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Keywords:

  • MESSENGER;
  • Mercury;
  • global kinetic simulations;
  • magnetosphere

[1] Mariner 10 and MESSENGER spacecraft observations have established that Mercury has an intrinsic magnetic field and magnetosphere. Following the March 2011 insertion of MESSENGER into orbit around Mercury, measurements show that ions and electrons with typical energies of about 1–10 keV form an equatorially centered distribution of plasma at 1.4 RM radial distance (where RMis Mercury's radius) around a substantial portion of the planet in local time from morning through night and into the afternoon sector. Coincident with the detection of plasma around Mercury, an observed drop in the total magnetic pressure is attributable to the ion and electron thermal pressure. Additionally, intense waves near the ion cyclotron frequency were observed at the same location as the quasi-trapped particle population, which are likely a result of anisotropic distributions created by the large loss cone (>30o) at these radial distances.