scholarly journals A new global model for the ionospheric F2 peak height for radio wave propagation

2012 ◽  
Vol 30 (5) ◽  
pp. 797-809 ◽  
Author(s):  
M. M. Hoque ◽  
N. Jakowski
Keyword(s):  
Observational Data ◽  
Electron Density ◽  
Temporal Variations ◽  
Global Scale ◽  
Peak Height ◽  
Frequency Planning ◽  
Spatial Dependencies ◽  
Planning And Operation ◽  
Height Model ◽  
Model Approach

Abstract. The F2-layer peak density height hmF2 is one of the most important ionospheric parameters characterizing HF propagation conditions. Therefore, the ability to model and predict the spatial and temporal variations of the peak electron density height is of great use for both ionospheric research and radio frequency planning and operation. For global hmF2 modelling we present a nonlinear model approach with 13 model coefficients and a few empirically fixed parameters. The model approach describes the temporal and spatial dependencies of hmF2 on global scale. For determining the 13 model coefficients, we apply this model approach to a large quantity of global hmF2 observational data obtained from GNSS radio occultation measurements onboard CHAMP, GRACE and COSMIC satellites and data from 69 worldwide ionosonde stations. We have found that the model fits to these input data with the same root mean squared (RMS) and standard deviations of 10%. In comparison with the electron density NeQuick model, the proposed Neustrelitz global hmF2 model (Neustrelitz Peak Height Model – NPHM) shows percentage RMS deviations of about 13% and 12% from the observational data during high and low solar activity conditions, respectively, whereas the corresponding deviations for the NeQuick model are found 18% and 16%, respectively.

Investigation of the ionosphere over Antarctica under quiet space weather conditions: results of vertical sounding of the ionosphere September 14–24, 2020

2020 ◽  
Vol 1 (1) ◽  
pp. 45-55
Author(s):  
Maryna Shulha ◽  
Oleksandr Bogomaz ◽  
Taras Zhivolup ◽  
Oleksander Koloskov ◽  
Andrey Zalizovski ◽  
...  
Keyword(s):  
Electron Density ◽  
Space Weather ◽  
Weather Conditions ◽  
Temporal Variations ◽  
Peak Height ◽  
International Reference Ionosphere ◽  
Antarctic Region ◽  
Model Predictions ◽  
The Antarctic ◽  
Layer Peak

We present observational results of variations in the ionospheric parameters hmF2 and NmF2 over the Ukrainian Antarctic station “Akademik Vernadsky” for magnetically quiet conditions. The results of comparative analysis of observational data and the International Reference Ionosphere-2016 model predictions are presented. The main objective of this study is to investigate the temporal variations of two key ionospheric parameters – the F2 layer peak height and electron density – during very quiet space weather conditions using data of vertical sounding of the ionosphere obtained over the Ukrainian Antarctic station “Akademik Vernadsky” and comparison the observation results with model values. Methods: The temporal variations of the F2 layer peak height and electron density were calculated from ionograms obtained with ionosonde installed at the Ukrainian Antarctic station “Akademik Vernadsky” with subsequent electron density profile inversion. Diurnal variations of hmF2 and NmF2 were calculated using a set of sub-models of the IRI-2016 model for comparison with results of observational studies. Results: We found that for the Antarctic region option of IRI-2016 model for the F2 layer peak height SHU-2015 provides a better fit for hmF2 through the investigated period compare to the AMTB-2013 model predictions. Electron density models (URSI, CCIR) generally well reproduce the observed variations of NmF2 during periods of absence non-standard manifestations of space weather, which are possible for quiet conditions too. Hypotheses regarding the possible reasons for experimental and model differences in variations of NmF2 are discussed. The analysis of effect of geomagnetic storm on September 24, 2020 on NmF2 variations was carried out. Conclusions: The obtained results demonstrate peculiarities of the state of the ionosphere-plasmasphere system over Antarctica under very quiet space weather conditions and provide evaluation of predictive capabilities of modern international reference ionosphere models. New knowledge about the features of electron density variations in the ionosphere for magnetically quiet conditions over the Antarctic region has practical value for specialists which are engaged in the study of the near-Earth space environment, in particular, at high latitudes, and also work on correction of global ionospheric models. Keywords: electron density, F2 layer peak height, ionosonde, quiet space weather, models of the ionosphere, downward plasma flux

scholarly journals Regional representation of F2 Chapman parameters based on electron density profiles

2013 ◽  
Vol 31 (12) ◽  
pp. 2215-2227 ◽  
Author(s):  
M. Limberger ◽  
W. Liang ◽  
M. Schmidt ◽  
D. Dettmering ◽  
U. Hugentobler
Keyword(s):  
Electron Density ◽  
Real Data ◽  
Peak Height ◽  
Electron Content ◽  
Density Profiles ◽  
Total Electron ◽  
Maximum Electron Density ◽  
Spatio Temporal ◽  
Electron Density Profiles ◽  
Model Approach

Abstract. Understanding the physical processes within the ionosphere is a key requirement to improve and extend ionospheric modeling approaches. The determination of meaningful parameters to describe the vertical electron density distribution and how they are influenced by the solar activity is an important topic in ionospheric research. In this regard, the F2 layer of the ionosphere plays a key role as it contains the highest concentration of electrons and ions. In this contribution, the maximum electron density NmF2, peak height hmF2 and scale height HF2 of the F2 layer are determined by employing a model approach for regional applications realized by the combination of endpoint-interpolating polynomial B splines with an adapted physics-motivated Chapman layer. For this purpose, electron density profiles derived from ionospheric GPS radio occultation measurements of the satellite missions FORMOSAT-3/COSMIC, GRACE and CHAMP have been successfully exploited. Profiles contain electron density observations at discrete spots, in contrast to the commonly used integrated total electron content from GNSS, and therefore are highly sensitive to obtaining the required information of the vertical electron density structure. The spatio-temporal availability of profiles is indeed rather sparse, but the model approach meets all requirements to combine observation techniques implicating the mutual support of the measurements concerning accuracy, sensitivity and data resolution. For the model initialization and to bridge observation gaps, the International Reference Ionosphere 2007 is applied. Validations by means of simulations and selected real data scenarios show that this model approach has significant potential and the ability to yield reliable results.

Equatorial F region evening vertical drift, and peak height, during southern winter months: A comparison of observational data with the IRI descriptions

2006 ◽  
Vol 37 (5) ◽  
pp. 1007-1017 ◽  
Author(s):  
M.A. Abdu ◽  
I.S. Batista ◽  
B.W. Reinisch ◽  
J.H.A. Sobral ◽  
A.J. Carrasco
Keyword(s):  
Observational Data ◽  
Peak Height ◽  
F Region ◽  
Vertical Drift

scholarly journals Different long-term trends of the oxygen red 630.0 nm line nightglow intensity as the result of lowering the ionosphere F2 layer

2008 ◽  
Vol 26 (8) ◽  
pp. 2069-2080 ◽  
Author(s):  
N. B. Gudadze ◽  
G. G. Didebulidze ◽  
L. N. Lomidze ◽  
G. Sh. Javakhishvili ◽  
M. A. Marsagishvili ◽  
...  
Keyword(s):  
Electron Density ◽  
Line Intensity ◽  
Peak Height ◽  
Height Distribution ◽  
Theoretical Simulation ◽  
Type Layer ◽  
Long Term Trends ◽  
The Mean ◽  
Long Term Trend

Abstract. Long-term observations of total nightglow intensity of the atomic oxygen red 630.0 nm line at Abastumani (41.75° N, 42.82° E) in 1957–1993 and measurements of the ionosphere F2 layer parameters from the Tbilisi ionosphere station (41.65° N, 44.75° E) in 1963–1986 have been analyzed. It is shown that a decrease in the long-term trend of the mean annual red 630.0 nm line intensity from the pre-midnight value (+0.770±1.045 R/year) to its minimum negative value (−1.080±0.670 R/year) at the midnight/after midnight is a possible result of the observed lowering of the peak height of the ionosphere F2 layer electron density hmF2 (−0.455±0.343 km/year). A theoretical simulation is carried out using a simple Chapman-type layer (damping in time) for the height distribution of the F2 layer electron density. The estimated values of the lowering in the hmF2, the increase in the red line intensity at pre-midnight and its decrease at midnight/after midnight are close to their observational ones, when a negative trend in the total neutral density of the upper atmosphere and an increase in the mean northward wind (or its possible consequence – a decrease in the southward one) are assumed.

scholarly journals Multi-species inversion of CH<sub>4</sub>, CO and H<sub>2</sub> emissions from surface measurements

2009 ◽  
Vol 9 (14) ◽  
pp. 5281-5297 ◽  
Author(s):  
I. Pison ◽  
P. Bousquet ◽  
F. Chevallier ◽  
S. Szopa ◽  
D. Hauglustaine
Keyword(s):  
Transport Model ◽  
Regional Scale ◽  
Surface Concentration ◽  
Temporal Variations ◽  
Global Scale ◽  
Chemical Transport Model ◽  
Methyl Chloroform ◽  
Emission Fluxes ◽  
Surface Measurements ◽  
One Year

Abstract. In order to study the spatial and temporal variations of the emissions of greenhouse gases and of their precursors, we developed a data assimilation system and applied it to infer emissions of CH4, CO and H2 for one year. It is based on an atmospheric chemical transport model and on a simplified scheme for the oxidation chain of hydrocarbons, including methane, formaldehyde, carbon monoxide and molecular hydrogen together with methyl chloroform. The methodology is exposed and a first attempt at evaluating the inverted fluxes is made. Inversions of the emission fluxes of CO, CH4 and H2 and concentrations of HCHO and OH were performed for the year 2004, using surface concentration measurements of CO, CH4, H2 and CH3CCl3 as constraints. Independent data from ship and aircraft measurements and satellite retrievals are used to evaluate the results. The total emitted mass of CO is 30% higher after the inversion, due to increased fluxes by up to 35% in the Northern Hemisphere. The spatial distribution of emissions of CH4 is modified by a decrease of fluxes in boreal areas up to 60%. The comparison between mono- and multi-species inversions shows that the results are close at a global scale but may significantly differ at a regional scale because of the interactions between the various tracers during the inversion.

scholarly journals Evaluation of spatial-temporal variation performance of ERA5 precipitation data in China

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Donglai Jiao ◽  
Nannan Xu ◽  
Fan Yang ◽  
Ke Xu
Keyword(s):  
Observational Data ◽  
Correlation Coefficient ◽  
Global Scale ◽  
Precipitation Trend ◽  
Strongly Correlated ◽  
Precipitation Data ◽  
Weather Forecasts ◽  
Fifth Generation ◽  
Data Assessment ◽  
Long Time

AbstractERA5 is the latest fifth-generation reanalysis global atmosphere dataset from the European Centre for Medium-Range Weather Forecasts, replacing ERA-Interim as the next generation of representative satellite-observational data on the global scale. ERA5 data have been evaluated and applied in different regions, but the performances are inconsistent. Meanwhile, there are few precise evaluations of ERA5 precipitation data over long time series have been performed in Chinese mainland. This study evaluates the temporal-spatial performance of ERA5 precipitation data from 1979 to 2018 based on gridded-ground meteorological station observational data across China. The results showed that ERA5 data could capture the annual and seasonal patterns of observed precipitation in China well, with correlation coefficient values ranging from 0.796 to 0.945, but ERA5 slightly overestimated precipitation in the summer. Nonetheless, the results also showed that the accuracy of the precipitation products was strongly correlated with topographic distribution and climatic divisions. The performance of ERA5 shows spatial inherently across China that the highest correlation coefficient values locate in eastern, Northwestern and North China and the lowest biases locate in Southeast China. This study provides a reliable data assessment of the ERA5 data and precipitation trend analyses in China. The results provide accuracy references for the further use of precipitation satellite data for hydrological calculations and climate numerical simulations.

The Interpretation of EUV Spectra of Sunspots

1983 ◽  
Vol 71 ◽  
pp. 325-326
Author(s):  
J.G. Doyle ◽  
J.C. Raymond ◽  
R.W. Noyes ◽  
A.E. Kingston
Keyword(s):  
Observational Data ◽  
Electron Density ◽  
Constant Pressure ◽  
Wavelength Region ◽  
Constant Density ◽  
Ionization Equilibrium ◽  
Sensitive Line ◽  
Temperature Diagnostic

We report here on EUV observations of a sunspot observed by the Harvard instrument on Skylab. The observational data used here have been presented in a previous paper by Noyes et al. (1982), in which line identifications and intensities for the wavelength region 350 – 1350 A were given. Several electron density sensitive line ratios suggest a constant density, rather than constant pressure, emitting region, while temperature diagnostic line ratios of several ions yield temperatures below the temperatures expected in ionization equilibrium.

Experimental Electron Density Study of NaH2PO4 at 30 K

1998 ◽  
Vol 54 (1) ◽  
pp. 29-34 ◽  
Author(s):  
M. Ichikawa ◽  
T. Gustafsson ◽  
I. Olovsson
Keyword(s):  
Electron Density ◽  
Bond Distance ◽  
Lone Pair ◽  
Peak Height ◽  
Dihydrogen Phosphate ◽  
Sodium Dihydrogen Phosphate ◽  
Deformation Density ◽  
Density Peaks ◽  
Deformation Electron Density ◽  
Lone Pair Electrons

The deformation electron density of sodium dihydrogen phosphate, NaH2PO4, at 30 K has been studied as a reference for the electron-density characteristics of hydrogen-bonded ferroelectrics containing phosphate ions. Clear peaks of deformation electron density (0.3–0.6 e Å−3) are seen in the middle of each P—O bond and electron deficiency (−0.2 to −0.4 e Å−3) on the opposite side of each P—O bond peak. The peak height is higher and the peak shape is more distinct in P—O bonds than in P—O(H) bonds as a whole; the distribution of deformation density in the region of lone-pair electrons is more diffuse. The O—H...O bond deformation-density peaks of around 0.2 e Å−3 appear in the middle of the O—H bond, followed by a deeper electron depletion of around −0.4 e Å−3 on the H...O contract, just outside the H atom. The effective charges, defined as the integral of the deformation electron density, have the following values: around +0.2 for Na, +1.8 for P, −0.8 for O and +0.6 for H. The correlation of the deformation-density peaks and the depth of the negative peak of the H atom with the hydrogen-bond distance are discussed.

scholarly journals Modelling the main ionospheric trough using the Electron Density Assimilative Model (EDAM) with assimilated GPS TEC

2018 ◽  
Vol 36 (1) ◽  
pp. 125-138 ◽  
Author(s):  
James A. D. Parker ◽  
S. Eleri Pryse ◽  
Natasha Jackson-Booth ◽  
Rachel A. Buckland
Keyword(s):  
Electron Density ◽  
Large Scale ◽  
Western Europe ◽  
Global Scale ◽  
Electron Content ◽  
Total Electron ◽  
Radio Science ◽  
Ionospheric Physics ◽  
Main Ionospheric Trough ◽  
Plasma Distribution

Abstract. The main ionospheric trough is a large-scale spatial depletion in the electron density distribution at the interface between the high- and mid-latitude ionosphere. In western Europe it appears in early evening, progresses equatorward during the night, and retreats rapidly poleward at dawn. It exhibits substantial day-to-day variability and under conditions of increased geomagnetic activity it moves progressively to lower latitudes. Steep gradients on the trough-walls on either side of the trough minimum, and their variability, can cause problems for radio applications. Numerous studies have sought to characterize and quantify the trough behaviour. The Electron Density Assimilative Model (EDAM) models the ionosphere on a global scale. It assimilates observations into a background ionosphere, the International Reference Ionosphere 2007 (IRI2007), to provide a full 3-D representation of the ionospheric plasma distribution at specified times and days. This current investigation studied the capability of EDAM to model the ionosphere in the region of the main trough. Total electron content (TEC) measurements from 46 GPS stations in western Europe from September to December 2002 were assimilated into EDAM to provide a model of the ionosphere in the trough region. Vertical electron content profiles through the model revealed the trough and the detail of its structure. Statistical results are presented of the latitude of the trough minimum, TEC at the minimum and of other defined parameters that characterize the trough structure. The results are compared with previous observations made with the Navy Ionospheric Monitoring System (NIMS), and reveal the potential of EDAM to model the large-scale structure of the ionosphere. Keywords. Ionosphere (midlatitude ionosphere; modelling and forecasting) – radio science (ionospheric physics)

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