scholarly journals Status of CAS global ionospheric maps after the maximum of solar cycle 24

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Zishen Li ◽  
Ningbo Wang ◽  
Ang Liu ◽  
Yunbin Yuan ◽  
Liang Wang ◽  
...  
Keyword(s):  
Solar Cycle ◽  
Southern Hemisphere ◽  
Single Layer ◽  
Latitudinal Gradients ◽  
Electron Content ◽  
International Gnss Service ◽  
Total Electron ◽  
Solar Cycle 24 ◽  
Cycle 24 ◽  
Global Ionospheric Maps

AbstractAs a new Ionosphere Associate Analysis Center (IAAC) of the International GNSS Service (IGS), Chinese Academy of Sciences (CAS) started the routine computation of the real-time, rapid, and final Global Ionospheric Maps (GIMs) in 2015. The method for the generation of CAS rapid and final GIMs and recent updates are presented in the paper. The quality of CAS post-processed GIMs is assessed during 2015–2018 after the maximum of solar cycle 24. To perform an independent and fair assessment, Jason-2/3 Vertical Total Electron Contents (VTEC) are first used as the references over the ocean. GPS differential Slant TECs (dSTEC) generated from 55 Multi-GNSS Experimental (MGEX) stations of the IGS are also employed, which provides a complementing way to evaluate the ability of electron content models to reproduce the spatial and temporal gradients in the ionosphere. During the test period, Jet Propulsion Laboratory (JPL) GIMs present significantly positive deviations compared to the Jason VTEC and GPS dSTEC. Technical University of Catalonia (UPC) rapid GIM UQRG exhibits the best performance in both Jason VTEC and GPS dSTEC analysis. The CAS GIMs show comparable performance with the results of the first four IAACs of the IGS. As expected, the poor performance of all GIMs is in equatorial regions and the high latitudes of the southern hemisphere. The consideration of generating multi-layer or three-dimensional ionospheric maps is emphasized to mitigate the inadequacy of ionospheric single-layer assumption in the presence of pronounced latitudinal gradients. The use of ionospheric observations from the new GNSS constellations and other space- or ground-based observation techniques is also suggested in the generation of future GIMs, given the sparse GPS/GLONASS stations in the southern hemisphere.

Perturbations of Global Wave Dynamics During Stratospheric Warming Events of the Solar Cycle 24

2020 ◽  
Author(s):  
Valery Yudin ◽  
Larisa Goncharenko ◽  
Svetlana Karol ◽  
Lynn Harvey
Keyword(s):  
Solar Cycle ◽  
Solar Maximum ◽  
Electron Content ◽  
Semidiurnal Tide ◽  
Stratospheric Warming ◽  
Total Electron ◽  
Wave Dynamics ◽  
Diurnal Cycles ◽  
Solar Cycle 24 ◽  
Cycle 24

<p>The paper presents analysis and interpretation of observed perturbations of global wave dynamics in the Ionosphere-Thermosphere-Mesosphere (ITM) during the recent mid-winter Arctic Sudden Stratospheric Warming (SSW) events under solar minimum (2009, 2010, 2018, and 2019), transition to solar maximum (2012) and solar maximum (2013) conditions of the Solar Cycle 24. Employing the 116-level configuration of the thermosphere extension of Whole Atmosphere Community Climate Model (WACCMX-116L), constrained by the meteorological troposphere-stratosphere analyses of Goddard Earth Observing System, version 5 (GEOS-5) of Global Modeling and Data Assimilation Office, we study and characterize the striking amplifications of the solar thermal semidiurnal tide, as one of the main drivers of the ITM variability, after onsets of major and minor SSW events. The dominance and growth of the semidiurnal tide over the diurnal and terdiurnal modes in the lower thermosphere above ~100 km are typical features of the tidal dynamics during major SSW events of the Solar Cycle 24 as suggested by model predictions. The growth of the semidiurnal tidal mode during SSW events is also supported by observational analysis of diurnal cycles from temperature space-borne observations (SABER/TIMED). In the vertical domain of the meteor radar observations at the Southern extra-tropics and low latitudes the model and data revealed the systematic presence of the strong quasi two-day wave wind oscillations that prevail over the tidal winds between 80 and 100 km during mid-January SSW events. In the high and middle latitudes of the Northern Hemisphere model simulations are capable to reproduce the day-to-day variability of tidal and PW oscillations deduced from satellite temperature data. The self-consistent whole atmosphere predictions of global-scale components of neutral dynamics (prevailing winds, planetary waves and tides) become important factor to reproduce and forecast the perturbed state of the ITM as observed from the ground and the space during SSW events of the Solar Cycle 24. The SSW-driven global perturbations of tides can significantly change diurnal cycles of the plasma in the low-latitude and extra-tropical E-region of the ionosphere as will be briefly illustrated by day-day variations of observed and simulated total electron content and plasma drifts.</p>

scholarly journals Sub-Auroral and Mid-Latitude GNSS ROTI Performance during Solar Cycle 24 Geomagnetic Disturbed Periods: Towards Storm’s Early Sensing

Sensors ◽  
2021 ◽  
Vol 21 (13) ◽  
pp. 4325
Author(s):  
Kacper Kotulak ◽  
Andrzej Krankowski ◽  
Adam Froń ◽  
Paweł Flisek ◽  
Ningbo Wang ◽  
...  
Keyword(s):  
Solar Cycle ◽  
Plasma Density ◽  
Ionospheric Plasma ◽  
Geomagnetic Storms ◽  
Electron Content ◽  
Total Electron ◽  
Content Index ◽  
Solar Cycle 24 ◽  
Ionospheric Plasma Density ◽  
Cycle 24

Geomagnetic storms—triggered by the interaction between Earth’s magnetosphere and interplanetary magnetic field, driven by solar activity—are important for many Earth-bound aspects of life. Serious events may impact the electroenergetic infrastructure, but even weaker storms generate noticeable irregularities in the density of ionospheric plasma. Ionosphere electron density gradients interact with electromagnetic radiation in the radiofrequency domain, affecting sub- and trans-ionospheric transmissions. The main objective of the manuscript is to find key features of the storm-induced plasma density behaviour irregularities in regard to the event’s magnitude and general geomagnetic conditions. We also aim to set the foundations for the mid-latitude ionospheric plasma density now-casting irregularities. In the manuscript, we calculate the GPS+GLONASS-derived rate of TEC (total electron content) index (ROTI) for the meridional sector of 10–20∘ E, covering the latitudes between 40 and 70∘ N. Such an approach reveals equatorward spread of the auroral TEC irregularities reaching down to mid-latitudes. We have assessed the ROTI performance for 57 moderate-to-severe storms that occurred during solar cycle 24 and analyzed their behaviors in regard to the geomagnetic conditions (described by Kp, Dst, AE, Sym-H and PC indices).

Ionospheric Variability: Response to Sudden Stratospheric Warming events during Solar Cycle 24

2021 ◽  
Author(s):  
Sumedha Gupta ◽  
Arun Kumar Upadhayaya ◽  
Devendraa Siingh
Keyword(s):  
Solar Activity ◽  
Solar Cycle ◽  
Electron Content ◽  
Vertical Total Electron Content ◽  
Stratospheric Warming ◽  
Sudden Stratospheric Warming ◽  
Total Electron ◽  
Ionospheric Response ◽  
Solar Cycle 24 ◽  
Cycle 24

<p>With low solar activity and unusual progression, Solar Cycle 24 lasted from December 2008 to December 2019 and is considered to be the weakest cycle in the last 100 years. During such quiet solar background conditions, the wave forcing from lower atmosphere will have a perceivable effect on the ionosphere. This study examines the ionospheric response to meteorological phenomenon of Sudden Stratospheric Warming (SSW) events during Solar Cycle 24 (Arctic winter 2008/09 to 2018/19). Ionospheric response to each of these identified warming periods is quantified by studying ground – based Global Positioning System (GPS) derived vertical Total Electron Content (VTEC) and its deviation from monthly median (ΔVTEC) for four longitudinal chains, selected from worldwide International GNSS service (IGS) stations. Each chain comprises of eight stations, chosen in such a way as to cover varied latitudes both in Northern and Southern Hemispheres. A strong latitude – dependent response of VTEC perturbations is observed after the peak stratospheric temperature anomaly (ΔT<sub>max</sub>). The semidiurnal behaviour of VTEC, with morning increase and afternoon decrease, is mostly observed at near-equatorial stations. This vertical coupling between lower and upper atmosphere during SSW is influenced by prominent 13-14 days periodicities in VTEC observations, along with other periodicities of 7, 5, and 3 days. It is seen that the ionospheric response increases with increase in solar activity. Further, under similar ionizing conditions, quite similar ionospheric response is observed, irrespective of ΔT<sub>max</sub> and type of SSW event being major or minor. However, under similar SSW strength (ΔT<sub>max</sub>), no prominent pattern in ionospheric response is observed. The causative mechanism for the coupling processes in the atmosphere during these SSW events is discussed in detail.</p>

scholarly journals Occurrence characteristics of equatorial plasma bubbles over Kisumu, Kenya during Solar maximum of Solar Cycle 24

2021 ◽  
Vol 9 (1) ◽  
pp. 1
Author(s):  
Edward Nyongesa ◽  
Ndinya Boniface ◽  
Omondi George
Keyword(s):  
Solar Cycle ◽  
Rate Of Change ◽  
Electron Content ◽  
Quiet Period ◽  
Total Electron ◽  
Plasma Bubbles ◽  
Equatorial Plasma Bubbles ◽  
Solar Cycle 24 ◽  
Cycle 24 ◽  
Year 2013

Equatorial Plasma Bubbles (EPBs) are irregular plasma density depletions in the ambient electron density in the equatorial F-region ionosphere generated after sunset. EPBs are known to bring disruptions to telecommunication and navigation systems. This paper investigates the occurrence of EPBs over Kisumu, Kenya (Geomagnetic coordinates: 9.64o S, 108.59o E; Geographic coordinates: 0.02o S, 34.6o E) for a few selected quiet and storm days between 1st January 2013 and 31st December 2014 which was a high Solar activity period for Solar Cycle 24. The study brings out EPB occurrence pattern over Kisumu, Kenya for the selected quiet and storm days of 2013 and 2014. The Receiver Independent Exchange (RINEX) data was retrieved from the Kisumu high data-rate NovAtel GSV4004B SCINDA-GPS receiver. The data was unzipped and processed to obtain Vertical Total Electron Content (VTEC), amplitude scintillation (S4) and Universal Time (UT) which were then fed into MATLAB to generate VTEC and S4 plots against UT for each selected quiet and storm day within the years 2013 and 2014. The Total Electron Content (TEC) depletion depths and S4 index values between 16:00 and 20:00 UT for each selected quiet and storm day were extracted from the VTEC and S4 plots and used to plot TEC depletion depths and S4 plots. The Rate of Change of TEC (ROT) and Rate of Change of TEC Index (ROTI) between 16:00 and 20:00 UT were generated from VTEC and used to plot ROT and the corresponding ROTI plots against UT. TEC depletion depths and ROTI values for each selected quiet and storm day between 16:00 and 20:00 UT were extracted and used to plot TEC depletion depths and ROTI plots and S4 index and ROTI plots. In this study, the enhancement of S4 index corresponded well with TEC depletions, increased fluctuation of ROT and higher ROTI values between 16:00UT and 20:00UT for most days. This correspondence was used in inferring the occurrence of EPBs during the selected quiet and storm days of the years 2013 and 2014. The obtained results showed that the highest EPB occurrence was during March equinox with 33.33% occurrence in the year 2013 and 30.76% occurrence in the year 2014, followed by the September equinox which had 20.38% occurrence in 2013 and 17.26% occurrence in 2014. The seasonal variation of EPB occurrence was attributed to the variation in the daytime E x B drift velocities. Larger E x B drift velocities resulted in increased EPB occurrence in the equinoctial period (March, April, August and September) and November solstice period (November and December) while lower E x B drift velocities resulted in reduced EPB occurrence in the June solstice period (June and July). The percentage EPB occurrence in the year 2013 was 6.49% while in the year 2014 was 4.32%. The storm period had percentage EPB occurrence of 21.42% in the year 2013 and 21.88% in the year 2014 while the quiet period had percentage EPB occurrence of 18.75% in the year 2013 and 7.89% in the year 2014. These results clearly showed that the percentage EPB occurrence was higher during the storm period than in the quiet period. Hence the development of EPBs was enhanced by geomagnetic activity through several competing dynamics such as Prompt Penetration Electric Field (PPEF), Disturbance Dynamo Electric Field (DDEF) and reduction in electron density due to increased recombination rates.  

scholarly journals Localized TEC enhancements in the Southern Hemisphere

2019 ◽  
Author(s):  
Ilya K. Edemskiy
Keyword(s):  
Magnetic Field ◽  
Solar Activity ◽  
Southern Hemisphere ◽  
Occurrence Rate ◽  
Continuous Series ◽  
Electron Content ◽  
Field Orientation ◽  
Total Electron ◽  
Magnetic Field Orientation ◽  
Global Ionospheric Maps

Abstract. The paper is dedicated to investigation of localized TEC (total electron content) enhancements (LTEs), particularly of LTE series, detected in the Southern Hemisphere using global ionospheric maps for different solar activity years (2014, 2015, 2018). It is shown that LTE intensity varies in dependence on solar flux and does not directly depend on interplanetary magnetic field orientation. The enhancements occur in a subsolar region and could be observed during a continuous series of days. The highest LTE occurrence rate is observed during period of local winter (April-September) for all analyzed years. The longest observed LTE series was detected during 2014 and lasted 80 days or 120 days if we exclude 2 daily gaps.

Localized enhancements of total electron content in Southern Hemisphere

2020 ◽  
Author(s):  
Ilya Edemskiy ◽  
Ilya Edemskiy
Keyword(s):  
Southern Hemisphere ◽  
Total Electron Content ◽  
Magnetic Storms ◽  
Occurrence Rate ◽  
Electron Content ◽  
Quiet Time ◽  
Total Electron ◽  
Middle Latitudes ◽  
Near Space ◽  
Global Ionospheric Maps

<p>Localized enhancements of total electron content (TEC) are usually registered during magnetic storms and are often believed to be connected with storm enhanced density (SED) events. Investigating global ionospheric maps we found that such localized TEC enhancements (LTE) could be observed in Southern Hemisphere during both disturbed and quiet time with no clear dependence on parameters of near space. Analysis of occurrence of LTEs in the regions of Indian and Southern Atlantic Oceans showed that part of them (observed during magnetic storms and localized in subpolar latitudes) can be connected with SEDs. Since another part of subpolar LTEs is detected during relatively quiet conditions its generation mechanism should be different despite they have similar spatial distribution. Most of the enhancements are observed in middle latitudes and is detected during all the investigated years. The occurrence rate of LTEs hardly depends on solar activity and the most probable season for LTE detection is April-September (autumn-winter).</p><p>Here we investigate reasons of generation both midlatitudinal and subpolar LTEs trying to define the mechanisms of their generation in details.</p>

scholarly journals Redes neurais artificiais aplicadas na previsão do VTEC no Brasil

2013 ◽  
Vol 19 (2) ◽  
pp. 227-246 ◽  
Author(s):  
Wagner Carrupt Machado ◽  
Edvaldo Simões da Fonseca Junior
Keyword(s):  
Total Electron Content ◽  
Electron Content ◽  
Vertical Total Electron Content ◽  
International Gnss Service ◽  
Total Electron ◽  
De Se ◽  
Pierce Point ◽  
Global Ionospheric Maps

Uma forma de se prever o conteúdo total de elétrons na direção vertical (VTEC - Vertical Total Electron Content) usando a arquitetura de redes neurais artificiais (RNA) denominada de perceptrons de múltiplas camadas (MLP - MultipLayer Percetrons) é apresentada e avaliada nesta pesquisa. As entradas do modelo foram definidas como sendo a posição dos pontos ionosféricos (IPP - Ionospheric Pierce Point) e o tempo universal (TU), enquanto que a saída é o VTEC. As variações sazonais e de períodos mais longos são levadas em conta através da atualização do treinamento diariamente. Testes foram conduzidos sobre uma área que abrange o Brasil e sua vizinhança considerando períodos de alta e baixa atividade solar. As RNA foram treinadas utilizando informações dos mapas globais da ionosfera (GIM - Global Ionospheric Maps) produzidos pelo serviço internacional do GNSS (IGS - International GNSS Service) das 72 horas anteriores à época de início da previsão. As RNA treinadas foram utilizadas para prever o VTEC por 72 horas (VTEC RNA). Os VTEC RNA foram comparados com os VTEC contidos nos GIM (VTEC GIM). A raiz do erro médio quadrático (RMS) da diferença entre o VTEC GIM e o VTEC RNA variou de 1,4 a 10,7 unidades de TEC (TECU). O erro relativo mostra que a RNA proposta foi capaz de prever o VTEC com 70 a 85% de acerto.

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