Measurement of the Coronal Electron Temperature at the Total Solar Eclipse on 1994 November 3

Abstract

A spectroscopic observation was carried out at the total solar eclipse on 1994 November 3 in Putre, Chile, in order to investigate the electron temperature and the expanding motion of the corona. The shape of weak depressions at 3900 Å and 4300 Å in the continuous coronal spectra was compared with the theoretical electron-scattered coronal spectra; thus, the magnitude of the electron thermal motion was determined directly. It was found that a coronal streamer on the eastern limb and a coronal hole on the south-pole have overall temperatures of about 1.5–1.7 MK and 0.9–1.1 MK, respectively. No significant height variation in the temperature was found in the streamer, while the coronal hole shows evidence of increasing temperature with height. An acceleration of the expanding motion between 1.1 R⊙ and 2.0 R⊙ by ∼ 80 km s−1 was found in the streamer.

Electron-Temperature Maps of the Low Solar Corona: ISCORE Results from the Total Solar Eclipse of 29 March 2006 in Libya

“…Earlier attempts using electron-based measurements include Grall et al (1996), using interplanetary radio scintillation measurements, and Fineschi et al (1998), using Ly α profiles obtained from observations through the Ultraviolet Coronagraph Spectrometer (UVCS) onboard the Solar and Heliospheric Observatory (SOHO). Ichimoto et al (1996) obtained a measurement also based on electron scattering. Reginald et al (2003) reported spectroscopic measurements at several locations in the K-corona from measurements obtained during the 2001 eclipse in Zambia.…”

The Effects of Streamers on the Shape of the K-Coronal Spectrum

“…The electron density model used by Cram (1976), in formulating the properties of the K-coronal intensity spectrum for the determination of the thermal electron temperature in the corona, is given in Equation (4): Ichimoto et al (1996) used the same electron density model given in Equation (4) in determining the coronal electron temperatures. Their eclipse observation of November 1994 coincided with the Sun at its minimum phase where the coronal brightness is prominently displayed in an elongated shape in the equatorial regions of the Sun.…”

“…This model is appropriate for the temperature determination by Ichimoto et al (1996) because their observations were confined to regions between 1.5R and 2.0R and also their observations on the total solar eclipse of November 1994 coincided with the minimum phase of the Sun.…”

“…Figure 8 is a comparison of the electron number density functions based on the models by Baumbach (1937;Equation (3)), Ichimoto et al (1996;Equation (4)), Newkirk (1961; Equation (5)), Cranmer et al (1999;Equation (6)) and Guhathakurta and Holzer (1994; Equation (8)). Figure 9 is a comparison of the shapes of the K-coronal intensity spectra based on the Baumbach (1937;Equation (3)), Ichimoto et al (1996;Equation (4)), Newkirk (1961; Equation (5)), Cranmer et al (1999;Equation (6)) and Guhathakurta and Holzer (1994;Equation (8)) models for the electron number density. The multiple model K-coronal intensity spectra plotted in Figure 9 pertain to a line of sight at 2.0R from the center of the Sun and are normalized at 4000.0Å.…”

“…This plot is simply for the comparison of the shapes of the modeled K-coronal spectra based on different electron density models. The Baumbach (1937;Equation (3)), Ichimoto et al (1996;Equation (4)), Newkirk (1961; Equation (5)), Cranmer et al (1999;Equation (6)) and Guhathakurta and Holzer (1994;Equation (8)). theory by Cram (1976) for the determination of the thermal electron temperature of the solar corona is based upon the shape of the K-coronal spectrum and not its absolute values.…”