Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Magnetostrophic MRI in the Earth's Outer Core   We show that a simple, modified version of the Magnetorotational Instability
(MRI) can develop in the outer liquid core of the Earth, in the presence of a
background shear. It requires either thermal wind, or a primary instability,
such as convection, to drive a weak differential rotation within the core. The
force balance in the Earth's core is very unlike classical astrophysical
applications of the MRI (such as gaseous disks around stars). Here, the weak
differential rotation in the Earth core yields an instability by its
constructive interaction with the planet's much larger rotation rate. The
resulting destabilising mechanism is just strong enough to counteract
stabilizing resistive effects, and produce growth on geophysically interesting
timescales. We give a simple physical explanation of the instability, and show
that it relies on a force balance appropriate to the Earth's core, known as
magnetostrophic balance.

21
The categories of this paper are: adap-org
16
The categories of this paper are: stat
35
The categories of this paper are: mtrl-th
26
The categories of this paper are: bayes-an
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The categories of this paper are: patt-sol
5
The categories of this paper are: gr-qc
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The categories of this paper are: q-alg
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The categories of this paper are: hep-th
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The categories of this paper are: chao-dyn
4
The categories of this paper are: cond-mat
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The categories of this paper are: quant-ph
0
The categories of this paper are: hep-ph
2
The categories of this paper are: math
15
The categories of this paper are: nucl-ex
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The categories of this paper are: econ
34
The categories of this paper are: chem-ph