Lookup NU author(s): Dr Rajesh Tiwari,
Dr Hal Strangeways,
Professor Satnam Dlay
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The Earth’s ionized atmosphere, above 100 km altitude, and at high latitudes, experiences auroral storms driven by space weather activity. Aurorae, visible in the form of dynamic light effects, coincide with time-varying ionospheric electron density irregularities and magnetic storms. When satellite signals pass through such irregularities, rapid random fluctuations in their received phase and amplitude are observed at ground-based receivers. This is a phenomenon termed ionospheric scintillation and it can be severe enough to cause loss of availability for a number of the GNSS (Global Navigation Satellite System) applications. There are also indications that ionospheric scintillation can also influence the Ionosphere-Free linear combination of carrier phase observables used in high-precision positioning, leading to degraded quality of GNSS measurements in surveying and scientific applications. In recent reports from the Royal Academy of Engineering and Lloyds, the potential threat of such storms for GNSS applications has been discussed, including its effects on aviation, road and maritime navigation, rail transport and oil drilling [1, 2]. The European GNSS system, Galileo, is proceeding towards its completion stage and has the facility to provide emergency services to users using two way satellite communications. However, it is also expected to suffer from a number of vulnerabilities including geomagnetic storm effects. Considering the commercial and life-safety issues of the abovementioned areas of research, our study helps in monitoring and modeling the auroral monitoring index (AMI) using the existing network of NMA GNSS receivers situated at European high latitudes (55 N to 75 N) and capable of logging RINEX data at 1Hz. Further, the derived index was used in mitigating ionospheric scintillation effects during auroral storms. New scintillation indices, the analogous phase index, and a regional phase scintillation alarming index, using GPS observations from EUREF (European Reference) GNSS stations, have been developed at Newcastle University developed [3,4]. This led to a study suggesting that GNSS software receivers can use this regional phase scintillation alarming index [4, 5] determined for their respective region to avoid loss of satellite lock, particularly during a strong geomagnetic storm period. In this method, for the area from 55 N to 75 N in the European region, raw phase and pseudorange observation data at 1Hz from 105 GPS receivers were collected, and further used in the estimation of TEC at 1Hz. The C/A-P code biases were corrected from the correction data provided by University of Bern. The, filtered rate of change of 1Hz TEC data from all 105 stations was then further employed in designing a spatial index for monitoring auroral storms. Based on one year (January 2014 to December 2014) of auroral storm data, a statistical normalized standard deviation estimate, called the aurora monitoring index (AMI), was determined which was found to be well correlated with the scintillation indices collected from three GISTM receivers installed in the same region. The auroral activities were further evaluated with space-based geomagnetic field variations using data from ESA’s new satellite called SWARM together with ground-based fluxgate magnetometer data collected by the British Geological Survey . Based on analysis and investigation of one year of scintillation indices, TEC and magnetometer data method to monitor auroral storms and provide ionospheric scintillation mitigation for precise positioning. References P. Cannon (2013), Extreme Space Weather: Impacts on engineered systems and infrastructure, Report: Royal Academy Engineering, available on www.raeng.org.uk/spaceweather. Lloyd (2013), Lloyd 360o Insight, Space weather: Its impact on Earth and implications for business, available, http://www.lloyds.com/~/media/lloyds/reports/360/360%20space%20weather/7311_lloyds_360_space%20weather_03.pdf.  R. Tiwari, S. Tiwari, H. J. Strangeways and A. Ahmed (2013), Investigation of ionospheric irregularities and scintillation using TEC at high latitude, Advances in Space Research, 52(6), pp. 1111-1124. R. Tiwari and H. J. Strangeways (2015), Regional alarming index for scintillation mitigation, Space Weather, doi: 10.1002/2014SW001115. R. Tiwari, H. J. Strangeways, S. Skone (2013), Modeling the effects of ionospheric scintillation on GPS carrier phase tracking using high rate TEC data (2013). In: ION GNSS+. 2013, Nashville, Tennessee: Institute of Navigation. R. Tiwari, F. Ghafoori, O-Al, Fenek, O. Hadad, S. Skone (2010), Investigation of high-latitude ionospheric scintillation observed over Canadian region.In: 23rd International Technical Meeting of The Satellite Division of the Institute of Navigation (ION GNSS). 2010, Portland, Oregon, USA: The Institute of Navigation.
Author(s): Tiwari R, Strangeways HJ, Dlay S
Publication type: Conference Proceedings (inc. Abstract)
Publication status: In Press
Conference Name: ION GNSS 2015
Year of Conference: 2015
Acceptance date: 09/04/2015
Publisher: Institute of Navigation