Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Magnetic Field Generation in Planets and Satellites by Natural Nuclear
  Fission Reactors   One of the most fundamental problems in physics has been to understand the
nature of the mechanism that generates the geomagnetic field and the magnetic
fields of other planets and satellites. For decades, the dynamo mechanism,
thought to be responsible for generating the geomagnetic field and other
planetary magnetic fields, has been ascribed to convection in each planet's
iron-alloy core. Recently, I described the problems inherent in Earth-core
convection and proposed instead that the geomagnetic field is produced by a
dynamo mechanism involving convection, not in the fluid core, but in the
electrically conductive, fluid, fission-product sub-shell of a natural nuclear
fission reactor at the center of the Earth, called the georeactor. Here I set
forth in detail the commonality in the Solar System of the matter like that of
the inside of the Earth, which is my basis for generalizing the concept of
planetary magnetic field generation by natural planetocentric nuclear fission
reactors.

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The categories of this paper are: q-bio
33
The categories of this paper are: plasm-ph
19
The categories of this paper are: eess
28
The categories of this paper are: alg-geom
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The categories of this paper are: econ
24
The categories of this paper are: dg-ga
9
The categories of this paper are: nlin
17
The categories of this paper are: q-fin
34
The categories of this paper are: chem-ph
35
The categories of this paper are: mtrl-th
32
The categories of this paper are: atom-ph
14
The categories of this paper are: math-ph
31
The categories of this paper are: ao-sci
6
The categories of this paper are: astro-ph
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The categories of this paper are: cond-mat
29
The categories of this paper are: funct-an