IONOSPHERIC ELECTRIC AND GROUND MAGNETIC PC5 VARIATIONS AT LOW-LATITUDE STATIONS

  1. Space Environment Research Center, Kyushu University, Fukuoka, Japan
  2. Department of Earth and Planetary Sciences, Kyushu University, Fukuoka, Japan
  3. Kagoshima National College of Technology, Kagoshima, Japan
  4. National Institute of Information and Communications Technology, Tokyo, Japan
  5. Institute of Cosmophysical Research and Radiowaves Propagation of the Far Eastern Branch of Russian Academy of Sciences, Russia

Low-latitude Pc5 pulsations (150-600 sec.) are observable by the
ground-based magnetometers. Ziesolleck and Chamalaun [1993]
examined the characteristics of low-latitude Pc5 pulsations. They
showed that the amplitude of Pc5 pulsation decreased with
decreasing of geomagnetic latitude, and concluded that the low-
latitude Pc5 was caused by the global compressional wave. On the
other hand, Motoba et al. [2002] examined Pc5 pulsation by ground
magnetic field data obtained from many stations. They found that the
DP2-type current system excited low-latitude ground Pc5 magnetic
pulsation.
Some researchers reported Pc5 pulsations by using ionosphere
Doppler observations. Reddy et al. [1994] showed that the Pc5
oscillation in the Doppler frequency at the daytime equator Figure 1. A schematic diagram of the
correlated with ground magnetic field variation at afternoon high- Doppler measurement by an FM-CW
latitude stations. They argued that the Pc5-range Doppler oscillations radar.
in the equatorial ionosphere were caused by the ionospheric electric
field penetrating from high latitudes to the equator. In addition,
Motoba et al. [2004] showed that daytime and nighttime Pc5
pulsations in the Doppler frequency were caused by dawn-to-dusk polar electric fields at low latitudes.
Thus the ionospheric oscillation is seems to be caused by DP2 type current system.
However, observations in the ionosphere are not so much reported. Especially phase relation between
ground magnetic Pc5 and ionospheric electric fields are not examined well.