Global empirical models of the density peak height and of the equivalent scale height for quiet conditions

Monthly average electron density profiles have been calculated from hourly electron density N(h) recorded in 26 digisonde stations distributed worldwide encompassing the time interval 1998–2006. The ionospheric electron density peak height of the F2 region, hmF2, and the effective scale height at the hmF2, Hm, deduced from average profiles have been analyzed to obtain the quiet-time behavior and have been analytically modeled by the spherical harmonic analysis (SH) technique using the modip latitude as the coordinate of the reference system. The coefficients of the SH models of hmF2 and Hm are bounded to the solar activity, and the temporal and seasonal variations are considered by Fourier expansion of the coefficients. The SH models provide a tool to predict hmF2 and Hm located anywhere in the range of latitudes between of 70°N and 70°S and at any time. The SH analytical model for hmF2 improves the fit to the observations by 10% in average compared to the IRI prediction, and it might improve the IRI prediction of hmF2 by more than 30% at high and low latitudes. The analytical model for Hm predicts the quiet behavior of the effective scale height with accuracy better than 15% in average which enables to obtain a good estimation of vertical profiles. These results could be useful to estimate information for the topside profile formulation.     

Interaction of oblique wave beam with ionospheric layer F2

Interaction of a powerful obliquely incident wave beam of decameter radio waves with the ionospheric F2 layer is analyzed. Much like the linear case, propagation through the natural anti-waveguide layer F2 splits the initial beam. Some part of its energy leaks through the ionospheric layer, the other part goes back along a downward trajectory. However, nonlinearity leads to further stratification of the ionospheric layer. A new feature, in comparison with the linear case, is appearing a narrow waveguide beneath the F2 layer maximum which traps a small part of the beam energy. We study the relationship between these parts of the wave field in a simplified model of parabolic F2 layer, with nonlinearity caused by thermal plasma expulsion from the high field intensity region. Analytical results are supplemented with numerical estimates of the effects.     

A simulation analysis of systematic errors in ion arrival angle and drift velocity from the satellite borne ion drift meter

As one payload of a Chinese seismic satellite program, an ion drift meter (IDM) will measure drift velocity of thermal ions at an altitude of 500 km. Previous works have shown that such instruments use biased grids to create nonuniform potential in the grid planes, which brings systematic errors to the inferred parameters. A commercial finite element analysis software is used to simulate this instrument in the exact size. The error sources from thermal velocity, nonuniform transparency of real grids and potential depression in the grid planes are explained. The simulation results show that the arrival angle and drift velocity will be underestimated in all the conditions and the maximal error will be about −0.87° and −121 m/s, respectively. Furthermore, the relative error of the inferred arrival angle and the drift velocity will be inversely correlated with the arrival angle because of the lensing effect of the potential depression. This simulation provides a quantificational method of evaluating and correcting the data during in situ operation.     

Application of HF Doppler measurements for the investigation of internal atmospheric waves in the ionosphere

We present results of the spectral analysis of data series of Doppler frequency shifted signals reflected from the ionosphere, using experimental data received at Kazan University, Russia. Spectra of variations with periods from 1 min to 60 days have been calculated and analyzed for different scales of periods. The power spectral density for spring and winter differs by a factor of 3–4. Local maxima of variation amplitude are detected, which are statistically significant. The periods of these amplitude increases range from 6 to 12 min for winter, and from 24 to 48 min for autumn. Properties of spectra for variations with the periods of 1–72 h have been analyzed. The maximum of variation intensity for all seasons and frequencies corresponds to the period of 24 h. Spectra of variations with periods from 3 to 60 days have been calculated. The maxima periods of power spectral density have been detected by the MUSIC method for the high spectral resolution. The detected periods correspond to planetary wave periods. Analysis of spectra for days with different level of geomagnetic activity shows that the intensity of variations for days with a high level of geomagnetic activity is higher.     

Comparison of standard TEC models with a Neural Network based TEC model using multistation GPS TEC around the northern crest of Equatorial Ionization Anomaly in the Indian longitude sector during the low and moderate solar activity levels of the 24th solar cycle

The highest Total Electron Content (TEC) values in the world normally occur at Equatorial Ionization Anomaly (EIA) region resulting in largest ionospheric range delay values observed for any potential Space Based Augmentation System (SBAS). Reliable forecasting of TEC is crucial for satellite based navigation systems. The day to day variability of the location of the anomaly peak and its intensity is very large. This imposes severe limitations on the applicability of commonly used ionospheric models to the low latitude regions. It is necessary to generate a mathematical ionospheric forecasting and mapping model for TEC based on physical ionospheric influencing parameters. A model, IRPE-TEC, has been developed based on real time low latitude total electron content data using GPS measurements from a number of stations situated around the northern crest of the EIA during 2007 through 2011 to predict the vertical TEC values during the low and moderate solar activity levels of the 24th solar cycle. This model is compared with standard ionospheric models like International Reference Ionosphere (IRI) and Parameterized Ionospheric Model (PIM) to establish its applicability in the equatorial region for accurate predictions.     

Four Contemporary Issues Concerning Ionospheric Plasma Flow to the Magnetosphere

Space Science Reviews - In this review, we examine four specific questions/issues of contemporary interest within the overall topic of ionospheric plasma outflow into the magnetosphere. These four...     

基于分段多项式建模的电离层污染校正算法研究

电离层污染使需要通过电离层传播的超视距雷达的回波谱展宽,影响雷达的目标检测性能。基于分段多项式建模的校正算法可用于解决电离层的相位污染问题,针对该算法在处理实际数据时遇到的问题,分析相位污染校正中可能出现的相位残差跳变的影响,并给出了相应的解决方案。此外,讨论电离层幅度污染的问题,给出简单的补偿方法,提供了电离层污染校正算法的完整流程。通过对实际数据的处理,验证了算法的有效性,算法更适合应用于工程实际。     

Behavior of F2-layer parameters and solar activity indices in the 24th cycle

The analysis of the behavior of the critical frequency foF2 during the 24th solar activity cycle (Danilov and Konstantinova, 2020a, c) is prolonged for two more months and the nighttime hours. In addition to the Rz and Ly-α indices used in the aforementioned papers for correction of the F10.7 index during the 24th cycle, the commonly used Mg II index is added. The results confirm the previous conclusions on the existence of the “vague” period with chaotic behavior of foF2 and the recovery of the negative trend in foF2 after 2008–2010. A comparison of the F10.7 index with three other SA indices (Ly-α, Rz, and Mg II) for the 22nd, 23rd, and 24th SA cycles is performed. It is shown that the relationship between F10.7 and other indices is close in the 22nd and 23rd cycles but differs from that in the 24th cycle. The corrected values of F10.7 in the 24th cycle are proposed for analysis of ionospheric trends during that cycle.     

Ionospheric disturbances detected by MEXART

The radio telescope MEXART was developed to make observations of interplanetary scintillation (IPS) produced by large scale disturbances associated with solar events. In this work it is shown that on occasion there are disturbances in the ionosphere that are related with these events and which cannot only contaminate the IPS but actually be the main contribution to the observed oscillations. This was the case of the event of 15 December 2006 observed by MEXART, which presented clear scintillation. The total electron content (TEC) of the ionosphere above Mexico was calculated for the same period. It was found that the variations in TEC were associated with the scintillations detected by MEXART.