Mercury's magnetic field measured by MESSENGER orbiter

May 15, 2012
Mercury. Credit: NASA

Researchers working with NASA's Mercury Surface, Space Environment, Geochemistry, and Ranging (MESSENGER) spacecraft report the frequent detections of Kelvin-Helmholtz (KH) waves at the edge of the innermost planet's magnetosphere.

In six different sets of measurements made by the orbiter as it passed through Mercury's magnetopause, the boundary that separates the planet's magnetosphere from the solar wind plasma in the magnetosheath, Sundberg et al. detect the magnetic field oscillations characteristic of fully developed KH waves. Kelvin-Helmholtz waves form when fluids of different speeds travel alongside each other-in this case, the magnetosphere and magnetosheath plasmas-and promote mixing of the plasmas on larger spatial scales, and shorter time scales, than diffusive transport. The observations, which span the first 88 days of MESSENGER's time in orbit, bring Mercury alongside Earth, Saturn, and Venus as planets for which such Kelvin-Helmholtz waves are of importance.

The waves seen at Mercury's magnetopause, however, differ markedly from those at Earth's. The authors' KH wave observations were all made in the postnoon and duskside region of Mercury's , whereas at Earth, KH waves are seen farther toward the nightside on both flanks. Moreover, the measured waves had periods averaging 10-20 seconds, whereas the periods of their terrestrial counterparts are several minutes. Also, the amplitudes of the measured magnetic field oscillations were 2-3 times larger than those seen at Earth. Wave growth at the magnetopause is known to be an important mechanism for transporting material across the largely impermeable boundary, and the authors propose that these newly identified Kelvin-Helmholtz waves could be the source of plasma for Mercury's dayside , discovered previously by the .

Explore further: France raises heat on decision for next Ariane rocket

More information: MESSENGER orbital observations of large-amplitude Kelvin-Helmholtz waves at Mercury's magnetopause, Journal of Geophysical Research-Space Physics, doi:10.1029/2011JA017268 , 2012

add to favorites email to friend print save as pdf

Related Stories

MESSENGER On Its Way

Aug 04, 2004

The MESSENGER spacecraft lifted off on-time aboard a Boeing Delta II rocket from pad 17-B at Cape Canaveral Air Force Station, Fla., at 2:15:56.537 a.m. EDT. MESSENGER has successfully begun its mission to u ...

A new way to measure Earth's magnetosphere

Jan 04, 2012

US researchers have demonstrated the potential use of a new way to measure properties of Earth's magnetosphere, the magnetic bubble that surrounds the planet.

Recommended for you

Winter in the southern uplands of Mars

9 hours ago

Over billions of years, the southern uplands of Mars have been pockmarked by numerous impact features, which are often so closely packed that they overlap. One such feature is Hooke crater, shown in this ...

Five facts about NASA's ISS-RapidScat

9 hours ago

NASA's ISS-RapidScat mission will observe ocean wind speed and direction over most of the globe, bringing a new eye on tropical storms, hurricanes and typhoons. Here are five fast facts about the mission.

User comments : 0