FREQUENCY-DEPENDENT POLARIZATION CHARACTERISTICS OF PC1 GEOMAGNETIC PULSATIONS OBSERVED BY MULTIPOINT GROUND STATIONS AT LOW LATITUDES

  1. Solar-Terrestrial Environment Laboratory, Nagoya University, Nagoya, Japan
  2. Institute of the Physics of the Earth, Moscow, Russia
  3. Institute of Cosmophysical Research and Radio Wave Propagation FEB RAS, Paratunka, Russia

 

We have investigated Pc1 geomagnetic pulsations observed by induction magnetometers at three low-latitude stations (Paratunka (PTK), Moshiri (MSR), and Sata (STA), L=1.2–2.1). A detailed polarization analysis shows that polarization parameters (angle of polarization ellipse orientation, Ψ, and polarization sense) of individual Pc1 bands depend on frequency at all three stations. The dependence of Ψ on frequency was seen in 70% of the 93 Pc1 events observed at MSR (L=1.5) from 14 July 2007 to 13 July 2009. The maxima of seasonal and diurnal variations of the occurrence rate were in winter and during the nighttime, as reported previously, indicating that the transmission of observed Pc1 pulsations to lower latitudes is controlled by the density of the F layer plasma. These facts suggest that spatially distributed Pc1 waves with varying frequencies depending on longitude or latitude at high latitudes propagated in the ionospheric duct to cause the frequency dependence of polarization parameters at low latitudes. We also suggest that the Pc1 pearl structure with a repetition period of 5–30 s observed at low latitudes is a beat of high-latitude waves with slightly different frequencies.

Nomura, R., K. Shiokawa, S. Pilipenko, B. Shevtsov, Frequency-dependent polarization characteristics of Pc1 geomagnetic pulsations observed by multi-point ground stations at low latitudes, J. Geophys. Res., 116, A01204, doi:10.1029/2010JA015684, 2011. (Jan.13, 2011)