Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Determining Energy Balance in the Flaring Chromosphere from Oxygen V
  Line Ratios   The impulsive phase of solar flares is a time of rapid energy deposition and
heating in the lower solar atmosphere, leading to changes in the temperature
and density structure of the region. We use an O V density diagnostic formed of
the 192 to 248 line ratio, provided by Hinode EIS, to determine the density of
flare footpoint plasma, at O V formation temperatures of 250,000 K, giving a
constraint on the properties of the heated transition region. Hinode EIS
rasters from 2 small flare events in December 2007 were used. Raster images
were co-aligned to identify and establish the footpoint pixels,
multiple-component Gaussian line fitting of the spectra was carried out to
isolate the diagnostic pair, and the density was calculated for several
footpoint areas. The assumptions of equilibrium ionization and optically thin
radiation for the O V lines were found to be acceptable. Properties of the
electron distribution, for one event, were deduced from earlier RHESSI hard
X-ray observations and used to calculate the plasma heating rate, delivered by
an electron beam adopting collisional thick-target assumptions, for 2 model
atmospheres. Electron number densities of at least log n = 12.3 cm-3 were
measured during the flare impulsive phase, far higher than previously expected.
For one footpoint, the radiative loss rate for this plasma was found to exceed
that which can be delivered by an electron beam implied by the RHESSI data.
However, when assuming a completely ionised target atmosphere the heating rate
exceeded the losses. A chromospheric thickness of 70-700 km was found to be
required to balance a conductive input to the O V-emitting region with
radiative losses. The analysis shows that for heating by collisional electrons,
it is difficult, or impossible to raise the temperature of the chromosphere to
explain the observed densities without assuming a completely ionised
atmosphere.

32
The categories of this paper are: atom-ph
21
The categories of this paper are: adap-org
15
The categories of this paper are: nucl-ex
16
The categories of this paper are: stat
35
The categories of this paper are: mtrl-th
37
The categories of this paper are: supr-con
24
The categories of this paper are: dg-ga
14
The categories of this paper are: math-ph
13
The categories of this paper are: quant-ph
33
The categories of this paper are: plasm-ph
8
The categories of this paper are: hep-ex
0
The categories of this paper are: hep-ph
31
The categories of this paper are: ao-sci
25
The categories of this paper are: patt-sol
22
The categories of this paper are: chao-dyn
1
The categories of this paper are: cs