F2 Parameters Research Articles

Correlation Analysis between Cortical Structural Features and Acoustic Features in Patients with Parkinson's Disease

Parkinson disease (PD) is a progressive neurodegenerative disease. The aim of this study is to investigate the association between acoustic and cortical brain features in Parkinson's disease patients. We recruited 19 (eight females, 11 males) Parkinson's disease patients and 19 (eight females, 11 males) healthy subjects to participate in the experiment. Speech samples of three vowels (/i/, /a/, /u/), six plosives (/p/, /pʰ/, /t/, /tʰ/, /k/, /kʰ/), and three voiced consonants (/l/, /m/, /n/) were collected for the experiment, and the acoustic parameters were extracted for fundamental frequency (F0), voice onset time (VOT), voicing onset-vocalic voicing onset (VO-VVO), first formant (F1), second formant (F2), third formant (F3), first bandwidth (B1), second bandwidth (B2), third bandwidth (B3), Jitter, Shimmer, andHarmonics-to-noise ratio (HNR). We also used Ingenia CX 3.0T to complete the cranial magnetic resonance scanning and did image processing based on the Desikan-Killiany-Tourville Atlas. We assessed the differences in acoustic and neuroimaging parameters between the PD andhealthy controls (HCs) groups using the Levene's test (LT), two-sample independent t test (TT), and Mann-Whitney U test (MWUT), and calculated Spearman's bias correlations for acoustic and neuroimaging parameters in the PD and HC groups, respectively. The results showed that in acoustic features, based on the results of the TT, it can be seen that the F3 of the PD group regarding the vowel /i/ is significantly smaller than that of the HC group. The jitter on the vowel /u/ was significantly higher in the male PD group than in the male HC group. For other acoustic measures, there were no statistically significant differences between the two groups. In the cortical features, the thickness, area, and volume of the cortex were reduced in the vast majority of the brains of the PD patients, however, there is also a small portion of the cortex that appears to be thickened. In the correlation analysis between cortical and acoustic features, F0, F1, F2, F3, B2, B3, VO-VVO, Jitter, HNR, and VOT acoustic parameters showed significant and strong correlation with thickness, area, and volume of cortical sites such as frontal, temporal, entorhinal, fusiform, andprecuneus in PD patients, whereas no significant correlation was found in HC group. This suggests that Parkinson's disease does have an effect on the acoustic and cortical features of the patient's brain, and that there is a correlation between the two features.

Coamorphous systems of rebamipide: Selection of amino acid coformers based on protein-ligand docking, in vitro assessment and study of interactions by computational and multivariate analysis

Three coamorphous systems of Rebamipide (REB) with the amino acids namely, Tryptophan (TRP), Phenylalanine (PHE) and Arginine (ARG) are reported. A unique approach for the virtual screening of amino acid coformers is presented by employing molecular docking studies based on interactions of the drug molecule with various amino acid fragments in the drug-receptor cocrystal structure. Successful formation of stable coamorphous systems with ARG, TRP and PHE served as the proof-of-concept along with negative benchmarking standards Histidine and Aspartic acid, wherein coamorphous systems could not be obtained despite multiple trials which resulted in crystalline physical mixtures. The coamorphous systems were characterized by a halo pattern in Powder XRD and a single glass transition temperature (Tg) in modulated DSC. Physical stability assessments of the coamorphous systems showed direct correlation of Tg with the observed stability of the amorphous phase which was found in the order ARGREB > TRPREB ≥ PHEREB. To determine the specific functional groups engaged in the interactions, multivariate analysis was performed on the FTIR spectra. These interactions were further validated by DFT and QTAIM analysis, which revealed key noncovalent interactions in the three coamorphous systems. All three coamorphous systems showed excellent release profiles of the API as demonstrated by the f2 and DE parameters in the order ARGREB ≥ TRPREB > PHEREB ≥ amorphous drug, far exceeding that of the crystalline drug. The interplay of multivariate analysis and QTAIM can be useful in estimating the interactions within the coamorphous systems which can further contribute to stability and physicochemical properties of the systems.

Ionosonde Measurement Comparison during an Interplanetary Coronal Mass Ejection (ICME)- and a Corotating Interaction Region (CIR)-Driven Geomagnetic Storm over Europe

A comparison of three types of ionosonde data from Europe during an interplanetary coronal mass ejection (ICME)- and a corotating interaction region (CIR)-driven geomagnetic storm event is detailed in this study. The selected events are 16–20 March 2015 for the ICME-driven storm and 30 May to 4 June 2013 for the CIR-driven one. Ionospheric data from three European ionosonde stations, namely Pruhonice (PQ), Sopron (SO) and Rome (RO), are investigated. The ionospheric F2-layer responses to these geomagnetic events are analyzed with the ionospheric foF2 and h’F2 parameters, the calculated deltafoF2 and deltahF2 values, the ratio of total electron content (rTEC) and Thermosphere, Ionosphere, Mesosphere, Energetics and Dynamics (TIMED) satellite Global Ultraviolet Imager (GUVI) thermospheric [O]/[N2] measurement data. The storm-time and the quiet-day mean values are also compared, and it can be concluded that the quiet-day curves are similar at all the stations while the storm-time ones show the latitudinal dependence during the development of the storm. As a result of the electron density comparison, during the two events, it can be concluded that the sudden storm commencement (SSC) that characterized the ICME induced a traveling atmospheric disturbance (TAD) seen in the European stations in the main phase, while this is not seen in the CIR-driven ionospheric storm, which shows a stronger and more prolonged negative effect in all the stations, probably due to the season and the depleted O/N2 ratio.

Climatology of atmospheric solar tidal mode effects on ionospheric F2 parameters over the American sector during solar minimum between cycles #23 and #24

This work presents the contribution of solar atmospheric tides (diurnal, semidiurnal, and terdiurnal modes) to the variability of the parameters critical frequency (foF2) and peak height of the F2-layer (hmF2) in the American sector during the transition of solar cycles #23 and #24, a period considered one of the lowest solar activities of the modern era. The Digisonde data available in the GIRO data center were analyzed (12 stations), and the solar tide modes were evaluated regarding their amplitude, latitude, and seasonal dependence. The results showed that the hmF2 and foF2 strongly depend on latitude and seasonality, being more intense in the stations located in the south hemisphere. The same behavior is seen for the tidal amplitude fitted in these parameters, except for hmF2 diurnal tide, which is more intense at latitudes farther from the equator. Moreover, the seasonal variability of the amplitude of hmF2 in most cases presented an annual and semiannual component. A terannual component was also observed in 8 h tide mode in the height and frequency parameters. Likewise, what was observed in foF2, the variability in the mean amplitude and different modes of tides of hmF2 are higher over the sectors located in the southern hemisphere.

Experimental investigation of thermal performance evaluation and thermodynamic analysis of domestic box type solar cooker with inclined aperture area

In this paper, the thermal performances of a box solar cooker were rated with F1 and F2 parameters as per Mullick’s procedure [1], the efficiency of the cooker was evaluated using energy and exergy analysis. The solar cooker was designed with an inclined aperture area, realized and experimentally tested at Applied Research Unit on Renewable Energies of Ghardaïa (32.39 °N, 3.78 °E, 463 m), Algeria. The developed cooker is equipped with one reflector mirror on its lid. The experiments have been carried out with the cooker empty, filled with one or two liters of water from 08:00 to 15:00 solar time, the thermal profiles of various components of the cooker were assessed at Ghardaïa site Sahara climatic conditions on clear days in both winter and summer months. According to the values of two figures of merits suggested by International Standards and evaluated by the experimental studies, the configuration with an inclined aperture area of the cooker resulted in good cooking performances, especially in winter when the sun’s elevation is low; keeping the realized cooker performances in range of the international standard tests. The results of this study indicate also that the average daily energy and exergy efficiency of the realized cooker was 16.2 % and 0.90 % respectively, during the experimental period, which indicate a significant difference between the results of energy and exergy analyses. Thus developing such a box solar cooker can improve the efficiency of the design and use a position of the system to prepare food in a shorter time.

Fabrication and Properties of Hydrophobically Modified ZnO–SiO2 Nanocomposite with Polysiloxane

Studies on the wettability properties of solid surfaces are very important in any of the scientific and industrial fields. The most common principle for a superhydrophobic self-cleaning surface is the lotus effect induced by surface roughness. In this study, silicate compounds have been used to produce hydrophobic surfaces. In this way, firstly, SiO2–ZnO nanocomposite was produced, and then vinyl trimethoxy silane was used to increase the water contact angle (WCA). The structure and morphology of nanocomposites were investigated by infrared spectroscopy (FT-IR), X-ray diffraction pattern (XRD), scanning electron microscopy (SEM) and energy-dispersion spectrometer (EDS) analyses. The thermal stability of nanocomposite coatings was examined by thermogravimetric analysis (TGA). In order to investigate the wetting properties, the surface roughness was measured using an atomic force microscope (AFM), where the subsurface roughness average was obtained at 37.79 nm. The WCA of the coated surfaces with ZnO–SiO2 and ZnO–SiO2 @Polysiloxane nanocomposites were measured at 69 and 160°, respectively, indicating the surface superhydrophobic properties of ZnO–SiO2 @Polysiloxane nanocomposites. Finally, superhydrophobic properties of nanocomposites were investigated by the Cassie-Baxter model. The value of the f2 parameter in the model was estimated at 0.9556. This means that air occupies about 95.56% of the contact area between the water droplet and nano-coating, which is responsible for the superhydrophobic property of the surface.

Modelling M(3000)F2 at an African Equatorial Location for Better IRI‐Model Prediction

AbstractThe F2‐layer propagation factor M(3000)F2 is important to ionospheric studies owning to its use in high High frequency radio communication/ionospheric modeling. This study focused on reducing the shortcomings in the use of M(3000)F2 IRI‐model for obtaining hmF2, especially in the African equatorial region, by obtaining an empirical “constructed model” (M(3000)F2CM) using the Korhogo (geomag. lat. 1.26°S, long. 67.38°E, dip. −0.67°S) data (M(3000)F2KOR). The data spans 8 years (1993–2000) under magnetically quiet conditions (Ap < 20 nT). The Regression method technique was used in obtaining the M(3000)F2CM. The regression coefficient (R2) for the M(3000)F2KOR versus F10.7 relationship was stronger during the solstices. The associated diurnal equations obtained for all seasons from the regression plot of the M(3000)F2KOR‐F10.7 relationship were used to obtained the constructed model equation given by M(3000)F2CM(m)i = ai(m) ∗ (F10.7) + bi(m), which allows the prediction of diurnal, seasonal and solar cycle variation of the M(3000)F2 parameter. M(3000)F2CM predicted well when tested at different solar activities. Generally, M(3000)F2CM performed reasonably well in comparison with the IRI model (M(3000)F2IRI) when validated with Ouagadougou (lat. 0.59°S, long. 71.46°E) observed data ‐ M(3000)F2OUA. The percentage deviation of M(3000)F2CM versus M(3000)F2OUA during high solar activity and low solar activity ranges from −10.8–5.3/−7.6–15.8 for solstices/equinoxes; whereas percentage deviation of M(3000)F2IRI versus M(3000)F2OUA spans −15.5–9.2 and −9.7–17.7 in similar order of seasons. The characteristic diurnal post‐sunset drop in M(3000)F2, a prominent feature of the equatorial ionosphere is well captured by the empirical model. These results suggest that the new model has a measure of potential for its use in the equatorial African region.

Potential of Regional Ionosphere Prediction Using a Long Short‐Term Memory Deep‐Learning Algorithm Specialized for Geomagnetic Storm Period

AbstractIn our previous study (Moon et al., 2020, https://doi.org/10.3938/jkps.77.1265), we developed a long short‐term memory (LSTM) deep‐learning model for geomagnetic quiet days (LSTM‐quiet) to perform effective long‐term predictions for the regional ionosphere. However, their model could not predict geomagnetic storm days effectively at all. This study developed an LSTM model suitable for geomagnetic storms using the new training data set and redesigning input parameters and hyper‐parameters. We collected 131 days of geomagnetic storm cases from January 1, 2009 to December 31, 2019, provided by the Japan Meteorological Agency's Kakioka Magnetic Observatory, and obtained the interplanetary magnetic field Bz, Dst, Kp, and AE indices related to the geomagnetic storm corresponding to each storm date from the OMNI database. These indices and F2 parameters (foF2 and hmF2) of Jeju ionosonde (33.43°N, 126.30°E) were used as input parameters for the LSTM model. To test and verify the predictive performance and the usability of the LSTM model for geomagnetic storms developed in this manner, we created and diagnosed the 0.5, 1, 2, 3, 6, 12, and 24‐h predictive LSTM models. According to the results of this study, the LSTM storm model for 24‐h developed in this study achieved a predictive performance during the three geomagnetic storms about 32% (10%), 34% (17%), and 37% (5%) better in root mean square error of foF2 (hmF2) than the LSTM quiet model (Moon et al., 2020, https://doi.org/10.3938/jkps.77.1265), SAMI2, and IRI‐2016 models. We propose that the short‐term predictions of less than 3 h are sufficiently competitive than other traditional ionospheric models. Thus, this study suggests that our model can be used for short‐term prediction and monitoring of the regional mid‐latitude ionosphere.

Contribution of Solar Radiation to the Long-Term Dynamics of Hydro-Ecological Parameters of Lake Ecosystems under Variable Nutrient Loading: Case Study on Naroch Lakes

Results of the continuous monitoring of the Naroch lake system, which includes eutrophic Lake Batorino, mesotrophic Lake Myastro, and oligomesotrophic Lake Naroch, have been used to study the factors that largely affect the long-term dynamics of the lakes ecosystem under variable nutrient loading. A set of continuous series of average seasonal values of eight parameters from each ecosystem over 1978–2015 is analyzed using the SSA and PCA methods. The second principal component (F2), which contributes 15.3, 20.5, and 22.1% to the dynamics of the ecosystems of lakes Myastro, Batorino, and Naroch, respectively, is associated with three parameters that reflect the processes of formation and decomposition of the organic matter. A comparison of the periods of the dominant cyclical components of principal component F2 and related ecosystem parameters allows us to interpret the second main factor behind these components as activity from solar radiation.

Autonomous PSO-DVSF<SUP align="right">2</SUP>: an optimised force field mobile robot motion planning approach for unknown dynamic environments

PSO-DVSF2 (Ziadi et al., 2016) is a PSO optimised mobile robot motion planning strategy based on the force field approach. PSO-DVSF2 has been previously developed to optimally guide the mobile robot in known dynamic environments. Autonomous PSO-DVSF2, the subject of this paper, is an improvement of PSO-DVSF2 to deal with unknown dynamic environments. In this new real-time PSO optimised mobile robot motion planning approach, the robot has to update F2 parameters all along the trajectory and not once in the beginning of the navigation as has been the case with the previous version. A comparison with the autonomous PSO-CF2 has been applied in various unknown environments (static and dynamic) using the 3D virtual Webots simulator. The robot localisation based on sensor readings with a local motion planning, and the variation of angular and linear speeds ensure the robot collision-free motion. Simulation results prove the efficiency of the autonomous PSO-DVSF2 to guide the robot along the shortest and safest path in complex unknown dynamic environments.

Assessment of physicochemical properties and comparison of the dissolution profile of amoxicillin caplets

Background: Marketed drugs must meet the required standards to guarantee product quality. Amoxicillin is a generic compound marketed under various trademarks as copy drugs. Amoxicillin caplets are an immediate release dosage form of BCS class I. An essential aspect of evaluating copy drugs is to assess the equivalence for their treatment to the innovator drugs to ensure the safety and effectiveness of the circulating copy drugs. Objective: The study aims to evaluate the physicochemical properties and compare the dissolution profile of amoxicillin caplets available in the market. Methods: Five amoxicillin caplet products, four test products, and one reference product were tested for their physicochemical properties and dissolution. The dissolution test was carried out with a type II device at a speed of 75 rpm in 900 mL of media buffered at pH 1.2, 4.5, and 6.8 and at a temperature of 37 +/- 0.5degrees celcius. The dissolution profile was analyzed by comparing it with the similarity factor (f2) parameters. Results: Two of the four amoxicillin caplet products had a similar dissolution profile to the reference products, namely products A and B. Products C and D were dissimilar because f2 was lower than 50 at pH 4.5. The caplets tested had almost the same dimensions, and all caplets met the requirements for uniformity of content, hardness, disintegration time, and dissolution. Conclusion: Not all of the amoxicillin caplets in the market have a similar dissolution profile to the reference products. Keywords: caplets, amoxicillin, dissolution, similarity factor

Forecasting the ionospheric F2 Parameters over Jeju Station (33.43°N, 126.30°E) by Using Long Short-Term Memory

Ionospheric models aim to simulate and predict variations in the ionosphere. In this study, we attempt to develop a regional ionospheric model to predict hourly the foF2s (peak frequencies of the F2 layer) and the hmF2s (peak heights of the F2 layer) over the Jeju station (33.43°N, 126.30°E) for up to 24 hours by using a deep learning method. For forecasting the F2 parameters, we adopt the method of long short-term memory (LSTM), which, unlike traditional neural networks, can shed light on sequential variation in time-series data. The inputs of the LSTM model are sequential data for the past 24 hours, which includes the sunspot number (SSN), the daily F10.7 solar flux, geomagnetic the Ap and Kp indices, the foF2 and the hmF2. The foF2 and the hmF2 data used to train the model are measured by the Jeju ionosonde, operated by the Korean Space Weather Center (KSWC) during the period from 2011 through 2016. To evaluate our model performance, we utilized the root mean square error (RMSE) and the correlation coefficient (CC) as the performance skill scores between the model prediction and the measurement during the 338 days of 2017–2018. The best foF2 model, having 21 hidden neurons and 3 batch sizes, performed with an RMSE of 0.65 MHz and a CC of 0.92 when compared with the value measured during the next hour. The best hmF2 model, having 41 hidden neurons and 24 batch sizes, preformed with an RMSE of 23.8 km and a CC of 0.80. When the forecasting steps were increased, the performances gradually deteriorated. The LSTM model results were compared with the results of the TIE-GCM and the IRI-2016 model for geomagnetically quiet and active periods. On geomagnetic quiet days, the LSTM model showed the best performance among the three models. When the RMSEs of the foF2 (hmF2) predictions were compared, the percentage improvements of the LSTM model were 45% (30%) or more than those of the other models during geomagnetically quiet days. On geomagnetic storm days, however, the LSTM model did not improve predictions any better than the IRI-2016 model, which may be due to the limited amount of training data under the storm condition.

Nutritive value of Tifton 85 hay ammoniated with urea

The effect of ammonization was evaluated with urea at doses of 1, 2, 3 and 4%, on the basis of dry matter (DM) on Tifton 85 hay harvested at an advanced stage of development in the periods of 30 and 45 days, through analysis of dry matter, ash, ether extract (EE), neutral (NDF) and acid (ADF) detergent fiber, NDF corrected for ash and protein (NDFap), cellulose, lignin, crude protein (CP), acid detergent insoluble nitrogen (ADIN), fractionation of carbohydrates and in vitro gas production (Parameters: V f1 , k 1 , V f2 , k 2 and L). The variables DM, EE, NDF, ADF, lignin, cellulose, NDFap, fraction A + B1, fraction B2 and C of carbohydrates, and the V f1 and V f2 parameters were influenced by treatments (p < 0.05). While DM, NDF, NDFap, fraction A + B1, C, CP and V f2 showed linear effects according to the dose, NIDA and hemicellulose presented quadratic effects. V f1 and V f2 were also influenced by the treatment period. The ammonization with 2.7% urea on the basis of DM promotes improvement of Tifton 85 hay treated for 45 days, observed after derivation of the regression equation and evaluation of the nutritional and kinetic degradation in vitro .

Plasma transport process in the equatorial/low-latitude ionosphere

The behaviour of the equatorial/low-latitude ionosphere and the transport processes during magnetic disturbed and quiet periods of a high solar activity year, 2014, in the American sector are investigated. Parameters used include vertical drift (Vz), transport term (W), NmF2, hmF2 and scale-height (H). The F2 plasma variations followed the diurnal local solar pattern, being higher at daytime. The sunset maximum and sunrise minimum peaks of hmF2 were directly opposite to the scale height (H) pattern. The plasma distribution was basically controlled by combined actions of the electrodynamic convection/thermospheric composition, which is geomagnetic activity dependent. The annual, semi-annual and winter-anomalies of the F2 parameters were higher at the dip equator in comparison with the low-latitude. The Vz pre-reversal peak magnitude coincided with hmF2 peak and the effects are more pronounced during geomagnetic disturbed conditions. The transport term pattern was similar to that of the scale height and it is suggested as a proxy parameter for quantifying low-latitude plasma irregularities and distribution of thermospheric composition.

THE EFFECT OF SINGING TRAINING ON ACOUSTIC PARAMETERS OF VOICE

The aim of the present study is to analyze the impact of singing training on the acoustic properties of students’ voices. The participants of the stuy were 20 students between 19 and 32 without absenteeism ranging from the 1st to the 4th grade. The voices of 12 female and 8 male students, enrolled at Selcuk University Dilek Sabanci State Conservatory Opera Maindepartment, Sub-department of Vocal Arts were recorded throughout 2014-2015 academic year using Shure Sm 48 model microphone in order to determine their acoustic properties using CSL (Computerized Speech Laboratory) 4500 to the computer with Kay Elemetrics MDVP (Multi Dimensional Voice Program). In order to determine changes in the acoustic parameters and evaluate the effectiveness of the singing training given, a single sample -pre and post-test research design was used. Hence, among the acoustic properties, F0, (Fundamental Frequency) F1, F2, F3, F4, F5, formant frequencies, jitter (%), shimmer (%), NHR (Ratio of harmonic noise) parameters were evaluated. The statistical analyses made for the comparison of MDVP parameters before and after the vocal training revealed no statistically significant difference in the students’ F0, Jitter, Shimmer, NHR, F1, F2, F3, and F4 acoustic parameters. However, the F5 formant value revealed statistically significant differences in all the students and a statistically significant difference was seen in the F0 parameter and F5 formant values of female students. Fundamental frequency (F0) is an important parameter changing throughout the singing training process among the female students’ acoustic characteristics. The increase in the F5 formant values of female students and the acoustic properties of all students within normal ranges could be considered as an indicator of the positive impact of the singing training received.

Comparison between manual scaling and Autoscala automatic scaling applied to Sodankylä Geophysical Observatory ionograms

Abstract. This paper presents a comparison between standard ionospheric parameters manually and automatically scaled from ionograms recorded at the high-latitude Sodankylä Geophysical Observatory (SGO, ionosonde SO166, 64.1° geomagnetic latitude), located in the vicinity of the auroral oval. The study is based on 2610 ionograms recorded during the period June–December 2013. The automatic scaling was made by means of the Autoscala software. A few typical examples are shown to outline the method, and statistics are presented regarding the differences between manually and automatically scaled values of F2, F1, E and sporadic E (Es) layer parameters. We draw the conclusions that: 1. The F2 parameters scaled by Autoscala, foF2 and M(3000)F2, are reliable. 2. F1 is identified by Autoscala in significantly fewer cases (about 50 %) than in the manual routine, but if identified the values of foF1 are reliable. 3. Autoscala frequently (30 % of the cases) detects an E layer when the manual scaling process does not. When identified by both methods, the Autoscala E-layer parameters are close to those manually scaled, foE agreeing to within 0.4 MHz. 4. Es and parameters of Es identified by Autoscala are in many cases different from those of the manual scaling. Scaling of Es at auroral latitudes is often a difficult task.

Dissolution Curve Comparisons Through the F2 Parameter, a Bayesian Extension of the f2 Statistic

Dissolution (or in vitro release) studies constitute an important aspect of pharmaceutical drug development. One important use of such studies is for justifying a biowaiver for post-approval changes which requires establishing equivalence between the new and old product. We propose a statistically rigorous modeling approach for this purpose based on the estimation of what we refer to as the F2 parameter, an extension of the commonly used f2 statistic. A Bayesian test procedure is proposed in relation to a set of composite hypotheses that capture the similarity requirement on the absolute mean differences between test and reference dissolution profiles. Several examples are provided to illustrate the application. Results of our simulation study comparing the performance of f2 and the proposed method show that our Bayesian approach is comparable to or in many cases superior to the f2 statistic as a decision rule. Further useful extensions of the method, such as the use of continuous-time dissolution modeling, are considered.

A new global version of M(3000)F2 prediction model based on artificial neural networks

A new version of global empirical model for the ionospheric propagation factor, M(3000)F2 prediction is presented. Artificial neural network (ANN) technique was employed by considering the relevant geophysical input parameters which are known to influence the M(3000)F2 parameter. This new version is an update to the previous neural network based M(3000)F2 global model developed by Oyeyemi et al. (2007), and aims to address the inadequacy of the International Reference Ionosphere (IRI) M(3000)F2 model (the International Radio Consultative Committee (CCIR) M(3000)F2 model). The M(3000)F2 has been found to be relatively inaccurate in representing the diurnal structure of the low latitude region and the equatorial ionosphere. In particular, the existing hmF2 IRI model is unable to reproduce the sharp post-sunset drop in M(3000)F2 values, which correspond to a sharp post-sunset peak in the peak height of the F2 layer, hmF2. Data from 80 ionospheric stations globally, including a good number of stations in the low latitude region were considered for this work. M(3000)F2 hourly values from 1987 to 2008, spanning all periods of low and high solar activity were used for model development and verification process. The ability of the new model to predict the M(3000)F2 parameter especially in the low latitude and equatorial regions, which is known to be problematic for the existing IRI model is demonstrated.

Ouagadougou station F2 layer parameters, yearly and seasonal variations during severe geomagnetic storms generated by coronal mass ejections (CMEs) and fluctuating wind streams

Solar sources of geomagnetic activity are determined by means of (1) Mayaud aa index values from 1868 to now; (2) sudden storm commencement (SSC) dates and (3) pixel diagrams. From 1966 to 1998 that is, during 33 years severe geomagnetic storms characterised by aa > = 100 nT have been identified and their solar sources determined. During these three solar cycles (cycles 20, 21 and 22) the effects of these solar disturbance events on Ouagadougou ionosphere F2 parameters (foF2 and h’F2) variations are studied. Each disturbed F2 parameters morphology variations are computed and shown and after compared to each whole F2 parameters morphology variation. The analysis of whole and disturbed F2 parameter morphologies and their variations gives the main following results: (1) Severe storms are responsible for equinoctial anomaly in foF2; (2) shock activity causes vernal equinoctial asymmetry in foF2 and autumnal equinoctial asymmetry in h’F2; (3) fluctuating wind streams produce autumnal equinoctial asymmetry in foF2 and vernal equinoctial asymmetry in h’F2; (4) Geomagnetic activities produced negative storms from 1966 to 1981 and positive storms from 1981 to 1987; (5) For the seasonal variation we have positive storms all through the year except in April where we observe negative storms. Key words: Coronal mass ejections (CMEs), fluctuating wind streams, equinoctial anomaly, geomagnetic activity.

Evaluation of global modeling of M(3000)F2 and hmF2 based on alternative empirical orthogonal function expansions

Global modeling of M(3000)F2 and hmF2 based on three alternative EOF (empirical orthogonal function) expansion methods is described briefly. Data used for the model construction is the monthly median hourly values of M(3000)F2 from the ionosonde/digisonde stations distributed around the world for the period of 1975–1985 and the hmF2 data of the same period converted from the measured M(3000)F2 based on the strong anti-correlation existing between them. Independent data of a low (1965) and a high (1970) solar activity year are used to validate the three alternative models based on different EOF expansion methods. Comparisons between the modeled results and observed data for both the low (1965) and high (1970) solar activity years showed good agreement for both M(3000)F2 and hmF2 parameters. Statistical analysis on the differences between model values and observed data showed that all the three alternative models (Model A, B and C) based on the different EOF expansion methods have better agreement with the observed data than the models currently used in IRI. All three alternative EOF based models have almost the same accuracy. Discussion on the preference of the three alternative EOF based models is given.