Electromagnetic electron and proton cyclotron waves in geospace: a Cassini snapshot

摘要: Abstract The Cassini spacecraft flew past the Earth in a trajectory almost along Sun-Earth line, giving unique perspective of low frequency waves geospace. Geotail was immediately upstream bow shock nose, allowing for an accurate assessment solar wind conditions driving geospace macroscale processes, latter which led to microinstabilities and electromagnetic plasma wave growth. We demonstrate presence nonlinear cyclotron foreshock, magnetosheath, outer magnetosphere, tail lobe. A predominance right-hand with f≈1.0 Hz (in frame) are detected foreshock. compressional Δ¯B/B0 ∼0.25. It is argued that these propagating electron (whistler) mode generated by low-energy electrons streaming into region parallel kinetic energies tens eV. This appears be pure magnetosheath largest amplitude (∼15 nT peak-to-peak ∼30 field) proton amplitudes near decrease ∼8 magnetopause. No discernible mirror structures were magnetosheath. possible abundance He++ ions high-speed stream may cause ion dominance, as previously predicted theory. However, other explanations well. magnetospheric intensity (∼4 peak-to-peak), can weak pitch angle diffusion concomitant diffuse aurora. Large-scale ram pressure pulses do not appear waves. small scale fluctuations possible. Two new low-intensity modes identified lobes associated substorm events. One transverse, elliptically polarized ∼7.5 s purely (∼0.1 amplitude) wave, quasiperiod. obliquely (∼70° 84°) magnetic field.