Observations and modeling of D-region ionospheric response of Annular Solar Eclipse on December 26, 2019, using VLF signal amplitude and phase variation

Solar eclipse is a unique phenomenon that produces an orderly disturbance in the ionosphere within a specific time frame. It provides us an opportunity to understand the ionospheric response due to its systematic variation during an eclipse. The amplitude and phase of a Very Low Frequency (VLF) signal carry the response of lower ionospheric perturbation due to the varying solar radiation impinging on Earth. During the Annular Solar Eclipse on December 26, 2019, (ASE2019), Indian Centre for Space Physics (ICSP), Kolkata, India conducted a nationwide VLF radio signal monitoring campaign to obtain the amplitude and phase variations of propagating VLF signal from fourteen different locations across India. The signal amplitude and phase profile exhibit unique profiles at these locations. These profiles in the VLF signal during ASE2019 are explained using the Long Wavelength Propagation Capability (LWPC) code and the modeled variation of solar disk obscuration by the moon. Furthermore, the lower ionospheric electron density ( N e ) computed from the model is in agreement with the observed lower ionospheric conditions.