Wednesday, November 13, 2013

NASA MAVEN Solar Wind Electron Analyzer: Examining microscopic levels

The Solar Wind Electron Analyzer is shown before being delivered to the MAVEN spacecraft. Credit: David L. Mitchell, SSL, UC Berkeley

When the Mars Atmosphere and Volatile Evolution Mission (Maven) launches in November to study why the Red Planet is losing its atmosphere, one of its instruments will look to electrically charged particles called electrons for answers.

The Solar Wind Electron Analyzer (SWEA) is one of the eight instruments aboard MAVEN that will try to solve the mystery of Mars' dwindling atmosphere, a process that has reduced the planet to a frozen desert.

Produced in a collaboration between the Space Sciences Laboratory (SSL) at the University of California, Berkeley, and the Institut de Recherche en Astrophysique et Plan├ętologie (IRAP) in France, SWEA's assignment is to analyze electrons found in two distinct regions around Mars: the solar wind passing by and a layer of Mars' upper atmosphere—the ionosphere.

Instrument lead David L. Mitchell of SSL said that SWEA would use the information on electrons to track how other charged particles, such as planetary oxygen ions, are escaping the planet's atmosphere.

Solar wind, which continuously blows off the sun's surface at around a million miles per hour, is packed with charged particles and magnetic field lines that can interact with particles in Mars' upper atmosphere, providing a fraction of them with enough energy to leave the planet.

Using electric fields to bend the paths of electrons onto its detectors, SWEA can differentiate between electrons found in the solar wind and those in the Martian ionosphere by identifying their different energies.

Mitchell said solar wind electrons possess a broad range of energies, while those in the planet's atmosphere are produced at specific energies.

"The instrument will tell whether the spacecraft is measuring planetary plasma or solar wind plasma," Mitchell said, referring to the mixture of electrons and other charged particles.

"It determines the environment, which is important for setting the stage for interpreting other measurements."

By identifying where solar wind plasma ends and planetary plasma begins, Mitchell said SWEA would be able to zero in on the top of the planet's ionosphere.

"We're trying to understand the boundary layer between the solar wind and the planet's ionosphere because this is a key region where planetary material is being lost," Mitchell said.

"We want to understand the loss processes and how the solar wind is stripping away the atmosphere."

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