Deep Electron Density Depletion Near Sunset Terminator on St. Patrick's Day Storm and Its Impacts on Skywave Propagation. Issue 3 (2nd March 2023)

• Record Type: Journal Article
• Authors: Ankita, M.; Tulasi Ram, S.; Ajith, K. K.; Sripathi, S.
• Is Part Of: Space weather. Volume 21:Issue 3(2023)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2023-03-02
• Subjects: geomagnetic storm -- equatorial ionosphere -- Skywave propagation; Space environment -- Periodicals; 551.509992
• DOI: 10.1029/2022SW003369
• Languages: English
• ISSNs: 1542-7390

Abstract

Abstract: The plasma density distribution in the equatorial and low latitude ionosphere can often be severely disturbed during active space weather events that can have paramount impacts on the long‐distance high frequency (HF) radio wave (Skywave) communications through the ionosphere. On the St. Patrick's Day storm of 17 March 2015, a deep depletion of plasma with more than two orders of magnitude was observed over a narrow longitudinal sector near the sunset terminator. The controlled SAMI2 (Sami2 is Another Model of the Ionosphere) simulations indicate that a large equatorial vertical drift around sunset terminator can produce such a deep electron density depletion and strong reinforcement of equatorial ionization anomaly. The impacts of these ionospheric density disturbances on the Skywave communication systems have been investigated using an HF propagation simulator that solves the propagation path of radio waves under given background ionospheric conditions. The results clearly demonstrate that the usable HF spectrum for Skywave communications is reduced by more than 50% over the region of depletion. Further, large areas of skip zones, where the Skywave signals are not receivable, are produced due to low ionospheric densities over this region. This study can have important applications in the planning and operation of Skywave systems during the active space weather periods. Plain Language Summary: Earth's ionosphere acts as a mirror in space that reflects back the radio waves to the ground and facilitates Radio communication links over very far distances beyond the horizon. However, the ionosphere which is primarily produced via photo‐ionization by solar radiations can often be greatly disturbed due to highly energetic events on the sun such as solar flares, Coronal Mass Ejection, etc., and the resultant changes in the Earth's near space. These ionospheric disturbances can have significant impacts on the usable radio wave spectrum and ground coverage area of reception for Skywave communication systems. This study investigates a unique event of deep ionospheric density depletion that occurred during the geomagnetic storm and its impacts on Skywave systems over equatorial and low latitude regions. This study provides important insights about the space weather impacts on long‐distance radio communications and can have potential applications in the planning and operation of Skywave communication systems. Key Points: A deep electron density depletion occurred over a narrow longitude sector near sunset terminator due to large equatorial vertical drift The depletion caused severe limitations on the usable high frequency spectrum of Skywave communication systems by reducing the maximum usable frequency by more than 50% The depletion also resulted in a wide area of skip zones over equatorial regions where Skywave communication signals cannot be received