H. Pérez de Tejada

Second Latin American conference on space geophysics

The Second Latin American Conference on Space Geophysics was organized under the auspices of the National University of Mexico (UNAM), with financial support from the Mexican Council for Science and Technology, the Pan-American Institute for Geography and History, and the Latin American School of Physics. It was held in Cuernavaca, Mexico July 8–12, 1991.

Acceleration of ionospheric plasma clouds in the Venus ionosheath

Abstract A discussion is presented to examine the acceleration and distribution of ionospheric plasma clouds around Venus. It is argued that magnetic forces may not be sufficient to accelerate those features and that their motion should also be influenced by the momentum of the solar wind around the flanks of the ionosheath. Plasma data obtained from selected Pioneer Venus Orbiter (PVO) passes show ionospheric clouds that have been displaced downstream from the planet, with a component directed away from the Venus plasma tail axis. The position and speed of these features suggests that they may not have been only accelerated by magnetic forces, but that most likely were also subject to effects produced by the kinetic energy of the solar wind. This suggestion derives from the observation of plasma tail rays with velocities comparable to the escape speed from the planet and also measurements of superalfvenic solar wind conditions around the flanks of the Venus ionosheath. While plasma clouds can be accelerated by magnetic forces near the subsolar region, where there is a strong accumulation of interplanetary magnetic field fluxes, the available experimental evidence shows that the Venus upper ionospheric plasma is accelerated mostly near the terminator, but not around the subsolar region. These views suggest that the ionospheric plasma clouds could be mostly accelerated around the flanks of the Venus ionosheath.

Geometry of comet Halley's outer plasma environment

Abstract A study of comet Halleys outer plasma environment is presented. It is argued that the intermediate transition detected nearly half way between the comets bow shock and the cometopause represents the outer boundary of a thick friction layer that develops along the flanks of the cometopause. In the subsolar region the cometopause and the intermediate transition are expected to reach nearly the same (∼ 3.5 10(5) km) distance from the nucleus. The plasma changes seen in the outer ionosheath (between the bow shock and the intermediate transition) are further interpreted as due to an intrinsic axial asymmetry of the cometopause which may have a highly oblate cross-sectional shape with respect to the solar wind direction.

Plasma Heating In The Saturn’s Magnetosphere

Voyager and Cassini plasma probe observations suggest that there are at least three fundamentally different plasma regimes in Saturn: the hot outer magnetosphere, the extended plasma sheet, and the inner plasma torus. At the outer regions of the inner torus some ions have been accelerated to reach energies of the order of 43 keV. Protons are the dominant species outside about 9 Rs, whereas inside, the plasma consists primarily of a corotating comet‐like mix of water‐derived ions with ∼3% N+. Over the A and B rings, an ionosphere —dominated by O2+ and O+ — can be observed. The energies of magnetospheric particles range from hundreds of keV to several MeV. Possible explanations to the observed high‐energy population of particles involve the release of magnetic energy which heats the ion component of the plasma and then accelerates electrons to energies of some MeV. In this work we develop a model that calculates the acceleration of charged particles in the Saturn’s magnetosphere. We propose that the stochas...