| 1. |
- Dovner, PO, et al.
(author)
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The occurrence of lower hybrid cavities in the upper ionosphere
- 1997
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In: GEOPHYSICAL RESEARCH LETTERS. - : AMER GEOPHYSICAL UNION. - 0094-8276. ; 24:5, s. 619-622
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Journal article (other academic/artistic)abstract
- Lower hybrid cavities (LHC), i. e., small-scale density depletions coinciding with enhanced lower hybrid waves, are frequent in the upper ionosphere. It is found that they exist in all regions the Freja satellite has scanned, as long as lower hybrid waves
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| 2. |
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| 3. |
- Knudsen, DJ, et al.
(author)
-
Effect of lower hybrid cavities on core plasma observed by Freja
- 1998
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In: JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS. - : AMER GEOPHYSICAL UNION. ; 103:A3, s. 4241-4249
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Journal article (other academic/artistic)abstract
- Sounding rocket experiments in the topside ionosphere have established previously a one-to-one relation between transversely heated ions and packets of lower hybrid waves trapped in localized density depletions (lower hybrid cavities (LHCs)). LHCs were ob
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| 4. |
- Persson, M. A. L., et al.
(author)
-
Near-Earth substorm onset - a coordinated study
- 1994
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In: Geophysical Research Letters. - 0094-8276 .- 1944-8007. ; 21:17, s. 1875-1878
-
Journal article (peer-reviewed)abstract
- We present simultaneous satellite and ground-based measurements of a substorm. Throughout the initial substorm expansion, southward drifting arcs are observed poleward of the expanding substorm aurora, indicating two independent systems of particle precipitation. Freja passes the brightening onset arc in the topside ionosphere near the moment of the substorm onset, observing an Alfven wave, field aligned current and oxygen ion outflow. The substorm onset occurs at low magnetospheric L-shells, near the poleward edge of the region of trapped particles. The location and time for the substorm injection are confirmed by geostationary spacecraft together with magnetometers, all-sky cameras and radar on the ground. We believe that the substorm onset may be triggered by modification of the oxygen content of the inner magnetosphere during the growth-phase caused by ionospheric ion outflow.
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