HR: 1400h
AN: SM23B-01    [Abstracts]
TI: Search for Na+ Pickup Ion Generated Waves at Mercury
AU: * Boardsen, S A
EM: Scott.A.Boardsen.1@gsfc.nasa.gov
AF: UMBC/GEST, Code 670.0 NASA/Goddard Space Flight Center, Greenbelt, Md 20771, United States
AU: Slavin, J A
EM: James.A.Slavin.1@gsfc.nasa.gov
AF: NASA, Code 670.0 NASA/Goddard Space Flight Center, Greenbelt, Md 20771, United States
AB: Telescopic observations by Potter et al. [2002] have discovered that Mercury's Sodium exosphere has a tail extending 10's of Mercury radii. Theory predicts that the shape of and the amount of Sodium [Smyth, 1986, 1995; Ip 1986, 1990] in this exospheric tail is highly dependent upon the true anomaly of Mercury. The exospheric Na that is not reabsorbed on Mercury's surface will be photo-ionized. Computations by Ip [1986] indicated that ionized exospheric Na could significantly mass load the plasma population in Mercury's magnetosphere. These freshly created ions will be rapidly energized by the convection electric field in Mercury's magnetosphere and sheath and should be highly unstable to the generation of plasma waves. These waves could play an important role in the thermalization and retention of the Na+. Because the gyro radii of Na+ can be comparable to the scale sizes in Mercury's geospace there is an open question whether Mercury's geospace can sustain such waves. After a brief review of what was observed in the Mariner 10 magnetometer data, we will present analytic calculations of the expected pickup ion distributions, the expected unstable waves, their frequencies, wavelengths and Doppler shifts, their variation with location in Mercury's geospace and Mercury's true anomaly for both high and low solar wind convection electric fields. We will assess if and when such waves can be generated and sustained.
DE: 0328 Exosphere
DE: 2152 Pickup ions
DE: 2700 MAGNETOSPHERIC PHYSICS (6939)
DE: 2772 Plasma waves and instabilities (2471)
DE: 6235 Mercury
SC: SPA-Magnetospheric Physics [SM]
MN: 2007 Joint Assembly