Statistical Mapping of Magnetic Topology at Venus

Despite Venus having insignificant intrinsic magnetic fields, the magnetic connectivity between the solar wind and the Venus ionosphere, or magnetic topology, is not as simple as expected and is also important for characterizing the Venus space environment. This study provides a technique combining superthermal electron energy and pitch angle distributions to infer up to 6 subtypes of magnetic topology at Venus. This enables us to determine magnetic topology with automated procedures using the Venus Express (VEx) observations from May 2006 to November 2014. We find that the draped topology (both ends of a field line not connected to the collisional ionosphere) is the dominant topology in the near-Venus space environment, >70%, except at low altitudes close to the ionosphere. The open (a field line connected to both the solar wind and the collisional ionosphere) and closed (a field line connected only to the collisional ionosphere) topologies make up 20%-30% on average of the magnetotail and up to 50% at low altitudes. This study provides the first characterization of the statistical distributions of different magnetic topologies at Venus.