scholarly journals Three-dimensional ionospheric electron density structure of the Weddell Sea Anomaly

2009 ◽  
Vol 114 (A2) ◽  
pp. n/a-n/a ◽  
Author(s):  
C. H. Lin ◽  
J. Y. Liu ◽  
C. Z. Cheng ◽  
C. H. Chen ◽  
C. H. Liu ◽  
...  
Keyword(s):  
Electron Density ◽  
Three Dimensional ◽  
Weddell Sea ◽  
Density Structure ◽  
Ionospheric Electron Density ◽  
Weddell Sea Anomaly

scholarly journals Variability of Weddell Sea ionospheric anomaly as deduced from observations at the Akademik Vernadsky station

2021 ◽  
pp. 47-55
Author(s):  
A. Zalizovski ◽  
◽  
I. Stanislawska ◽  
V. Lisachenko ◽  
O. Charkina ◽  
...  
Keyword(s):  
Diurnal Variation ◽  
Electron Density ◽  
Geomagnetic Activity ◽  
Dynamic Equilibrium ◽  
Doppler Frequency ◽  
Weddell Sea ◽  
K Index ◽  
Weddell Sea Anomaly ◽  
Index Level ◽  
Solar Ultraviolet

Ionospheric Weddell Sea anomaly is an inversion of diurnal variation of the electron density in the ionosphere over Antarctic Peninsula, Weddell Sea, and neighbor territories observed during Antarctic summer. This paper aims at analyzing the reaction of the ionosphere during the Weddell Sea anomaly to changes in solar and geomagnetic activity as deduced from the data of vertical sounding of the ionosphere conducted at the Akademik Vernadsky station. The aim is achieved by comparing the monthly median values of the critical frequencies of the ionosphere (foF2) during Weddell Sea anomaly for the years of high and low solar activity; as well as by comparison of median December height-time diagrams (HT-diagrams) of foF2 calculated separately for the time intervals characterized by low or high levels of F10.7 and K indices for the period from 2007 till 2016. It was experimentally demonstrated that the Weddell Sea anomaly depends on the levels of solar ultraviolet flux and local K indices. The biggest nighttime maximum of ionization corresponds to low K indices and high values of F10.7. The most accurate inversion of diurnal variation of electron density in the F region is observed under the low values of K index and low F10.7 flux. The growth of geomagnetic activity decreases the nighttime ionization under both low and high levels of F10.7 fluxes and leads to a blur of the night maximum. Visible virtual heights of maximums increase together with F10.7 independently of the K index level. Blurring of the night maximum can be explained by destruction of the field of thermospheric winds supporting the nighttime anomaly, and/or by increasing role of plasma drifts in comparison with wind impact. The growth of visible virtual height of the nighttime maximum with increasing solar F10.7 flux could be explained by the gain of equatorward thermospheric wind with increasing solar ultraviolet flux that leads to growth of plasma upwelling effect. The Doppler frequency shift of the signals reflected from the ionosphere during nighttime in presence of the Weddell Sea anomaly is close to zero which could be explained by a stable F2 layer formed as a result of dynamic equilibrium between photochemical processes and upward plasma transport.

scholarly journals Numerical simulation of oblique ionospheric heating by powerful radio waves

2018 ◽  
Vol 36 (3) ◽  
pp. 855-866
Author(s):  
Moran Liu ◽  
Chen Zhou ◽  
Xiang Wang ◽  
Bin Bin Ni ◽  
Zhengyu Zhao
Keyword(s):  
Ray Tracing ◽  
Electron Density ◽  
Oblique Incidence ◽  
Three Dimensional ◽  
Radio Waves ◽  
Powerful Radio ◽  
Ionospheric Electron Density ◽  
Ionospheric Heating ◽  
Tracing Algorithm ◽  
Electron Density And Temperature

<p><strong>Abstract.</strong> In this paper, we investigate the ionospheric heating by oblique incidence of powerful high-frequency (HF) radio waves using three-dimensional numerical simulations. The ionospheric electron density and temperature perturbations are examined by incorporating the ionospheric electron transport equations and ray-tracing algorithm. The energy distribution of oblique incidence heating waves in the ionosphere is calculated by the three-dimensional ray-tracing algorithm. The calculation takes into consideration the electric field of heating waves in the caustic region by the plane wave spectral integral method. The simulation results show that the ionospheric electron density and temperature can be disturbed by oblique incidence of powerful radio waves, especially in the caustic region of heating waves. The oblique ionospheric heating with wave incidence parallel and perpendicular to the geomagnetic field in the mid-latitude ionosphere is explored by simulations, results of which indicate that the ionospheric modulation is more effective when the heating wave propagates along the magnetic field line. Ionospheric density and temperature striations in the caustic region due to thermal self-focusing instability are demonstrated, as well as the time evolution of the corresponding fluctuation spectra.</p>

scholarly journals Seasonal dependence of the longitudinal variations of nighttime ionospheric electron density and equivalent winds at southern midlatitudes

2013 ◽  
Vol 31 (10) ◽  
pp. 1699-1708 ◽  
Author(s):  
X. Luan ◽  
X. Dou
Keyword(s):  
Electron Density ◽  
Local Time ◽  
Weddell Sea ◽  
Western Hemisphere ◽  
Minimum Condition ◽  
Weddell Sea Anomaly ◽  
Magnetic Inclination ◽  
Plasma Drifts ◽  
Meridional Winds ◽  
Longitudinal Variations

Abstract. It has been indicated that the observed Weddell Sea anomaly (WSA) appeared to be an extreme manifestation of the longitudinal variations in the Southern Hemisphere, since the WSA is characterized by greater evening electron density than the daytime density in the region near the Weddell Sea. In the present study, the longitudinal variations of the nighttime F2-layer peak electron density at southern midlatitudes are analyzed using the observations of the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) satellites between 2006 and 2008. It is found that significant longitudinal difference (> 150%) relative to the minimum density at each local time prevails in all seasons, although the WSA phenomenon is only evident in summer under this solar minimum condition. Another interesting feature is that in summer, the maximum longitudinal differences occur around midnight (~ 23:00–00:00 LT) rather than in the evening (19:00–21:00 LT) in the evening, when the most prominent electron density enhancement occurs for the WSA phenomenon. Thus the seasonal–local time patterns of the electron density longitudinal variations during nighttime at southern midlatitudes cannot be simply explained in terms of the WSA. Meanwhile, the variations of the geomagnetic configuration and the equivalent magnetic meridional winds/upward plasma drifts are analyzed to explore their contributions to the longitudinal variations of the nighttime electron density. The maximum longitudinal differences are associated with the strongest wind-induced vertical plasma drifts after 21:00 LT in the Western Hemisphere. Besides the magnetic declination–zonal wind effects, the geographic meridional winds and the magnetic inclination also have significant effects on the upward plasma drifts and the resultant electron density.

scholarly journals Electron density profiles probed by radio occultation of FORMOSAT-7/COSMIC-2 at 520 and 800 km altitude

2015 ◽  
Vol 8 (8) ◽  
pp. 3069-3074 ◽  
Author(s):  
J. Y. Liu ◽  
C. Y. Lin ◽  
H. F. Tsai
Keyword(s):  
Electron Density ◽  
Simulation Experiment ◽  
Three Dimensional ◽  
Peak Height ◽  
Density Structure ◽  
Density Profiles ◽  
Structure And Dynamics ◽  
Parking Orbit ◽  
Electron Density Profiles ◽  
Observing System Simulation Experiment

Abstract. The FORMOSAT-7/COSMIC-2 (F7/C2) will ultimately place 12 satellites in orbit with two launches with 24–28.5° inclination and 520–550 km altitude in 2016 and with 72° inclination and 720–750 km altitude in 2018. It would be very useful for the community to construct the global three-dimensional electron density structure by simultaneously combining the two launch observations for studying ionospheric structure and dynamics. However, to properly construct the global electron density structure, it is essential to know and evaluate differences between the ionospheric electron densities probed by the two launches. To mimic the F7/C2 observations, we examine the electron density probed at the two satellite altitudes 500 and 800 km by means of FORMOSAT-3/COSMIC (F3/C) observations at the parking orbit 500 km altitude and mission orbit 800 km altitude, as well as a corresponding observing system simulation experiment (OSSE). Observation and OSSE results show that the sounding geometries by satellite orbiting at 500 and 800 km altitudes can cause the overall differences in the electron density, the F2 peak electron density, and the F2 peak height of about 18–24, 12–28 %, and 7–19 km, respectively. Results confirm that the discrepancies mainly result from the sounding geometry and the grid (contour) bias of the electron density.

scholarly journals Investigation of the causes of the longitudinal variation of the electron density in the Weddell Sea Anomaly

2017 ◽  
Vol 122 (6) ◽  
pp. 6562-6583 ◽  
Author(s):  
P. G. Richards ◽  
R. R. Meier ◽  
Shih‐Ping Chen ◽  
D. P. Drob ◽  
P. Dandenault
Keyword(s):  
Electron Density ◽  
Weddell Sea ◽  
Longitudinal Variation ◽  
Weddell Sea Anomaly

Pushing the Envelope

2018 ◽  
Author(s):  
Eaton E. Lattman ◽  
Thomas D. Grant ◽  
Edward H. Snell
Keyword(s):  
High Resolution ◽  
Electron Density ◽  
Structural Information ◽  
Hydration Shell ◽  
Three Dimensional ◽  
Scattering Data ◽  
Saxs Data ◽  
Electron Density Function ◽  
Angle Scattering ◽  
Iterative Structure

Direct electron density determination from SAXS data opens up new opportunities. The ability to model density at high resolution and the implicit direct estimation of solvent terms such as the hydration shell may enable high-resolution wide angle scattering data to be used to calculate density when combined with additional structural information. Other diffraction methods that do not measure three-dimensional intensities, such as fiber diffraction, may also be able to take advantage of iterative structure factor retrieval. While the ability to reconstruct electron density ab initio is a major breakthrough in the field of solution scattering, the potential of the technique has yet to be fully uncovered. Additional structural information from techniques such as crystallography, NMR, and electron microscopy and density modification procedures can now be integrated to perform advanced modeling of the electron density function at high resolution, pushing the boundaries of solution scattering further than ever before.

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