SHEDDING NEW LIGHT ON SOLITARY WAVES OBSERVED IN SPACE

Abstract

Electrostatic solitary waves are routinely observed by the Cluster Wideband (WBD) plasma wave receiver as the Cluster spacecraft cross boundary layers and regions of turbulence. These solitary waves are observed in the electric field waveform data as isolated pulses of various shapes, but primarily in the bipolar and tripolar forms. The amplitudes of the solitary waves appear to follow a somewhat general trend of increasing amplitude with increasing background magnetic field strength. Thus, the largest amplitude solitary waves are usually found closer to Earth as Cluster crosses magnetic field lines at about 4.5-6.5 RE that map to the auroral acceleration region and the smallest amplitudes farthest from Earth in the plasmasheet, magnetosheath and solar wind at 18-19.5 RE. Bow shock crossings are particularly interesting as there are significant differences in the number, amplitude and time duration of solitary wave pulses detected which probably indicate a dependence on the upstream environment and configuration of the interplanetary magnetic field. Continuing closer to earth into the magnetosheath we find that on the dayside, solitary waves are almost always present and the characteristics of them do not change appreciably from the bow shock to the magnetopause. This suggests that the solitary waves observed in the magnetosheath are being locally produced in the magnetosheath through one or more generation mechanisms. As we explore the properties of these solitary waves in the various regions, as well as the methods by which they could be produced, we hope to determine if and how these solitary waves are involved in more fundamental macroscale plasma processes.