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| Titel |
Analysis of the enhanced negative correlation between electron density and electron temperature related to earthquakes |
| VerfasserIn |
X. H. Shen, X. Zhang, J. Liu, S. F. Zhao, G. P. Yuan |
| 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 ; 33, no. 4 ; Nr. 33, no. 4 (2015-04-20), S.471-479 |
| Datensatznummer |
250121189
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| Publikation (Nr.) |
 copernicus.org/angeo-33-471-2015.pdf |
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| Zusammenfassung |
| Ionospheric perturbations in plasma
parameters have been observed before large earthquakes,
but the correlation between different parameters has been less studied in previous research.
The present study is focused on the relationship between electron density (Ne) and temperature
(Te) observed by the DEMETER (Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions) satellite during local nighttime, in which a positive correlation has been
revealed near the equator and a weak correlation at mid- and low latitudes over both hemispheres.
Based on this normal background analysis, the negative correlation with the lowest percent in all
Ne and Te points is studied before and after large earthquakes at mid- and low latitudes. The multiparameter
observations exhibited typical synchronous disturbances before the Chile M8.8 earthquake in 2010 and the Pu'er
M6.4 in 2007, and Te varied inversely with Ne over the epicentral areas. Moreover,
statistical analysis has been done by selecting the orbits at a distance of 1000 km and ±7 days
before and after the global earthquakes. Enhanced negative correlation coefficients lower than −0.5 between Ne and Te
are found in 42% of points to be connected with earthquakes. The correlation median values
at different seismic levels show a clear decrease with earthquakes larger than 7. Finally, the
electric-field-coupling model is discussed; furthermore, a digital simulation has been carried out by SAMI2 (Sami2 is Another Model of
the Ionosphere), which illustrates
that the external electric field in the ionosphere can strengthen the negative correlation in Ne and Te at a lower
latitude relative to the disturbed source due to the effects of the geomagnetic field. Although seismic
activity is not the only source to cause the inverse Ne–Te variations, the present results demonstrate
one possibly useful tool in seismo-electromagnetic anomaly differentiation, and a comprehensive analysis
with multiple parameters helps to further understand the seismo–ionospheric coupling mechanism.
\keywords{Ionosphere (plasma temperature and density)} |
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