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| Titel |
Sub-ionospheric VLF signal anomaly due to geomagnetic storms: a statistical study |
| VerfasserIn |
K. Tatsuta, Y. Hobara, S. Pal, M. Balikhin |
| 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. 11 ; Nr. 33, no. 11 (2015-11-30), S.1457-1467 |
| Datensatznummer |
250121273
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| Publikation (Nr.) |
 copernicus.org/angeo-33-1457-2015.pdf |
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| Zusammenfassung |
| We investigate quantitatively the effect of geomagnetic storms on the
sub-ionospheric VLF/LF (Very Low Frequency/Low Frequency) propagations for different latitudes based on 2-year
nighttime data from Japanese VLF/LF observation network. Three statistical
parameters such as average signal amplitude, variability of the signal
amplitude, and nighttime fluctuation were calculated daily for 2 years
for 16–21 independent VLF/LF transmitter–receiver
propagation paths consisting of three transmitters and seven receiving stations.
These propagation paths are suitable to simultaneously study high-latitude,
low-mid-latitude and mid-latitude D/E-region ionospheric properties. We
found that these three statistical parameters indicate significant anomalies
exceeding at least 2 times of their standard deviation from the mean value
during the geomagnetic storm time period in the high-latitude paths with an
occurrence rate of anomaly between 40 and 50 % presumably due to the
auroral energetic electron precipitation. The mid-latitude and low-mid-latitude paths have a smaller influence from the geomagnetic activity
because of a lower occurrence rate of anomalies even during the geomagnetically active
time period (from 20 to 30 %). The anomalies except geomagnetic storm
periods may be caused by atmospheric and/or lithospheric origins. The
statistical occurrence rates of ionospheric anomalies for different
latitudinal paths during geomagnetic storm and non-storm time periods are
basic and important information not only to identify the space weather
effects toward the lower ionosphere depending on the latitudes but also to
separate various external physical causes of lower ionospheric
disturbances. |
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