Astronomy and Astrophysics – Astrophysics
Scientific paper
Dec 2011
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011agufmsh43f..02r&link_type=abstract
American Geophysical Union, Fall Meeting 2011, abstract #SH43F-02
Astronomy and Astrophysics
Astrophysics
[7594] Solar Physics, Astrophysics, And Astronomy / Instruments And Techniques
Scientific paper
During the March 2006 total solar eclipse we conducted an imaging experiment using the Imaging Spectrograph of Coronal Electrons (ISCORE) to determine the coronal electron temperature and its radial flow speed in the low solar corona. This technique required taking images of the solar eclipse through four broadband filters centered at 385.0, 398.7, 410.0 and 423.3 nm. The K-coronal temperature is determined from intensity ratios from the 385.0 and 410.0 nm filters, and the K-coronal radial flow speed is determined from intensity ratios from the 398.7 and 423.3 nm filters. The theoretical model for this technique assumes a symmetric corona devoid of any features like streamers that might alter the coronal symmetry. The model also requires an isothermal temperature and a uniform outflow speed all along the line of sight. We will call this the Constant Parameter Thomson Scattering Model (CPTSM). The latter assumption may sound unreasonable but in the symmetric corona with rapid fall of the electron density with height in the solar corona, the major contributions to the K-coronal intensity along a given line of sight comes from the plasma properties in the vicinity of the plane of the sky. But the pressing question is how is the derived plasma properties by ISCORE compare with the nature of the true corona. For this we turn to the CORHEL model by Predictive Science Inc. which used magnetogram data to create a realistic model of the solar corona that are made available through the Community Coordinated Modeling Center (CCMC) at GSFC. That team has consistently produced the expected coronal image days prior to many total eclipses where the major coronal features from their model matched actual coronal image on the day of the eclipse. Using the CORHEL model data we have calculated the K-coronal intensities at 385.0, 398.7, 410.0 and 423.3 nm using the electron density, plasma temperature (assumed to be electron temperature) and the flow speeds of the plasma along the line of sight in the CORHEL model and have calculated the temperature and radial flow speed sensitive intensity ratios. Next we identify the isothermal electron temperature and the radial flow speed in the CPTSM model that would match the temperature sensitive and radial flow speed sensitive intensity ratios from the CORHEL model and compare the CPTSM temperature and flow speed values with the corresponding values in the CORHEL model in the plane of the sky. These comparisons were made for Carrington Rotation 1977 with the CORHEL model of the solar corona rotated in intervals of 45 degrees with respect to the observer located at 1 AU. The average of the difference between the electron temperatures and the radial flow speed at 5 solar radii in the East-West direction were (underestimated by 0.02 MK or an error of 1.7%) and (overestimated by 22.km/sec or an error of 18%), respectively and in the South-North direction were (underestimated by 0.04 MK or an error of 3.2%) and (overestimated by 42 km/sec or an error of 21%), respectively.
Davila Jose Manuel
Reginald Nelson Leslie
St Cyr O. C.
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