Low-latitude coronal holes at the minimum of the 23rd solar cycle

Valentyna Abramenko, Vasyl Yurchyshyn, Jon Linker, Zoran Mikić, Janet Luhmann, Christina O. Lee

Research output: Contribution to journalArticlepeer-review

58 Scopus citations

Abstract

Low- and mid-latitude coronal holes (CHs) observed on the Sun during the current solar activity minimum (from 2006 September 21, Carrington rotation (CR) 2048, to 2009 June 26, CR 2084) were analyzed using Solar and Heliospheric Observatory/Extreme ultraviolet Imaging Telescope and STEREO-A SECCHI EUVI data. From both the observations and Potential Field Source Surface modeling, we find that the area occupied by CHs inside a belt of ±40° around the solar equator is larger in the current 2007 solar minimum relative to the similar phase of the previous 1996 solar minimum. The enhanced CH area is related to a recurrent appearance of five persistent CHs, which survived during 7-27 solar rotations. Three of the CHs are of positive magnetic polarity and two are negative. The most long-lived CH was being formed during 2 days and existed for 27rotations. This CH was associated with fast solar wind at 1 AU of approximately 620 ± 40 km s-1. The three-dimensional magnetohydrodynamic modeling for this time period shows an open field structure above this CH. We conclude that the global magnetic field of the Sun possessed a multi-pole structure during this time period. Calculation of the harmonic power spectrum of the solar magnetic field demonstrates a greater prevalence of multi-pole components over the dipole component in the 2007 solar minimum compared to the 1996 solar minimum. The unusual large separation between the dipole and multi-pole components is due to the very low magnitude of the dipole component, which is three times lower than that in the previous 1996 solar minimum.

Original languageEnglish (US)
Pages (from-to)813-818
Number of pages6
JournalAstrophysical Journal
Volume712
Issue number2
DOIs
StatePublished - 2010

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Keywords

  • Solar
  • Sun: activity
  • Sun: chromosphere
  • Sun: corona
  • Sun: magnetic topology
  • Terrestrial relations

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