AGU journal highlights - July 2, 2009

Title: Geomagnetic dipole moment collapse by convective mixing in the core

Authors: Lijun Liu: Seismological Laboratory, California Institute of Technology, Pasadena, California, USA;

Peter Olson: Department of Earth and Planetary Sciences, Johns Hopkins University, Baltimore, Maryland, USA.

Source: Geophysical Research Letters (GRL) paper 10.1029/2009GL038130, 2009; http://dx.doi.org/10.1029/2009GL038130

12. Energetic particles slow solar wind at the edge of the solar system

In 2007, the Voyager 2 spacecraft crossed the solar wind termination shock, the boundary with interstellar space where the solar wind—the stream of charged particles emitted by the Sun—collides with the interstellar medium and slows from supersonic to subsonic speeds. In the 40 days prior to crossing the termination shock, Voyager 2 measured a gradual decrease in the solar wind speed from about 380 to 300 kilometers per second (236 to 186 miles per second), as well as an exponential increase in the intensity of energetic ions in the region. Using a simple two-fluid model and plasma and energetic particle conservation laws, Florinski et al. show that the ions, with energies of a few megaelectron volts, could produce enough pressure to create a precursor shock that caused the observed deceleration of the solar wind. The source of these ions has not been determined, but the study sheds light on this distant region at the edge of the solar system.

Title: An energetic-particle-mediated termination shock observed by Voyager 2

Authors: V. Florinski, J. A. le Roux, G. P. Zank: Department of Physics and Center for Space Plasma and Aeronomic Research, University of Alabama in Huntsville, Huntsville, Alabama, USA;

R. B. Decker: Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland, USA.

Source: Geophysical Research Letters (GRL) paper 10.1029/2009GL038423, 2009; http://dx.doi.org/10.1029/2009GL038423

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