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Exploring the outer emission corona spectroscopically by using Visible Emission Line Coronagraph (VELC) on board ADITYA–L1 mission

Publication date: Available online 17 July 2019

Source: Advances in Space Research

Author(s): Jagdev Singh, B Raghavendra Prasad, Suresh Venkata, Amit Kumar

Abstract

It is very important to make the spectrographic observations of the outer emission corona in number of emission lines simultaneously in view of the results of the observations made in [Fe x] 6374 Å, [Fe xi] 7892 Å, [Fe xiv] 5303 Åand [Fe xiii] 10747 Åcoronal emission lines with the 25 cm coronagraph at Norikura Observatory in Japan. At ground based observatories, availability of number of hours of clear sky for coronagraphic observations is limited due to aerosols scattering and scattering from the internal coronagraph reflections . A space based coronagraph Visible Emission Line Coronagraph (VELC) on board ADITYA–L1 has been planned to perform spectroscopy in 3 out of the 4 emission lines mentioned above. Here, we discuss the various requirements for the parameters of the payload, given the specifications of the satellite, to observe the outer emission corona reliably with good Signal to Noise Ratio (SNR), realize the projected scientific goals and make the mission a great success.

Onboard Distributed Autonomous Orbit Determination based on State Caching Approach

Publication date: Available online 16 July 2019

Source: Advances in Space Research

Author(s): Jun Lai, Yongbin Zhou, Yifan Zhou, Jun Yang

Abstract

Autonomous Orbit Determination (AOD) using inter-satellite ranging measurement can maintain the functionality of the Global Navigation Satellite System (GNSS) for a long time without the assistance of the ground facilities, even though it has the rank deficiency problem. This paper proposes an onboard distributed algorithm to implement AOD based on the extended Kalman filter. It exploits the inter-satellite ranging schedule as a priori information and maintains a cache of the estimated global states and the corresponding covariance on each satellite. Simulation results show that the mean User Range Error (URE) of a 31-satellite GPS constellation is less than 0.5m in 120 days using our algorithm, which has a similar accuracy level as the centralized Kalman filter, and outperforms the conventional distributed algorithm. It also shows that our algorithm is robust to constellation size and ranging measurement noise level. Meanwhile, due to the distributed architecture, our algorithm does not require any additional communication among satellites. All these features make our algorithm more applicable to practical scenario compared to the existing algorithms.

Noise estimation and probability of detection in non-resolved images: application to space object observation

Publication date: Available online 16 July 2019

Source: Advances in Space Research

Author(s): Francois Sanson, Carolin Frueh

Abstract

Charged Couple Device (CCD) technology is widely used in various scientific measurement contexts. CCD equipped cameras have revolutionized astronomy and space-related optical telescope measurements in recent years. They are also used in electroscopic measurements, e.g., in fields such as geology, biology, and medicine. The signal-to-noise ratio and the probability of detection are crucial to design experiments observation setups properly and to employ further mathematical methods for data exploitation such as, e.g. multi-target tracking methods. Previous attempts to correctly characterize the signal-to-noise ratio for star observations are revisited in this work and adapted for the application of near-Earth object observations and high precision measurements, leading to a modified CCD equation. Our formulation proposes a novel distribution of the signal noise that accurately accounts for the truncation noise and the presence of ambiguous pixels. These improvements are employed to derive the probability of detection and the SNR with significant improvements compared to existing formulations when ambiguous pixels are present.

An algorithm for deriving the electron temperature and electron density probed by Langmuir probe onboard cube satellites

Publication date: Available online 15 July 2019

Source: Advances in Space Research

Author(s): Chen-Kang Chiang, Tse-Liang Yeh, Jann-Yenq Liu, Chi-Kuang Chao, Loren C.Chang, Li-Wu Chen, Chung-Jen Chou, Shyh-Biau Jiang

Abstract

The paper purposes an algorithm for a Langmuir probe (LP) onboard CubeSat to correctly probe of ionospheric electron temperature and electron density. The algorithm consists of two parts of deriving the current-voltage (I–V) curve for the probe, and refining the electron temperature and the electron density by an iteration method. The small surface area of a CubeSat’s body has a strong influence on the reference potential of the satellite body, which can significantly distort the I–V curve and affect the accuracy of electron temperature and electron density observations. Here, we utilize a digital circuit simulation to construct the circuit model, including the satellite DS (Debye-Sheath), the probe DS, and the scan voltage source. Simulation data describe that the satellite DS shares the scan voltage, which is the main causal of the distortion of the aforementioned I–V curve and the change of the turning point. We also find that an underestimated turning point is due to the ion saturation of the satellite shell DS rather than the electron saturation of the probe DS. Therefore, small satellite LPs should not directly use the turning point to calculate the electron temperature and the electron density. To resolve this small-area problem, a theoretical relationship between the satellite DS voltage, the probe DS voltage, and the scan voltage is deduced, which allows us finding the probe voltage from the scan voltage, yielding the correct I–V curve for LPs, and estimating the electron temperature/density for small satellites. To more accurately derive the electron temperature and electron density, an iteration method is introduced, that the electron current-voltage curve needs to be separated from the I–V curve, and then iterates between the electron temperature estimation and the I–V curve correction. Finally, observed ionospheric electron temperature and density are used to test our algorithm. Good agreements between derived results and the observations conform that the purposed algorithm can correctly obtain the electron temperature and the electron density.

Data processing center of RadioAstron space VLBI project

Publication date: Available online 9 July 2019

Source: Advances in Space Research

Author(s): M.V. Shatskaya, A.A. Abramov, N.A. Fedorov, V.I. Kostenko, S.F. Likhachev, S.I. Seliverstov, D.A. Sychev

Abstract

In this paper, questions on development, implementation, and operation of RadioAstron project Data Processing Center (DPC) are reviewed. The main components of the dedicated DPC are the computer complex with 1 TFlops/s performance, storage with memory capacity of approximately 10 PB, the network infrastructure, and the corresponding communication channels. Performance enhancement methods and resolution of information storage, archiving, and process problems of space VLBI high-speed digital data flows are analyzed. It is shown that successful operation of DPC is mainly provided by optimal organization of computer system structure, storage, and networking transmission. Some of the important key features of RadioAstron project DPC and its comparative differences from the standard VLBI procedures are considered.

Real-time clock prediction of multi-GNSS satellites and its application in precise point positioning

Publication date: Available online 8 July 2019

Source: Advances in Space Research

Author(s): Yaquan Peng, Yidong Lou, Xiaopeng Gong, Yintong Wang, Xiaolei Dai

Abstract

With the development of Global Navigation Satellite System (GNSS), multi-GNSS is expected to greatly benefit precise point positioning (PPP), especially during the outage of real time service (RTS). In this paper, we focus on the performance of multi-GNSS satellite clock prediction and its application in real-time PPP. Based on the statistical analysis of multi-system satellite clock products, a model consisting of polynomial and periodic terms is employed for multi-system satellite clock prediction. To evaluate the method proposed, both post-processed and real-time satellite clock products are employed in simulated real-time processing mode. The results show that the accuracy of satellite clock prediction is related to atomic clock type and satellite type. For GPS satellites, the average standard deviations (STDs) of Cs atomic clocks will reach as high as 0.65 ns while the STD of Rb atomic clocks is only about 0.15 ns. As for BDS and Galileo, the average STD of 2-hour satellite clock prediction are 0.30 ns and 0.06 ns, respectively. In addition, it is validated that real-time PPP can still achieve positioning accuracy of one to three decimeters by using products of 2-hour satellite clock prediction. Moreover, compared to the results of GPS-only PPP, multi-system can greatly enhance the accuracy of real-time PPP from 12.5% to 18.5% in different situations.

Seasonal variation of plasma bubbles during solar cycle 23 - 24 over the Brazilian equatorial region

Publication date: Available online 8 July 2019

Source: Advances in Space Research

Author(s): Ebenezer Agyei-Yeboah, Igo Paulino, Amauri Fragaso de Medeiros, Ricardo Arlen Buriti, Ana Roberta Paulino, Patrick Essien, Solomon Otoo Lomotey, Hisao Takashi, Cristiano Max Wrasse

Abstract

In this study, OI 630.0 nm nightglow image data obtained from an all-sky imaging station located at Sao Joao do Cariri (7.4°S, 36.5°W), have been used to study the occurrence of equatorial plasma bubbles (EPBs) over the Brazilian equatorial region. The observations, which took place from September 2000 to December 2010 (almost eleven years), covered a significant part of solar cycle 23 (descending phase of SC23) and the very beginning of solar cycle 24 (ascending phase of SC24). There were 1337 nights of observations with 666 nights with EPB events, which translates to an occurrence rate of ∼49.8 %. Of these nights, 1290 were considered quiet (Dst ≥ -50 nT) with ∼ 50 % plasma bubbles occurrence rate. The occurrence of EPBs was studied under three solar activity phases – high solar activity phase (HSA, September 2000 – March 2004), moderate solar activity phase (MSA or descending phase, March 2004 – October 2006) and low solar activity phase (LSA, October 2006 – December 2010). The low solar activity phase is part of the peculiar solar cycle 24, considered the weakest in over a century with most sunspotless days (2008 - 2009). The maximum occurrence of bubbles, equal to 54.2 %, was found during the HSA phase, with percentages characterizing MSA and LSA being respectively 52.4 % and 45.8 %. The analysis also showed clear seasonal variation in the EPB occurrence with maximum rates in summer, spring, autumn, and the minimum rates in winter for all solar activity phases. Overall, there was observed solar cycle variation in each season with maximum occurrence in HSA followed by MSA and then LSA except in autumn where higher occurrence rate was observed in LSA phase than in MSA phase.

Ionospheric Es layer scintillation characteristics studied with Hilbert-Huang transform

Publication date: Available online 8 July 2019

Source: Advances in Space Research

Author(s): S.-Y. Su, L.-C. Tsai, C.H. Liu, C. Nayak, R. Caton, K. Groves

Abstract

A coincident event of daytime ionospheric Es layer scintillation observations is analyzed with the Hilbert-Huang transform (HHT) to study its layer structure. One of the coincident observations is made by a radio beacon passing through the Es layer at a slant angle received by the SCINDA (Scintillation Decision Aide) receivers located at southern Taiwan. The data indicates that the Es layer consists of scattering blocks of  ∼ 650 to 970 m in size as revealed in the dominant components of the HHT analysis. The time shift in the two spaced receiving antennas implies that the daytime E region westward drift is about 36 m/s. On the other hand, the same Es layer is observed by the radio occultation (RO) experiment with the L1 signal from the Global Positioning System (GPS) satellites to the FORMOSAT-3/Constellation-Observing-System-for-Meteorology (FS-3/COSMIC) satellites. The GPS L1 signal passes through the Es layer horizontally. The observed signal variations reveal a dense slab structure that blocks the L1 signal to cause a diffraction pattern. The slab thickness in the vertical direction is about 780 m. The HHT analyses of the coincident observations thus conclude that the observed daytime Es layer has a vertical dense slab structure and patches of scattering blocks in the horizontal structure.

Downshifted peak features of stimulated electromagnetic emissions during a two-pump wave heating experiment

Publication date: Available online 4 July 2019

Source: Advances in Space Research

Author(s): Guanglin Ma, Lixin Guo, Qingliang Li, Jutao Yang, Libin Lv, Jing Chen, Tong Xu, Shuji Hao, Jian Wu

Abstract

Experimental results of the downshifted peak (DP) in stimulated electromagnetic emissions under two-pump wave ionospheric heating near the third electron gyroharmonic frequency are presented. The European Incoherent Scatter Scientific Association heating antenna array was divided into two parts, one of which worked at constant pump wave frequency f1 and the other part worked at varied pump wave frequency f2 which was not larger than f1. It was found that when the second pump wave was turned on at different frequency with f1, the f1 DP power declined by more than 10 dB with respect to the background noise level, while the downshifted maximum belonging to f1 was further enhanced. The time needed to reach a steady state for DP was shortened from approximately 10 s under cold background conditions belonging to f1, which was nearly consistent with growth time of small-scale artificially field-aligned irregularity (AFAI), to less than 1 s under the preconditioned heating belonging to f2 with pre-existing AFAI. According to the difference in DP temporal evolution under two experimental conditions, it could be deduced that AFAI plays an important role in the DP generation process. Similar to single-pump wave heating, the frequency offset of DP decreases as f2 increases toward the third electron gyroharmonic frequency. These experimental findings provide new insights into the theoretical study of ionospheric plasma nonlinearity.

Characterizing inter-frequency bias and signal quality for GLONASS satellites with triple-frequency transmissions

Publication date: Available online 4 July 2019

Source: Advances in Space Research

Author(s): Lin Pan, Xiaohong Zhang, Fei Guo

Abstract

The GLONASS SVNs 702K (R09), 755 (R21) and 701K (R26) satellites currently provide G1, G2 and G3 signals. The difference between satellite clocks calculated by G1/G2 and G1/G3 ionospheric-free combinations, termed inter-frequency bias (IFB), is identified. The presence of IFB limits the application of G3 signal in precise positioning. The IFB is investigated using the datasets from 70 stations with a global distribution spanning 30 consecutive days. The epoch-wise phase-specific IFB (PIFB) estimates show periodic variations with a period of eight days and an average peak-to-peak amplitude of 0.107, 0.327 and 1.663 m for the R09, R21 and R26 satellites, respectively. The daily stable code-specific IFB (CIFB) estimates also show 8-day periodic signal. The day-to-day scattering of daily stable CIFB is 0.060–0.085 m. The estimation accuracy and prediction accuracy of PIFB are 0.025 and 0.019 m, respectively, while the corresponding statistics for the daily stable CIFB are 0.452 and 0.056 m, respectively. A modified estimation approach is developed to derive the time-varying epoch-wise CIFB. The epoch-wise CIFB and PIFB shows sub-daily periodic variations with the most notable periods of 5.625 and 11.250 h, respectively. The correction rate is 32% in terms of the prediction of the time-varying part of the epoch-wise CIFB. In addition, the signal quality is assessed from such aspects as carrier-to-noise density ratio, measurement noise and multipath errors.

Analysis of the Change of Orbital Elements in the Process of Gravity Assist

Publication date: Available online 3 July 2019

Source: Advances in Space Research

Author(s): Jingxi Liu, Bo Xu, Lei Zhang

Abstract

Gravity assist is widely applied in the deep space exploration because of its reliability and practicability. There are lots of research in the literature about the nearly coplanar situations. In this work, a three-dimensional model of gravity assist model is developed in a semi-analytical manner on the basis of the geometry relationship between the parameters of spacecraft before gravity assist and the orbital elements after gravity assist. The parameters include V∞in (the hyperbolic excess velocity vector of the spacecraft before fly-by), H (the height of fly-by) and θ (the dihedral angle between approach plane and fly-by plane). These equations can be used for analyzing the change of orbital elements in the process of gravity assist, discussing the influence of different parameters on them and deriving the condition that remains the semi-major axis unchanged. Curve fitting of the feasible region boundary of Δi and contour plot of Δi are utilized to analyze the pattern of Δi changing with different parameters. This method is a valuable reference for designing gravity assist trajectories to high inclination targets in the Solar system.

Regional ionosphere specification by assimilating ionosonde data into the SAMI2 model

Publication date: Available online 3 July 2019

Source: Advances in Space Research

Author(s): Jeong Heon Kim, Yong Ha Kim, Nicholas Ssessanga, Se Heon Jeong, Su In Moon, Young-Sil Kwak, Jong Yeon Yun

Abstract

This paper explains an algorithm of estimating the regional ionosphere at mid-latitude by assimilating ionosonde measured data into a first principle physics-based model (SAMI2-CNU). It has been known that many first principle models underperform due to inadequate input drivers, such as neutral winds and compositions in the background thermosphere. As a pilot study, equivalent meridional winds and electron density scale factors were derived every 15 min using F2 peak heights (hmF2) and densities (NmF2) obtained from Jeju ionosonde (33.43 N°, 126.30 E°), and then were used as inputs to SAMI2-CNU. SAMI2-CNU is an in-house revised version of the 2- dimensional ionosphere model (SAMI2), developed at Naval Research Laboratory (Huba et al., 2000; Kim and Kim, 2016). Results are obtained at a meridional plane of 127° geographic longitude on a geomagnetically quiet day of each season in the year 2014. SAMI2-CNU was found to predict the next 15-min hmF2s and NmF2s reasonably close to measured values at Jeju, Icheon (37.14 N°, 127.54 E°) and Okinawa (26.68 N°, 128.15 E°) (sites near the same meridional plane), showing a superior performance, compared to the original SAMI2 and the International Reference Ionosphere (IRI) 2016 model. Thus, this study demonstrates that a physic model, SAMI2-CNU, can be used as a nowcast model of the regional mid-latitude ionosphere by assimilating ionosonde data in near-real time.

Vertical ground displacements in the Shandong Province derived from long-term GNSS and leveling surveying

Publication date: Available online 2 July 2019

Source: Advances in Space Research

Author(s): Chunxi Guo, Jianliang Nie, Jie Tian, Wenli Wang, Chuanlu Cheng, Bin Wang, Huifang Yin, Haiping Zhang

Abstract

The vertical movement is comprised of both vertical crustal movements and vertical ground movements. Vertical crustal movement is established by using a cubic polynomial model with first-order leveling data from four separate time periods (1958-2015) in the Shandong Province and neighboring areas, and the vertical motion is formed from continuously operating reference stations (CORS) data (2010-2015) with GAMIT/GLOBK and a linear regression estimation in the Shandong Province. Vertical ground movement can be obtained by subtracting vertical crustal movement from vertical motion. Vertical crustal movement of Shandong Province gradually changes from descending to ascending along the northwest to the southeast, and the rate varies from -5.9 to 6.2 millimeter/year (mm/yr). Three distinct settlement areas including Guangrao, Dezhou and Heze are analyzed in detail. Substantial subsidence with a maximum rate of 78.2 mm/yr occurred in northern and western areas of Shandong Province. Slight uplift with a maximum rate of 8.4mm/yr occurred in central region and Jiaozhou Peninsula of Shandong Province. The vertical ground movements are basically consistent with vertical movements in the Shandong Province.

Cosmic ray origin: Why cosmic ray (Astroparticle) phenomenon is universal in the Universe? What is the main driver of cosmic ray particle generation?

Publication date: Available online 2 July 2019

Source: Advances in Space Research

Author(s): Lev Dorman

Abstract

During many years energetic particles generated on the Sun were called as Solar Cosmic Rays (SCR), but now increased the tendency to rename this phenomenon as Solar Energetic Particles (SEP) event. We will show that SEP, as well as energetic particles generated in magnetospheres of the Earth, Jupiter, Saturn and other planets, in interplanetary space, and in atmospheres of stars have the same nature as Galactic and Intergalactic CR: they are all runaway particles from the Maxwell-Boltzmann distribution of background plasma where they were generated. Energy of these run-away particles is much higher than average energy of background thermal particles. It is shown in this paper that the energy of all these run-away particles have the same general nature: it is always transfer energy from the Macro-objects and Macro-processes directly to Micro World (to charged runaway particles). This transfer energy is formatted in dynamic plasma with frozen in magnetic fields: really magnetic fields ‘glues’ billions thermal background particles into Macro-objects and Macro-processes. So, thank to frozen in magnetic fields runaway particles can interact not only with thermal background particles (and loose energy), but also directly with Macro-objects and Macro-processes with very high macro-energy (many order higher than energy of run-away particle). Thermodynamically Macro-objects and Macro-processes have much bigger “effective temperature” than runaway particles and though the energy always transferred from Macro World to runaway particles of Micro World. We come to conclusion that main cause of origin of all types of Cosmic Rays in the Universe is the transform energy from Macro-world directly to Micro-world through frozen in magnetic fields in plasmas. At the stage when in early Universe were formatted small density plasmas objects with frozen in magnetic fields, where formatted also Cosmic Rays of different types, but these “relict” Cosmic Ray particles have now very small energy thanks to extension Universe. So, observed now CR particles of different types are generated continuously by transfer energy from Macro World to runaway charged particles of Micro World through frozen in magnetic fields (including the main sources as Supernova explosions, Supernova remnants, and some smaller sources, as stars, star’s winds, planetary magnetospheres, and others).

Secondary cosmic rays in the NUCLEON space experiment

Publication date: Available online 2 July 2019

Source: Advances in Space Research

Author(s): V. Grebenyuk, D. Karmanov, I. Kovalev, I. Kudryashov, A. Kurganov, A. Panov, D. Podorozhny, A. Tkachenko, L. Tkachev, A. Turundaevskiy, O. Vasiliev, A. Voronin

Abstract

The NUCLEON space observatory is a direct cosmic ray spectrometer designed to study cosmic ray nuclei with Z=1-30 at energies 1012-1015 eV. It was launched as an additional payload onboard the Russian Resource-P No. 2 satellite in December of 2014. In this work B/C, N/O and subFe/Fe ratios are presented. The experiment has worked for half of its expected time, so the data have preliminary status, but they already give clear indications of several astrophysical phenomena, which are briefly discussed in this paper.

Evaluation of CryoSat-2 water level derived from different retracking scenarios over selected inland water bodies

Publication date: Available online 2 July 2019

Source: Advances in Space Research

Author(s): Sh. Roohi, N. Sneeuw, J. Benveniste, S. Dinardo, E.A. Issawy, G. Zhang

Abstract

As the first satellite altimetry mission operating in sar (delay-Doppler) mode, CryoSat-2 is an interesting mission to analyze its performance for water level monitoring over inland water bodies. It offers the opportunity to make comparison of sar and conventional altimeters by a multi-mode altimeter mounted on the same platform with a long repeat orbit. This comparison gives us more knowledge about the performance of the sar altimeter. Even tough it is not possible to perform it over same objects.

In this paper we analyze the CryoSat-2 performance for water level monitoring via full- and sub-waveform retracking against in-situ gauge and L2 products of other satellite altimetry missions, e.g. Envisat and Jason-2. To this end, we retrack the full-waveforms and sub-waveforms with different empirical and physical retracking algorithms such as ocog, threshold, β-parameters and samosa3. We evaluate its capability in all measurement modes, i.e. lrm, sar and sarin, over inland water bodies located in different climatic zones. We selected study areas with different shapes and sizes.

Relative to in situ measurements we find a precision of the CryoSat-2 lrm mode of 15cmrms over Qinghai lake (China) and 13cm over Erie lake (usa). This is an improvement over Envisat, yielding precision of 17cm in both cases. For the sar mode over Neagh lake (Northern Ireland) and Derg lake (Ireland) we obtain 15cm and 13cm where Envisat yields 28cm and 100cm, respectively. The sarin mode’s precision is assessed over Nasser lake (Egypt) with 25cmrms and Athabasca lake (Canada) with 16cm. Over these lakes Jason-2 achieved 54cm and Envisat 19cm, respectively. The most precise results of CryoSat-2 are obtained with our retracking and sub-waveform selection scenarios. Comparing CryoSat-2 results from our retracking scenarios using L1b data with those results obtained from L2 products (data) of this mission shows an improvement of 4–17 cm. The minimum and maximum improvements belong to Erie and Derg lakes respectively, the largest and smallest lakes.

From the waveform analysis over lakes with different shapes and sizes, we found that the first and the mean-all sub-waveforms (mean correction from all sub-waveforms) retracked with the threshold and samosa3 (only for sar mode) retrackers are appropriate to retrieve water level variation of small lakes and complex shaped lakes in this study. Over large lakes the full-waveform retracking leads to better results. In the case of icy-lake objects, sub-waveform retracking scenarios (the first and mean-all sub-waveforms) are more precise than the other scenarios. These are our findings over few samples, though more samples need to be analyzed to support them strongly.

Relative equilibria of an intermediary model for the roto-orbital dynamics. The low rotation regime

Publication date: Available online 2 July 2019

Source: Advances in Space Research

Author(s): J.L. Zapata, F. Crespo, S. Ferrer, F.J. Molero

Abstract

We address the attitude dynamics of a triaxial rigid body in a circular orbit. This task is done by means of an intermediary model, which is obtained by splitting the Hamiltonian in the form H=H0+H1, where H0 is required to be a non-degenerate integrable Hamiltonian system. A numerical study is presented comparing the dynamics of the new intermediary model with the full system (MacCullagh’s truncation) and showing a competitive performance for the cases Sun-asteroid and Earth-spacecraft. This model defines a Poisson flow endowed with invariants defining a SM2×SM2 reduced space. We analyze the coupling between the orbital mean motion and rotational variables. The key role played by the moments of inertia and the value of the angular momentum is shown in detail. The analysis of the intermediary shows that, under slow rotation regime, the classic dynamics of the free rigid body is no longer maintained: bifurcations with changes of stability are displayed for several critical inclinations of the rotational angular momentum plane and for critical orientations of the body frame. Moreover, the evolution of the angular momentum plane is given by a time dependent harmonic oscillator.

Statistical analysis and modelling of sporadic E layer over Europe

Publication date: Available online 1 July 2019

Source: Advances in Space Research

Author(s): N.Y. Zaalov, E.V. Moskaleva

Abstract

This paper describes a study of the daily and yearly variability of one of the main characteristics of sporadic E layers (Es), the critical frequency (foEs). Our analysis is based on ionograms recorded by GIRO network ionosondes. The study estimates the spatial and temporal variability of the Es layer parameters and generates their statistics at different seasons and phases of the solar cycle. In turn, the statistics of the Es layer parameters can provide an assessment of the capability of the HF propagation forecasting. Further, maps of the distribution of Es layer critical frequency are produced. This paper implements the “cloud” model of Es layer in HF propagation model (Northern Ionosphere Model & Ray Tracing, NIM-RT) that can accurately reproduce many features observed in experimental measurements. Within this framework, a number of vertical sounding ionograms with the presence of Es layer are simulated based on the NIM-RT software.

Author Index

Publication date: 15 August 2019

Source: Advances in Space Research, Volume 64, Issue 4

Author(s):

List of Referees

Publication date: 15 August 2019

Source: Advances in Space Research, Volume 64, Issue 4

Author(s):

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