Тип публикации: статья из журнала
Год издания: 1998
Идентификатор DOI: 10.1029/GM105p0167
Аннотация: The combination of the tailored orbit of the Geotail spacecraft during its extensive tour of Earth's magnetotail with its state-of-the-art instrumentation has allowed many significant advances in our knowledge of this region. Three such advances are discussed. The first advance obtains from a rigorous survey for "bursty, bulk flowsПоказать полностью" of plasmas in the near-Earth plasma sheet that have been reported from observations with previous spacecraft. The near-equatorial orbit of the spacecraft at radial distances in the range of 10 to 50 Rj? was ideally suitable for such a study. The plasma measurements were sufficiently accurate to separate the bulk flows into their perpendicular and parallel components. Examination of the histograms for the perpendicular flows finds that there is no evidence for the bursty bulk flow of plasmas and magnetic flux at geocentric radial distances of about 10 to 25 RE in the central plasma sheet. On the other hand, there is substantial evidence of the presence of previously reported high-speed flows of plasmas at larger distances of about 50 Re which were associated with "magnetotail fireballs". A second advance in the studies of magnetotail physics is the finding that the ion pitch angle distributions in the near-Earth plasma sheet are not quasiisotropic but exhibit such features as "eyes" and "wings" that are associated with the previous history of transport and acceleration of these ions in the magnetotail. These "memories" in the complex ion velocity distributions can be used as remote sounding tools for the magnetotail when they are decoded with a realistic simulation model. Finally it is now possible to directly detect the currents flowing in the magnetotail with plasma instrumentation. Such measurements allow the in-situ determinations of current densities and the nature of the electron and ion velocity distributions which are associated with these current densities. These direct determinations of the current densities are expected to contribute significantly in revealing the current diversions and disruptions in the magnetotail that are associated with magnetic substorms. In addition the capability of determining the offdiagonal elements of the pressure tensor appears to provide new insight into the dynamics of the magnetotail current sheet.
Журнал: Geophysical Monograph Series
Выпуск журнала: Т. 105
Номера страниц: 167-180
ISSN журнала: 00658448