Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The magnetization degree of the outflow powering the highly-polarized
  reverse shock emission of GRB 120308A   GRB 120308A, a long duration $\gamma-$ray burst detected by {\it Swift}, was
distinguished by a highly-polarized early optical afterglow emission that
strongly suggests an ordered magnetic field component in the emitting region.
In this work we model the optical and X-ray emission in the reverse and forward
shock scenario and show that the strength of the magnetic field in reverse
shock region is $\sim 10$ times stronger than that in the forward shock region.
Consequently the outflow powering the highly-polarized reverse shock optical
emission was mildly-magnetized at a degree $\sigma \sim$ a few percent.
Considering the plausible magnetic energy dissipation in both the acceleration
and prompt emission phases of the Gamma-ray Burst (GRB) outflow, the afterglow
data of GRB 120308A provides us the compelling evidence that at least for some
GRBs a non-ignorable fraction of the energy was released in the form of
Poynting-flux, confirming the finding firstly made in the reverse-forward shock
emission modeling of the optical afterglow of GRB 990123 (Fan et al. 2002;
Zhang et al. 2003).

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The categories of this paper are: atom-ph
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The categories of this paper are: plasm-ph
1
The categories of this paper are: cs
17
The categories of this paper are: q-fin
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The categories of this paper are: comp-gas
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The categories of this paper are: cmp-lg
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The categories of this paper are: q-bio
22
The categories of this paper are: chao-dyn
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The categories of this paper are: bayes-an
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The categories of this paper are: supr-con
0
The categories of this paper are: hep-ph
14
The categories of this paper are: math-ph
13
The categories of this paper are: quant-ph
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The categories of this paper are: mtrl-th
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The categories of this paper are: funct-an
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The categories of this paper are: solv-int