Electron density fluctuations are regularly observed near the plasmapause together with electromagnetic waves below the electron cyclotron frequency (usually called hiss or chorus). Instruments on board CLUSTER spacecraft often observe two such emission bands with fluctuating wave intensities that suggest wave ducting in density enhancements as well as troughs. Near perigee the CLUSTER density measurements are usually limited to the electron density from 0.2 to 80 cm−3. To establish a correlation between density and wave intensity deeper inside the outer plasmasphere, we extrapolate the electron density from the spacecraft potential after fitting a relationship between observed plasma frequency and spacecraft potential. During a plasmapause crossing on June 5, 2001 (near the geomagnetic equator, L = 4 − 6, afternoon sector), density fluctuations up to hundreds cm−3 are found while whistler mode waves are observed in two separate frequency bands, at 100–500 Hz (correlated to the density fluctuations) and 3–6 kHz (anti‐correlated).

[1] Multipoint measurements from Cluster of a particularly slow encounter with the Earth's bow shock are presented. The shock is classified as high Mach number, quasiperpendicular, and high plasma beta. Coherent oscillations of the plasma density and the magnetic field amplitude are seen in the foot and ramp of the shock with period approximately 15 s; the traversal of the shock layer lasts 2 min. The oscillation amplitude decreases upstream from a maximum value at the location of the shock overshoot so that it is confined within the shock layer. Phase differences in the oscillations as seen on the four Cluster spacecraft indicate that the oscillations are propagating, and cannot be explained by a one-dimensional shock profile fluctuating in position. Four-point timing shows that the oscillations correspond to ripples traveling across the surface of the shock, with wavelength 1000-2000 km and propagation direction roughly parallel to the magnetic field. The presence of these oscillations could have major implications for the analysis of crossings observed at higher relative shock-spacecraft speeds or where the interspacecraft spacing is larger and the shock velocity is changing.

Abstract. Whistler waves propagating along the ambient magnetic field are observed within a coronal mass ejection (on January 10, 1997) associated in time with Langmuir waves and electron distributions of a single loss cone type. In addition, background observations are made on the plasma wave activity in the sheath and foreshock regions that precede the magnetic cloud, on the observed radio emissions (including a type II radio burst) and on the geometry of the cloud. All the data comes from the WIND spacecraft. The whistler waves are identified using full magnetic waveforms while possible evidence of coexisting parallel, and antiparallel propagating Langmuir modes are found in the waveform and spectral wave data from the WAVES experiment. A few hundred low energy electron distributions from the Three-Dimensional Plasma (3DP) experiment are investigated. Finally, we tentatively suggest that this type of plasma wave particle activity is linked to the type II emission observed, i.e., that the emission mechanisms are proceeding and taking place within the magnetic cloud instead of at the shock region as usually thought. The extra suprathermal electrons could source from electrons accelerated at reconnection sites between the magnetic cloud and the ambient interplanetary magnetic field. A linear instability study using observed properties of the electron distributions is to be presented in a following paper.

Abstract. We present the application of a numerical method to correct electron moments calculated on-board spacecraft from the effects of potential broadening and energy range truncation. Assuming a shape for the natural distribution of the ambient plasma and employing the scalar approximation, the on-board moments can be represented as non-linear integral functions of the underlying distribution. We have implemented an algorithm which inverts this system successfully over a wide range of parameters for an assumed underlying drifting Maxwellian distribution. The outputs of the solver are the corrected electron plasma temperature T e , density N e and velocity vector V e . We also make an estimation of the temperature anisotropy A of the distribution. We present corrected moment data from Cluster's PEACE experiment for a range of plasma environments and make comparisons with electron and ion data from other Cluster instruments, as well as the equivalent ground-based calculations using full 3-D distribution PEACE telemetry.

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