Alfven wave generation by means of high orbital injection of barium cloud in magnetosphere

Abstract

An analysis of the Alfven wave generation associated with the barium vapor release at altitudes ~ 5.2 R E in the magnetosphere is presented. Such injections were executed in G-8 and G-10 experiments of the Combined Radiation and Radiation Effects Satellite (CRRES) mission. It is shown that the generation of Alfven waves is possible during the total time of the expansion of plasma cloud. The maximum intensity of these waves corresponds to the time of complete retardation of the diamagnetic cavity created by the expansion of the plasma cloud. The Alfven wave exhibits a form of an impulse with an effective frequency ~ 0.03-0.05 Hz. Due to the background conditions and wave frequency, the wave mainly oscillates along the geomagnetic field between the mirror reflection points situated at ~ 0.7 R E i.e. the wave is trapped by the magnetospheric Alfven resonator. The reflection coefficient is about 80-85%. The wave amplitude is sufficient to the generation of plasma instabilities and longitudinal electric field, and to an increase in the longitudinal energy of electrons accelerated by this field up to ~ 1 keV. These processes are the most probable for altitudes ~ 1 R E . The auroral kilometric radiation (AKR) at frequencies ~ 100 kHz is associated with these accelerated electrons. It is shown that the acceleration of electrons and AKR can be observed almost continuously during the first minute and then from time to time with pauses about 35-40 s till 6-8 min after the release. Apparently, these findings do not contradict the experimental data.The betatron acceleration of electrons at the recovery of the geomagnetic field is also discussed. This mechanism could be responsible for the acceleration of electrons resulting in the aurorae and ultra short radio wave storm at frequencies 50-300 MHz observed at the 8-10th min after the release. impulse in detail. Note that the quantities V, R, and J R are estimated under an assumption on the homogeneous density distribution of barium atoms inside the sphere of the radius R 0 . For a more realistic Gauss distribution, the decrease in the density maximum is slower: t B ≈ 50 s, R B ≈ 37 km (Huba et al., 1992); and we can expect that the J R current will reach its maximum at a later time after the release.The currents J R arising in the spherical plasma layer (envelope) will generate the azimuthal currents J Φ and the currents J Θ . We assume an azimuthal symmetry of the plasma envelope and, consequently, the currents J Φ do not contribute to the current continuity divJ = 0. In addition, the contribution of J Φ is taken into account by the implication of magnetic field changes. For this reason, we consider the currents J R and J Θ only. In this case, the currents J Θ flow along the magnetic field (see Figure 1a where the lower hemisphere of the plasma envelope is shown for 0.5π < Θ < 1.5π). The currents J Θ do not close inside the plasma layer and transit (near Θ ≈ π) into the longitudinal currents J z which flow out from the envelope.Outside the plasma layer, we assume a cylindrica...

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