Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Role of poloidal-pressure-asymmetry-driven flows in L-H transition and
  impurity transport during MGI shutdowns   Poloidal asymmetries in tokamaks are usually investigated in the context of
various transport processes, usually invoking neoclassical physics. A simpler
approach based on magnetohydrodynamics (MHD), focusing on the effects rather
than the causes of asymmetries, yields useful insights into the generation of
shear flows and radial electric field. The crucial point to recognize is that
an MHD equilibrium in which the plasma pressure is not a flux function can be
maintained only by contributions from mass flows. Coupling between the
asymmetry-generated forces and toroidal geometry results in a strongly up-down
asymmetric effect, where the flows exhibit a strong dependence on the location
of the asymmetry with respect to the midplane. This location-dependence can be
used as an effective control mechanism for the edge and thus the global
confinement in tokamaks. It can also explain a number of poorly-understood
observations. For instance, strong dependence of the low to high (L-H)
confinement transition power threshold $P_{LH}$ on the magnetic topology can be
qualitatively explained within this framework. Similarly, upper-lower midplane
dependence of the poloidal flow direction after massive gas injections (MGI)
naturally follows from this discussion. Similar arguments suggest that the ITER
fueling ports above the midplane, to the extent they can generate a positive
pressure asymmetry at the edge, are misplaced and may lead to higher input
power requirements.

2
The categories of this paper are: math
18
The categories of this paper are: econ
5
The categories of this paper are: gr-qc
28
The categories of this paper are: alg-geom
10
The categories of this paper are: q-bio
7
The categories of this paper are: hep-th
26
The categories of this paper are: bayes-an
9
The categories of this paper are: nlin
23
The categories of this paper are: solv-int
1
The categories of this paper are: cs
37
The categories of this paper are: supr-con
27
The categories of this paper are: comp-gas
25
The categories of this paper are: patt-sol
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The categories of this paper are: plasm-ph
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The categories of this paper are: acc-phys
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The categories of this paper are: chao-dyn