Investigations of ionospheric disturbances using coherent HF instrumentation

Abstract

This work is based on long term monitoring the HF signal data at 9.996 MHz at mid-latitudes from the short radio-path Moscow-Kharkiv and at high-latitudes from the longer radio-path Moscow-Tromso for 2013. The HF signal transmitter is the radio station RWM in Moscow, Russia. The receiver stations are located in Tromso (Norway) and Kharkiv (Ukraine). Using intensity and the Doppler frequency shift of the HF received signals we evaluated the effects of ionospheric disturbances. For the interpretation of the results additional information was also used about Total electron content (TEC) above Tromso, Kiruna (Sweden), Joensuu (Finland, mid-point of radio path Moscow – Tromso), Kharkiv; the critical frequency data F0F2 above Tromso and Moscow; the local magnetic K-indices in Tromso and Kharkiv; the planetary Kp-indices; the solar flux F10.7, Sun spot number, X-ray background flux. The focus of the work was to write a program for processing the HF signals using the MatLab language. We also wrote the programs to visualize all data. The work confirmed the standard behavior of the HF signals. Effects, such as an increase in intensity of signal during the day and decrease at night; the positive Doppler frequency shift at sunrise and the negative at sunset were observed. We found some new features in the behavior of the HF signals in quiet conditions and during ionospheric disturbances. These include an increase of HF signal intensity after sunset in summer, a decrease of the intensity in the afternoon in summer and reduced intensity and unsteady behavior during magnetic storms.