Modeling the sun's small-scale global photospheric magnetic field
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We present a new model for the Sun's global photospheric magnetic field during a deep minimum of activity, in which no active regions emerge. The emergence and subsequent evolution of small-scale magnetic features across the full solar surface is simulated, subject to the influence of a global supergranular flow pattern. Visually, the resulting simulated magnetograms reproduce the typical structure and scale observed in quiet Sun magnetograms. Quantitatively, the simulation quickly reaches a steady state, resulting in a mean field and flux distribution that are in good agreement with those determined from observations. A potential coronal magnetic field is extrapolated from the simulated full Sun magnetograms to consider the implications of such a quiet photospheric magnetic field on the corona and inner heliosphere. The bulk of the coronal magnetic field closes very low down, in short connections between small-scale features in the simulated magnetic network. Just 0.1% of the photospheric magnetic flux is found to be open at 2.5 R⊙, around 10–100 times less than that determined for typical Helioseismic and Magnetic Imager synoptic map observations. If such conditions were to exist on the Sun, this would lead to a significantly weaker interplanetary magnetic field than is currently observed, and hence a much higher cosmic ray flux at Earth.
Meyer , K A & Mackay , D H 2016 , ' Modeling the sun's small-scale global photospheric magnetic field ' Astrophysical Journal , vol 830 , no. 2 , 160 . DOI: 10.3847/0004-637X/830/2/160
© 2016, The American Astronomical Society. This work has been made available online in accordance with the publisher’s policies. This is the final published version of the work, which was originally published at iopscience.iop.org / https://doi.org/10.3847/0004-637X/830/2/160
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