Comparison of Pioneer Venus and Venera bow shock observations: Evidence for a solar cycle variation

Journal Article · Thu Nov 01 04:00:00 EST 1979 · Geophys. Res. Lett.; (United States)

DOI:https://doi.org/10.1029/GL006i011p00905· OSTI ID:5730285

Slavin, J A; Elphic, R C; Russell, C T

Observations by the Venera 9 and 10 orbiters in 1975--1976 have been used in previous studies to determmine the mean location and shape of the Cytherean bow shock. In addition it has also been reported that the shock is found to be more distant from the planet above regions of the ionosheath where draped IMF field lines are oriented perpendicular to the flow as opposed to parallel. An examination of the dependence of shock altitude in the terminator plane on upstream IMF direction using 86 Pioneer Venus orbiter bow shock crossings in 1978--79 sets an upper limmit on this asymmetry of 12% or approximately half that derived earlier from the Venera data. More significantly, the mean distance to the bow shock observed by Pioneer Venus Orbiter is 35% greater than was the case in 1975--76 near solar minimum. As the growth in effective obstacle radius is an order of magnitude larger than can be accounted for in terms of varying ionopause altitude due to all causes, these results strongly suggest that Venus can absorb significantly more of the incident solar wind plasma diring solar minimum when EUV flux is low than during the current epoch in which maximum is approaching.

• Research Organization: Institute of Geophysics and Planetary Physics, University of California, Los Angeles, California 90024
• OSTI ID: 5730285
• Journal Information: Geophys. Res. Lett.; (United States), Journal Name: Geophys. Res. Lett.; (United States) Vol. 6:11; ISSN GPRLA
• Country of Publication: United States
• Language: English

Related Subjects

640107* -- Astrophysics & Cosmology-- Planetary Phenomena
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ABSORPTION
ATMOSPHERES
ENERGY ABSORPTION
INTERPLANETARY MAGNETIC FIELDS
MAGNETIC FIELDS
MAGNETOPAUSE
PIONEER SPACE PROBES
PLANETARY ATMOSPHERES
PLANETARY MAGNETOSPHERES
PLANETS
SOLAR ACTIVITY
SOLAR CYCLE
SOLAR WIND
SPACE VEHICLES
VENERA SPACE PROBES
VENUS PLANET