TY - JOUR
T1 - Strongest Coronal Magnetic Fields in Solar Cycles 23 and 24
T2 - Probing, Statistics, and Implications
AU - Fedenev, Viktor V.
AU - Anfinogentov, Sergey A.
AU - Fleishman, Gregory D.
N1 - Funding Information:
The authors thank Dr. Dale Gary for useful discussions. NoRH package routines from the SolarSoft (Freeland & Handy ) library of programming language IDL were used to synthesize NoRH imaging data from raw visibilities. Python programming language and SunPy library (SunPy Community et al. ) were used for the data analysis described above. G.D.F. was supported in part by NSF grant Nos. AGS-2121632 and AST-2206424 and NASA grant No. 80NSSC19K0068, and to New Jersey Institute of Technology. V.V.F. and S.A.A. acknowledge support from the Russian Scientific Foundation under project No. 21-72-10139. This research benefited from the support of the International Space Science Institute ISSI Team 497.
Publisher Copyright:
© 2023. The Author(s). Published by the American Astronomical Society.
PY - 2023/2/1
Y1 - 2023/2/1
N2 - A strong coronal magnetic field, when present, manifests itself as bright microwave sources at high frequencies produced by the gyroresonant (GR) emission mechanism in thermal coronal plasma. The highest frequency at which this emission is observed is proportional to the absolute value of the strongest coronal magnetic field on the line of sight. Although no coronal magnetic field larger than roughly 2000 G has been expected, recently a field at least 2 times larger has been reported. Here, we report on a search for and a statistical study of such strong coronal magnetic fields using high-frequency GR emission. A historic record of spatially resolved microwave observations at high frequencies, 17 and 34 GHz, is available from the Nobeyama RadioHeliograph for a period covering more than 20 yr (1995-2018). Here, we employ this data set to identify sources of bright GR emission at 34 GHz and perform a statistical analysis of the identified GR cases to quantify the strongest coronal magnetic fields during two solar cycles. We found that although active regions with a strong magnetic field are relatively rare (less than 1% of all active regions), they appear regularly on the Sun. These active regions are associated with prominent manifestations of solar activity.
AB - A strong coronal magnetic field, when present, manifests itself as bright microwave sources at high frequencies produced by the gyroresonant (GR) emission mechanism in thermal coronal plasma. The highest frequency at which this emission is observed is proportional to the absolute value of the strongest coronal magnetic field on the line of sight. Although no coronal magnetic field larger than roughly 2000 G has been expected, recently a field at least 2 times larger has been reported. Here, we report on a search for and a statistical study of such strong coronal magnetic fields using high-frequency GR emission. A historic record of spatially resolved microwave observations at high frequencies, 17 and 34 GHz, is available from the Nobeyama RadioHeliograph for a period covering more than 20 yr (1995-2018). Here, we employ this data set to identify sources of bright GR emission at 34 GHz and perform a statistical analysis of the identified GR cases to quantify the strongest coronal magnetic fields during two solar cycles. We found that although active regions with a strong magnetic field are relatively rare (less than 1% of all active regions), they appear regularly on the Sun. These active regions are associated with prominent manifestations of solar activity.
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U2 - 10.3847/1538-4357/acac33
DO - 10.3847/1538-4357/acac33
M3 - Article
AN - SCOPUS:85147823156
SN - 0004-637X
VL - 943
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 2
M1 - 160
ER -