SHEDDING NEW LIGHT ON SOLITARY WAVES OBSERVED IN SPACE

摘要

Electrostatic solitary waves are routinely observed byrnthe Cluster Wideband (WBD) plasma wave receiver asrnthe Cluster spacecraft cross boundary layers and regionsrnof turbulence. These solitary waves are observed in thernelectric field waveform data as isolated pulses ofrnvarious shapes, but primarily in the bipolar and tripolarrnforms. The amplitudes of the solitary waves appear tornfollow a somewhat general trend of increasingrnamplitude with increasing background magnetic fieldrnstrength. Thus, the largest amplitude solitary waves arernusually found closer to Earth as Cluster crossesrnmagnetic field lines at about 4.5-6.5 RE that map to thernauroral acceleration region and the smallest amplitudesrnfarthest from Earth in the plasmasheet, magnetosheathrnand solar wind at 18-19.5 RE. Bow shock crossings arernparticularly interesting as there are significantrndifferences in the number, amplitude and time durationrnof solitary wave pulses detected which probablyrnindicate a dependence on the upstream environment andrnconfiguration of the interplanetary magnetic field.rnContinuing closer to earth into the magnetosheath wernfind that on the dayside, solitary waves are almostrnalways present and the characteristics of them do notrnchange appreciably from the bow shock to thernmagnetopause. This suggests that the solitary wavesrnobserved in the magnetosheath are being locallyrnproduced in the magnetosheath through one or morerngeneration mechanisms. As we explore the propertiesrnof these solitary waves in the various regions, as well asrnthe methods by which they could be produced, we hopernto determine if and how these solitary waves arerninvolved in more fundamental macroscale plasmarnprocesses.