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 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 Quasi-10 d wave modulation of an equatorial ionization anomaly during the Southern Hemisphere stratospheric warming of 2002

2020 ◽  
Vol 38 (1) ◽  
pp. 9-16 ◽  
Author(s):  
Xiaohua Mo ◽  
Donghe Zhang
Keyword(s):  
Southern Hemisphere ◽  
Planetary Wave ◽  
Lower Thermosphere ◽  
Periodic Oscillation ◽  
Electron Content ◽  
Stratospheric Warming ◽  
Total Electron ◽  
Equatorial Ionization Anomaly ◽  
E Region ◽  
D Wave

Abstract. The present paper studies the perturbations in an 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, the total electron content (TEC) obtained by the International GNSS (global navigation satellite system) Service (IGS) global ionospheric TEC map (GIMs) and the equatorial electrojet (EEJ) estimated by the geomagnetic field in the Asian sector. The results indicate the existence of an obvious quasi-10 d periodic oscillation in the location and TEC of the northern and southern EIA crest. An eastward phase progression of the quasi-10 d wave producing the SH SSW of 2002 is also identified in polar stratospheric temperature. Previous studies have shown that a strong quasi-10 d planetary wave with zonal wave numbers s=1 extended from the lower stratosphere to the mesosphere and lower thermosphere during the SH SSW of 2002 (Palo et al., 2005). Moreover, the EEJ driven by the equatorial zonal electric field exhibits quasi-10 d oscillation, suggesting the enhanced quasi-10 d planetary wave associated with SSW penetrates into the ionosphere E region and produces oscillation in the EIA region through modulating the E-region electric fields. Our results reveal some newer features of ionospheric variation that have not been reported during Northern Hemisphere (NH) SSWs.

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 Latitude Oscillations of Zonal Mean Total Electron Content and Super-Fountain Effects Provided from Global GNSS Stations

2021 ◽  
Author(s):  
Mohammad Joghataei ◽  
Niloofar Jooyandeh ◽  
Mohammad Hossein Memarian
Keyword(s):  
Wave Propagation ◽  
Solar Activity ◽  
Total Electron Content ◽  
Planetary Wave ◽  
Electron Content ◽  
Total Electron ◽  
Equatorial Ionization Anomaly ◽  
Gnss Data ◽  
Planetary Wave Propagation

Abstract. Seasonal and latitude oscillations of equatorial ionization anomaly (EIA) were investigated by zonal mean total electron content (TEC) provided from global gridded GNSS data from 1999 to 2017. Maximum monthly zonal mean TEC values showed NH spring equinox’s value is higher than fall's. Some fluctuations are observed due to upward planetary wave propagation in equinoxes and winter especially in low solar activity. Two cases of super-fountain effect were also clearly detected on zonal mean TEC.

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 Interdecadal Change in the Relationship between Northern and Southern Hemisphere Meridional Circulation over the Western Pacific Ocean

Atmosphere ◽  
2020 ◽  
Vol 11 (10) ◽  
pp. 1106
Author(s):  
Ya Gao ◽  
Dong Chen ◽  
Huijun Wang
Keyword(s):  
Pacific Ocean ◽  
Southern Hemisphere ◽  
Meridional Circulation ◽  
Negative Relationship ◽  
Walker Circulation ◽  
Meridional Wind ◽  
Western Pacific ◽  
Interdecadal Change ◽  
Western Pacific Ocean ◽  
The Western Pacific

The western North Pacific monsoon in the Northern Hemisphere (NH) and the local Hadley circulation in the Southern Hemisphere (SH) are important components of the vertical meridional circulation over the western Pacific Ocean. Here, we define the SH meridional circulation (SHMC) and NH meridional circulation (NHMC) and investigate their relationship over the western Pacific Ocean. Although they are consistent integrally in the climatological circulation, the NHMC and SHMC do not have a positive change relationship but a significantly negative relationship. In addition, this negative correlation experiences an interdecadal change, with one closely related period during 1989–2003 (Period 2, P2) and two weakened related periods during 1979–1988 (Period 1, P1) and 2004–2017 (Period 3, P3). Through the analysis of the meridional wind field at lower and upper levels, we found that the SHMC moves northward during P2, which can result in a close relationship with the NHMC. The possible mechanism is as follows: The Walker circulation strengthened in P2, which strengthened the ascending motion over the western Pacific Ocean, thus inducing the SHMC to strengthen and move northward, resulting in a significantly stronger relationship with the NHMC.

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.

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