Laboratory Investigation of the Effect of the Lower Ionosphere Conductivity on FACs, Particles Acceleration, Auroral Luminosity, and Ionospheric Plasma Depletion

Details Laboratory Investigation of the Effect of the Lower Ionosphere Conductivity on FACs, Particles Acceleration, Auroral Luminosity, and Ionospheric Plasma Depletion Laboratory Investigation of the Effect of the Lower Ionosphere Conductivity on FACs, Particles Acceleration, Auroral Luminosity, and Ionospheric Plasma Depletion

Dec 2004

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2004agufmsm44a..05g&link_type=abstract

American Geophysical Union, Fall Meeting 2004, abstract #SM44A-05

Physics

2407 Auroral Ionosphere (2704), 2411 Electric Fields (2712), 2431 Ionosphere/Magnetosphere Interactions (2736), 2451 Particle Acceleration, 2471 Plasma Waves And Instabilities

Scientific paper

Investigation of the influence of local conductivity in the artificial lower ionosphere on distributions of the ionospheric plasma density, currents and luminosity is carried out in the model laboratory experiments. The effects of local conductivity are notable when the field-aligned current (FAC) exceeds some critical value. At this case the regions of anomalous conductivity and field-aligned electric fields appear and cause electron acceleration. The FAC have fine spatial structure and contains high-frequency oscillations. The spatial and temporal parameters of the electron fluxes are determined predominantly by these high-frequency components and to lesser degree by FAC total magnitude. When the region of reduced conductivity is located under the FAC layer, the "auroral" luminosity disappears or gets weaker. Above the region of reduced conductivity the effect of plasma depletion is observed. If spatial distribution of the conductivity under the plasma jet that generates the FAC has periodic character, a temporal modulation of the horizontal currents, which close the FAC, is revealed. These horizontal currents correspond to the Pedersen and Hall currents in the real ionosphere. The magnetic field induced by these current alternates with a frequency determined by spatial characteristics of the conductivity region and by the velocity of the plasma jet. Qualitatively this effect simulates the electrojet modulation and ELF pulsation generation by varying power in the radio heating experiments. The effect of "plasma memory" was also revealed. It consists in persistence of the "plasma bubble" when the plasma jet abandons the magnetic flux tube treaded the region of reduced conductivity. The pattern of plasma density changing in the plasma depletion regions above the regions of reduced conductivity and effect of "plasma memory" are similar an appearance of plasma bubbles observed in RF heater experiments in the ionosphere. At the same time, generally accepted interpretation of their results and the models of ionospheric ducts and plasma bubble formation cannot explain the effects observed in the laboratory conditions. We believe that effects revealed in our experiments should be taken into account at consideration of the phenomena in the real ionosphere.

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