A new model for radio wave propagation through the ionosphere developed by scientists can help estimate the impact of space weather and facilitate the planning and operation of High Frequency (HF) radio communications, a vital means of communication during the situations like natural disasters, and mid-ocean surveillance.

The ionosphere is a region of Earth’s upper atmosphere ranging from about 100 - 1000 km and acts as a gateway for radio communication between the ground and space. Radio waves of certain frequencies (HF band) are reflected back to the ground by the ionosphere which facilitates long-distance HF communications beyond the horizon, known as Skywave communications. Despite the increasing use of satellite communications, traditional long-distance high-frequency (HF) radio communication, remains a vital means of communication during the situations like natural disasters, mid-ocean surveillance, over-the-horizon target detection, and so on.  Severe ionospheric disturbances that arise due to a range of space weather events like Solar flares, Coronal Mass Ejections (CMEs), and Geomagnetic storms significantly affect Skywave communications.  This variability of ionosphere due to disturbances in space weather can significantly limit the usage of Skywave communications

Scientists of the Indian Institute of Geomagnetism (IIG), an autonomous institute of the Department of Science and Technology have recently developed a model for HF radio wave propagation through the ionosphere which helps in studying the impacts of space weather effects on the ionosphere and Skywave communication systems.  In their recent study published in the journal Space Weather, a group of scientists from IIG have found a deep depletion of the ionosphere over the low latitudes of the Indian sub-continent region due to a severe geomagnetic storm on 17^th March 2015.  The HF radio wave propagation model developed by IIG scientists indicates that this ionospheric depletion can severely limit the usable HF spectrum by more than 50% for Skywave communication during this disturbed period.  Also, the skip-zones where the Skywave signals are not receivable are expanded for very large areas resulting in the loss of communications. This information is crucial for developing robust strategies in mitigating the space effects on Skywave communication systems. 

The HF radio propagation model developed by IIG scientists has important applications in planning the right strategies for the operation of Skywave communication systems during active space weather periods. The development of such strategies is essential for ensuring reliable Skywave communication systems in the face of natural disasters and other emergencies.

Publication link:  https://doi.org/10.1029/2022SW003369

Figure:  Significant decrease of Usable HF spectrum and increase of Skip zone on Disturbed day (right) compared to Usual day (left) predicted by HF propagation model developed by IIG scientists.

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