Simultaneous observation of traveling ionospheric disturbances in the Northern and Southern Hemispheres

Valladares, C. E.; Villalobos, J.; Hei, M. A.; Sheehan, R.; Basu, Susanto; MacKenzie, E.; Doherty, Patricia H.; Ríos, V. H.

doi:10.5194/angeo-27-1501-2009

Cited by 67 publications

(68 citation statements)

References 21 publications

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“…A large number of geomagnetic storms could be expected since during previous solar maximums several ionospheric storms occurred (Valladares et al 2009). Geomagnetic storms are disturbances in the magnetosphere which, due to its close coupling with the ionosphere, can sometimes severely affect GNSS signal propagation.…”

Section: Introductionmentioning

confidence: 99%

Impact of the Halloween 2003 ionospheric storm on kinematic GPS positioning in Europe

et al. 2010

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Using dual-frequency data from 36 GPS stations from the EUREF Permanent Network (EPN), the influence of the October 30, 2003 Halloween geomagnetic storm on kinematic GPS positioning is investigated. The Halloween storm induced ionospheric disturbances above the northern part of Europe and Scandinavia. It is shown that kinematic position repeatabilities for this period are mainly affected for stations in northern Europe with outliers reaching 12 cm in the horizontal, and 26 cm in the vertical. These magnitudes are shown to be possibly due to the second-order ionospheric delays on GPS signals, not accounted for in the kinematic GPS positioning analysis performed. In parallel, we generate hourly TEC (Total Electron Content) maps on a 1°9 1°grid using the dense EPN network. These TEC maps do not use any interpolation but provide a high resolution in the time and space and therefore allow to better evidence small structures in the ionosphere than the classical 2-hourly 2.5°9 5°grid Global Ionospheric TEC Maps (GIM). Using the hourly 1°9 1°TEC maps, we reconstruct and refine exactly the zones of intense ionosphere activity during the storm, and we show the correlation between the ionospheric activity and assess the quality of GPS-based kinematic positioning performed in the European region.

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Section: Introductionmentioning

confidence: 99%

Impact of the Halloween 2003 ionospheric storm on kinematic GPS positioning in Europe

et al. 2010

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“…These relative STEC values contain the differential instrument biases related to the satellite and receiver. The last step is to calculate the absolute vertical TEC (VTEC) values using the relationship VTEC = [STEC − (b R + b S )] / S(E), which takes into account the satellite biases (b S ) provided by the University of Bern and the receiver biases (b R ) that are obtained by minimizing the TEC variability between 02:00 and 06:00 LT (Valladares et al, 2009). S(E) is the slant factor used to map slant TEC into vertical TEC and is given by…”

Section: Experimental Datamentioning

confidence: 99%

Total electron content responses to HILDCAAs and geomagnetic storms over South America

2017

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Abstract. Total electron content (TEC) is extensively used to monitor the ionospheric behavior under geomagnetically quiet and disturbed conditions. This subject is of greatest importance for space weather applications. Under disturbed conditions the two main sources of electric fields, which are responsible for changes in the plasma drifts and for current perturbations, are the short-lived prompt penetration electric fields (PPEFs) and the longer-lasting ionospheric disturbance dynamo (DD) electric fields. Both mechanisms modulate the TEC around the globe and the equatorial ionization anomaly (EIA) at low latitudes. In this work we computed vertical absolute TEC over the low latitude of South America. The analysis was performed considering HILDCAA (high-intensity, long-duration, continuous auroral electrojet (AE) activity) events and geomagnetic storms. The characteristics of stormtime TEC and HILDCAA-associated TEC will be presented and discussed. For both case studies presented in this work (March and August 2013) the HILDCAA event follows a geomagnetic storm, and then a global scenario of geomagnetic disturbances will be discussed. Solar wind parameters, geomagnetic indices, O / N 2 ratios retrieved by GUVI instrument onboard the TIMED satellite and TEC observations will be analyzed and discussed. Data from the RBMC/IBGE (Brazil) and IGS GNSS networks were used to calculate TEC over South America. We show that a HILDCAA event may generate larger TEC differences compared to the TEC observed during the main phase of the precedent geomagnetic storm; thus, a HILDCAA event may be more effective for ionospheric response in comparison to moderate geomagnetic storms, considering the seasonal conditions. During the August HILDCAA event, TEC enhancements from ∼ 25 to 80 % (compared to quiet time) were observed. These enhancements are much higher than the quiet-time variability observed in the ionosphere. We show that ionosphere is quite sensitive to solar wind forcing and considering the events studied here, this was the most important source of ionospheric responses. Furthermore, the most important source of TEC changes were the long-lasting PPEFs observed on August 2013, during the HILDCAA event. The importance of this study relies on the peculiarity of the region analyzed characterized by high declination angle and ionospheric gradients which are responsible for creating a complex response during disturbed periods.

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“…The satellite biases are obtained from those published by the University of Bern and the receiver biases are calculated by minimizing the TEC variability between 0200 and 0600 LT [Valladares et al, 2009;Seemala and Valladeres, 2011]. The mapping function S(E) is defined as [Mannucci et al, 1993 andLangley et al, 2002]…”

Section: Databasementioning

confidence: 99%

On the performance of the IRI‐2012 and NeQuick2 models during the increasing phase of the unusual 24th solar cycle in the Brazilian equatorial and low‐latitude sectors

Venkatesh

Fagundes

Seemala³

et al. 2014

JGR Space Physics

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It is known that the equatorial and low-latitude ionosphere is characterized with typical dynamical phenomena namely, the equatorial ionization anomaly (EIA). Accurate modeling of the characteristic variations of the EIA is more important to arrive at the correct estimation of range delays required for the communication and navigation applications. The total electron content (TEC) data from a chain of Global Positioning System (GPS) receivers at seven identified locations from equator to the anomaly crest and beyond along 315°E geographic longitude in the Brazilian sector are considered. The performances of the latest available IRI-2012 and NeQuick2 models have been investigated during 2010-2013 in the increasing phase of the 24th solar cycle. A comparative study on the morphological variations of the GPS measured and modeled TEC revealed that the performances of the models are improved during low solar activity periods compared to that during the increased solar activity years. The strength and the locations of the EIA crest are nearly well represented by both the models during the low solar activity while the models underestimate the peak TEC at the EIA during the increased solar activity conditions. The deviations between the GPS-measured and model-derived TEC are more during equinoctial and summer months at and around the anomaly crest locations. Significant differences have also been observed in between the TEC values derived from both the models. The causes for the discrepancies in the modeled TEC values are discussed based on the model-derived and ionosonde-measured vertical electron density profiles variations.

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Simultaneous observation of traveling ionospheric disturbances in the Northern and Southern Hemispheres

Cited by 67 publications

References 21 publications

Impact of the Halloween 2003 ionospheric storm on kinematic GPS positioning in Europe

Impact of the Halloween 2003 ionospheric storm on kinematic GPS positioning in Europe

Total electron content responses to HILDCAAs and geomagnetic storms over South America

On the performance of the IRI‐2012 and NeQuick2 models during the increasing phase of the unusual 24th solar cycle in the Brazilian equatorial and low‐latitude sectors

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