Asymmetries of the magnetic field line draping shape around Venus

The magnetic field data observed by Venus Express (VEX) from April 2006 to December 2009 are analyzed in order to describe the magnetic configuration around Venus. All the magnetic observations are organized in a coordinate system which is determined by the solar wind (SW) flow and the interplanetary magnetic field. By averaging and compiling the VEX data, we compile a global picture of the magnetic field for the SW interaction with Venus. The magnetic field around the planet displays a clear asymmetry on both field strength and pattern. The magnetic field is stronger on the +E hemisphere where the convective electric field E→SW points away from the planet, and is wrapped around the planet more tightly on the -E hemisphere where E→SW points toward the planet. The underlying physics of this E→SW asymmetry is still under debate. Except in ideal single-fluid MHD simulation, the E→SW asymmetry can be observed in both multifluid MHD and hybrid simulations. Key Points The magnetic field around Venus displays a clear hemispheric asymmetry The field is stronger on the +E hemisphere, and more wrapped on the other This asymmetry may be associated with finite ion gyroradius effects