|Author||Ohtani, S. ♦ Lui, A. T. Y. ♦ Higuchi, T.|
|Source||United States Department of Energy Office of Scientific and Technical Information|
|Subject Keyword||PHYSICS ♦ MAGNETIC FIELDS ♦ FLUCTUATIONS ♦ TIME-SERIES ANALYSIS ♦ ELECTRIC CURRENTS ♦ MAGNETOTAIL ♦ MAGNETIC STORMS ♦ FRACTALS|
|Abstract||The objective of the present study is to assess the mechanism of substorm associated tail current disruption on the basis of magnetic field observations in the near-Earth tail. The authors examined 15 events observed by the Charge Composition Explorer (CCE) of the Active Magnetospheric Particle Tracer Explorers (AMPTE), with an emphasis on the August 28, 1986, event. In these events the satellite observed magnetic fluctuations to start almost simultaneously with ground substorm onsets, strongly suggesting that these fluctuations are related to the trigger of substorms. In this study the authors applied the new method, fractal analysis, to these fluctuations. This method enables them to examine fluctuations quantitatively and to pick up characteristic timescale(s) of fluctuations, even if fluctuations are far from sinusoidal. The results are summarized as follows: (1) Whereas before the onset of tail current disruption, magnetic fluctuations are suppressed in each of the magnetic components, after the onset, the magnitude of the H (north-south) component fluctuations is about 30% larger than the magnitudes of the fluctuations of the other components. (2) The magnetic fluctuations have a characteristic timescale, which is several times the proton gyroperiod. The first result suggests that observed magnetic fluctuations are actually related to changes in the tail current intensity, that is, tail current disruption. This result also indicates that the microprocess of tail current disruption should be described in terms of turbulent perturbation electric currents, although away from the onset region the effects of tail current disruption may be approximated by those of an orderly decrease in the tail current intensity. The second result strongly suggests that tail current disruption is driven by a certain instability, which grows most rapidly around that characteristic time scale, and in which ions should play an important role. 47 refs., 9 figs., 1 tab.|
|Learning Resource Type||Article|
|Publisher Place||United States|
|Journal||Journal of Geophysical Research|
National Digital Library of India (NDLI) is a virtual repository of learning resources which is not just a repository with search/browse facilities but provides a host of services for the learner community. It is sponsored and mentored by Ministry of Education, Government of India, through its National Mission on Education through Information and Communication Technology (NMEICT). Filtered and federated searching is employed to facilitate focused searching so that learners can find the right resource with least effort and in minimum time. NDLI provides user group-specific services such as Examination Preparatory for School and College students and job aspirants. Services for Researchers and general learners are also provided. NDLI is designed to hold content of any language and provides interface support for 10 most widely used Indian languages. It is built to provide support for all academic levels including researchers and life-long learners, all disciplines, all popular forms of access devices and differently-abled learners. It is designed to enable people to learn and prepare from best practices from all over the world and to facilitate researchers to perform inter-linked exploration from multiple sources. It is developed, operated and maintained from Indian Institute of Technology Kharagpur.
NDLI is a conglomeration of freely available or institutionally contributed or donated or publisher managed contents. Almost all these contents are hosted and accessed from respective sources. The responsibility for authenticity, relevance, completeness, accuracy, reliability and suitability of these contents rests with the respective organization and NDLI has no responsibility or liability for these. Every effort is made to keep the NDLI portal up and running smoothly unless there are some unavoidable technical issues.
Ministry of Education, through its National Mission on Education through Information and Communication Technology (NMEICT), has sponsored and funded the National Digital Library of India (NDLI) project.
For any issue or feedback, please write to email@example.com