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Dr Mark Koepke, West Virginia University

Location: 520A/B

The dispersive Alfvén wave in the time-stationary limit with a
focus on the collisional and warm-plasma effects inherent in the
18-m-long plasma column at UCLA's Basic Plasma Science Facility

 M. E. Koepke^1, S. M. Finnegan^1, D. J. Knudsen^2, and S. Vincena^3

1 West Virginia University, Morgantown, WV, USA
2 University of Calgary, Calgary, Alberta, Canada
3 University of California-Los Angeles, Los Angeles, CA, USA

A  nonlinear, collisional, two-fluid model of uniform plasma convection
across a field-aligned current sheet, describing the stationary Alfvén
wave is presented.  In a previous work, Knudsen showed that, for cold,
collisionless plasma [D. J. Knudsen, J. Geophys. Res. 101, 10761
(1996)], the stationary inertial Alfvén wave can accelerate electrons
parallel to a background magnetic field and cause large,
time-independent plasma-density variations having spatial periodicity in
the direction of the convective flow over a broad range of spatial
scales and energies.  Knudsen suggested that these fundamental
properties of the stationary inertial Alfvén wave may play a role in the
formation of discrete auroral arcs.  Here, Knudsen's model has been
generalized for warm, collisional plasma to make possible predictions
for laboratory plasma experiments.  From this generalization, it is
shown that nonzero ion-neutral and electron-ion collisional resistivity
significantly alters the perpendicular ac and dc structure of magnetic
field-aligned electron drift, and can either dissipate or enhance the
field-aligned electron energy depending on the initial value of
field-aligned electron drift velocity.  It is also shown that nonzero
values of plasma pressure reduce the dominant Fourier component of
perpendicular wavenumber.  Experimentally, an off-axis, fixed channel of
electron current (and depleted density) is created in the Large Plasma
Device Upgrade at UCLA's Basic Plasma Science Facility while the
surrounding larger plasma column rotates about its cylindrical axis. A
variety of diagnostic methods are employed to study plasma equilibrium
and stability.  We use a small, heated, oxide-coated electrode at one
plasma-column end and we show that the larger plasma column rotates
about its cylindrical axis from a radial electric field imposed by a
special termination electrode on the same end.  We show that both
launched and spontaneously arising inertial Alfvén waves concentrate in
this off-axis channel of electron current and depleted plasma density,
consistent with predictions. 

Tags: CFSA Seminar

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