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Monitoring and predicting the effects of space weather events on the near-Earth space
environments
is very crucial for modern satellites and space-based technologies. Space weather events
such as solar flares, and geomagnetic storms disturb both the upper and lower
ionosphere. Low electron density makes it challenging to continuously monitor the lower
ionosphere below 100 km with ionosonde, GNSS TEC measurements, or radar studies.
Neither satellites nor weather balloons are able to make in-situ measurements of this
region. However, this lower portion of the ionosphere partially reflects Very Low
Frequency/Low Frequency (VLF/LF) radio signals from communication transmitters or
lightning discharge in the range of 10–60 kHz, which presents a fantastic opportunity to
monitor this region. We have developed a VLF/LF network with four permanent receiving
stations for continuous long-range observations of the lower-ionosphere in the low-latitude
Indian region. Our aim is to monitor the changes in ionization levels from ~50-100 km
altitude continuously with high time resolution for understanding the energy coupling
between the Earth's atmosphere, the Sun, and space. Most space weather events are
detected by the ionosphere, which acts as a massive detector. In this presentation, we
shall show how space weather events can be effectively monitored using the sub-
ionospheric VLF/LF radio remote sensing method. In particular, we demonstrate how solar
flares, geomagnetic storms, and solar eclipses impact the lower ionosphere and how the
VLF/LF approach offers a stunning alternate option for tracking such occurrences and their
intensity from the ground. We also discuss the identification of global ionospheric
disruptions linked to the strongest Gamma-Ray Burst GRB221009A ever observed on
Earth. |