Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The nonpotentiality of coronae of solar active regions, the dynamics of
  the surface magnetic field, and the potential for large flares   Flares and eruptions from solar active regions are associated with
atmospheric electrical currents accompanying distortions of the coronal field
away from a lowest-energy potential state. In order to better understand the
origin of these currents and their role in M- and X-class flares, I review all
active-region observations made with SDO/HMI and SDO/AIA from 2010/05 through
2014/10 within approximately 40 degrees from disk center. I select the roughly
4% of all regions that display a distinctly nonpotential coronal configuration
in loops with a length comparable to the scale of the active region, and all
that emit GOES X-class flares. The data for 41 regions confirm, with a single
exception, that strong-field, high-gradient polarity inversion lines (SHILs)
created during emergence of magnetic flux into, and related displacement
within, pre-existing active regions are associated with X-class flares. Obvious
nonpotentiality in the active region-scale loops occurs in 6 of 10 selected
regions with X-class flares, all with relatively long SHILs along their primary
polarity inversion line, or with a long internal filament there.
Nonpotentiality can exist in active regions well past the flux-emergence phase,
often with reduced or absent flaring. I conclude that the dynamics of the flux
involved in the compact SHILs is of preeminent importance for the large-flare
potential of active regions within the next day, but that their associated
currents may not reveal themselves in active region-scale nonpotentiality. In
contrast, active region-scale nonpotentiality, which can persist for many days,
may inform us about the eruption potential other than those from SHILs which is
almost never associated with X-class flaring.

17
The categories of this paper are: q-fin
34
The categories of this paper are: chem-ph
4
The categories of this paper are: cond-mat
20
The categories of this paper are: acc-phys
25
The categories of this paper are: patt-sol
3
The categories of this paper are: physics
12
The categories of this paper are: nucl-th
10
The categories of this paper are: q-bio
2
The categories of this paper are: math
23
The categories of this paper are: solv-int
28
The categories of this paper are: alg-geom
33
The categories of this paper are: plasm-ph
30
The categories of this paper are: q-alg
15
The categories of this paper are: nucl-ex
9
The categories of this paper are: nlin
5
The categories of this paper are: gr-qc