Ionospheric oscillations caused by geomagnetic Pi2 pulsations and their observations by multipoint continuous Doppler sounding; first results Original Research Article

In 2004, we started operating a continuous Doppler sounding system to investigate ionospheric signatures of infrasonic, short period acoustic gravity waves and geomagnetic pulsations. Since January 2007, four stable 3.59 MHz transmitters have been in operation in the western part of the Czech Republic. Multipoint measurements enable us to investigate horizontal propagation of waves and disturbances in the ionosphere and to estimate horizontal distances over which these waves (disturbances) are correlated. We focus on cross-correlations between Doppler shift records and irregular night-time Pi2 pulsations of the geomagnetic field measured on the ground at the observatory of Budkov. These pulsations have periods ∼1–3 min and occur simultaneously (within the precision of the measurements) on all Doppler sounding signals. The sounding signals (Doppler records) are usually best correlated with the variations of the horizontal component of the geomagnetic field. Generally, a good correlation with the variations of the magnetic field amplitude is also observed. The observed geomagnetic pulsations were predominantly left-handed with an elliptical or nearly linear polarization. In one case, we have also observed right-handed pulsations. Our observations show that the time/phase shifts between geomagnetic field components and Doppler shift signals can change from case to case.