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TitleData-based optimization of a simple shortwave fadeout absorption model
AuthorFiori, R A DORCID logo; Chakraborty, SORCID logo; Nikitina, LORCID logo
SourceJournal of Atmospheric and Solar-Terrestrial Physics vol. 230, 105843, 2022 p. 1-11, Open
Access logo Open Access
Alt SeriesNatural Resources Canada, Contribution Series 20210218
PublisherEuropean Geophysical Union
Mediapaper; on-line; digital
File formatpdf; html
ProvinceCanada; British Columbia; Alberta; Saskatchewan; Manitoba; Ontario; Quebec; New Brunswick; Nova Scotia; Prince Edward Island; Newfoundland and Labrador; Northwest Territories; Yukon; Nunavut
NTS1; 2; 3; 10; 11; 12; 13; 14; 15; 16; 20; 21; 22; 23; 24; 25; 26; 27; 28; 29; 30; 31; 32; 33; 34; 35; 36; 37; 38; 39; 40; 41; 42; 43; 44; 45; 46; 47; 48; 49; 52; 53; 54; 55; 56; 57; 58; 59; 62; 63; 64; 65; 66; 67; 68; 69; 72; 73; 74; 75; 76; 77; 78; 79; 82; 83; 84; 85; 86; 87; 88; 89; 92; 93; 94; 95; 96; 97; 98; 99; 102; 103; 104; 105; 106; 107; 114O; 114P; 115; 116; 117; 120; 340; 560
Subjectsgeophysics; Science and Technology; Nature and Environment; modelling; models; ionosphere; solar variations; absorption; statistical analyses; D-RAP Model; Natural hazards; Methodology; Communications
Illustrationslocation maps; tables; time series; plots; rose diagrams; bar graphs
ProgramPublic Safety Geoscience Assessing space weather hazards
Released2022 03 03
AbstractElectron density enhancement caused by electromagnetic radiation emitted during a solar X-ray flare has the potential to increase high frequency (HF; 3-30 MHz) absorption in the dayside D-region ionosphere, impacting shortwave radio signals by reducing the signal strength, a phenomenon commonly referred to as shortwave fadeout. Data-based optimization of a simple absorption model is performed incorporating solar X-ray flux data and 30 MHz riometer data from stations distributed across Canada. In a single event study the data-based optimization model is shown to overestimate absorption by 1% for the duration of an X2.1 solar X-ray flare. This corrects an underestimation by the NOAA D-region Absorption Prediction (D-RAP) model. In a statistical study, based on 87 events, data-based optimization performed on an event-by-event basis showed excellent overall agreement between measured and modelled data: the Pearson correlation coefficient was R=0.88, and the slope of the best-fit line to the data was m=0.91. A generalized model was developed using data from all 87 events collectively. Although good agreement was found between the measured and modelled data sets, correlation and slope were slightly reduced to R=0.75 and m=0.80. Model accuracy is characterized by prediction efficiency (PE) which peaked at PE=0.78 for the event-by-event evaluation and PE=0.48 for the collective data set. The results of this study highlight the advantages of data-based optimization in modelling absorption due to shortwave fadeout.
Summary(Plain Language Summary, not published)
Space weather refers to the dynamic conditions on the Sun and in the space environment, in particular, in the near-Earth environment, that can affect critical infrastructure. NRCan operates the Canadian Space Weather Forecast Centre and conducts research into space weather effects on power systems, pipelines, radio communications and GNSS positioning to help Canadian industry understand and mitigate the effects of space weather. This paper presents a simple model, developed from a Canadian network of riometer instruments, of the absorption of radio signals caused by a solar flare.

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