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| Titel |
Ionospheric manifestations of acoustic-gravity waves under quiet and disturbed conditions |
| VerfasserIn |
Vladimir Barabash, Leonid Chernogor, Sergii Panasenko, Igor Domnin |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250091849
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| Publikation (Nr.) |
 EGU/EGU2014-6162.pdf |
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| Zusammenfassung |
| We present the observation results of wave disturbances in the ionosphere, which are known
to be manifestations of atmospheric acoustic-gravity waves (AGWs). The observations have
been conducted under quiet and naturally or artificially disturbed conditions by ionosonde
and incoherent scatter radar located near Kharkiv, Ukraine.
Wave disturbance parameters under quiet conditions were obtained and analysed during
geophysical periods including vernal and autumn equinoxes as well as summer and winter
solstices. The prevailing oscillation in ionospheric F2- layer had the period of 140 – 200 min
and relative amplitude of 0.1 – 0.2. The duration of this oscillation changed from 5 – 7 to 24
hours, depending on a season. The amplitude of fluctuations with other periods was
noticeably smaller.
The time intervals at which the intensity of incoherent scatter signals varied
quasi-periodically in the altitude range from 150 to 300 km were detected. The parameters of
these variations were estimated using statistical analysis and bandpass filtering. The periods
of wave processes were shown to be of 30 – 120 min, there durations did not exceed of 2 – 6
periods and relative amplitudes usually ranged from 0.03 to 0.15. The phase of oscillations
was detected to propagate downwards. The vertical phase velocity of travelling ionospheric
disturbances (TIDs) was estimated to be in the range from 50 to 200 m/s and increased with
altitude.
The observations of the partial solar eclipse on January, 4, 2011 near Kharkiv were used
to study the ionospheric parameters in naturally disturbed conditions. The F2-layer critical
frequency dropped by a factor of 2.1. The time delay of these variations with respect to the
main magnitude of the solar disk obscuration was equal to about 16 minutes. The virtual
height of signal reflection near the maximum of the F2-layer ionization increased
by 70 km, and the height of the model parabolic layer increased by 10 km. Some
decrease in electron density and growth of quasi-periodic variations with periods
of about 30 and 60 min were detected at all observable heights during this solar
eclipse.
The diagnostics of wave processes has been performed during ionospheric modification
experiments with EISCAT heater. This heater is at a distance of about 2400 km from
Kharkiv incoherent scatter radar. We have detected the TIDs over Kharkiv with
periods of 40 – 80 min. The duration of these disturbances has not exceeded 120
– 180 min. The relative amplitudes of the TIDs in electron density ranged from
0.05 to 0.15 and those in electron and ion temperatures were about 0.02 – 0.05.
The possible mechanisms for the generation of AGWs and TIDs by high power
HF radio waves are sharp thermal gradients at the edge of the heated region and
modulation of the ionospheric current systems by periodic high power radio transmission. |
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