Abstract:
Based on the very low frequency (VLF) data obtained from Suizhou observation station, we analyze the amplitude response characteristics, including the similarities and the differences between the longitudinal propagated NWC signal and the latitudinal propagated JJI signal, to reveal the differences in the disturbances of the VLF transmitter signals propagating along these two paths during the solar flares. It is shown that the NWC signal has only one mode of response, that is, to rise first and then recover, while the JJI signal has three modes of responses, including the rise before recovery, the fall before recovery, and the rise-and-fall before recovery. The response startup time and the peak time of the NWC signal are consistent with those of the JJI signal, but the response duration of the JJI signal is longer than that of the NWC signal. The maximum disturbance of the M-class solar flares to the NWC signal is between 1 dB and 4 dB, the maximum disturbance of the JJI signal is between 1 dB and 3 dB, and the maximum disturbance of the C-class solar flares to the two station signals is between 0 to 1 dB. The integral disturbed amplitude to the station signal is linearly correlated with the integrated X-ray flux, and the slope of the fitting line for the NWC signal is greater than that for the JJI signal.