Variation of Thermal Structure with Height of a Solar Active Region Derived from SOHO CDS and YOHKOH BCS Observations
Title | Variation of Thermal Structure with Height of a Solar Active Region Derived from SOHO CDS and YOHKOH BCS Observations |
Publication Type | Journal Article |
Year of Publication | 1999 |
Authors | Sterling, A. C., Pike C. D., Mason H. E., Watanabe T., and Antiochos S. K. |
Journal | Astrophysical Journal |
Volume | 524 |
Pagination | 1096-1104 |
Date Published | Oct |
Abstract | We present observations of NOAA solar Active Region 7999 when it was near the west solar limb on 1996 December 2 and 3, using data from the Coronal Diagnostic Spectrometer (CDS) experiment on the SOHO satellite. Ratios of intensities of 2 MK material (as observed in CDS Fe XVI images) to 1 MK material (from CDS Mg IX images) indicate that there is a drop in the ratio of the hotter to the cooler material with height in the region, up to an altitude of about 10\^ 5 km. At low altitudes the relative amount of 2 MK emission measure to 1 MK emission measure ranges from 8 to 10, while the ratio is minimum near 10\^ 5 km, ranging from 1.3 to 3.5. The decrease with height of the CDS ratio qualitatively resembles the decrease in S XV election temperature with height (measurable up to \~ 85,000 km) in the same active region obtained from the Bragg crystal spectrometer instrument on Yohkoh. The CDS images indicate that the highest S XV temperatures and largest CDS ratios correspond to regions of microflares, and somewhat lower S XV temperatures and CDS ratios correspond to diffuse regions. Above 10\^ 5 km, the trend of the CDS ratios changes, either increasing or remaining approximately constant with height. At these altitudes the CDS images show faint, large-scale diffuse structures. |
DOI | 10.1086/307820 |
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