Temperatures of coronal holes observed with the YOHKOH SXT

Details Temperatures of coronal holes observed with the YOHKOH SXT Temperatures of coronal holes observed with the YOHKOH SXT

Oct 1994

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994pasj...46..493h&link_type=abstract

PASJ: Publications of the Astronomical Society of Japan (ISSN 0004-6264), vol. 46, no. 5, p. 493-502

Astronomy and Astrophysics

Astronomy

55

Coronal Holes, Density (Mass/Volume), Mathematical Models, Point Spread Functions, Solar Activity, Solar Corona, Solar Temperature, Solar X-Rays, X Ray Astronomy, X Ray Imagery, Calibrating, Cameras, Charge Coupled Devices, Plasma Temperature, Satellite Instruments, Solar Wind, X Ray Scattering, X Ray Telescopes

Scientific paper

Temperatures of coronal holes have been estimated from several sets of soft X-ray images taken through various broad-band filters with the Soft X-ray Telescope (SXT) aboard Yohkoh. Since coronal holes are dark areas, a detailed examination of the telescope point spread function, which is slightly dependent on the X-ray wavelength, is of crucial importance. The calibration is made using post-launch data, and the effect of scattered X-rays from bright regions surrounding coronal holes, especially those from nearby active regions, is carefully removed. An isothermal approximation is applied to the thus-corrected data. The temperatures of coronal holes near the disk center are found to be 1.8-2.4 x 106 K, which is almost the same as those derived for quiet regions not including active regions. The emission measures in coronal holes are estimated to be (1025.5-26.2)/(cm5), about ten times smaller than those of quiet regions. We conclude that temperatures in coronal holes do not differ from those in quiet regions, and that the depression in the soft X-ray intensity of coronal hole regions results from a lower density by a factor of 3 than quiet regions.

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