Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Gas-dynamic shock heating of post-flare loops due to retraction
  following localized, impulsive reconnection   We present a novel model in which shortening of a magnetic flux tube
following localized, three-dimensional reconnection generates strong
gas-dynamic shocks around its apex. The shortening releases magnetic energy by
progressing away from the reconnection site at the Alfven speed. This launches
inward flows along the field lines whose collision creates a pair of
gas-dynamic shocks. The shocks raise both the mass density and temperature
inside the newly shortened flux tube. Reconnecting field lines whose initial
directions differ by more that 100 degrees can produce a concentrated knot of
plasma hotter that 20 MK, consistent with observations. In spite of these high
temperatures, the shocks convert less than 10% of the liberated magnetic energy
into heat - the rest remains as kinetic energy of bulk motion. These
gas-dynamic shocks arise only when the reconnection is impulsive and localized
in all three dimensions; they are distinct from the slow magnetosonic shocks of
the Petschek steady-state reconnection model.

23
The categories of this paper are: solv-int
17
The categories of this paper are: q-fin
24
The categories of this paper are: dg-ga
12
The categories of this paper are: nucl-th
32
The categories of this paper are: atom-ph
10
The categories of this paper are: q-bio
30
The categories of this paper are: q-alg
25
The categories of this paper are: patt-sol
33
The categories of this paper are: plasm-ph
0
The categories of this paper are: hep-ph
13
The categories of this paper are: quant-ph
18
The categories of this paper are: econ
8
The categories of this paper are: hep-ex
37
The categories of this paper are: supr-con
14
The categories of this paper are: math-ph
16
The categories of this paper are: stat