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arXiv · 1704.07470

Magnetic nulls and super-radial expansion in the solar corona

Sarah E. Gibson·Kevin Dalmasse·Laurel A. Rachmeler·Marc L. De Rosa·Steven Tomczyk·Giuliana de Toma·Joan Burkepile·Michael Galloy
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Abstract

Magnetic fields in the sun's outer atmosphere -- the corona -- control both solar-wind acceleration and the dynamics of solar eruptions. We present the first clear observational evidence of coronal magnetic nulls in off-limb linearly polarized observations of pseudostreamers, taken by the Coronal Multichannel Polarimeter (CoMP) telescope. These nulls represent regions where magnetic reconnection is likely to act as a catalyst for solar activity. CoMP linear-polarization observations also provide an independent, coronal proxy for magnetic expansion into the solar wind, a quantity often used to parameterize and predict the solar wind speed at Earth. We introduce a new method for explicitly calculating expansion factors from CoMP coronal linear-polarization observations, which does not require photospheric extrapolations. We conclude that linearly-polarized light is a powerful new diagnostic of critical coronal magnetic topologies and the expanding magnetic flux tubes that channel the solar wind.

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Sarah E. Gibson, Kevin Dalmasse, Laurel A. Rachmeler, Marc L. De Rosa, Steven Tomczyk, Giuliana de Toma, Joan Burkepile, Michael Galloy. 2017-05-15. Magnetic nulls and super-radial expansion in the solar corona. https://doi.org/10.3847/2041-8213%2Faa6fac

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