Authors: B I Ryabov D E Gary N G Peterova K Shibasaki N A Topchilo
Publish Date: 2014/12/02
Volume: 290, Issue: 1, Pages: 21-35
Abstract
We analysed specific regions of reduced soft Xray and microwave emission in five large isolated sunspots The Nobeyama Radioheliograph 17 GHz observations reveal a local depression of microwave brightness in the peripheral area of the sunspots The depression regions appear light weak absorption in the He 10830 Å line in areas with extended open field lines as indicated by potential field source surface model PFSS extrapolations up to 15 R⊙ The observed depressions of 3 – 8 in ordinary mode at 17 GHz are interpreted as resulting from free–free emission when the plasma density is lower by 5 – 10 Our model estimates show that the decrease in density in both the coronal and the lower layers above the depression region accounts for the depression These depression regions lend themselves well to marking the location of outward plasma motionsThis work was supported by the Latvian Council of sciences in the frame of the project Nr 111856 DG is supported by NSF grants AGS09059761 AST1312802 AGS1250374 and NASA grant NNX11AB49G to NJIT NT is supported by SPbSU grant 60262010 BR appreciates the hospitality and help of the Nobeyama Solar group during his stay at the Nobeyama Radio Observatory We are grateful to the National Solar Observatory Kitt Peak the Mauna Loa Solar Observatory the Debrecen Heliophysical Observatory and the Nobeyama Radio Observatory teams for making their data available This work was partly carried out on the Solar Data Analysis System operated by the Astronomy Data Center in cooperation with the Hinode Science Center of the National Astronomical Observatory of Japan We thank the anonymous referee for the useful comments that helped improve the manuscript We are grateful to Kazumasa Iwai and Dmitry Bezrukov for the assistance in preparing the data and model estimates
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