Institut national de recherche scientifique français Univerité Pierre et Marie Curie Université Paris Diderot - Paris 7

Voyager 1 and 2 at the Termination Shock and Heliosheath : Similarities and Differences

mercredi 6 août 2008, par S. M. Krimigis (Applied Physics Laboratory/Johns Hopkins University, Laurel, MD, USA and Academy of Athens, Athens, Greece)

Mardi 17 juin 2008 à 11h00 , Lieu : Salle de conférence du bât. 17

Voyager 2 (85.3 AU, S28° lat.) is in the inner heliosheath downstream of the solar wind termination shock, having crossed the shock at 83.7 AU several times during days 242-244 of 2007 under relatively quiet solar wind conditions. Large fluctuations in intensities of heliosheath ions, particularly those with energies below 0.2-0.3 MeV, measured throughout the past 185 days suggest that Voyager 2 remains near the shock.

This differs from the situation at Voyager 1, which was evidently left several AU behind the termination shock that moved rapidly sunward over the spacecraft at 94 AU in late 2004, and this difference may help us to separate injection and/or acceleration processes associated with the shock from those associated with the turbulent heliosheath. For example, energy spectra of low-energy heliosheath ions differ at the two spacecraft. The high intensities of these suprathermal heliosheath ions and their relatively hard energy spectra produce high ion partial pressures that dominate those associated with the thermal plasma and magnetic field, indicating that suprathermal ions play a major role in dynamical processes occurring at the termination shock and in the heliosheath.