EGU21-1393
https://doi.org/10.5194/egusphere-egu21-1393
EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

The effects of solar flare-driven ionospheric electron density change on Doppler Flash

Shibaji Chakraborty1, Liying Qian2, J. Michael Ruohoniemi1, Joseph Baker1, and Joseph McInerney2
Shibaji Chakraborty et al.
  • 1Virginia Tech, Space@VT, ECE, Blacksburg, United States of America (shibaji7@vt.edu)
  • 2High Altitude Observatory, NCAR, HAO

Trans–ionospheric high frequency (HF) signals experience a strong attenuation following a solar flare, commonly referred to as Short–Wave Fadeout (SWF). Although solar flare-driven HF absorption is a well-known impact of SWF, the occurrence of a frequency shift on radio wave signal traversing the lower ionosphere in the early stages of SWF, also known as "Doppler Flash", is newly reported and not well understood. Some prior investigations have suggested two possible sources that might contribute to the manifestation of Doppler Flash: first,  enhancements of plasma density in the D and lower E regions; second, the lowering of the reflection point in the F region. Observations and modeling evidence regarding the manifestation and evolution of Doppler Flash in the ionosphere are limited. This study seeks to advance our understanding of the initial impacts of solar flare-driven SWF. We use WACCM-X to estimate flare-driven enhanced ionization in D, E, and F-regions and a ray-tracing code (Pharlap) to simulate a 1-hop HF communication through the modified ionosphere. Once the ray traveling path has been identified, the model estimates the Doppler frequency shift along the ray path. Finally, the outputs are validated against observations of SWF made with SuperDARN HF radars. We find that changes in the refractive index due to the F-region's plasma density enhancement is the primary cause of Doppler Flash.

How to cite: Chakraborty, S., Qian, L., Ruohoniemi, J. M., Baker, J., and McInerney, J.: The effects of solar flare-driven ionospheric electron density change on Doppler Flash, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1393, https://doi.org/10.5194/egusphere-egu21-1393, 2021.