Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Using dimensionality reduction and clustering techniques to classify
  space plasma regimes   Collisionless space plasma environments are typically characterised by
distinct particle populations. Although moments of their velocity distribution
functions help in distinguishing different plasma regimes, the distribution
functions themselves provide more comprehensive information about the plasma
state, especially at times when the distribution function includes non-thermal
effects. Unlike moments, however, distribution functions are not easily
characterised by a small number of parameters, making their classification more
difficult to achieve. In order to perform this classification, we propose to
distinguish between the different plasma regions by applying dimensionality
reduction and clustering methods to electron distributions in pitch angle and
energy space. We utilise four separate algorithms to achieve our plasma
classifications: autoencoders, principal component analysis, mean shift, and
agglomerative clustering. We test our classification algorithms by applying our
scheme to data from the Cluster-PEACE instrument measured in the Earth's
magnetotail. Traditionally, it is thought that the Earth's magnetotail is split
into three different regions (the plasma sheet, the plasma sheet boundary
layer, and the lobes), that are primarily defined by their plasma
characteristics. Starting with the ECLAT database with associated
classifications based on the plasma parameters, we identify 8 distinct groups
of distributions, that are dependent upon significantly more complex plasma and
field dynamics. By comparing the average distributions as well as the plasma
and magnetic field parameters for each region, we relate several of the groups
to different plasma sheet populations, and the rest we attribute to the plasma
sheet boundary layer and the lobes. We find clear distinctions between each of
our classified regions and the ECLAT results.

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The categories of this paper are: nucl-th
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The categories of this paper are: econ
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The categories of this paper are: q-fin
27
The categories of this paper are: comp-gas
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The categories of this paper are: quant-ph
1
The categories of this paper are: cs
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The categories of this paper are: q-bio
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The categories of this paper are: math-ph
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The categories of this paper are: astro-ph
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The categories of this paper are: nlin
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The categories of this paper are: patt-sol
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The categories of this paper are: hep-lat
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The categories of this paper are: eess
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The categories of this paper are: plasm-ph
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The categories of this paper are: q-alg
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The categories of this paper are: hep-ex