Speaker
Description
The ionospheric D-region (60 - 90 km) is responsible for a large part of HF absorption (Zawdie, 2017). It is a variable region, responding to increases in the solar radiation. Real-time surveillance of the D-region is thus crucial to offer real-time alerts in case of solar flares and mitigate their impact on radio communications. However, continuous in situ monitoring of this region is difficult. Instead, Very Low Frequency (VLF, 15-45 kHz) waves propagating in the Earth-Ionosphere waveguide offer indirect insights on the D-region state.
Here is presented vlf4ions, a Python package destined for VLF antenna owners. It provides tools and methods for real-time analysis of VLF waves. Alerts for solar flares are thus sent to specified recipients, independently of satellite data. Real-time detection of solar flares relies on an automated algorithm searching for trend breaks in VLF phase data (Guralnik & Srivastava, 1999). Analysis of one year of data shows that 88% of M and X flares are detected within one-fourth of their rising time. Solar X-ray flux is then estimated in real-time from VLF phase variations during flares.
In addition, modelling of the propagating VLF waves is achieved from propagation codes such as LMP (Gasdia & Marshall, 2021) or LWPC (Ferguson, 1998). Comparing the modelled amplitude and phase to real-time measurement provides estimates of the electron density profile along each transmitter/receiver path. Future improvements of this package will include estimation of the HF absorption on each path.
