Magnetic nulls and super-radial expansion in the solar corona

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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Copyright 2017 the American Astronomical Society.

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Author Gibson, Sarah E.
Dalmasse, Kevin
Rachmeler, Laurel A.
De Rosa, Marc L.
Tomczyk, Steven
de Toma, Giuliana
Burkepile, Joan
Galloy, Michael
Publisher UCAR/NCAR - Library
Publication Date 2017-05-08T00:00:00
Digital Object Identifier (DOI) Not Assigned
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Topic Category geoscientificInformation
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Metadata Date 2023-04-14T22:03:39.612591
Metadata Record Identifier edu.ucar.opensky::articles:19755
Metadata Language eng; USA
Suggested Citation Gibson, Sarah E., Dalmasse, Kevin, Rachmeler, Laurel A., De Rosa, Marc L., Tomczyk, Steven, de Toma, Giuliana, Burkepile, Joan, Galloy, Michael. (2017). Magnetic nulls and super-radial expansion in the solar corona. UCAR/NCAR - Library. Accessed 02 June 2023.

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