Multi-spacecraft observations of small-scale fluctuations in density and fields in plasmaspheric plumes
2012 (English)In: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 30, no 3, 623-637 p.Article in journal (Refereed) Published
In this event study, small-scale fluctuations in plasmaspheric plumes with time scales of similar to 10 s to minutes in the spacecraft frame are examined. In one event, plasmaspheric plumes are observed by Cluster, while IMAGE measured density enhancement at a similar location. Fluctuations in density exist in plumes as detected by Cluster and are accompanied by fluctuations in magnetic fields and electric fields. Magnetic fluctuations are transverse and along the direction of the plumes. The E/B ratio is smaller than the Alfv,n velocity. Another similar event is briefly presented. We then consider physical properties of the fluctuations. Alfv,n mode modulated by the feedback instability is one possibility, although non-local generation is likely. It is hard to show that the fluctuations represent a fast mode. Interchange motion is possible due to the consistency between measurements and expectations. The energy source could be a pressure or density gradient in plasmaspheric plumes. When more events are accumulated so that statistical analysis becomes feasible, this type of study will be useful to understand the time evolution of plumes.
Place, publisher, year, edition, pages
2012. Vol. 30, no 3, 623-637 p.
Magnetospheric physics, Plasmasphere
IdentifiersURN: urn:nbn:se:uu:diva-174220DOI: 10.5194/angeo-30-623-2012ISI: 000302269700017OAI: oai:DiVA.org:uu-174220DiVA: diva2:526657