[Baps] Thursday 8th - Ralph McNutt (APL) Mercury magnetosphere talk

[Paul Withers]

Space physics seminar
Ralph McNutt
Johns Hopkins University, Applied Physics Laboratory
*“*Taking the Measure of Mercury’s Magnetosphere:
Energetic Electrons and MESSENGER Mission*”*

*Thursday, November 8, 2012*
*Refreshments at 3:30pm in CAS 500*
*Talk begins at 4:00pm in CAS 502*

Abstract:

Twice in 1974 and a third time in 1975, the Mariner 10spacecraft flew by
the innermost planet of the solar system, providing our first close-up
views of the planet Mercury. One of the greatest scientific surprises
was the presence of an active magnetic dynamo of sufficient strength to
provide a magnetosphere, at that time only the third such system known
in the solar system. On the first flyby, Mariner also observed what were
interpreted as significant particle acceleration events, but
instrumental limitations left significant uncertainties as to their
nature. Hence, when the MErcury Surface, Space ENvironment,
GEochemistry, and Ranging (MESSENGER) mission was first proposed to
NASA’s Discovery program of planetary missions in the Fall of 1996,
understanding the elusive energetic particle measurements was not a
primary goal, as too little was known to frame a proper scientific
question regarding their role in planetary science at Mercury. However,
an energetic particle instrument was included in the payload to help
understand any particle-induced corrections to the internal magnetic
field, the measurement of which was a primary goal. For the same
reasons, a small plasma instrument was added at the time of the second –
and successful – MESSENGER proposal in 1998. In spite of extreme mass
limitations, and with little to go on for sizing the instrument
capabilities, these experiments were included in MESSENGER’s payload as
the Energetic Particle and Plasma Spectrometer (EPPS). Following no
detections of energetic particles on the three gravity-assist flybys of
Mercury, MESSENGER’s year of orbital operations has shown energetic
electrons to be a quasi-permanent feature of the magnetosphere, and
their further investigation is a primary goal of the ongoing extended
mission. Mercury’s magnetosphere has proven to be highly dynamic and its
activity, coupled with the rise in solar activity toward solar maximum,
continues to provide clues to the nature of these enigmatic particles
first briefly glimpsed by Mariner 10 over 35 years ago.

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Alyson Savoie

Fiscal Administrator

Boston University

Center for Space Physics

Institute for Astrophysical Research

725 Commonwealth Avenue, Room 506

Boston, Massachusetts 02215

Tel: 617-358-0603

Fax:617-353-6463