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The dawn and dusk electrojet response to substorm onset
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
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2000 (English)In: Annales Geophysicae, ISSN 0992-7689, Vol. 18, no 9, 1097-1107 p.Article in journal (Refereed) Published
Abstract [en]

We have investigated the time delay between substorm onset and related reactions in the dawn and dusk ionospheric electrojets, clearly separated from the nightside located substorm current wedge by several hours in MLT. We looked for substorm onsets occurring over Greenland, where the onset was identified by a LANL satellite and DMI magnetometers located on Greenland. With this setup the MARIA magnetometer network was located at dusk, monitoring the eastward electrojet, and the IMAGE chain at dawn, for the westward jet. In the first few minutes following substorm onset, sudden enhancements of the electrojets were identified by looking for rapid changes in magnetograms. These results show that the speed of information transfer between the region of onset and the dawn and dusk ionosphere is very high. A number of events where the reaction seemed to preceed the onset were explained by either unfavorable instrument locations, preventing proper onset timing, or by the inner magnetosphere's reaction to the Earthward fast flows from the near-Earth neutral line model. Case studies with ionospheric coherent (SuperDARN) and incoherent (EISCAT) radars have been performed to see whether a convection-induced electric field or enhanced conductivity is the main agent for the reactions in the electrojets. The results indicate an imposed electric field enhancement.

Place, publisher, year, edition, pages
2000. Vol. 18, no 9, 1097-1107 p.
Keyword [en]
Polar ionosphere, Electric field, Magnetospheric substorm, Delay time, Auroral electrojet, Radar observation, Magnetometry, Satellite observation, Greenland, North America, America
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:uu:diva-90580OAI: oai:DiVA.org:uu-90580DiVA: diva2:162981
Available from: 2003-05-15 Created: 2003-05-15 Last updated: 2009-11-18Bibliographically approved
In thesis
1. Substorm Features in the High-Latitude Ionosphere and Magnetosphere: Multi-Instrument Observations
Open this publication in new window or tab >>Substorm Features in the High-Latitude Ionosphere and Magnetosphere: Multi-Instrument Observations
2003 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The space around Earth, confined in the terrestrial magnetosphere, is to some extent shielded from the Sun's solar wind plasma and magnetic field. During certain conditions, however, strong interaction can occur between the solar wind and the magnetosphere, resulting in magnetospheric activity of several forms, among which substorms and storms are the most prominent. A general framework for how these processes work have been outlayed through the history of research, however, there still remain questions to be answered. The most striking example regards the onset of substorms, where both the onset cause and location in the magnetosphere/ionosphere are still debated. These are clearly not easily solved problems, since a substorm is a global process, ideally requiring simultaneous measurements in the magnetotail and ionosphere. Investigated in this work are temporal and spatial scales for substorm and convection processes in the Earth's magnetosphere and ionosphere. This is performed by combining observations from a number of both ground-based and spacecraft-borne instruments. The observations indicate that the magnetotail's cross-section is involved to a larger spatial extent than previously considered in the substorm process. Furthermore, convection changes result in topological changes of the magnetosphere on a fast time scale. The results show that the magnetosphere is, on a global magnetospheric scale, highly dynamic during convection changes and ensuing substorms.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2003. 50 p.
Series
Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1104-232X ; 860
Keyword
Space and plasma physics, Substorm, Convection, magnetosphere-ionosphere coupling, Rymd- och plasmafysik
National Category
Fusion, Plasma and Space Physics
Research subject
Space and Plasma Physics
Identifiers
urn:nbn:se:uu:diva-3478 (URN)91-554-5670-7 (ISBN)
Public defence
2003-06-05, Polhem, Ångström, Uppsala, 14:00 (English)
Opponent
Supervisors
Available from: 2003-05-15 Created: 2003-05-15 Last updated: 2009-11-18Bibliographically approved

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