3,127 research outputs found
NHDS: The New Hampshire Dispersion Relation Solver
NHDS is the New Hampshire Dispersion Relation Solver. This article describes
the numerics of the solver and its capabilities. The code is available for
download on https://github.com/danielver02/NHDS.Comment: 3 pages, 1 figur
When is an area law not an area law?
Entanglement entropy is typically proportional to area, but sometimes it
acquires an additional logarithmic pre-factor. We offer some intuitive
explanations for these facts.Comment: plainTeX, 12 pages, 3 figures. A more current version may be
available at http://www.perimeterinstitute.ca/personal/rsorkin/some.papers
Instabilities Driven by the Drift and Temperature Anisotropy of Alpha Particles in the Solar Wind
We investigate the conditions under which parallel-propagating
Alfv\'en/ion-cyclotron (A/IC) waves and fast-magnetosonic/whistler (FM/W) waves
are driven unstable by the differential flow and temperature anisotropy of
alpha particles in the solar wind. We focus on the limit in which , where is the
parallel alpha-particle thermal speed and is the Alfv\'en
speed. We derive analytic expressions for the instability thresholds of these
waves, which show, e.g., how the minimum unstable alpha-particle beam speed
depends upon , the degree of alpha-particle
temperature anisotropy, and the alpha-to-proton temperature ratio. We validate
our analytical results using numerical solutions to the full hot-plasma
dispersion relation. Consistent with previous work, we find that temperature
anisotropy allows A/IC waves and FM/W waves to become unstable at significantly
lower values of the alpha-particle beam speed than in the
isotropic-temperature case. Likewise, differential flow lowers the minimum
temperature anisotropy needed to excite A/IC or FM/W waves relative to the case
in which . We discuss the relevance of our results to alpha
particles in the solar wind near 1 AU.Comment: 13 pages, 13 figure
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