Declination Angle Research Articles

Design and Analysis of Solar Dryer for Mid-Latitude Region

In this study, an indirect natural convection updraft solar dryer was designed and fabricated with objectives to; suit mid-latitude applications, determine its performance efficiency, analyze air properties by use of psychrometric chart and assess the quality of dried product. The dryer was fabricated using low cost and locally available materials. For mid-latitude regions, zenith angle is dependent on latitude, solar declination angle, time of the year and of the day. Based on these changing parameters, the solar dryer was designed to suit the conditions. The main parts of the dryer are; hinged flexible angled solar collector, drying chamber consisting of three drying trays, updraft chimney with metallic absorber plate. The experiments were carried out to dry sliced apples of 2.5 mm thickness spread over the drying trays. Temperature and relative humidity of airflow were taken at the collector inlet, drying chamber inlet and drying chamber outlet to chimney using data loggers. Airflow inlet to solar collector and from drying chamber was determined using hot wire anemometers, irradiation in W/m2 was measured by radiation meter. Drying characteristics such as the collected solar energy to evaporated moisture, average drying rate, moisture content, etc., were determined. Natural convectional flow was adopted with an advantage of utilizing updraft air chimney to induce thermo-siphoning effect hence improving efficiency. In our current study, fresh apples of 886.64 grams with moisture content of 86% were dried to moisture content of 8.12% (wet basis) within 9 hours 20 minutes at an average irradiance of 534.45W/m2. The overall dryer efficiency was estimated to be 17.89%. The possibility of formation of water droplets within the drying chamber, which is a challenge to most direct solar dryers was considered to be minimal. This was based on analysis of the dew-point of drying chamber inlet air in comparison to outlet air properties. This design is simple; it can easily be replicated elsewhere in the world, products can be dried in one day and has capability to dry products at commercial scale while retaining the color, flavor and nutrients.

Equatorial E region electric fields at the dip equator: 1. Variabilities in eastern Brazil and Peru

AbstractThe equatorial electrojet (EEJ) is an intense eastward ionospheric electric current centered at about 105 km of altitude along the dip equator, set up by the global neutral wind dynamo that generates the eastward zonal (Ey) and the daytime vertical (Ez) electric fields. The temporal variation of the EEJ is believed to be well understood. However, the longitudinal variability of the Ey and Ez between 100 and 110 km is still quite scarce. Due to their importance overall phenomenology of the equatorial ionosphere, we investigate the variabilities of the Ey and Ez inferred from measurements of the Doppler frequency of Type II echoes provided by coherent backscatter radars installed in locations close to the magnetic equator in the eastern Brazil (2.33°S, 44.20°W) and Peru (11.95°S, 76.87°W). This study is based on long‐term (609 days for both systems) radar soundings collected from 2001 to 2010. The variabilities of the electric fields are studied in terms of the position of the soundings with respect to the dip equator and the magnetic declination angle. Among the results, Ey and Ez show longitudinal dependence, being higher in Peru than east Brazil. Under quiet geomagnetic activity, the mean diurnal variations of Ey ranged from 0.21 to 0.35 mV/m between 8 and 18 h (LT) in Brazil and from 0.23 mV/m to 0.45 mV/m in Peru, while the mean diurnal variations of the Ez ranges from 7.09 to 8.80 mV/m in Brazil and from 9.00 to 11.18 mV/m in Peru.

Abrasives for water-jet cutting of high-strength and thick hard materials

The paper discusses abrasive water-jet cutting of hard-to-cut materials represented by high carbon steel DIN norm No.1.2436 (CSN EN 19437) plate 61–mm-thick and high-strength concrete cube sized 150 mm. Four relatively hard minerals with different densities not commonly used in water-jet technology were tested and their cutting results compared to those of three types of almandine garnets: Ukraine, Australian, and sorted Australian. Cutting efficiency was evaluated utilizing declination angle. Dependence of cutting efficiency on abrasive density and hardness was investigated. High density of abrasive appeared to be disadvantageous in our experiment. Cutting efficiency dependence on hardness exhibited nearly linear course, the increase was much more significant for concrete than for steel. Evaluation of experimental results led to the conclusion that cutting mechanism in case of very thick samples is different from common abrasive waterjet cutting. The limit declination angle for thick samples is significantly smaller, it was found to be approximately 22°. This result represents entirely new finding. The most promising finding from the economical point of view appears to be behavior of corundum, when cutting concrete. Our experimental results promise 20 % increase in cutting speed for brittle materials.

Local material removal model considering the tool posture in deterministic polishing

Polishing process is the final step for the fabrication of optical surfaces. This paper presents a theoretical and experimental investigation on the removal of material from a surface during the polishing process. The model in this paper assumes that the material removal rate follows Preston equation and the pressure distribution at the contact area is Hertzian. Particularly, the effect of the tool posture, which is described by the inclination angle and declination angle, upon the local material removal profile is modeled and analyzed. On the basis of the analysis, a novel method is proposed to optimize the tool angles. A series of polishing experiments were conducted to verify the effectiveness of the proposed model. The theoretical and experimental results indicate that (1) the inclination angle has large effect on the local removal depth, and (2) the location of the maximum removal depth bias away from the center of the profile and the direction of this bias is determined by the declination angle. The model in this paper is potentially useful for the planning of the polishing posture and the tool path during the polishing process.

Comparison of Radiographic Outcomes Between Dynamic Medial Column Stabilization and Lateral Column Lengthening

Category: Midfoot/Forefoot Introduction/Purpose: Lateral column lengthening (LCL) has been recognized as a most effective surgical treatment for flexible flatfoot. But the LCL is known to be associated with many complications, which are lateral foot pain or calcaneocuboid arthrosis. In order to correct flexible flatfoot without these complications, we have developed a novel technique-dynamic medial column stabilization (dynamic-MCS). The dynamic-MCS consists of flexor hallucis longus transfer to the medial cuneiform, arthrodesis of first tarsometatarsal joint and medial displacement calcaneal osteotomy. The dynamic-MCS had different mechanism from the LCL. The dynamic-MCS directly restores longitudinal arch of flexible flatfoot, while the LCL indirectly restores the longitudinal arch. The purpose of this study is to investigate difference of radiographic outcomes between the dynamic-MCS and the LCL. Methods: Dynamic-MCS group included 16 flexible flatfeet of 16 patients which were treated with the dynamic-MCS from January 2014 to February 2015. The LCL group included 23 flexible flatfeet of 21 patients which were treated with the LCL from January 2011 to January 2014. A single surgeon performed the dynamic-MCS and the LCL in our clinic. We retrospectively evaluated radiological outcomes of the dynamic-MCS group and the LCL group. The preoperative and postoperative radiographic parameters were measured. Talonavicular coverage angle was measured on plain weight-bearing anteroposterior radiograph. Calcaneal pitch, talocalcaneal angle, talar angle, meary angle and 1st metatarsal declination angle were measured on plain weight- bearing lateral radiograph. Hindfoot alignment angle was measured on hindfoot alignment view. We compared postoperative improvements of the dynamic-MCS group with those of the LCL group in each radiographic parameters. All the postoperative values were obtained at the last follow-up. Results: The average age in the dynamic-MCS group was 41 years (95% CI: 33.5-47.9) and mean follow-up period was 12.9 months (minimum 10months). The average age in the LCL group was 36 years (95% CI: 27.9-43.1) and mean follow-up period was 22.2 months (minimum 12 months). The talonavicular coverage angle (P=0.002) and calcaneal pitch (P=0.002) of the LCL group showed significant higher improvement than that of the dynamic-MCS group. The talocalcaneal angle (P=0.030) and hindfoot alignment angle (P=0.005) of the dynamic-MCS group showed significant higher improvement than that of the LCL group. The improvement of the other radiographic parameters showed no significant difference between the dynamic-MCS group and the LCL group (Fig 1-B). Conclusion: Radiographic outcomes between the dynamic-MCS and the LCL were different for flatfoot correction in this study. The LCL showed higher correction of forefoot abduction than the dynamic-MCS. The dynamic-MCS showed higher correction of heel valgus than the LCL. Correction of flat longitudinal arch was not different between the dynamic-MCS and the LCL. To restore the flat longitudinal arch,the dynamic-MCS corrected the plantar-flexed talus and the LCL corrected the low calcaneal pitch. Lateral plantar pain and calcaneocuboid arthrosis did not occurred after the dynamic-MCS in our experience. We concluded that the dynamic-MCS could be a good treatment option for flexible flatfoot.

Degradation nonuniformity in the solar diffuser bidirectional reflectance distribution function.

The assumption of angular dependence stability of the solar diffuser (SD) throughout degradation is critical to the on-orbit calibration of the reflective solar bands (RSBs) in many satellite sensors. Recent evidence has pointed to the contrary, and in this work, we present a thorough investigative effort into the angular dependence of the SD degradation for the Visible Infrared Imaging Radiometer Suite (VIIRS) onboard the Suomi National Polar-orbiting Partnership (SNPP) satellite and for the twin Moderate-resolution Imaging Spectroradiometer (MODIS) onboard Terra and Aqua spacecrafts. One common key step in the RSB calibration is the use of the SD degradation performance measured by an accompanying solar diffuser stability monitor (SDSM) as a valid substitute for the SD degradation factor in the direction of the RSB view. If SD degradations between these two respective directions do not maintain the same relative relationship over time, then the unmitigated use of the SDSM-measured SD degradation factor in the RSB calibration calculation will generate bias, and consequently, long-term drift in derived science products. We exploit the available history of the on-orbit calibration events to examine the response of the SDSM and the RSB detectors to the incident illumination reflecting off SD versus solar declination angle and show that the angular dependency, particularly at short wavelengths, evolves with respect to time. The generalized and the decisive conclusion is that the bidirectional reflectance distribution function (BRDF) of the SD degrades nonuniformly with respect to both incident and outgoing directions. Thus, the SDSM-based measurements provide SD degradation factors that are biased relative to the RSB view direction with respect to the SD. The analysis also reveals additional interesting phenomena, for example, the sharp behavioral change in the evolving angular dependence observed in Terra MODIS and SNPP VIIRS. For SNPP VIIRS the mitigation for this "SD degradation nonuniformity effect" with respect to angles relies on a "hybrid methodology" using lunar-based calibration to set the reliable long-term baseline. For MODIS, the use of earth targets in the major release Collection 6 to improve calibration coefficients and time-dependent response-versus-scan-angle characterization inherently averts the use of SD and its associated issues. The work further supports that having an open-close operational capability for the space view door can minimize SD degradation and its associated effects due to solar exposure, and thus provide long-term benefits for maintaining calibration and science data accuracy.

Innovative system for energy collection and management integrated within a photovoltaic module

The dynamic development of battery technology and design based on the flow of lithium ions, mainly driven by the needs of the automotive industry, leads to the conclusion that these batteries are becoming a more viable alternative to traditional lead-acid batteries. Their use is driven by the ability to quickly charge and discharge, a higher durability, maintenance-free operation, much smaller dimensions and lighter weight. The emergence of super-thin LiFePO4 battery technology became an inspiration for the design and implementation of a prototype of a portable photovoltaic module that is integrated with the battery and innovative system for gathering and power management. This paper presents a block diagram of a prototype and discusses issues related to the selection of components, design and implementation of individual blocks. In particular, it considers an innovative system that quickly and accurately supports the elevation and declination angle of the module and the system for monitoring the state of battery charge and discharge.Basic technical parameters are described, as well as the possibility of scaling up the system. Mechanical construction details and the concept of research stations and the results obtained during research were presented. An analysis of the application areas and economic aspects of the solution were also taken into consideration.

Numerical and analytical approach for the spin-stabilized satellite attitude propagation

This paper presents the comparison between the numerical and analytical results of a spacecraft attitude propagation for a spin-stabilized satellite. Some external torques are introduced in the equations of the motion and the comparisons are done considering that these torques are acting together, which are: gravity gradient, aerodynamic, solar radiation, magnetic residual and eddy current. In the numerical approach it is used the quaternion to represent the attitude. This numerical approach can be applied for any kind of satellite. The analytical approach is applied directly for a spin-stabilized satellite and the equations of motion are described in terms of the spin velocity, spin axis right ascension and declination angles. An analytical solution of these equations is presented and valid for one orbit period. Applications are developed considering the Brazilian spin-stabilized satellites SCD1 and SCD2. The comparisons are important to validate some simplifications that are required in the analytical approach. The results show that the average components of the external torque are sufficient to observe the main influence of the considered torques.

Correlation of Global Solar Radiation of Eight Synoptic Stations in Burkina Faso Based on Linear and Multiple Linear Regression Methods

We utilize the multiple linear regression method to analyse meteorological data for eight cities in Burkina Faso. A correlation between the monthly mean daily global solar radiation on a horizontal surface and five meteorological and geographical parameters, which are the mean daily extraterrestrial solar radiation intensity, the average daily ratio of sunshine duration, the mean daily relative humidity, the mean daily maximum air temperature, and the sine of the solar declination angle, was examined. A second correlation is established for the entire country, using, this time, the monthly mean global solar radiation on a horizontal surface and the following climatic variables: the average daily ratio of sunshine duration, the latitude, and the longitude. The results show that the coefficients of correlation vary between 0.96 and 0.99 depending on the station while the relative errors spread between −3.16% (Pô) and 3.65% (Dédougou). The maximum value of the RMSD which is 312.36 kJ/m2 is obtained at Dori, which receives the strongest radiation. For the entire cities, the values of the MBD are found to be in the acceptable margin.

Factors Affecting Solar Photovoltaic Power Output at Particular Location and Cost Estimation

Fossil fuels like coal, gas, diesel etc., used for generate electrical energy are in exhaust stage and causes pollution. This necessitates alternative sources of fuels which are renewable and non-pollutant like wind, solar, tidal to generate electrical energy. These renewable fuels cannot be supplied to generate power as required like conventional fuels, as they are naturally available and depends on environmental conditions. Hence they have to be efficiently utilized when they are available. Solar energy is the electromagnetic waves in the form of light which contains packets of energy known as photons. These photons produce electrical energy by the process known photovoltaic effect. In this paper studies are made to utilization of solar energy to produce electrical energy, for this sun-earth angular relation was found using declination angle of earth based on day number, azimuth angle, altitude angle, angle of incidence for particular location i.e., Andhra university, Visakhapatnam with latitude 17.680° N and longitude 83.320° E. Collecting radiation data for the consider site and calculating actual radiation on tilt surface by applying correction to the data collected. Simulation of solar photovoltaic panel using five parameter model of cell considering top Indian manufactured Solar Panels and estimating output DC power by using location Radiation, temperature and wind as input. Comparing output of simulation with on-line simulators like PV watts and off-line software’s SAM, PVs yst. Second part of this paper is estimation of installation cost of solar power plant, cost of generations, Performance ratio, Capacity utilization Factor, LCOE, return of investment, comparing with conventional utility rates.

AWJ cutting of copper processed by ECAP

Copper samples, processed by equal channel angular pressing (ECAP), were cut using abrasive water jet (AWJ) and the cut walls were investigated. The aim was to prove a relation between AWJ declination angle and selected material properties, especially hardness, strength, and grain size. Three groups of samples were cut: the first one just after pressing (fresh samples), the second one after 1 month past ECAP application, and the third one after 6 months after ECAP processing. The comparison shows the following results. Just after the ECAP process, the declination angle increases with increasing number of passes through the ECAP die, i.e., the characteristic material properties (strength and hardness) increase throughout the tested angle range. The character of relations between number of passes and investigated parameters, such as declination angle, hardness, or strength, is parabolic for 1-month-old samples, with maximum around eight ECAP passes. The last group of samples, cut after 6 months after their preparation, does not indicate simple relations between number of ECAP passes and either the declination angle or material parameters, namely hardness. The mutual comparison of a theoretical model based on values of material properties from measurements and literature and experiment shows maximum relative uncertainty 5.9 %. This result proves that declination angle measurement on striations present on cut walls of AWJ can be used for evaluation of hardness, strength, and grain size.

Pulling out all the stops to make the distance: Effects of effort and optical information in distance perception responses made by rope pulling.

Human observers perceive distance in remarkably stable and consistent manner across response methods and experimental paradigms. Most empirical work on the problem focused exclusively on geometrical variables, such as angle of declination below the horizon (Ooi, Wu, & He, 2001), with more recent considerations of nonvisual factors, such as effort (Proffitt, 2006). Hajnal, Bunch, and Kelty-Stephen (2014) showed that in addition to the object's physical angle of declination below the horizon, nonvisual variables related to effort were utilized when making distance estimates to objects placed on a sloped ramp. In that experiment, the horizontal ground surface was visible in the background when viewing objects placed on the sloped surface. To further investigate the joint utility of geometric and effort-based variables, we tested the effect of both classes of predictors on a natural hillside where a flat, horizontal surface was not visible in the background. This setup allowed us to evaluate whether observers rely on the same information to perceive distance on ramps versus real hills. The present research implicates the hypothesis that perceived effort and the geometry of space determine distance perception through interactions across multiple temporal scales of perceptual competence.

Minimum Number of Observation Points for LEO Satellite Orbit Estimation by OWL Network

By using the Optical Wide-field Patrol (OWL) network developed by the Korea Astronomy and Space Science Institute (KASI) we generated the right ascension and declination angle data from optical observation of Low Earth Orbit (LEO) satellites. We performed an analysis to verify the optimum number of observations needed per arc for successful estimation of orbit. The currently functioning OWL observatories are located in Daejeon (South Korea), Songino (Mongolia), and Oukaimeden (Morocco). The Daejeon Observatory is functioning as a test bed. In this study, the observed targets were Gravity Probe B, COSMOS 1455, COSMOS 1726, COSMOS 2428, SEASAT 1, ATV-5, and CryoSat-2 (all in LEO). These satellites were observed from the test bed and the Songino Observatory of the OWL network during 21 nights in 2014 and 2015. After we estimated the orbit from systematically selected sets of observation points (20, 50, 100, and 150) for each pass, we compared the difference between the orbit estimates for each case, and the Two Line Element set (TLE) from the Joint Space Operation Center (JSpOC). Then, we determined the average of the difference and selected the optimal observation points by comparing the average values.

Dynamic stability analysis of single walled carbon nanocone conveying fluid

This report aims the study of dynamic stability of single walled carbon nanocone for some axial length conditions and declination angles of 60°, 120° and 240°. For dynamic stability analysis of Single Walled Carbon Nanocone (SWCNC), the mode shapes and frequencies of the carbon nanocone are extracted using the molecular mechanics approach. The mechanical properties of SWCNC were obtained by the Molecular Mechanics (MM) method. The obtained parameters are used for extraction of the conical shell virtual model of nanocone with the same dimensions. The equations of coupled fluid-structural dynamics of SWCNC are derived using the modal expansion for the structural displacements of the conical shell. In addition, for a velocity field, dimensionless frequencies were drawn according to the dimensionless velocities and critical dimensionless velocity of the fluid was obtained at the first mode of dynamics instability. For validation of these results, one test case is selected and a good agreement is found between the obtained carbon nanotube results using shell-like model and those reported in the literature. Using the developed model, the dimensionless divergence velocities were drawn according to the axial length of carbon nanocone for declination angles of 60° and 240°.

Influence of the external torques in the angle between the spin axis and the Sun direction for spin stabilized satellite

The goal of this paper is the study of the influence of the environmental torques in the angle between the spin axis and the Sun direction (solar aspect angle) for spin stabilized satellite. The theory uses a cylindrical satellite in an illumined orbit, considering the gravity gradient, aerodynamic, solar radiation, residual magnetic and eddy current torques. The mathematic model for each torque is shown. The dynamic equations are represented in a reference system fixed in the satellite and described by spin velocity and the right ascension and declination angles of the spin axis. An analytical solution for the spin velocity and the attitude angles is used to study the behavior of the solar aspect angle. The theory is applied for the real data of the Brazilian Satellite of Data Collection - SCD1 and SCD2. Two approaches are presented. The results agree with the real satellite behavior for specific time simulation. Then the theory has consistency and can be applied to predict the behavior of the solar aspect angle.

Calibration Device Development for Spherical Solar Radiation Sensors

Measuring the solar radiation received by a plant canopy is necessary to analyze its physiological aspects. A spherical photodiode has been developed for this purpose. However, a horizontally set calibrated solarimeter using a flat type sensor cannot be used for calibration because it must remain unaffected by the cosine law. Therefore, an inexpensive automatic tracking solar disk system has been developed for the calibration of a spherical type solarimeter. A calibrated solarimeter was mounted on the tracking system and was inclined according to the altitude and the declination angle of the location on the day of the experiment. The system calibrated all four spherical solarimeters with high correlation coefficients . Some data exceed the so-called solar constant, which is measured similarly, but outside of the earth atmospheric layer because the device developed this time measured hemispherical solar radiation normal to the sun disk. Similar data were reported even from horizontal measurements.

Descriptive Quantitative Analysis of Rearfoot Alignment Radiographic Parameters

Although the radiographic parameters of the transverse talocalcaneal angle (tTCA), calcaneocuboid angle (CCA), talar head uncovering (THU), calcaneal inclination angle (CIA), talar declination angle (TDA), lateral talar–first metatarsal angle (lTFA), and lateral talocalcaneal angle (lTCA) form the basis of the preoperative evaluation and procedure selection for pes planovalgus deformity, the so-called normal values of these measurements are not well-established. The objectives of the present study were to retrospectively evaluate the descriptive statistics of these radiographic parameters (tTCA, CCA, THU, CIA, TDA, lTFA, and lTCA) in a large population, and, second, to determine an objective basis for defining “normal” versus “abnormal” measurements. As a secondary outcome, the relationship of these variables to the body mass index was assessed. Anteroposterior and lateral foot radiographs from 250 consecutive patients without a history of previous foot and ankle surgery and/or trauma were evaluated. The results revealed a mean measurement of 24.12°, 13.20°, 74.32%, 16.41°, 26.64°, 8.37°, and 43.41° for the tTCA, CCA, THU, CIA, TDA, lTFA, and lTCA, respectively. These were generally in line with the reported historical normal values. Descriptive statistical analysis demonstrated that the tTCA, THU, and TDA met the standards to be considered normally distributed but that the CCA, CIA, lTFA, and lTCA demonstrated data characteristics of both parametric and nonparametric distributions. Furthermore, only the CIA (R = −0.2428) and lTCA (R = −0.2449) demonstrated substantial correlation with the body mass index. No differentiations in deformity progression were observed when the radiographic parameters were plotted against each other to lead to a quantitative basis for defining “normal” versus “abnormal” measurements.

Isolated Subtalar Distraction Arthrodesis Using Porous Tantalum: A Pilot Study.

During reconstructive procedures of the hindfoot, a structural graft is often needed to fill gaps. To eliminate donor site morbidity and limited availability of autografts, porous tantalum was used. Eighteen patients who underwent subtalar joint distraction arthrodesis by means of trabecular metal augment were reviewed retrospectively. The results were evaluated clinically, with the American Orthopaedic Foot & Ankle Society (AOFAS) score and the visual analog scale (VAS) for pain, and were assessed radiologically. The mean follow-up period was 18 months. Computed tomography showed sound fusion. There was a marked increase in AOFAS scores and a decrease in VAS scores. Arthrodesis was achieved in all cases with no major postoperative complications. Radiographically, there was a marked increase in all measured parameters (talocalcaneal angle, talocalcaneal height, talar declination angle), and the intraoperatively achieved correction was maintained at the last follow-up visit. Our data suggest that porous tantalum may be used as a structural graft option for subtalar arthrodesis. Level IV, retrospective case series.

Field‐aligned neutral wind bias correction scheme for global ionospheric modeling at midlatitudes by assimilating FORMOSAT‐3/COSMIC hmF2 data under geomagnetically quiet conditions

AbstractThis study demonstrates the usage of a data assimilation procedure, which ingests the FORMOSAT‐3/COSMIC (F3/C) hmF2 observations to correct the model wind biases to enhance the capability of the new global Ionosphere Plasmasphere Electrodynamics (IPE) model under geomagnetically quiet conditions. The IPE model is built upon the field line interhemispheric plasma model with a realistic geomagnetic field model and empirical model drivers. The hmF2 observed by the F3/C radio occultation technique is utilized to adjust global thermospheric field‐aligned neutral winds (i.e., a component of the thermospheric neutral wind parallel to the magnetic field) at midlatitudes according to a linear relationship between time differentials of the field‐aligned wind and hmF2. The adjusted winds are further applied to drive the IPE model. The comparison of the modeled electron density with the observations of F3/C and ground‐based GPS receivers at the 2012 March equinox suggests that the modeled electron density can be significantly improved in the midlatitude regions of the Southern Hemisphere, if the wind correction scheme is applied. Moreover, the F3/C observation, the IPE model, and the wind bias correction scheme are applied to study the 2012 Southern Hemisphere Midlatitude Summer Nighttime Anomaly (southern MSNA)/Weddell Sea Anomaly (WSA) event at December solstice for examining the role of the neutral winds in controlling the longitudinal variation of the southern MSNA/WSA behavior. With the help of the wind bias correction scheme, the IPE model better tracks the F3/C‐observed eastward movement of the southern MSNA/WSA feature. The apparent eastward movement of the southern MSNA/WSA features in the local time coordinate is primarily caused by the longitudinal variation in the declination angle of the geomagnetic field that controls the field‐aligned projection of both geographic meridional and zonal components of the neutral wind. Both the IPE simulations and the F3/C observations show the significant longitudinal variation in the speed of the eastward movement of the southern MSNA/WSA.

Role of neutral wind in the performance of artificial neural‐network based TEC models at diverse longitudes in the low latitudes

AbstractThe equatorial ionosphere is characterized by (i) large values of total electron content (TEC) and sharp latitudinal gradients of TEC, (ii) steep temporal variation of TEC, (iii) large diurnal variation of TEC, and (iv) postsunset secondary enhancement of TEC. These features cause major limitations in the accuracy of standard ionospheric TEC models in this region. Three artificial neural‐network (ANN) based models have been developed based on real‐time low‐latitude TEC data along 77°E, 88°E, and 121°E longitudes in the region between the magnetic equator and locations beyond the northern crest of equatorial ionization anomaly to predict the vertical TEC values. ANN models have shown more accurate predictions than other standard ionospheric TEC models like International Reference Ionosphere, Parameterized Ionospheric Model, and NeQuick. The effects of the neutral wind in the variation of TEC are significant and have been incorporated as inputs to these ANN models. The outputs with neutral wind incorporated shows better correspondence with measured TEC than the models without neutral wind inputs. The longitudinally separated models have been used to find any longitudinal differences in TEC along equatorial regions. The causes behind the longitudinal differences in TEC and its diurnal variations in these regions have been explained in terms of the geomagnetic declination and inclination angles along with the role of zonal wind.