Other
Scientific paper
Jan 1992
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1992phdt.......109s&link_type=abstract
Thesis (PH.D.)--CORNELL UNIVERSITY, 1992.Source: Dissertation Abstracts International, Volume: 52-12, Section: B, page: 6462.
Other
3
Space Plasma, Barium Release
Scientific paper
The critical ionization velocity effect (CIV), proposed by Hannes Alfven, may play a major role in the formation, shaping, and distribution of matter in the universe. It is a mechanism whereby the kinetic energy of a neutral cloud relative to a magnetized plasma is used for self -ionization of the neutral cloud. The magnetized plasma through which the neutral cloud passes acts as a type of catalyst, promoting a reaction that would not otherwise occur. For the past 30 years the question of whether a magnetized plasma can act as such a catalyst for the ionization of a streaming gas has been studied in the laboratory where the basic concept has been proven correct. In this thesis we report on a set of rocket borne CIV experiments, CRIT I & II, which were conducted in the ionosphere with barium. We present measurements of the plasma density, electric fields, magnetic fields, energetic electrons, and energetic ions within the ionizing barium stream. Plasma density enhancements were observed and are shown to be signatures of a CIV process albeit one which is less efficient than theory suggests. Other signatures of CIV such as scattering and slowing of the newly created barium ions, heating of electrons, and the emission of an Alfven waves from the ionization region were also detected. We have found that waves within the region where CIV is active are not the classical lower hybrid waves as predicted by current theories. Since waves of some sort are required by all conceivable theories linking the beam energy to the electron gas, this result is quite important. Instead we find a low-frequency long-wavelength mode that is in resonance with the barium ion beam (omega ~ vec k cdotvec V_{ rm beam}). Through an interferometric analysis of the electric field data we show that the wave vector vec k of these waves is aligned with the barium beam (57^circ to vec B_0) while the electric field of the waves is almost perpendicular to vec B_0. Therefore, the wave appears to be a mixed electrostatic and electromagnetic mode. We present a theory for the electrostatic component, which appears to dominate the wave characteristics.
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