Summer-winter hemispheric asymmetry of the sudden increase in ionospheric total electron content and of the O/N2ratio: Solar activity dependence

2007 ◽  
Vol 112 (A8) ◽  
pp. n/a-n/a ◽  
Author(s):  
T. Tsugawa ◽  
S.-R. Zhang ◽  
A. J. Coster ◽  
Y. Otsuka ◽  
J. Sato ◽  
...  
Keyword(s):  
Solar Activity ◽  
Total Electron Content ◽  
Hemispheric Asymmetry ◽  
Electron Content ◽  
Sudden Increase ◽  
Total Electron ◽  
Ionospheric Total Electron Content ◽  
Activity Dependence

scholarly journals Spatial and Temporal Variations of Polar Ionospheric Total Electron Content over Nearly Thirteen Years

Sensors ◽  
2020 ◽  
Vol 20 (2) ◽  
pp. 540 ◽  
Author(s):  
Hui Xi ◽  
Hu Jiang ◽  
Jiachun An ◽  
Zemin Wang ◽  
Xueyong Xu ◽  
...  
Keyword(s):  
Solar Activity ◽  
Total Electron Content ◽  
Geomagnetic Storms ◽  
Weddell Sea ◽  
The Arctic ◽  
Electron Content ◽  
Spherical Cap ◽  
Total Electron ◽  
Ionospheric Total Electron Content ◽  
The Antarctic

It is of great significance for the global navigation satellite system (GNSS) service to detect the polar ionospheric total electron content (TEC) and its variations, particularly under disturbed ionosphere conditions, including different phases of solar activity, the polar day and night alternation, the Weddell Sea anomaly (WSA) as well as geomagnetic storms. In this paper, four different models are utilized to map the ionospheric TEC over the Arctic and Antarctic for about one solar cycle: the polynomial (POLY) model, the generalized trigonometric series function (GTSF) model, the spherical harmonic (SH) model, and the spherical cap harmonic (SCH) model. Compared to other models, the SCH model has the best performance with ±0.8 TECU of residual mean value and 1.5–3.5 TECU of root mean square error. The spatiotemporal distributions and variations of the polar ionospheric TEC are investigated and compared under different ionosphere conditions in the Arctic and Antarctic. The results show that the solar activity significantly affects the TEC variations. During polar days, the ionospheric TEC is more active than it is during polar nights. In polar days over the Antarctic, the maximum value of TEC always appears at night in the Antarctic Peninsula and Weddell Sea area affected by the WSA. In the same year, the ionospheric TEC of the Antarctic has a larger amplitude of annual variation than that of the TEC in the Arctic. In addition, the evolution of the ionization patch during a geomagnetic storm over the Antarctic can be clearly tracked employing the SCH model, which appears to be adequate for mapping the polar TEC, and provides a sound basis for further automatic identification of ionization patches.

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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