Parameters of the magnetic flux inside coronal holes

Valentyna Abramenko, Vasyl Yurchyshyn, Hiroko Watanabe

Research output: Contribution to journalArticlepeer-review

28 Scopus citations

Abstract

The parameters of the magnetic flux distribution inside low-latitude coronal holes (CHs) were analyzed. A statistical study of 44 CHs based on Solar and Heliospheric Observatory (SOHO)/MDI full disk magnetograms and SOHO/EIT 284 Å images showed that the density of the net magnetic flux, Bnet, does not correlate with the associated solar wind speeds, Vx. Both the area and net flux of CHs correlate with the solar wind speed and the corresponding spatial Pearson correlation coefficients are 0. 75 and 0. 71, respectively. A possible explanation for the low correlation between Bnet and Vx is proposed. The observed non-correlation might be rooted in the structural complexity of the magnetic field. As a measure of the complexity of the magnetic field, the filling factor, f(r), was calculated as a function of spatial scales. In CHs, f(r) was found to be nearly constant at scales above 2 Mm, which indicates a monofractal structural organization and smooth temporal evolution. The magnitude of the filling factor is 0. 04 from the Hinode SOT/SP data and 0. 07 from the MDI/HR data. The Hinode data show that at scales smaller than 2 Mm, the filling factor decreases rapidly, which means a multifractal structure and highly intermittent, burst-like energy release regime. The absence of the necessary complexity in CH magnetic fields at scales above 2 Mm seems to be the most plausible reason why the net magnetic flux density does not seem to be related to the solar wind speed: the energy release dynamics, needed for solar wind acceleration, appears to occur at small scales below 1 Mm.

Original languageEnglish (US)
Pages (from-to)43-57
Number of pages15
JournalSolar Physics
Volume260
Issue number1
DOIs
StatePublished - Jan 2009

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Keywords

  • Coronal holes
  • Solar wind
  • Sun: magnetic fields

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