Modeling D-region ionospheric response of the Great American TSE of August 21, 2017 from VLF signal perturbation

Abstract

Solar eclipse is an unique opportunity to study the lower ionospheric variabilities under a controlled perturbation when the solar ultraviolet and X-ray are temporally occulted by the lunar disk. Sub-ionospheric Very Low Frequency (VLF) radio signal displays the ionospheric response of solar eclipse by modulating its amplitude and phase. During the Total Solar Eclipse (TSE) on August 21, 2017 in North America, data was recorded by a number of receivers as presented in public archive. Out of these, two receiving stations YADA in McBaine and K5TD in Tulsa could procure a reasonable quality of noise free data where the signal amplitude was clearly modulated due to the eclipse. During the lunar occultation, a C3.0 solar flare occurred and the signal received from Tulsa manifested the effect of sudden ionization due to the flare. The VLF amplitude in Tulsa shows the effect which is generally understood by superimposing effects of both the solar eclipse and flare. However, the signal by YADA did not perturb by the solar flare, as the flaring * Corresponding author region was totally behind the lunar disk for the entire period. We numerically reproduced the observed signal amplitude variation at both the receiving locations by using Wait's two component D-region ionospheric model and the well-known Long Wavelength Propagation Capability (LWPC) code. The perturbed electron density for both the cases is computed which matches satisfactorily with the true ionospheric conditions.

Effects of the Great American Solar Eclipse on the lower ionosphere observed with VLF waves

“…Finally, our model of the C3 X-ray flare observed during the eclipse is in very good accordance with the results obtained through LWPC simulations reported in Chakrabarti et al (2018), for a short-length propagation path. This gives support to the use of this model to study of the eclipsed ionosphere.…”

“…We express the flare-induced ionospheric height difference ∆z f (t) to quantify the flare contribution to the total effective ionospheric height change and then compare the ionospheric height profile during both: the solar eclipse and the solar eclipse combined with the solar flare input, see figure 5. Our results are in good agreement with the same obtained by Chakrabarti et al (2018), who measured the signal amplitude of 2 receiving stations in North America, YADA in McBaine and KSTD in Tulsa. In the latter they observed similar effects caused by a C3.0 flare.…”

“…The authors used the LWPC code and the Wait's two-component D-region ionospheric model, to numerically reproduce the observed signal amplitude variation at both receiving locations. Their altitude profile at maximum electron density for combined effects (solar eclipse and solar flare) correspond well with our results, see Figure 8 in Chakrabarti et al (2018). This is remarkable due to the relative simplicity of our approach.…”

Amplitude and phase changes of the LF radio signal of the transmitter JJY40 registered in Yakutsk and Tixie Bay during the solar eclipse on June 10, 2021

“…A solar eclipse makes it possible to study the mechanisms of ionosphere changes. The time of the eclipse is predetermined, which allows to prepare an experiment 2 .…”

A Modeling Framework for Estimating Ionospheric HF Absorption Produced by Solar Flares

“…ISR observations are used to study ionospheric temperature, plasma density, and horizontal and vertical plasma drift parameters. SuperDARN radars have observed a different feature of flare driven HF anomaly, namely the "Doppler flash" (see Figure 3 in Chakrabarti et al, 2018). Digisondes and SuperD-ARN HF radars are affected severely by radio blackout while riometers are better suited to capture the full spatiotemporal evolution of HF absorption.…”