Sizes of solar active regions at 8 mm

J. Kallunki*, M. Uunila

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

4 Citations (Scopus)


We investigate the sizes of 86 non-flaring solar active regions with respect to the brightness temperature at 8 mm and active region magnetic field strength. The data were collected in AprilŰSeptember, 2014, and AprilŰJuly, 2015 at Aalto University, Metsähovi Radio Observatory with the 14-m radio telescope. The observations were made at the maximum of the solar cycle 24. We used active region magnetic field strength values measured with the Helioseismic and Magnetic Imager instrument aboard the Solar Dynamics Observatory. We calculated that the mean active region size in percentage of the full solar disk is 3.7 ś 0.86%. In addition, the mean temperature of selected active regions is around 109% of the quiet Sun level and the average magnetic field strength of the studied active region is 1,400 G. Our results show correlation between active region sizes, the total brightness temperature of the Sun, and the active region magnetic field strengths.
Original languageEnglish
Pages (from-to)398-406
Number of pages9
JournalAstronomische Nachrichten
Issue number4
Publication statusPublished - 1 May 2017
MoE publication typeA1 Journal article-refereed


  • Magnetic field
  • Radio brightening
  • Sun: Solar activity
  • Sunspot

Fingerprint Dive into the research topics of 'Sizes of solar active regions at 8 mm'. Together they form a unique fingerprint.

Cite this