Graduate of the Physics School at the National University of Mexico in Mexico City with a Masters and Doctorate degree from the University of Colorado in Boulder, Colorado (1970). Full time researcher at the Institute of Geophysics of the National University of Mexico since 1970. President of the Mexican Geophysical Union (1982-1984) and head of the Space Physics Department in the Institute of Geophysics (2016-2018)
Measurements conducted with the Venus Express (VEX) spacecraft at its entry and exit through vortex structures in the Venus wake reveal that their position varies with the solar cycle. Both crossings are consistently measured closer to Venus during minimum solar cycle conditions and are gradually encountered at larger distances downstream from the planet along the solar cycle. At the same time their width along the VEX trajectory on the plane transverse to the solar wind direction is larger during minimum solar cycle conditions and show a gradual decrease along the solar cycle. As a result the vortex structures are envisioned as features that gradually become thinner as they extend along the Venus wake and agree with the geometry of a vortex flow in fluid dynamics whose thickness decreases with the downstream distance from an obstacle. Similar conditions should also be applicable to Mars and other bodies within the solar system and also possibly to exo-planets in external stellar systems.
Part of the book: Solar System Planets and Exoplanets
Measurements conducted with spacecraft around Venus and Mars have shown the presence of vortex structures in their plasma wake. Such features extend across distances of the order of a planetary radius and travel along their wake with a few minutes rotation period. At Venus, they are oriented in the counterclockwise sense when viewed from the wake. Vortex structures have also been reported from measurements conducted by the solar wind-Mars ionospheric boundary. Their position in the Venus wake varies during the solar cycle and becomes located closer to Venus with narrower width values during minimum solar cycle conditions. As a whole there is a tendency for the thickness of the vortex structures to become smaller with the downstream distance from Venus in a configuration similar to that of a corkscrew flow in fluid dynamics and that gradually becomes smaller with increasing distance downstream from an obstacle. It is argued that such process derives from the transport of momentum from vortex structures to motion directed along the Venus wake and that it is driven by the thermal expansion of the solar wind. The implications of that momentum transport are examined to stress an enhancement in the kinetic energy of particles that move along the wake after reducing the rotational kinetic energy of particles streaming in a vortex flow. As a result, the kinetic energy of plasma articles along the Venus wake becomes enhanced by the momentum of the vortex flow, which decreases its size in that direction. Particle fluxes with such properties should be measured with increasing distance downstream from Venus. Similar conditions should also be expected in vortex flows subject to pressure forces that drive them behind an obstacle.
Part of the book: Vortex Dynamics
Measurements conducted with the PVO and the VEX spacecraft have shown that the solar wind that streams around the Venus ionosphere produces plasma vortex-shaped structures across its wake. Those features are a varying property whose width gradually decreases with the downstream distance along the wake. Further studies suggest that as the width of the vortex structures becomes smaller with distance and since the total energy of the particles involved in the vortex motion should be maintained, the energy of particles that move in the central part of the wake should be enhanced. As a result, there should be a continuous energization of the planetary ions that are carried off by the solar wind from the Venus ionosphere; namely, accelerated planetary ions should be measured along the Venus wake. Different from measurements conducted in the Venus near wake where planetary O+ ions move with speeds smaller than those of the solar wind, the conditions far downstream along the wake imply that as a result of the gradual decrease of the vortex width with distance downstream from Venus, the planetary ions that stream in that direction acquire larger speed values and thus become accelerated.
Part of the book: Plasma Science
Measurements conducted with the Venus Express spacecraft (VEX) around Venus have provided evidence for the presence of a vortex structure in its wake. A configuration of the form of a corkscrew flow with a cross-section comparable to the planet’s radius has been inferred from those measurements and exhibits a rotation in the counterclockwise sense when viewed from the wake back to Venus. Such structure is generated by the solar wind and also by planetary ions driven along the wake as inferred from the analysis of data obtained in several orbits of that spacecraft. It has also been learned that the width of the corkscrew structure gradually decreases with distance along the wake and its position varies along the solar cycle occurring closer to the planet during minimum solar cycle conditions. Measurements also show that the flow speed of the planetary ions driven from the nightside ionosphere is modified as they move through the corkscrew flow structure and become accelerated as the width of a corkscrew structure decreases with increasing distance downstream from Venus. Measurements also show that the mass flux of the planetary ions increases at high altitudes above the planet when they are conducted across the narrow part of a corkscrew shape in the particle distribution along the wake.
Part of the book: Vortex Simulation and Identification