Reduced Coronal Emission Above Large Isolated Sunspots

B. I. Ryabov; Dale Gary; N. G. Peterova; K. Shibasaki; N. A. Topchilo

doi:10.1007/s11207-014-0634-3

Reduced Coronal Emission Above Large Isolated Sunspots

B. I. Ryabov, Dale Gary, N. G. Peterova, K. Shibasaki, N. A. Topchilo

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7 Scopus citations

Abstract

We analysed specific regions of reduced soft X-ray 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 1.5 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 motions.

Original language	English (US)
Pages (from-to)	21-35
Number of pages	15
Journal	Solar Physics
Volume	290
Issue number	1
DOIs	https://doi.org/10.1007/s11207-014-0634-3
State	Published - Jan 2015

All Science Journal Classification (ASJC) codes

Astronomy and Astrophysics
Space and Planetary Science

Keywords

Sun: corona, magnetic fields, radio emission

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10.1007/s11207-014-0634-3

Cite this

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title = "Reduced Coronal Emission Above Large Isolated Sunspots",

abstract = "We analysed specific regions of reduced soft X-ray 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 {\AA} line in areas with extended (open) field lines, as indicated by potential field source surface model (PFSS) extrapolations up to 1.5 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 motions.",

keywords = "Sun: corona, magnetic fields, radio emission",

author = "Ryabov, {B. I.} and Dale Gary and Peterova, {N. G.} and K. Shibasaki and Topchilo, {N. A.}",

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language = "English (US)",

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T1 - Reduced Coronal Emission Above Large Isolated Sunspots

AU - Ryabov, B. I.

AU - Gary, Dale

AU - Peterova, N. G.

AU - Shibasaki, K.

AU - Topchilo, N. A.

PY - 2015/1

Y1 - 2015/1

N2 - We analysed specific regions of reduced soft X-ray 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 1.5 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 motions.

AB - We analysed specific regions of reduced soft X-ray 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 1.5 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 motions.

KW - Sun: corona, magnetic fields, radio emission

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Reduced Coronal Emission Above Large Isolated Sunspots

Abstract

All Science Journal Classification (ASJC) codes

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