Search

In this study we present the first statistical analysis on the effects of heliospheric current sheet crossings on the induced magnetosphere of Venus. These events are of particular interest because they lead to the reconfiguration of the induced magnetosphere with opposite polarity. We use a statistical approach based on 117 orbit pairs, and we study the spatial distribution of the heavy ion flux measurements in the plasma environment of Venus. The average and median heavy ion flux measurements are compared before and after the polarity reversal events. The results show that after the events the average and median heavy ion fluxes in the magnetotail are reduced by the factors of 0.75 ± 0.09 and 0.52, respectively. We find that even if a passage of a current sheet is a short time scale event lasting about 10 min, its effect on the near-Venus plasma environment lasts for a few hours. We conclude that the observations show similarities to the previous comet studies and the polarity reversal of the induced magnetosphere might be accompanied with dayside reconnection and magnetic disconnection of the plasma tail from the planetary ionosphere.

[1] In this paper we present a study of the beam-driven wave generation mechanisms in linear approximation which are viable in the flowside plasma mantle of Saturn's moon, Titan. The flowside plasma mantle is defined, by analogy with the dayside plasma mantle of the planet Venus and Mars, as being the interaction region between the “cold” ionospheric plasma and “hot” streaming plasma of magnetospheric or solar wind origin, with both types of plasma being present in comparable densities. Since no in situ plasma and field measurements are currently available in Titan's flowside mantle, we performed our model calculations in a broad plasma parameter space encompassing the plasma characteristics determined by Voyager 1 in Titan's wake. Two types of beam instability modes were found to be dominant: a fluid-like (nonresonant) modified two-stream instability (MTSI) and the kinetic (beam resonant) ion-ion acoustic instability (IIAI). The two instability modes are characterized by distinct frequency ranges (an order or below the lower hybrid frequency for the MTSI and a few times the lower hybrid frequency for the IIAI) and are found to be dominant in well-separated spatial regions determined by the presence/absence of cold ionospheric electrons. Giving a global rather than a specific description of the instability types expected to be the most important growing modes within Titan's flowside mantle, we intend to make predictions concerning the wave characteristics of the dominant wave modes measurable by the plasma wave instrument on board the Cassini spacecraft.

The elastic decay width of some πN resonances is evaluated in the SL(2, C) model of Regge poles. Two families of resonances are examined in the first order of symmetry breaking, one of them has isotopic spinI=1/2, the otherI=3/2. The width of other resonances along the trajectories is calculated in symmetry limit and the differential cross-section is examined for πN backward scattering. The results are in good agreement with experiments.