SM31A-2475
The Quasi-Monochromatic ULF Wave Boundary in the Venusian Foreshock: VEX Observations
Wednesday, 16 December 2015
Poster Hall (Moscone South)
Christian Xavier Mazelle, University Paul Sabatier, IRAP, Toulouse, France; IRAP CNRS, Toulouse, France, Lican Shan, Chinese Academy of Sciences, Institute of Geology and Geophysics, Beijing, China, Karim Meziane, University of New Brunswick, Fredericton, NB, Canada and Magda Delva, Space Research Institute, Austrian Academy of Sciences, Graz, Austria
Abstract:
It is believed that the foreshock ultra-low frequency (ULF) waves are generated by the interactions of the solar wind with backstreaming ions produced at the bow shock. Previous studies have shown an ULF foreshock boundary exists upstream of the Earth, Venus and Saturn bow shocks below which no interplanetary magnetic field (IMF) fluctuations are present. Using data from Venus Express (VEX) magnetometer, we revisit the properties of the ULF boundary upstream of Venus bow shock after the study reported from PVO data by Greenstadt et al., JGR, 1987. On the basis of 1 Hz magnetic field measurements form VEX, we precisely investigate the boundary of monochromatic foreshock ULF waves at Venus for IMF cone angle from 10 to 70 degrees. Similarly to Earth and Saturn boundaries, we found that Venusian ULF foreshock boundary characteristics are very sensitive to the IMF direction. Precisely, both Earth and Venus boundary have a similar slope with respect to the Sun-Earth direction. Interestingly we have found that Venus ULF foreshock boundary slope increases monotonically with the IMF cone-angle. This results clearly contrasts with previous determinations.
