May 25, 2012, 12:00 pm - 1:00 pm

May 25, 12:00 pm - 1:00 pm

Coherent ~1 Hz waves in Mercury's Inner Magnetosphere

Dr. Scott Boardsen, NASA Goddard Space Flight Center/University of Maryland

Coherent waves occurring at frequencies between the He+ and proton cyclotron frequencies are observed on about 50% of the orbital crossings of Mercury's magnetic equator by MESSENGER when inside of 2 Mercury radii. These waves tend to be strongly compressional around the equator and they become transverse as they propagate away the equator. The wave power maximizes around the equator, and is larger for equatorial crossings that encounter the plasma sheet. There are two schools of thought on the source of these waves: 1) field-line resonances feed by waves propagating from the magnetopause and 2) waves generated by unstable ion distributions in and at the edges of the plasma sheet in high proton beta plasmas. We present of statistical study and our interpretation of the results of this study for the first two Hermian solar years of orbital phase of the MESSENGER mission.