Propagation of VLF & ELF Waves during Sudden Ionospheric Disturbances

Abstract

The attenuation factors are calculated from the usual mode theory considerations adopting experimentally determined exponential model for electron density profiles both during normal and disturbed conditions. Our calculations show that while in the ELF range the attenuation decreases during any type of flare, in the VLF range both increase and decrease could occur depending on the frequency and the type of flare. All these theoretical results are qualitatively in agreement with the experimental results reported by other workers. The effect of geomagnetic field has also been considered on the propagation of VLF and ELF waves during solar flares and is found to introduce significant changes in the east-to-west asymmetric propagation.