87 Figure 7: Critical pitch angle (charge-exchange loss cone angle) is shown as function of radial distance from LEO at various L-values. It is seen that the loss cone narrows drastically for all L-values at radial distances greater than ~ 2000 km from LEO. Figure 8: Schematic representation of the beam-magnetosphere and beamionosphere interactions involving propagation and reflection of an Alfven wave. The curvature of the magnetic field lines and the gradient of magnetic field intensity are not represented in this schematic model. Figure 9: The Alfven speed is shown as function of radial distance from the earth’s surface for geomagnetic field lines of various L-values. It is seen that with the exception of a very local region near 500 km altitude the Alfven speed is well above the 3.5 keV argon beam speed. Near LEO a substantial fraction of the beam may precipitate promptly anyway. Figure 10: Model calculation of the plasma flow speed as result of plasma beam injection at the equatorial plane at two field lines: L=4 and L=3. Each panel is a plot of flow speed as function of time at a fixed point on the field line. Solid lines indicate plasma flow in +x direction and dashed lines indicate plasma flow in -x direction. Figure 11: Comparison of charge exchange and Coulomb lifetimes of Ar+ ions at various geocentric distances in the equatorial plane. The charge exchange cross section used in the calculation of the lifetime was measured by Gilbody and Hasted (1956). Note that Ar+ ions are assumed to have lower energies because of the beam stopping mechanism.
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