July 21, 2010

AGU Selects MESSENGER Paper As Eos Research Spotlight

The American Geophysical Union has selected a research paper detailing observations of Mercury's magnetosphere during the probe's third flyby as a "Research Highlight" in today's issue of Eos, the AGU's weekly online and print newspaper.

"Observations of Kelvin-Helmholtz waves along the dusk-side boundary of Mercury's magnetosphere during MESSENGER's third flyby," by Scott Boardsen and coauthors, originally published in Geophysical Research Letters, is available online at http://www.agu.org/pubs/crossref/2010/2010GL043606.shtml.

In it, Boardsen, an associate research scientist at the Goddard Earth Sciences and Technology Center, and his colleagues report the first detection at Mercury's magnetospheric boundary of Kelvin-Helmholtz waves, surface waves that form when two fluids with different speeds move past one another. Such waves can be created along a planet's magnetopause when solar wind plasma interacts with the magnetosphere.

During MESSENGER's previous flybys, no such waves were detected. But during the third flyby, 15 crossings of the dusk"side magnetopause were observed in the magnetic field data over a two-minute period, during which the spacecraft traveled a distance of 0.2 Mercury radii.

"The quasi"periodic nature of the magnetic field variations during the crossings, the characteristic time separations of about 16 s between pairs of crossings, and the variations of the magnetopause normal directions indicate that the signals are likely the signature of surface waves highly steepened at their leading edge that arose from the Kelvin"Helmholtz instability," Boardsen and coauthors wrote. "At Earth, the Kelvin"Helmholtz instability is believed to lead to the turbulent transport of solar wind plasma into Earth's plasma sheet. This solar wind entry mechanism could also be important at Mercury."


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