Amplitude and phase time series of low frequency standard radio transmitter signals at 40.0(JJY), 60.0(JJY), and 67.5kHz(BPC) received at the Zao observaroty (Miyagi, Japan) of Tohoku University. Variations in the phase and amplitude reflect changes of the ionization state in the lower ionosphere which is caused by energetic electron precipitation from inner magnetosphere (radiation belt), solar x-rays, lightning dischanges, and so on.