Small scale Alfvénic structures
in the Earth's magnetosphere
A project sponsored by the International
Space Science Institute (ISSI), Bern, Switzerland.
The team has published a review article:
K. Stasiewicz, P. Bellan, C. Chaston, C. Kletzing, R. Lysak, J. Maggs,
Pokhotelov, C. Seyler, P. Shukla, L. Stenflo, A. Streltsov, and J-E.
Scale Alfvénic Structure in the Aurora (PDF
1.5MB) , Space Sci.
vol 92, no. 3-4, 423-533, 2000.
Thin auroral arcs 100-1000 m width (possibly related to Alfvenic
structures) pictured by Trond
High time resolution measurements performed in
plasma provide growing evidence that thin auroral forms with thickness
of ~1 km are related to solitary electromagnetic structures of
similar thickness. These structures are most clearly observed
in data from medium altitude satellites, as for example Freja
at h~1500 km, and are associated with strong electric fields,
field-aligned currents, large electron energy fluxes, density
depletions, and a wealth of high frequency waves. The electromagnetic
structures are being explained in the literature by a number
of competing theoretical models as for example:
(1) dispersive field line resonances
(2) solitary kinetic Alfven waves
(3) nonlinear Alfven solitons
(4) magnetic field line fractures
(5) vortex street structures
(6) Alfvenic shocks
(7) drift Alfven waves
(8) Alfven resonance cones.
This indicates great uncertainty and insufficient understanding
of the fundamentals of the ionosphere-magnetosphere coupling.
The measurements gathered on satellites Viking, Freja, Polar,
and Fast combined with high resolution ground based optical imagery,
as for example ALIS facility
in northern Scandinavia, portable
auroral imager in Canada, provide invaluable experimental
base for resolving some fundamental problems in auroral electrodynamics
and the coupling between the magnetosphere and the ionosphere.
In addition, a number of laboratory plasma devices, as for
facility in Los Angeles are being used in the parameter regime
encountered in space, and provide important clues for understanding
the plasma phenomena in space. The importance of Alfven waves
for laboratory physics, space physics and astrophysics is that
they represent a fundamental mode of transmitting information
and electromagnetic energy througth magnetized plasmas.