Effects of variations of geomagnetic field on VLF waves induced by beating of two HF waves.

Abstract Beat wave (BW) high frequency (HF) ionospheric heating experiments were conducted to generate very low frequency (VLF) waves. The VLF waves were registered with a VLF receiver located ∼15 km east of the European Incoherent Scatter (EISCAT) heating facility in Tromsø, Norway. A fluxgate magnetometer was used to monitor auroral electrojet current, and ionospheric conditions were measured using a Dynasonde. Correlation coefficients between VLF amplitudes and the deviation of geomagnetic north–south components were calculated. Experimental results show that strong and positive correlation exists the majority of the time, but sometimes no correlation or even a negative correlation occurred. This is consistent with similar past experiments that took place with exclusively AM generation. These results therefore support the conclusion that BW generation of VLF waves is no different than with AM, likely occurring in the D or lower E ionospheric region. [ABSTRACT FROM AUTHOR]