Evaluation of the NeQuick model performance under different geomagnetic conditions over South Africa during the ascending phase of the solar cycle (2009–2012)

Abstract

Abstract. In order to provide a scientific base to the NeQuick characterisation under disturbed conditions, the comparison of its performance for quiet and storm days is investigated in the southern mid-latitude. This investigation was realised using the two versions of the NeQuick model which were adapted to local and storm-specific response by using the critical frequency of the F2 layer (foF2) and the propagation factor (M(3000)F2) derived from three South African ionosonde measurements, Hermanus (34.40∘ S, 19.20∘ E), Grahamstown (33.30∘ S, 26.50∘ E) and Louisvale (28.50∘ S, 21.20∘ E). The number of free electrons contained within a 1 m squared column section known as total electron content (TEC) is a widely used ionospheric parameter to estimate its impact on the radio signal passing through. In this study, the TEC derived from the adapted NeQuick version is compared with observed TEC derived from Global Navigation Satellite System (GNSS) data from co-located or nearby GNSS dual-frequency receivers. The Hermanus K-index is used to select all the disturbed days (K-index ≥ 5) upon moving from low to high solar activity (from 2009 to 2012). For each disturbed day, a quiet reference day of the same month was chosen for the investigation. The study reveals that the NeQuick model shows similar reliability for both magnetic quiet and disturbed conditions, but its accuracy is affected by the solar activity. The model is much better for moderate solar activity epochs (2009 and 2010), while it exhibits a discrepancy with observations during high solar activity epochs. For instance in Hermanus, the difference between GPS TEC and NeQuick TEC (ΔTEC) is generally lower than 10 TECu in 2009, and it sometimes reaches 20 TECu in 2011 and 2012. It is also noticed that NeQuick 2 is more accurate than NeQuick 1, with an improvement in TEC estimation more significant for the high solar activity epochs. The improvement realised in the latest version of NeQuick is more than 15 % and sometimes reaches 50 %. Keywords. Ionosphere (mid-latitude ionosphere; modelling and forecasting)

A study of vTEC above Nepal exploring different calibration techniques, including a comparison with the NeQuick-2 model

“…Twinomugish et al ( 2017) also reported a similar result over the east African equatorial region. Ahoua et al (2018) also concluded that the NeQuick model has comparable reliability in quiet and disturbed days; somewhat, its accuracy is affected by solar activity (better in moderate than in high solar activity). During the storm's main phase, an interplanetary electric field penetrates the ionospheric area for several hours, loading interplanetary particles into the ionosphere (Kumar and Singh, 2010).…”

“…Researchers (Ezquer et al, 2018;Okoh et al, 2018;Teriku, 2020) conducted a comparison of different ionospheric TEC models (IRI, IRI-plas, and NeQ-2) using GNSS measurements and concluded that NeQ-2 performs better than other models regardless of time or location. Ahoua et al (2018) compared observed 4 TEC derived from a nearby GNSS dual-frequency receiver to the NeQ-2 model performance for quiet and storm days over south Africa during the ascending phase of the solar cycle (2009)(2010)(2011). Yu et al (2012) evaluated the monthly average of the NeQ-2 model over China during the quietest period and discovered that the NeQ-2 predicts GPS TEC accurately (except for few cases).…”

The Benefit and Importance of Mobile Satellite Signal in Northern Nigeria: GPS Approach

“…'49' refers to the SNR and *78 is the checksum data and always begin with *. Since the sentence contained four satellites propagation data, thus, the numbers will be repeated continuously for the other satellite in view [8], [11].…”

Measurement and Comparison of Total Electron Content for Assessment of Ionospheric Models during April 7, 2000 Geomagnetic Storms

“…This shows that the geomagnetic storm observed during 7 April 2000 was driven by a Corona Mass Ejection (CME). Geomagmetic storms have great influence on the earth's ionosphere and it usually leads to changes in ionospheric density structure (Ahoua et al, 2015). The sharp and rapid changes in Total Electron Content (TEC) are very important conditions for eruptions of ionospheric plasma density irregularities which invariably causes scintillations in radio waves (Akala et al, 2013).…”