[1] Plasma lines excited by a powerful, high-frequency (HF) radio wave are studied using data obtained with an ultrahigh frequency (UHF) radar at HAARP (High Frequency Active Auroral Research Program) from 3 to 5 February 2005. Of particular interest is persistent enhancement of the radar backscatter power during HF on at several HF frequencies. The persistent enhancement is induced with the HF...

The temporal variations of the ionospheric critical frequency foF2 is a typical example of a time series in which deterministic variations at various time scales and nonstationary stochastic variations are involved. In a series of journal and conference papers we have obtained various modelling, prediction and forecast algorithms for foF2 variations over Europe, based on data from about 15 iono...


 A geomagnetic storm is a major disturbance of Earth’s magnetosphere that occurs when there very efficient exchange energy from the solar wind into space environment surrounding Earth. During and activities, critical frequency F2 layer (foF2) varies in great extent. The focus current study on variations foF2, layer, during intense cycle 24 quiet 25. foF2 data mid latitude station BC840 (B...

In the past the global, fully coupled, timedependent mathematical model of the Earth’s thermosphere/ionosphere/plasmasphere (CTIP) has been unable to reproduce accurately observed values of the maximum plasma frequency, foF2, at extreme geophysical locations such as the Argentine Islands during the summer solstice where the ionosphere remains in sunlight throughout the day. This is probably bec...

[1] Empirical evidence of the preearthquake ionospheric anomalies (PEIAs) is reported by statistically investigating the relationship between variations of the plasma frequency at the ionospheric F2 peak foF2 and 184 earthquakes with magnitude M 5.0 during 1994– 1999 in the Taiwan area. The PEIA, defined as the abnormal decrease more than about 25% in the ionospheric foF2 during the afternoon p...

[1] The short-term relationship between equatorial ionosphere and geomagnetic activity is examined. Hourly averages of the total electron content (TEC) and critical frequency of the F2 layer (foF2) are compared with the Dst index, a proxy for equatorial geomagnetic activity, at three local times (0700–0800, 1200–1300, and 1600–1700 LT) from March 1998 to August 1999. Owing to the geomagnetic la...

[1] The ratio of monthly median foF2 values between the ionosondes at Maui (20.8 N, 156 E geographic; 21.2 N, 90.4 E geomagnetic) and Yamagawa (31.2 N, 130.6 E geographic; 20.6 N, 160.9 E geomagnetic) from January 1960 to June 1993 are used to investigate interannual variability in the wave-4 longitudinal structure of the low-latitude F region ionosphere. Analysis of Global Positioning System t...

We present the result of studies into characteristics high-latitude ionospheric F-region longitudinal plasma waves (Langmuir and ion-acoustic), caused by impact powerful HF radio ordinary (O-mode) or extraordinary (X-mode) polarization EISCAT/Heating facility, Tromsø, Norway. The on October 20, 2012 February 26, 2013 were emitted in direction magnetic zenith with a step change effective radiati...

More than 70 years ago, it was recognised that ionospheric F2-layer critical frequencies [foF2] had a strong relationship to sunspot number. Using historic datasets from the Slough and Washington ionosondes, we evaluate the best statistical fits of foF2 to sunspot numbers (at each Universal Time [UT] separately) in order to search for drifts and abrupt changes in the fit residuals over Solar Cy...