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| Titel |
Type-1 echoes from the mid-latitude E-Region ionosphere |
| VerfasserIn |
C. Haldoupis, D. T. Farley, K. Schlegel |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
0992-7689
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| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 15, no. 7 ; Nr. 15, no. 7, S.908-917 |
| Datensatznummer |
250012875
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| Publikation (Nr.) |
 copernicus.org/angeo-15-908-1997.pdf |
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| Zusammenfassung |
| This paper presents more data on the
properties of type-1 irregularities in the nighttime mid-latitude E-region
ionosphere. The measurements were made with a 50-MHz Doppler radar system
operating in Crete, Greece. The type-1 echoes last from several seconds to a few
minutes and are characterized by narrow Doppler spectra with peaks corresponding
to wave phase velocities of 250–350 m/s. The average velocity of 285 m/s is
about 20% lower than nominal E-region ion-acoustic speeds, probably
because of the presence of heavy metallic ions in the sporadic-E-layers
that appear to be associated with the mid-latitude plasma instabilities.
Sometimes the type-1 echoes are combined with a broad spectrum of type-2 echoes;
at other times they dominate the spectrum or may appear in the absence of any
type-2 spectral component. We believe these echoes are due to the modified
two-stream plasma instability driven by a polarization electric field that must
be larger than 10 mV/m. This field is similar in nature to the equatorial
electrojet polarization field and can arise when patchy nighttime sporadic-E-layers
have the right geometry. |
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