Observations of global modes outside the plasmasphere Michael Hartinger1, Vassilis Angelopoulos1, Mark Moldwin1,2, Karl-Heinz Glassmeier3, Yukitoshi Nishimura4,5, Drew Turner1, Margaret Kivelson1,2, Kazue Takahashi6, John Bonnell7, Jürgen Matzka8, Claudia Stolle8 GEM 2012 NOTE: This work has since been published as: M. Hartinger et al. (2012), Observations of a Pc5 global (cavity/waveguide) mode outside the plasmasphere by THEMIS, J. Geophys. Res., DOI: 10.1029/2011JA017266. 1UCLA ESS Dept, 2University of Michigan, AOSS Dept, 3Technical University of Braunschweig, 4Solar-Terrestrial Environment Laboratory, Nagoya University, 5UCLA AOS Dept, 6Applied Physics Laboratory, 7UC Berkeley SSL, 8DTU Space, Technical University of Denmark Global modes [Freeman, 2000] • Global modes are a mechanism that can explain the origin of monochromatic ULF waves in the magnetosphere even in the absence of a driver with a monochromatic frequency spectrum UT [Hartinger et al., 2012] Advantages of THEMIS for global mode observations [Lee, 1996] • The THEMIS probes have a low inclination orbit and are located near the magnetic equator, where fast mode wave energy tends to be confined [NOAA] • THEMIS flew during a solar minimum [NASA] • Multi-point observations, electric/magnetic/plasma observations at each point multiple lines of evidence for wave mode ID • Sensitive instruments observe low amplitude waves • For example, CRRES was used for global mode case studies. CRRES FGM: sensitivity of ~500 pT THEMIS FGM:sensitivity of ~12 pT Identifying global modes Global mode detected Global mode not detected • Only global modes that persist for long enough for THEMIS to detect coherent electric and magnetic perturbations can be detected • Global modes can never be observed at their peak amplitudes • Superpositions of waveguide modes can not be detected • Other wave activity obscures global modes Statistical study of global modes • Using ground observations and electric, magnetic, and plasma observations from single and multi- spacecraft we identified 72 events • A lower bound for the occurrence rate of global modes is 1.0% Results, spatial locations • Global modes are detected more often near noon • See our poster on Tuesday for more details on the statistical study (e.g., favored driving conditions) • Also see our recent publication in JGR “Observations of a Pc5 global (cavity/ waveguide) mode outside the plasmasphere by THEMIS” for more details on the case study .