Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Successive Injection of Opposite Magnetic Helicity in Solar Active
  Region NOAA 11928   Understanding the nature and evolution of the photospheric helicity flux
transfer is a key to reveal the role of magnetic helicity in coronal dynamics
of solar active regions. Using SDO/HMI photospheric vector magnetograms and the
derived flow velocity field, we computed boundary driven helicity flux with a
12 minute cadence during the emergence of AR 11928. Accounting the foot point
connectivity defined by non-linear force-free magnetic extrapolations, we
derived and analyzed the corrected distribution of helicity flux maps. The
photospheric helicity flux injection is found to changes sign during the steady
emergence of the AR. This reversal is confirmed with the evolution of the
photospheric electric currents and with the coronal connectivity as observed in
EUV wavelengths with SDO/AIA. During about the three first days of emergence,
the AR coronal helicity is positive while later on the field configuration is
close to a potential field. As theoretically expected, the magnetic helicity
cancelation is associated to enhanced coronal activity. The study suggests a
boundary driven transformation of the chirality in the global AR magnetic
structure. This may be the result of the emergence of a flux rope with positive
twist around its apex while it has negative twist in its legs. The origin of
such mixed helicity flux rope in the convective zone is challenging for models.

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The categories of this paper are: q-bio
35
The categories of this paper are: mtrl-th
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The categories of this paper are: nucl-ex
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The categories of this paper are: acc-phys
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The categories of this paper are: patt-sol
37
The categories of this paper are: supr-con
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The categories of this paper are: nlin
34
The categories of this paper are: chem-ph
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The categories of this paper are: chao-dyn
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The categories of this paper are: hep-ex
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The categories of this paper are: comp-gas
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The categories of this paper are: gr-qc
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The categories of this paper are: bayes-an
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The categories of this paper are: hep-lat
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The categories of this paper are: ao-sci
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The categories of this paper are: eess