Dayside Field‐Aligned Current Impacts on Ionospheric Irregularities. Issue 11 (1st June 2020)

• Record Type: Journal Article
• Authors: Fæhn Follestad, A.; Herlingshaw, K.; Ghadjari, H.; Knudsen, D. J.; McWilliams, K. A.; Moen, J. I.; Spicher, A.; Wu, J.; Oksavik, Kjellmar
• Is Part Of: Geophysical research letters. Volume 47:Issue 11(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-06-01
• Subjects: FACs -- ionosphere -- scintillations -- aurora; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1029/2019GL086722
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: Global Navigation Satellite Systems (GNSS) are subject to disturbances caused by plasma irregularities in the ionosphere. Studies have suggested that in addition to the gradient drift and Kelvin‐Helmholtz instabilities, electron precipitation may be important for phase scintillations in the dayside auroral region. This study combines in situ Swarm data with ground GNSS observations to investigate the potential role of filamentary field‐aligned currents (FACs) on phase scintillations in the dayside auroral region by analyzing 22 events with phase scintillations exceeding 0.45 radians. We observe colocation between regions of severe phase scintillations and highly filamented FACs with fluctuations measured in the spacecraft frame of the order of 20 Hz. The observations indicate that filamentary FACs are crucial drivers for irregularities responsible for creating severe phase scintillations measured in the dayside auroral region and are thus of significant importance in the context of space weather impact on satellite communication. Plain Language Summary: Satellite‐based navigation systems such as Global Positioning System (GPS) are known to be affected by dynamic phenomena in the upper atmosphere. The signals are subject to disturbances, resulting in reduced position accuracy or even a loss of signal reception. Several processes have been suggested as being responsible for these disturbances in the dayside auroral region, but their relative importance is still unclear. Thus, we used Swarm data as well as ground‐based instrumentation to investigate this issue. We identified 22 events with severe disturbances that were located where we could compare data from the satellite and from ground‐based instruments. We find that the occurrences of severe phase scintillation coincide with structured field‐aligned currents (FACs), making them potentially a primary driver for signal disturbances in the daytime auroral region. Key Points: Severe GNSS phase scintillations in the winter dayside auroral ionosphere coincide with filamentary FACs Filamentary FACs appear to be essential for the creation of severe phase scintillations