scholarly journals Ionospheric response to solar extreme ultraviolet radiation variations: comparison based on CTIPe model simulations and satellite measurements

2021 ◽  
Vol 39 (2) ◽  
pp. 341-355
Author(s):  
Rajesh Vaishnav ◽  
Erik Schmölter ◽  
Christoph Jacobi ◽  
Jens Berdermann ◽  
Mihail Codrescu
Keyword(s):  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
Extreme Ultraviolet ◽  
Electron Content ◽  
Solar Dynamics Observatory ◽  
International Gnss Service ◽  
Average Delay ◽  
Total Electron ◽  
Ionospheric Response ◽  
Flux Model

Abstract. The ionospheric total electron content (TEC) provided by the International GNSS Service (IGS) and the TEC simulated by the Coupled Thermosphere Ionosphere Plasmasphere Electrodynamics (CTIPe) model have been used to investigate the delayed ionospheric response against solar flux and its trend during the years 2011 to 2013. The analysis of the distinct low-latitude and midlatitude TEC response over 15∘ E shows a better correlation of observed TEC and the solar radio flux index F10.7 in the Southern Hemisphere compared to the Northern Hemisphere. Thus, a significant hemispheric asymmetry is observed. The ionospheric delay estimated using model-simulated TEC is in good agreement with the delay estimated for observed TEC against the flux measured by the Solar Dynamics Observatory (SDO) extreme ultraviolet (EUV) Variability Experiment (EVE). The average delay for the observed (modeled) TEC is 17(16) h. The average delay calculated for observed and modeled TEC is 1 and 2 h longer in the Southern Hemisphere compared to the Northern Hemisphere. Furthermore, the observed TEC is compared with the modeled TEC simulated using the SOLAR2000 and EUVAC flux models within CTIPe over northern and southern hemispheric grid points. The analysis suggests that TEC simulated using the SOLAR2000 flux model overestimates the observed TEC, which is not the case when using the EUVAC flux model.

scholarly journals Ionospheric Response to Solar EUV Radiation Variations: Comparison based on CTIPe Model Simulations and Satellite Measurements

2020 ◽  
Author(s):  
Rajesh Vaishnav ◽  
Erik Schmölter ◽  
Christoph Jacobi ◽  
Jens Berdermann ◽  
Mihail Codrescu
Keyword(s):  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
Electron Content ◽  
Solar Dynamics Observatory ◽  
International Gnss Service ◽  
Average Delay ◽  
Total Electron ◽  
Ionospheric Response ◽  
Solar Radio Flux ◽  
Flux Model

Abstract. The ionospheric Total Electron Content (TEC) provided by the International GNSS Service (IGS), and the Coupled Thermosphere Ionosphere Plasmasphere Electrodynamics (CTIPe) model simulated TEC have been used to investigate the delayed ionospheric response against solar flux and its trend during the years 2011 to 2013. The analysis of the distinct low and mid-latitudes TEC response over 15° E shows a better correlation of observed TEC and the solar radio flux index F10.7 in the Southern Hemisphere compared to the Northern Hemisphere. Thus, a significant hemispheric asymmetry is observed. The ionospheric delay estimated using model simulated TEC is in good agreement with the delay estimated for observed TEC against Solar Dynamics Observatory (SDO) EUV Variability Experiment (EVE) measured flux. The average delay for the observed (modeled) TEC is 17(16) h. The average delay calculated for observed and modeled TEC is 1 and 2 h longer in the Southern Hemisphere compared to the Northern Hemisphere. Furthermore, the observed TEC is compared with the modeled TEC simulated using the SOLAR2000 and EUVAC flux models within CTIPe over Northern and Southern Hemispheric grid points. The analysis suggests that TEC simulated using the SOLAR2000 flux model overestimates the observed TEC, which is not the case when using the EUVAC flux model.

scholarly journals Spatial and seasonal effects on the delayed ionospheric response to solar EUV changes

2020 ◽  
Vol 38 (1) ◽  
pp. 149-162
Author(s):  
Erik Schmölter ◽  
Jens Berdermann ◽  
Norbert Jakowski ◽  
Christoph Jacobi
Keyword(s):  
Geomagnetic Activity ◽  
Extreme Ultraviolet ◽  
Ionospheric Delay ◽  
Seasonal Effects ◽  
Electron Content ◽  
Average Delay ◽  
Total Electron ◽  
Ionospheric Response ◽  
The Impact ◽  
Northern And Southern Hemispheres

Abstract. This study correlates different ionospheric parameters with the integrated solar extreme ultraviolet radiation (EUV) radiation to analyze the delayed ionospheric response, testing and improving upon previous studies on the ionospheric delay. Several time series of correlation coefficients and delays are presented to characterize the trend of the ionospheric delay from January 2011 to December 2013. The impact of the diurnal variations of ionospheric parameters in the analysis at an hourly resolution for fixed locations are discussed and specified with calculations in different timescales and with comparison to solar and geomagnetic activity. An average delay for the total electron content (TEC) of ≈18.7 h and for foF2 of ≈18.6 h is calculated at four European stations. The difference between the Northern and Southern hemispheres is analyzed by comparisons with the Australian region. A seasonal variation of the delay between the Northern and Southern hemispheres is calculated for TEC with ≈5±0.7 h and foF2 with ≈8±0.8 h. The latitudinal and longitudinal variability of the delay is analyzed for the European region, and found to be characterized by a decrease in the delay from ≈21.5 h at 30∘ N to ≈19.0 h at 70∘ N for summer months. For winter months, a roughly constant delay of ≈19.5 h is calculated. The results based on solar and ionospheric data at an hourly resolution and the analysis of the delayed ionospheric response to solar EUV show seasonal and latitudinal variations. Results also indicate a relationship of the ionospheric delay with geomagnetic activity and a possible correlation with the 11-year solar cycle in the analyzed time period.

scholarly journals Unexpected Southern Hemisphere ionospheric response to geomagnetic storm of 15 August 2015

2018 ◽  
Vol 36 (1) ◽  
pp. 71-79 ◽  
Author(s):  
Ilya Edemskiy ◽  
Jan Lastovicka ◽  
Dalia Buresova ◽  
John Bosco Habarulema ◽  
Ivan Nepomnyashchikh
Keyword(s):  
South Africa ◽  
Southern Hemisphere ◽  
Geomagnetic Storms ◽  
Geomagnetic Latitude ◽  
Electron Content ◽  
Solar Activity Minimum ◽  
Total Electron ◽  
Ionospheric Response ◽  
Middle Latitudes ◽  
Local Noon

Abstract. Geomagnetic storms are the most pronounced phenomenon of space weather. When studying ionospheric response to a storm of 15 August 2015, an unexpected phenomenon was observed at higher middle latitudes of the Southern Hemisphere. This phenomenon was a localized total electron content (TEC) enhancement (LTE) in the form of two separated plumes, which peaked southward of South Africa. The plumes were first observed at 05:00 UT near the southwestern coast of Australia. The southern plume was associated with local time slightly after noontime (1–2 h after local noon). The plumes moved with the Sun. They peaked near 13:00 UT southward of South Africa. The southern plume kept constant geomagnetic latitude (63–64° S); it persisted for about 10 h, whereas the northern plume persisted for about 2 h more. Both plumes disappeared over the South Atlantic Ocean. No similar LTE event was observed during the prolonged solar activity minimum period of 2006–2009. In 2012–2016 we detected altogether 26 LTEs and all of them were associated with the southward excursion of Bz. The negative Bz excursion is a necessary but not sufficient condition for the LTE occurrence as during some geomagnetic storms associated with negative Bz excursions the LTE events did not appear.

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.

scholarly journals Role of eddy diffusion in the delayed ionospheric response to solar flux changes

2021 ◽  
Vol 39 (4) ◽  
pp. 641-655
Author(s):  
Rajesh Vaishnav ◽  
Christoph Jacobi ◽  
Jens Berdermann ◽  
Mihail Codrescu ◽  
Erik Schmölter
Keyword(s):  
Solar Activity ◽  
Extreme Ultraviolet ◽  
Solar Rotation ◽  
Eddy Diffusion ◽  
Transport Processes ◽  
Solar Flux ◽  
Ionospheric Delay ◽  
Electron Content ◽  
Total Electron ◽  
Ionospheric Response

Abstract. Simulations of the ionospheric response to solar flux changes driven by the 27 d solar rotation have been performed using the global 3-D Coupled Thermosphere Ionosphere Plasmasphere electrodynamics (CTIPe) physics-based numerical model. Using the F10.7 index as a proxy for solar extreme ultraviolet (EUV) variations in the model, the ionospheric delay at the solar rotation period is well reproduced and amounts to about 1 d, which is consistent with satellite and in situ measurements. From mechanistic CTIPe studies with reduced and increased eddy diffusion, we conclude that the eddy diffusion is an important factor that influences the delay of the ionospheric total electron content (TEC). We observed that the peak response time of the atomic oxygen to molecular nitrogen ratio to the solar EUV flux changes quickly during the increased eddy diffusion compared with weaker eddy diffusion. These results suggest that an increase in the eddy diffusion leads to faster transport processes and an increased loss rate, resulting in a decrease in the ionospheric time delay. Furthermore, we found that an increase in solar activity leads to an enhanced ionospheric delay. At low latitudes, the influence of solar activity is stronger because EUV radiation drives ionization processes that lead to compositional changes. Therefore, the combined effect of eddy diffusion and solar activity leads to a longer delay in the low-latitude and midlatitude region.

scholarly journals Quasi 10-day wave modulation of equatorial ionization anomaly during the Southern Hemisphere stratospheric warming of 2002

2019 ◽  
Author(s):  
Xiaohua Mo
Keyword(s):  
Southern Hemisphere ◽  
Phase Relationship ◽  
Periodic Oscillation ◽  
Electron Content ◽  
Stratospheric Warming ◽  
International Gnss Service ◽  
Total Electron ◽  
Stratospheric Temperature ◽  
Equatorial Ionization Anomaly ◽  
Gps Station

Abstract. The present paper studies the perturbations in equatorial ionization anomaly (EIA) region during the Southern Hemisphere (SH) sudden stratospheric warming (SSW) of 2002, using the location of EIA crests derived from Global Positioning System (GPS) station observations and the Total Electron Content (TEC) obtained by International GNSS Service (IGS) global ionospheric TEC map (GIMs) in Asian sector. A strong quasi 10-day periodic oscillation is clearly identified in EIA region, and it has in-phase relationship between northern and southern EIA crests. An eastward phase progression of quasi 10-day wave is also seen in polar stratospheric temperature during this period, suggesting the enhanced quasi-10-day planetary wave associated with SSW produced oscillation in EIA region through modulating the equatorial fountain effect. Our results reveal some newer features of ionospheric variation that have not been reported during Northern Hemisphere (SH) SSWs.

scholarly journals Study of the Spatiotemporal Characteristics of the Equatorial Ionization Anomaly Using Shipborne Multi-GNSS Data: A Case Analysis (120–150°E, Western Pacific Ocean, 2014–2015)

2021 ◽  
Vol 13 (15) ◽  
pp. 3051
Author(s):  
Xiaowen Luo ◽  
Di Wang ◽  
Jinling Wang ◽  
Ziyin Wu ◽  
Jinyao Gao ◽  
...  
Keyword(s):  
Pacific Ocean ◽  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
Temporal Resolution ◽  
Western Pacific ◽  
Electron Content ◽  
Western Pacific Ocean ◽  
Total Electron ◽  
Equatorial Ionization Anomaly ◽  
Gnss Data

Ground-based GNSS (Global Navigation Satellite System) reference stations lack the capacity to provide data for ocean regions with sufficient spatial-temporal resolution, limiting the detailed study of the equatorial ionization anomaly (EIA). Thus, this study collected kinematic multi-GNSS data on the ionospheric Total Electron Content (TEC) during two research cruises across the equator in the Western Pacific Ocean in 2014 (31 October–8 November) and 2015 (29 March–6 April). The purpose of the study was to use sufficient spatial–temporal resolution data to conduct a detailed analysis of the diurnal variation of the equatorial ionization anomaly in different seasons. The two-year data collected were used to draw the following conclusions. During the test in 2014, the EIA phenomenon in the Northern and Southern Hemispheres was relatively obvious. The maximum values occurred at local time (LT) 15:00 (~136TECu) and LT22:00 (~107TECu) in the Northern Hemisphere and at LT14:00 (100TECu) and LT22:00 (80TECu) in the Southern Hemisphere. During the test in 2015, the EIA in the Southern Hemisphere reached its maximum level at LT14:00 (~115TECu) and LT20:00 (~85TECu). However, the EIA phenomenon in the Northern Hemisphere was weakened, and a maximum value occurred only at LT 15:00 (~85TECu). The intensity contrast was reversed. The EIA phenomenon manifests a strong hemisphere asymmetry in this region.

scholarly journals Delayed response of the global total electron content to solar EUV variations

2016 ◽  
Vol 14 ◽  
pp. 175-180 ◽  
Author(s):  
Christoph Jacobi ◽  
Norbert Jakowski ◽  
Gerhard Schmidtke ◽  
Thomas N. Woods
Keyword(s):  
Total Electron Content ◽  
Time Scales ◽  
Extreme Ultraviolet ◽  
Solar Rotation ◽  
Time Lag ◽  
Delayed Response ◽  
Electron Content ◽  
Solar Dynamics Observatory ◽  
Total Electron ◽  
Tec Variability

Abstract. The ionospheric response to solar extreme ultraviolet (EUV) variability during 2011–2014 is shown by simple proxies based on Solar Dynamics Observatory/Extreme Ultraviolet Variability Experiment solar EUV spectra. The daily proxies are compared with global mean total electron content (TEC) computed from global TEC maps derived from Global Navigation Satellite System dual frequency measurements. They describe about 74 % of the intra-seasonal TEC variability. At time scales of the solar rotation up to about 40 days there is a time lag between EUV and TEC variability of about one day, with a tendency to increase for longer time scales.

scholarly journals Ionospheric total electron content of comet 67P/Churyumov-Gerasimenko

2020 ◽  
Vol 635 ◽  
pp. A51
Author(s):  
Rajkumar Hajra ◽  
Pierre Henri ◽  
Xavier Vallières ◽  
Marina Galand ◽  
Martin Rubin ◽  
...  
Keyword(s):  
Southern Hemisphere ◽  
Total Electron Content ◽  
Northern Hemisphere ◽  
Hemispheric Asymmetry ◽  
Heliocentric Distance ◽  
Electron Content ◽  
Total Electron ◽  
Ionospheric Total Electron Content ◽  
Tec Variability ◽  
Comet 67P

We study the evolution of a cometary ionosphere, using approximately two years of plasma measurements by the Mutual Impedance Probe on board the Rosetta spacecraft monitoring comet 67P/Churyumov-Gerasimenko (67P) during August 2014–September 2016. The in situ plasma density measurements are utilized to estimate the altitude-integrated electron number density or cometary ionospheric total electron content (TEC) of 67P based on the assumption of radially expanding plasma. The TEC is shown to increase with decreasing heliocentric distance (rh) of the comet, reaching a peak value of ~(133 ± 84) × 109 cm−2 averaged around perihelion (rh < 1.5 au). At large heliocentric distances (rh > 2.5 au), the TEC decreases by ~2 orders of magnitude. For the same heliocentric distance, TEC values are found to be significantly larger during the post-perihelion periods compared to the pre-perihelion TEC values. This “ionospheric hysteresis effect” is more prominent in the southern hemisphere of the comet and at large heliocentric distances. A significant hemispheric asymmetry is observed during perihelion with approximately two times larger TEC values in the northern hemisphere compared to the southern hemisphere. The asymmetry is reversed and stronger during post-perihelion (rh > 1.5 au) periods with approximately three times larger TEC values in the southern hemisphere compared to the northern hemisphere. Hemispheric asymmetry was less prominent during the pre-perihelion intervals. The correlation of the cometary TEC with the incident solar ionizing fluxes is maximum around and slightly after perihelion (1.5 au < rh < 2 au), while it significantly decreases at larger heliocentric distances (rh > 2.5 au) where the photo-ionization contribution to the TEC variability decreases. The results are discussed based on cometary ionospheric production and loss processes.

scholarly journals Ionospheric response to solar EUV variations: Preliminary results

2018 ◽  
Vol 16 ◽  
pp. 157-165 ◽  
Author(s):  
Rajesh Vaishnav ◽  
Christoph Jacobi ◽  
Jens Berdermann ◽  
Erik Schmölter ◽  
Mihail Codrescu
Keyword(s):  
Extreme Ultraviolet ◽  
Solar Rotation ◽  
Rotation Period ◽  
Transport Processes ◽  
Ionospheric Delay ◽  
Electron Content ◽  
Delay Model ◽  
Total Electron ◽  
Ionospheric Response ◽  
Preliminary Results

Abstract. We investigate the ionospheric response to solar Extreme Ultraviolet (EUV) variations using different proxies, based on solar EUV spectra observed from the Solar Extreme Ultraviolet Experiment (SEE) onboard the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) satellite, the F10.7 index (solar irradiance at 10.7 cm), and the Bremen composite Mg-II index during January 2003 to December 2016. The daily mean solar proxies are compared with global mean Total Electron Content (GTEC) values calculated from global IGS TEC maps. The preliminary analysis shows a significant correlation between GTEC and both the integrated flux from SEE and the Mg II index, while F10.7 correlates less strongly with GTEC. The correlations of EUV proxies and GTEC at different time periods are presented. An ionospheric delay in GTEC is observed at the 27 days solar rotation period with the time scale of about ∼1–2 days. An experiment with the physics based global 3-D Coupled Thermosphere/Ionosphere Plasmasphere electrodynamics (CTIPe) numerical model was performed to reproduce the ionospheric delay. Model simulations were performed for different values of the F10.7 index while keeping all the other model inputs constant. Preliminary results qualitatively reproduce the observed ∼1–2 days delay in GTEC, which is might be due to vertical transport processes.

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