Abstract
Tailward flow of energetic neutral atoms observed at Venus
Physikalisches Institut, Universität Bern, Bern, Switzerland
Geospace Physics Laboratory, NASA Goddard Space Flight Center, Greenbelt, Maryland, USA
Physikalisches Institut, Universität Bern, Bern, Switzerland
Instituted för Rymdfysik, Kiruna, Sweden
Instituted för Rymdfysik, Kiruna, Sweden
Instituted för Rymdfysik, Kiruna, Sweden
Instituted för Rymdfysik, Kiruna, Sweden
Instituted för Rymdfysik, Kiruna, Sweden
Finnish Meteorological Institute, Helsinki, Finland
Department of Physics, West Virginia University, Morgantown, West Virginia, USA
The Analyzer of Space Plasma and Energetic Atoms (ASPERA-4) experiment on Venus Express provides the first measurements of energetic neutral atoms (ENAs) from Venus. The results improve our knowledge on the interaction of the solar wind with a nonmagnetized planet and they present an observational constraint to existing plasma models. We characterize the tailward flow of hydrogen ENAs observed on the nightside by providing global images of the ENA intensity. The images show a highly concentrated tailward flow of hydrogen ENAs tangential to the Venus limb around the Sun's direction. No oxygen ENAs above the instrument threshold are detected. The observed ENA intensities are reproduced with a simple ENA model within a factor of 2, indicating that the observed hydrogen ENAs originate from shocked solar wind protons that charge exchange with the neutral hydrogen exosphere.
Received 31 January 2008; accepted 26 August 2008; published 2 December 2008.
Citation: (2008), Tailward flow of energetic neutral atoms observed at Venus, J. Geophys. Res., 113, E00B15, doi:10.1029/2008JE003096.
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