipse, flash spectrum, spectral line Total solar eclipse (TSE) provides an excellent opportunity to observe the high chromosphere and low corona in optically thin spectral lines (e.g., the HeI D3 line) and coronal forbidden lines (e.g., the Fe xiv 5303Å and Fe x 6374Å lines). Even though some lines are also observable during the non-eclipse time, they suffer from serious sky brightness, which may be comparable with the line intensity [1] . Therefore, solar physicists always congregate from all over the world to conduct various scientific observations whenever a TSE happens.Helium is the second abundant element in the solar atmosphere. However, due to the small optical thickness, among the spectral lines of helium in the optical waveband, only the HeI D3 line, the strongest line, most commonly used in TSE observations, shows weak emission close to the solar limb. This line is important to both solar physics and the study of the excitation mechanism of helium lines. It is commonly accepted that the height distributions of surface brightness for all helium lines, including the HeI D3 line, are simi-

Recent progress in solar physics made during the program of 2008 August 1st solar total eclipse

“…By inspecting the central eclipse video records, he retrieved the data for the time when the Baily beads appeared, and deduced the value for the solar radius. Li et al [28] obtained the flash spectra in the He I D3 line during the 2008 total solar eclipse. The initial results of their observations confirmed that the He I D3 emission is negatively correlated with the solar activity.…”

Helium shells and faint emission lines from slitless flash spectra

“…Flash spectra are known for a long time [1] . Recently, observations of flash spectra were carried out by different observers at total solar eclipses using a CCD camera [2] and flash spectra experiments using optical fibers were made for polarization analysis [3] . During our observations, we performed a high cadence CCD slitless spectra in the region of the neutral helium He I 4713 Å line and of the ionized helium He II 4686 Å line, with the aim of studying the top of the photosphere and the chromosphere to corona transition region [4] .…”

Polar plumes observed at the total solar eclipse in 2009

“…Observations at total solar eclipses have their advantages for scientific studies though lots of space-borne observatories are working [10,11]. At the total solar eclipse on August 1, 2008, several groups organized by the Chinese Academy of Sciences carried out scientific observations in Jiuquan, Gansu Province, and obtained many observational results [12][13][14][15][16][17]. Those results are related to many subjects of solar physics, such as the spectra and polarizations of the solar chromosphere and corona, and the fine structures of corona.…”