Abstract
This paper discusses the occurrence of Global Positioning System (GPS) loss of lock events obtained by considering total electron content (TEC) measurements carried out by the three satellites of the European Space Agency Swarm constellation from December 2013 to December 2020, which represents the longest dataset ever used to perform such an analysis. After describing the approach used to classify a GPS loss of lock, the corresponding occurrence is analyzed as a function of latitude, local time, season, and solar activity to identify well-defined patterns. Moreover, the strict relation of the occurrence of the GPS loss of lock events with defined values of both the rate of change of electron density index (RODI) and the rate of change of TEC index (ROTI) is highlighted. The scope of this study is, on one hand, to characterize the background conditions of the ionosphere for such events and, on the other hand, to pave the way for their possible future modeling. The results shown, especially the fact that GPS loss of lock events tend to happen for well-defined values of both RODI and ROTI, are of utmost importance in the light of Space Weather effects mitigation.
Highlights
In this work, rate of change of electron density index (RODI) and rate of change of TEC index (ROTI) values associated with a specific loss of lock (LoL) event will be the corresponding maximum values in a 10-s wide window centered at the LoL start timestamp
Considering data from the EuropeanSpace Agency (ESA) Swarm constellation recorded from December 2013 to December 2020, we analyzed the occurrence of Global Positioning System (GPS) LoL events and characterized them in terms of RODI and ROTI
LoL events are mainly located at low and high latitudes, for both hemispheres. At low latitudes they maximize along the equatorial ionospheric anomaly (EIA) crests between about 70◦ W and 10◦ E of longitude; The high-latitude LoL occurrence is higher in the Southern hemisphere than in the Northern hemisphere
Summary
Electron density irregularities are at the base of sudden and rapid fluctuations characterizing both amplitude and phase of electromagnetic waves propagating through the ionospheric plasma, e.g., [1,2,3,4,5]. System (GPS) radio occultation observations of the Constellation Observing System for Meteorology, Ionosphere, and Climate, Yue et al [7] analyzed the signal cycle slip occurrence from 2007 to 2011 They correlated it with the appearance of sporadic E layers, and with F-region irregularities and the equatorial ionospheric anomaly (EIA) at low and equatorial latitudes, and with the polar cap electron density gradients in the polar regions. Our analyses aim at finding a relation between the LoL occurrence and defined values of the following two ionospheric indices: the rate of change of electron density index (RODI) and the rate of change of total electron content (TEC) index (ROTI) This kind of investigation is done both to characterize the background conditions of the ionosphere for such events, and to start understanding whether these events can be somehow forecast, which would be very important for Space Weather effects mitigation purposes.
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