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Stable Auroral Red (SAR) arcs are enhanced OI 630.0 nm emissions formed due to an increased electron temperature (Te) near the equatorward wall of mid‐latitude trough during geomagnetic disturbances. The Te enhancement associated with SAR arcs is driven by electron heating through heat flux precipitation from near plasmapause region to ionospheric F‐region via heat conduction. Although Te enhancements have been reported by radar/satellite measurements along with increased 630.0 nm brightness during SAR arc events, measurements of corresponding heat flux are sparse, and almost none in the daytime. This work presents the results on the estimation of electron heat flux incident during SAR arcs formed during daytime obtained by a comprehensive suite of measurements, and forward modeling. We present observations of several SAR arc events when the ground‐based OI 630.0 nm emissions were larger than the model values during disturbed periods and were found to be existing in conjunction with increased Te at the altitude of DMSP (∼840 km). Forward modeling was carried out to determine the values of Te that would cause an enhancement in these emissions during daytime at much lower altitudes (∼400–500 km). These values of Te were used to estimate the required electron heat flux varying in the range of ∼1.0–4.6 × 1010 eV‐cm−2‐s−1. These results present the first estimates of F‐region heat flux enabled using ground‐based OI 630.0 nm emissions and open a new approach in the investigations of energy released into the ionosphere through heat conduction for daytime conditions during geomagnetically disturbed periods. Plain Language Summary: Stable Auroral Red (SAR) arcs are atomic oxygen redline (630.0 nm) emissions observed in the mid‐latitude ionosphere. These are optical manifestations of direct energy transfer from high‐altitude regions of inner‐magnetosphere to the ionospheric altitudes. The process of energy transfer occurs in the form of electron heat flux or soft particle precipitation (<10 eV) along closed geomagnetic field lines. Downward heat flux increases the ambient electron temperature in the topside ionosphere, which contributes in imparting energy to the Oxygen atoms and exciting them to higher energy states. The return of excited atoms to ground‐state results in the formation of SAR arcs. Although the electron temperature can be measured at high‐altitudes by satellites during SAR arc events, the corresponding electron heat flux cannot be measured directly using existing experimental space plasma techniques. Therefore, model calculations are preferred. Important to this study is the estimation of required heat flux that caused enhancements in the measured daytime redline emissions from the ground, which were beyond the model estimates. This study finds the daytime energy flux required for producing SAR arcs is larger than that for the nighttime SAR arcs. Such findings are being reported for the first time. Key Points: Enhancements were observed in daytime O(1D) red‐line emissions during geomagnetically disturbed days over Boston, a mid‐latitude locationDirect measurement of electron temperature (Te) by DMSP showed increased brightness accompanied by increased Te at mid‐latitudesThe downward heat flux associated with larger Te in the daytime using O(1D) emissions has been obtained for the first time [ABSTRACT FROM AUTHOR]

An atmospheric‐pressure plasma system is developed and is used to treat carbon nanotube assemblies, producing a hybrid carbon‐zinc structure. This system is integrated into a floating‐catalyst chemical vapor deposition furnace used for the synthesis of macroscopic assemblies of carbon nanotubes to allow for the in‐line, continuous, and single‐step production of nano‐composite materials. Material is deposited from a sacrificial zinc wire in the form of nanoparticles and can coat the surface of the individual carbon nanotubes as they form. Additionally, it is found that the deposited materials penetrate further into the carbon nanotube matrix than a comparable post‐synthesis deposition, improving the uniformity of the material through the thickness. Thus, a single‐step metal‐based coating and carbon nanotube synthesis process which can form the basis of production scale manufacturing of metal‐carbon nanotube composite materials with an atmospheric‐pressure plasma system are demonstrated. [ABSTRACT FROM AUTHOR]

The mid‐latitude upper atmosphere is directly affected by the inner magnetosphere through the interactions at the closed geomagnetic field line boundary. Several space weather phenomena associated with magnetospheric‐plasmaspheric exchanges can be mapped to mid‐latitudes. One such phenomena that occurs over mid‐latitudes during geomagnetic storms is the storm enhanced density (SED). So far, storm time ionospheric features have been studied primarily using radar, GPS and in situ measurements. We present high spectral resolution ground‐based measurements of OI 630.0 nm dayglow emissions obtained from Boston to investigate thermospheric behavior during both geomagnetic quiet and disturbed times, as these are very sensitive to changes in the ionospheric plasma temperatures, and densities. During a geomagnetic storm on 7–9 Nov 2004 (Kp = 9‐), an anomalous enhancement in brightness (>1 kR) was observed in the dayglow for about an hour duration near local sunset (dusk hours), which was not seen on other neighboring days. This enhancement in OI 630.0 nm dayglow observed on 9 Nov 2004 is confirmed to be a SED event as seen from the complimentary datasets, the Millstone Hill incoherent scatter radar (ISR), Defence Meteorological Satellite Program satellite and GPS total electron content. Further, model estimates of OI 630.0 nm dayglow intensities using ISR measured electron/ion temperature and electron densities as inputs show good agreement with our measurements. These results make this study possibly the first report on the daytime optical signatures of SED. Key Points: Anomalous enhancement in OI 630.0 nm dayglow emissions was observed during superstorm over mid‐latitude location, BostonThis enhanced dayglow intensity is in simultaneity with increased electron density possibly making it the first daytime storm enhanced density (SED) observationsModel estimates show the peak emission altitude of dayglow emission shifted to higher altitudes during the SED observation duration [ABSTRACT FROM AUTHOR]

Airglow emissions serve as good tracers of the altitudinal regions at which they originate. OI 630 nm (red line) nocturnal emissions originate from around 250 km altitude. A total of 142 nights of data corresponding to the months of January, February, and March in the years 2013, 2014, and 2016, obtained from Mt. Abu (24.6°N, 72.7°E, 16°N Mag), Gurushikhar, India, a low‐latitude location, are investigated. These are compared with the column integrated emission rates calculated using, as inputs, the measured electron density profiles obtained from a digisonde from Ahmedabad (AMD, 23.0°N, 72.6°E, 15°N Mag), India. Following the expected monotonic decrement in the emissions after sunset, an enhancement is observed on several nights that peaks at around 20–21 local time (LT). The cause for this enhancement has been investigated in detail and it is found that the neutral winds, as obtained using digisondes at two locations, show almost a very good correlation between a poleward directed wind or cessation of equatorward wind over AMD and the observed airglow emission enhancement in the post‐sunset time. Further, the percentage enhancement in emissions also shows a decrease in magnitudes from January to March which has a broad similarity to the decrease in the model climatological meridional wind magnitudes in the same duration. Based on the data spanning over different years, it is inferred that, during geomagnetic quiet periods, almost all of the nocturnal variability in OI 630 nm emissions is due to the variations in the neutral wind. Plain Language Summary: Some atoms in the Earth's upper atmosphere emit light due to internal processes known as airglow. The processes prevalent at those altitudes can be understood by remotely observing the modulations/variations of this airglow brightness. One such emission at 630 nm, known as redline airglow showed large enhancements in post‐sunset time over a low‐latitude location. While such redline emission enhancements can, on occasions, possibly occur due to a process at magnetic equator, known as pre‐reversal enhancement in electric field, systematic measurements carried out in this study over a three year duration in the months of January to March revealed that the meridional wind at thermospheric altitudes is the dominant cause of such enhancements. This conclusion has been made by measuring the relative variations in winds in the post‐sunset times that vary from night‐to‐night and the climatological model output that shows a broad month‐to‐month variation. We use the fact that poleward winds bring in electrons, one of the ingredients that produces redline emission, to low‐latitudes thereby causing these emission enhancements. Key Points: Enhancement in OI 630 nm red line emissions observed during the post‐sunset time from a low‐latitude locationColumn integrated volume emission rate and relative meridional wind variations have been calculated using digisondes at two locationsPoleward meridional winds play an important role in causing the observed enhancements in the post‐sunset OI 630 nm emissions [ABSTRACT FROM AUTHOR]

The Rocket Experiment for Neutral Upwelling 2 (RENU2) sounding rocket launched from the Andøya Space Center on 13 December 2015 into the dayside polar cusp. An ultraviolet photomultiplier tube (UV PMT) on the RENU2 payload was oriented to look up along the spin axis for emissions of neutral atomic oxygen above the payload. Data from the UV PMT have been compared to predicted auroral emissions calculated by the Global Airglow (GLOW) model. The comparison between GLOW calculations driven by RENU2 electron precipitation measurements and UV PMT data suggest enhanced neutral density in the cusp at altitudes above the RENU2 trajectory. Key Points: Elevated UV PMT signal relative to GLOW prediction indicates an enhanced neutral density population above the RENU2 trajectorySimple, low‐resource instruments like the RENU2 UV PMT can be a powerful diagnostic tool for thermospheric structurePhysics‐based models like GLOW are useful for understanding dynamic behavior in the cusp [ABSTRACT FROM AUTHOR]

Alkali‐activated functionalized carbon nanotubes (AFCNTs) and 2D nanostructured MoS2 are investigated as a novel hybrid material for energy‐storage applications. The nanoflower‐like 2D MoS2 is grown on the surface of AFCNT using the controlled one‐step hydrothermal technique. The activation of functionalized carbon nanotubes results in greater performance due to the improved surface area. The Brunauer–Emmett–Teller (BET) surface area of the AFCNTs is found to be 594.7 m2 g−1 which is almost 30 times of the as‐prepared carbon nanotubes (CNTs). The improved surface area with attached hydroxyl and carboxylic functional groups helps in the attachment of MoS2 nanoflowers onto the AFCNT, thus reducing the interfacial resistance and providing an easy path for electron transfer. The electrochemical analysis shows a high specific capacitance of 516 F g−1 at 0.5 A g−1 with a corresponding energy density of 71.76 Wh kg−1, which is an encouraging reported value from AFCNT and MoS2 hybrid material. To the best of our knowledge, herein, the first report on AFCNTs and 2D MoS2 nanostructured hybrid electrode material for supercapacitor applications is provided, and promising results in terms of specific capacitance, energy density, and power density by boosting the properties of individual material are explained. [ABSTRACT FROM AUTHOR]

Wave‐like structures in the upper atmospheric nightglow brightness were observed on the night of 22 August 2017, approximately 8 hr following a total solar eclipse. These wave‐like perturbations are signatures of atmospheric gravity waves and associated traveling ionospheric disturbances (TIDs). Observations were made in the red line (OI 630.0 nm) and the green line (OI 557.7 nm) from Carbondale, IL, at 2–10 UTC on 22 August 2017. Based on wavelet analyses, the dominant time period in both the red and green lines was around 1.5 hr. Differential total electron content data obtained from Global Positioning System total electron content measurements at Carbondale, IL, and ionospheric parameters from digisonde measurements at Idaho National Laboratory and Millstone Hill showed a similar dominant time period. Based on these observations and their correlation with geomagnetic indices, the TIDs appear to be associated with geomagnetic disturbances. In addition, by modeling the ionosphere‐thermosphere system's response to the eclipse, it was seen that while the eclipse enhanced the O/N2 ratio and electron density (Ne) at 250 km during our observation period, it did not affect the TIDs. Vertical (7 m/s) and meridional (616 m/s) phase velocities of the TIDs were estimated using cross‐correlation analysis between red and green line brightness profiles and spectral analysis of the differential total electron content keogram, respectively. This provides a method to characterize the three‐dimensional wave properties of TIDs. Key Points: Meridional and vertical wave properties of LSTIDs are characterized based on multi‐instrument observationsEffects of the solar eclipse that preceded the LSTID are also studied based on modelingModel estimates suggest that the IT system was preconditioned due to the eclipse but there is no evidence of this affecting the LSTIDs [ABSTRACT FROM AUTHOR]

Abstract: Energies and fluxes of precipitating electrons in an aurora over Lowell, MA on 22–23 June 2015 were derived based on simultaneous, high‐resolution (≈ 0.02 nm) brightness measurements of N 2 + (427.8 nm, blue line), OI (557.7 nm, green line), and OI (630.0 nm, red line) emissions. The electron energies and energy fluxes as a function of time and look direction were derived by nonlinear minimization of model predictions with respect to the measurements. Three different methods were compared; in the first two methods, we constrained the modeled brightnesses and brightness ratios, respectively, with measurements to simultaneously derive energies and fluxes. Then we used a hybrid method where we constrained the individual modeled brightness ratios with measurements to derive energies and then constrained modeled brightnesses with measurements to derive fluxes. Derived energy, assuming Maxwellian distribution, during this storm ranged from 109 to 262 eV and the total energy flux ranged from 0.8 to 2.2 ergs·cm−2·s−1. This approach provides a way to estimate energies and energy fluxes of the precipitating electrons using simultaneous multispectral measurements. [ABSTRACT FROM AUTHOR]

Front Cover: The development of multifunctional nanocomposite materials is of great interest for various biomedical applications. A popular approach to produce tailored nanocomposites is to incorporate functional nanoparticles into hydrogels. A benign atmospheric pressure microplasma synthesis approach has been deployed for the synthesis of metal and alloy NP/PVA hydrogels. Practical applications of the NP/PVA nanocomposites have been demonstrated by anti‐bacterial testing, showing their potential for a range of biomedical applications. Further details can be found in the article by Hugo Nolan, Daye Sun, Brian Falzon, et al. (e1800112) [ABSTRACT FROM AUTHOR]

The development of multifunctional nanocomposite materials is of great interest for various biomedical applications. A popular approach to produce tailored nanocomposites is to incorporate functional nanoparticles into hydrogels. Here, a benign atmospheric pressure microplasma synthesis approach has been deployed for the synthesis of metal and alloy NPs in‐situ in a poly (vinyl alcohol) hydrogel. The formation of gold, silver, and gold‐silver alloy NPs was confirmed via spectroscopic and microscopic characterization techniques. The properties of the hydrogel were not compromised during formation of the composites. Practical applications of the NP/PVA nanocomposites has been demonstrated by anti‐bacterial testing. This establishes AMP processing as a viable one‐step technique for the fabrication of NP/hydrogel composites, with potential multifunctionality for a range of biomedical applications. An Atmospheric Pressure Microplasma technique has been used for in‐situ synthesis of metal NP/PVA composite hydrogels. Au, Ag, and AuAg NPs have been synthesized in a PVA solution in a green one‐step process to produce composite hydrogels. Anti‐bacterial properties of these hydrogels have been demonstrated, showing their potential in biomedical applications. [ABSTRACT FROM AUTHOR]