Morphology of GPS and DPS TEC over an equatorial station: validation of IRI and NeQuick 2 models

We investigated total electron content (TEC) at Ilorin (8.50°&thinsp;N 4.65°&thinsp;E, dip lat. 2.95) for the year 2010, a year of low solar activity in 2010 with Rz = 15.8. The investigation involved the use of TEC derived from GPS, estimated TEC from digisonde portable sounder data (DPS), and the International Reference Ionosphere (IRI) and NeQuick 2 (NeQ) models. During the sunrise period, we found that the rate of increase in DPS TEC, IRI TEC, and NeQ TEC was higher compared with GPS TEC. One reason for this can be attributed to an overestimation of plasmaspheric electron content (PEC) contribution in modeled TEC and DPS TEC. A correction factor around the sunrise, where our finding showed a significant percentage deviation between the modeled TEC and GPS TEC, will correct the differences. Our finding revealed that during the daytime when PEC contribution is known to be absent or insignificant, GPS TEC and DPS TEC in April, September, and December predict TEC very well. The lowest discrepancies were observed in May, June, and July (June solstice) between the observed values and all the model values at all hours. There is an overestimation in DPS TEC that could be due to extrapolation error while integrating from the peak electron density of F2 (NmF2) to around  ∼ 1000&thinsp;km in the Ne profile. The underestimation observed in NeQ TEC must have come from the inadequate representation of contribution from PEC on the topside of the NeQ model profile, whereas the exaggeration of PEC contribution in IRI TEC amounts to overestimation in GPS TEC. The excess bite-out observed in DPS TEC and modeled TEC indicates over-prediction of the fountain effect in these models. Therefore, the daytime bite-out observed in these models requires a modifier that could moderate the perceived fountain effect morphology in the models accordingly. The daytime DPS TEC performs better than the daytime IRI TEC and NeQ TEC in all the months. However, the dusk period requires attention due to the highest percentage deviation recorded, especially for the models, in March, November, and December. Seasonally, we found that all the TECs maximize and minimize during the March equinox and June solstice, respectively. Therefore, GPS TEC and modeled TEC reveal the semiannual variations in TEC.</p

Synthesis and crystal structures of zinc(II) coordination polymers of trimethylenedipyridine (tmdp), 4-nitrobenzoic (Hnba) and 4-biphenylcarboxylic acid (Hbiphen) for adsorptive removal of methyl orange from aqueous solution

Two novel Zn(II) coordination polymers (CPs), [Zn(nba)2(tmdp)]n (1) and [Zn(biphen)2(tmdp)]n (2), were synthesised by reacting Zn(NO3)2·6H2O and 4,4′-trimethylenedipyridine (tmdp) with corresponding carboxylates: 4-nitrobenzoic (Hnba) and 4-biphenylcarboxylic acid (Hbiphen). Their structures were characterized by elemental analysis, IR spectroscopy, thermogravimetric analysis (TGA), powder X-ray diffraction (PXRD) and single-crystal X-ray diffraction. Compounds 1 and 2 are one-dimensional CPs with the zinc(II) carboxylate units bridged through the N-donor spacer ligand. The zinc (II) atom adopts a tetrahedral arrangement in 1 and 2 coordinated by two nitrogen atoms from two tmdp ligand molecules and two deprotonated oxygen atoms from two carboxylate ligand molecules. The adsorption capacities of MO in this study was found to be 546.31 mg/g and 22.67 mg/g for 1 and 2, respectively. DFT studies confirmed that adsorption is primarily due to π-π stacking and electrostatic interactions between MO and 1. It is noteworthy that binding energy (BE) values for 1 (-74.14 KJ/mol) and 2 (-61.11 KJ/mol) correlate reasonably well with the observed adsorption capacities of MO. The study demonstrated that 1 has higher adsorption efficiency in comparison to 2 and could be an effective and easily reusable adsorbent for the removal of MO from wastewater

Geomagnetic Field Variations from some Equatorial Electrojet Stations

Abstract.Quiet day variations of the equatorial electrojet along the dip equator from 10 MAGDAS stations show that there could be substantial day to day variability in the electrojet (EEJ) strength. Variations of greater than 80 nT are found in pairs of stations on the same day. The analyses show that the correlation between pairs of stations decreases as a function of increasing distance between them. The results confirm the presence of counter electrojet occurring mainly in the morning and evening hours with strengths of up to 30 nT in certain instances. The data show a longitudinal variability in the EEJ, with results showing strongest EEJ current in the South American sector and weakest in the Malaysian sector

Latitudinal and Seasonal Investigations of Storm-Time TEC Variation

The ionosphere responds markedly and unpredictably to varying magnetospheric energy inputs caused by solar disturbances on the geospace. Knowledge of the impact of the space weather events on the ionosphere is important to assess the environmental effect on the operations of ground- and space-based technologies. Thus, global positioning system (GPS) measurements from the international GNSS service (IGS) database were used to investigate the ionospheric response to 56 geomagnetic storm events at six different latitudes comprising the northern and southern hemispheres in the Afro-European sector. Statistical distributions of total electron content (TEC) response show that during the main phase of the storms, enhancement of TEC is more pronounced in most of the seasons, regardless of the latitude and hemisphere. However, a strong seasonal dependence appears in the TEC response during the recovery phase. Depletion of TEC is majorly observed at the high latitude stations, and its appearance at lower latitudes is seasonally dependent. In summer hemisphere, the depletion of TEC is more pronounced in nearly all the latitudinal bands. In winter hemisphere, enhancement as well as depletion of TEC is observed over the high latitude, while enhancement is majorly observed over the mid and low latitudes. In equinoxes, the storm-time TEC distribution shows a fairly consistent characteristic with the summer distribution, particularly in the northern hemisphere

Pattern of Ionization Gradient, Solar Quiet Magnetic Element, and F2-Layer Bottomside Thickness Parameter at African Equatorial Location

The study of ionization gradient (dN/dh) profile in the description of ionospheric dynamics is not common. This is the first attempt at finding the dependence of ionization gradient, solar quiet component (Sq (BH)), and bottomside thickness parameter (B0) in the African equatorial sector. Digisonde and Magnetic Data Acquisition System data collocated at an equatorial location were employed. Result was presented for sunrise (00 LT), midday (12 LT), sunset (18 LT), and midnight (00 LT) hours. The ionization gradient peak height remains unchanged at midday across all months. A percentage correlation of 93% existed in the inverse and direct linear relationship of dN/dh‐B0 at sunrise, and of Sq (BH)‐B0 at midday, respectively. Significant relationship between dN/dh and Sq (BH) was at sunset; for other hours, the relationship is poor. The multiple linear relationship of dN/dh‐Sq (BH)‐B0 parameters revealed that the dependence of dN/dh on Sq (BH) and B0 is highest at midday, and a model equation was presented. The dependence of dN/dh on the solar activity index (F10.7) holds at all the selected hours, and distinct only at midday and midnight for the Sq (BH)‐F10.7 and B0‐F10.7 patterns. Both the peak ionization gradient and the height it occurs maximizes/minimizes at 18 LT/06 LT. The importance of the F region dynamo at heights above 150 km was reported

Synthesis, structural and DFT investigation of Zn(nba) 2 (meim) 2 for adsorptive removal of eosin yellow dye from aqueous solution

A novel Zn(II) mixed‐ligand complex, Zn(nba)2(meim)2 (1), synthesized from Zn(NO3)2.6H2O, nitrobenzoic acid (Hnba) and 1‐methylimidazole (meim) is reported. The complex was characterized by elemental analysis, FT‐IR, powder and single crystal X‐ray crystallography and TGA/DSC. 1 exhibits a tetrahedral geometry for Zn(II), which is coordinated to two carboxylate oxygen atoms from two nba anions and two imidazole nitrogen atoms from two meim molecules. Thermal analysis shows the stability of 1 up to 260 °C. The adsorption of eosin yellow (EY) dye on 1 was investigated. The adsorption capacity of 1 for EY amounted to 65.32 mg/g, fitting best into Langmuir isotherm and pseudo second order kinetic models. From DFT studies, it was determined that adsorption is predominantly due to electrostatic, hydrogen bonding and π‐π interactions

Synthesis, structural and DFT investigation of Zn(nba)2(meim)2 for adsorptive removal of eosin yellow dye from aqueous solution

A novel Zn(II) mixed-ligand complex, Zn(nba)2(meim)2 (1), synthesized from Zn(NO3)2.6H2O, nitrobenzoic acid (Hnba) and 1-methylimidazole (meim) is reported. The complex was characterized by elemental analysis, FT-IR, powder and single crystal X-ray crystallography and TGA/DSC. 1 exhibits a tetrahedral geometry for Zn(II), which is coordinated to two carboxylate oxygen atoms from two nba anions and two imidazole nitrogen atoms from two meim molecules. Thermal analysis shows the stability of 1 up to 260°C. The adsorption of eosin yellow (EY) dye on 1 was investigated. The adsorption capacity of 1 for EY amounted to 65.32 mg/g, fitting best into Langmuir isotherm and pseudo second order kinetic models. From DFT studies, it was determined that adsorption is predominantly due to electrostatic, hydrogen bonding and π-π interactions