Response of data-driven artificial neural network-based TEC models to neutral wind for different locations, seasons, and solar activity levels from the Indian longitude sector
TL;DR: In this article, a set of observations carried out in the Indian longitude sector have been reported in order to find the amount of improvement in performance accuracy of an ANN-based Vertical Total Electron Content (VTEC) model after incorporation of neutral wind as model input.
Abstract: The perturbations imposed on transionospheric signals by the ionosphere are a major concern for navigation. The dynamic nature of the ionosphere in the low latitude equatorial region and the Indian longitude sector has some specific characteristics such as sharp temporal and latitudinal variation of Total Electron Content (TEC). TEC in the Indian longitude sector also undergoes seasonal variations. The large magnitude and sharp variation of TEC causes large and variable range errors for satellite based navigation system such as Global Positioning System (GPS) throughout the day. For accurate navigation using Satellite Based Augmentation Systems (SBAS), proper prediction of TEC under certain geophysical conditions is necessary in the equatorial region. It has been reported in the literature that prediction accuracy of TEC has been improved using measured data driven Artificial Neural Network (ANN) based VTEC models, compared to standard ionospheric models. A set of observations carried out in the Indian longitude sector have been reported in this paper in order to find the amount of improvement in performance accuracy of an ANN-based Vertical TEC (VTEC) model after incorporation of neutral wind as model input. The variations of this improvement in prediction accuracy with respect to latitude, longitude, season and solar activity have also been reported in this paper.
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TL;DR: In this article , a commentary about the state of Integrated, Coordinated, Open, and Networked (ICON) principles in Space Physics and Aeronomy and a discussion on several scopes and limitations to implementing them are discussed.
Abstract: This article is a commentary about the state of Integrated, Coordinated, Open, and Networked (ICON) principles (Goldman et al., 2021) in Space Physics and Aeronomy and a discussion on several scopes and limitations to implementing them. The commentary focuses on the basic introduction and brief literature survey (Section 1); possibilities of implementation of ICON in Space Physics and Aeronomy (Section 2) and limitations or challenges in this field with possible solutions using ICON principles (Section 3). The Space Physics and Aeronomy section of the American Geophysical Union (AGU) comprises the interactions between solar wind, Interplanetary Magnetic Field (IMF) and different planetary magnetospheres and ionospheres. The section also deals with solar physics, mechanisms behind existence of solar magnetic fields, and evaluations of high and low speed solar winds. This field is a collection of different interdisciplinary subtopics, making this an excellent example of integrated research. Similar and transparent methodologies are adopted to solve problems all over the world which shows a coordinated approach of research. Freely available data from different space agencies and universities are also great assets for this domain which supports open research. The scopes of possible networked research with mutual benefits are also highlighted. Examples of ICON-based international collaborations and support mechanisms towards young scientists are elaborated which are helpful to mitigate limitations in this domain. Space Physics and Aeronomy Perspectives on Integrated, Coordinated, Open, Networked (ICON) Science
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TL;DR: In this article, f0F2 data from ionosonde measurements for three low latitude Indian stations (Delhi (28.6°N, 77.2°E), Ahmedabad (23.0°N and 72.5°E) are analysed and compared to the IRI-90.
23 citations
TL;DR: In this paper, a provisional horizontal wind model (HWM07) and its implications for the meridional structure of the equatorial electrojet (EEJ) were investigated.
Abstract: [1] Horizontal neutral winds play an important role in low-latitude ionospheric E and F-region dynamics. In particular, the zonal winds have strong effects on the local structure of the low-latitude ionospheric current system. Accurate wind specification is therefore essential for modeling these currents. In order to investigate the retrieval of eastward electric fields from satellite-derived equatorial electrojet (EEJ) profiles, we consider a provisional Horizontal Wind Model (HWM07) and its implications for the meridional structure of the EEJ. We find that EEJ current profiles predicted using HWM07 agree better with CHAMP magnetometer-derived current profiles than EEJ profiles predicted using the older HWM93 model. The improved wind model opens exciting new possibilities of determining the day-side eastward electric field in the equatorial ionosphere from satellite magnetic field measurements.
20 citations
TL;DR: In this paper, an optimum grid size for reliable operation of the Satellite-Based Augmentation System (SBAS) in the Indian subcontinent (GAGAN), or GPS and Geo Augmented Navigation, is estimated.
Abstract: The Total Electron Content (TEC) measured from a station situated near the northern crest of the equatorial anomaly is compared with that obtained from models such as the Parameterized Ionospheric Model (PIM 1.6) and International Reference Ionosphere (IRI-95) for well over one solar cycle (1977–1990). The limitations of conversion from vertical to slant TEC and vice versa as required for GPS ionospheric corrections in the equatorial region are discussed. It is found that the correspondence among the vertical TEC at the ionospheric pierce point, geometrically (sec χ) converted slant TEC, and slant TEC along a GPS signal propagation path becomes poor for elevation angles of less than 80 deg. Based on this finding, an optimum grid size for reliable operation of the Satellite-Based Augmentation System (SBAS) in the Indian subcontinent (GAGAN, or GPS and Geo Augmented Navigation) is estimated. The suggested grid size is much smaller than the standard 5 × 5 deg.
19 citations
TL;DR: In this article, the authors highlight the necessity for a differential grid size around the northern crest of the EIA using data recorded from stations under the Indian SBAS GAGAN during the moderate sunspot number year 2004.
19 citations
TL;DR: In this article, the authors analyzed ten years of measurements of the ionospheric F-layer peak height hmax and peak density nmax and of the horizontal neutral wind at these heights with the Japanese MU Radar to detail the causes of the temporal variations of the peak parameters.
Abstract: [1] Ten years of measurements of the ionospheric F-layer peak height hmax and peak density nmax and of the horizontal neutral wind at these heights with the Japanese MU Radar are analyzed to detail the causes of the temporal variations of the peak parameters. In the absence of winds hmax rides the height of a constant product of the atomic and molecular densities of the thermosphere. Since the mean wind does not change with solar activity, the hmax change with solar activity is driven almost solely by a thermal expansion of the thermosphere. The seasonal variation of hmax, on the other hand, is driven almost solely by the seasonal change in winds. The diurnal variation of hmax is driven most importantly by winds, secondarily by thermal expansion. nmax is proportional to the ratio of the atomic and molecular densities of the thermosphere at altitude hmax but that ratio is insensitive to thermal expansion. The solar-activity change in nmax is largely due to the change in solar EUV intensity, secondarily due to changes in neutral composition at the base of the thermosphere. The seasonal change in nmax is semiannual in response to the semiannual change in neutral O density. The wind itself shows features of ion-drag control in almost every facet of its behavior except that its diurnal amplitude does not change with season, a result consistent with the explanation that one day is insufficient time to set up a nondivergent circulation pattern in the upper atmosphere. Our numerical results are valid only for the location of the MU Radar, but the understandings involved are broadly applicable to the midlatitude ionosphere.
18 citations