Low-altitude Emissions Research Articles

Improving modeling of low-altitude particulate matter emission and dispersion: A cotton gin case study

Monitoring and modeling of airborne particulate matter (PM) from low-altitude sources is becoming an important regulatory target as the adverse health consequences of PM become better understood. However, application of models not specifically designed for simulation of PM from low-altitude emissions may bias predictions. To address this problem, we describe the modification and validation of an air dispersion model for the simulation of low-altitude PM dispersion from a typical cotton ginning facility. We found that the regulatory recommended model (AERMOD) overestimated pollutant concentrations by factors of 64.7, 6.97 and 7.44 on average for PM2.5, PM10, and TSP, respectively. Pollutant concentrations were negatively correlated with height (p < 0.05), distance from source (p < 0.05) and standard deviation of wind direction (p < 0.001), and positively correlated with average wind speed (p < 0.001). Based on these results, we developed dispersion correction factors for AERMOD and cross-validated the revised model against independent observations, reducing overestimation factors to 3.75, 1.52 and 1.44 for PM2.5, PM10 and TSP, respectively. Further reductions in model error may be obtained from use of additional observations and refinement of dispersive correction factors. More generally, the correction permits the validated adjustment and application of pre-existing models for risk assessment and development of remediation techniques. The same approach may also be applied to improve simulations of other air pollutants and environmental conditions of concern.

Assessing the Responses of Aviation-Related SO2 and NO2 Emissions to COVID-19 Lockdown Regulations in South Africa

Aircraft emit harmful substances, such as carbon dioxide (CO2), water vapour (H2O), nitrogen oxides (NOx), sulphur oxides (SOx), particulates, and other trace compounds. These emissions degrade air quality and can deteriorate human health and negatively impact climate change. Airports are the nucleus of the ground and low-altitude emissions from aircraft during approach, landing, take-off, and taxi. During the global lockdown due to the COVID-19 pandemic, tight restrictions of the movement were imposed, leading to temporary closures of airports globally. In this study, we look at the variability of emissions at two major airports in South Africa, namely the OR Tambo international airport (FAOR) and the Cape Town international airport (FACT). Trend analysis of aircraft movements, i.e., departures and arrivals, showed a sharp decline at the two airports coinciding with the lockdowns to prevent the spread of the COVID-19. Consequently, a decrease in NO2 emissions by 70.45% (12.6 × 10−5 mol/m2) and 64.58% (11.6 × 10−5 mol/m2) at FAOR and FACT were observed, respectively. A noticeable SO2 emission decline was also observed, particularly over FAOR during the lockdown period in South Africa. Overall, this study observed that the global lockdown regulations had a positive impact on the air quality, causing a brief decline in emissions from commercial aviation at the South African major airports.

Development of Renewable Energy Sources in the Context of Threats Resulting from Low-Altitude Emissions in Rural Areas in Poland: A Review

The process of transformation of the Polish economy, traditionally based on coal, into an economy that uses low-carbon technologies, faces a problem associated with the diversification of energy sources, especially in rural areas. The scale of the use of conventional energy carriers in households located in rural areas in Poland has a very negative impact on the natural environment. The aim of the paper is to indicate possibilities of reducing low-altitude emissions (with emitters not exceeding 40 m in height) in rural areas in Poland, through the development of renewable energy sources. This paper provides an overview of the specific character of rural areas in Poland and the development challenges faced in these areas in the investigated scope. In order to reduce greenhouse gas emissions and improve energy efficiency, it is necessary to dynamize pro-ecological activities in agriculture and in rural areas, including the development of agricultural biogas plants, wind and photovoltaic farms. The use of renewable energy sources can be an important factor in the development and sustainable growth of rural areas in Poland.

Empirical Characterization of Low‐Altitude Ion Flux Derived from TWINS

AbstractIn this study we analyze ion differential flux from 10 events between 2008 and 2015. The ion fluxes are derived from low‐altitude emissions (LAEs) in energetic neutral atom (ENA) images obtained by Two Wide‐angle Imaging Neutral‐atom Spectrometers (TWINS). The data set comprises 119.44 hr of observations, including 4,284 per energy images with 128,277 values of differential ENA flux from pixels near Earth's limb. Limb pixel data are extracted and mapped to a common polar ionospheric grid and associated with values of the Dst index. Statistical analysis is restricted to pixels within 10% of the LAE emissivity peak. For weak Dst conditions we find a premidnight peak in the average ion precipitation, whose flux and location are relatively insensitive to energy. For moderate Dst, elevated flux levels appear over a wider magnetic local time (MLT) range, with a separation of peak locations by energy. Strong disturbances bring a dramatic flux increase across the entire nightside at all energies but strongest for low energies in the postmidnight sector. The arrival of low‐energy ions can lower the average energy for strong Dst, even as it raises the total integral number flux. TWINS‐derived ion fluxes provide a macroscale measurement of the average precipitating ion distribution and confirm that convection, either quasi‐steady or bursty, is an important process controlling the spatial and spectral properties of precipitating ions. The premidnight peak (weak Dst), MLT widening and energy‐versus‐MLT dependence (moderate Dst), and postmidnight low‐energy ion enhancement (strong Dst) are consistent with observations and models of steady or bursty convective transport.

Magnetosphere dynamics during the 14 November 2012 storm inferred from TWINS, AMPERE, Van Allen Probes, and BATS-R-US–CRCM

Abstract. During the 14 November 2012 geomagnetic storm, the Van Allen Probes spacecraft observed a number of sharp decreases (“dropouts”) in particle fluxes for ions and electrons of different energies. In this paper, we investigate the global magnetosphere dynamics and magnetosphere–ionosphere (M–I) coupling during the dropout events using multipoint measurements by Van Allen Probes, TWINS, and AMPERE together with the output of the two-way coupled global BATS-R-US–CRCM model. We find different behavior for two pairs of dropouts. For one pair, the same pattern was repeated: (1) weak nightside Region 1 and 2 Birkeland currents before and during the dropout; (2) intensification of Region 2 currents after the dropout; and (3) a particle injection detected by TWINS after the dropout. The model predicted similar behavior of Birkeland currents. TWINS low-altitude emissions demonstrated high variability during these intervals, indicating high geomagnetic activity in the near-Earth tail region. For the second pair of dropouts, the structure of both Birkeland currents and ENA emissions was relatively stable. The model also showed quasi-stationary behavior of Birkeland currents and simulated ENA emissions with gradual ring current buildup. We confirm that the first pair of dropouts was caused by large-scale motions of the OCB (open–closed boundary) during substorm activity. We show the new result that this OCB motion was associated with global changes in Birkeland (M–I coupling) currents and strong modulation of low-altitude ion precipitation. The second pair of dropouts is the result of smaller OCB disturbances not related to magnetospheric substorms. The local observations of the first pair of dropouts result from a global magnetospheric reconfiguration, which is manifested by ion injections and enhanced ion precipitation detected by TWINS and changes in the structure of Birkeland currents detected by AMPERE. This study demonstrates that multipoint measurements along with the global model results enable the reconstruction of a more complete system-level picture of the dropout events and provides insight into M–I coupling aspects that have not previously been investigated. Keywords. Magnetospheric physics (magnetosphere–ionosphere interactions; magnetospheric configuration and dynamics); space plasma physics (numerical simulation studies)

Solar flare impact on FUV based thermospheric O/N2 estimation

During/after intense solar flares, FUV based thermospheric O/N2 ratio decreases and recovers instantly, indicating that the decrease is not physical. Simulations with an increased solar X-ray (0–10nm) flux and a fixed O and N2 profiles show a significant 135.6nm/LBHS decrease that is sufficient to explain the O/N2 decrease. The false O/N2 decrease is mostly due to increased differences in O2 absorption at 135.6nm and LBHS caused by low-altitude emissions associated with enhanced X-rays. However, the heating from solar flares may cause a weak depletion in O/N2.

Statistical correlation of low‐altitude ENA emissions with geomagnetic activity from IMAGE/MENA observations

AbstractPlasma sheet particles transported Earthward during times of active magnetospheric convection can interact with exospheric/thermospheric neutrals through charge exchange. The resulting Energetic Neutral Atoms (ENAs) are free to leave the influence of the magnetosphere and can be remotely detected. ENAs associated with low‐altitude (300–800 km) ion precipitation in the high‐latitude atmosphere/ionosphere are termed low‐altitude emissions (LAEs). Remotely observed LAEs are highly nonisotropic in velocity space such that the pitch angle distribution at the time of charge exchange is near 90°. The Geomagnetic Emission Cone of LAEs can be mapped spatially, showing where proton energy is deposited during times of varying geomagnetic activity. In this study we present a statistical look at the correlation between LAE flux (intensity and location) and geomagnetic activity. The LAE data are from the MENA imager on the IMAGE satellite over the declining phase of solar cycle 23 (2000–2005). The SYM‐H, AE, and Kp indices are used to describe geomagnetic activity. The goal of the study is to evaluate properties of LAEs in ENA images and determine if those images can be used to infer properties of ion precipitation. Results indicate a general positive correlation to LAE flux for all three indices, with the SYM‐H showing the greatest sensitivity. The magnetic local time distribution of LAEs is centered about midnight and spreads with increasing activity. The invariant latitude for all indices has a slightly negative correlation. The combined results indicate LAE behavior similar to that of ion precipitation.

Analytical estimate for low‐altitude ENA emissivity

AbstractWe formulate the first analytical model for energetic neutral atom (ENA) emissivity that partially corrects for the global viewing geometry dependence of low‐altitude emissions (LAEs) observed by Two Wide‐angle Imaging Neutral‐atom Spectrometers (TWINS). The emissivity correction requires the pitch angle distribution (PAD) and geophysical location of low‐altitude ENAs. To estimate PAD, we create an energy‐dependent analytical model, based on a Monte Carlo simulation. We account for energy binning by integrating model PAD over each energy bin. We account for finite angular pixels by computing emissivity as an integral over the pitch angle range sampled by the pixel. We investigate location uncertainty in TWINS pixels by performing nine variations of the emissivity calculation. Using TWINS 2 ENA imaging data from 1131 to 1145 UT on 6 April 2010, we derive emissivity‐corrected ion fluxes for two angular pixel sizes: 4° and 1°. To evaluate the method, we compare TWINS‐derived ion fluxes to simultaneous in situ data from the National Oceanic and Atmospheric Administration (NOAA) 17 satellite. The TWINS‐NOAA agreement for emissivity‐corrected flux is improved by up to a factor of 7, compared to uncorrected flux. The highest 1° pixel fluxes are a factor of 2 higher than for 4° pixels, consistent with pixel‐derived fluxes that are artificially low because subpixel structures are smoothed out, and indicating a possible slight advantage to oversampling the instrument‐measured LAE signal. Both TWINS and NOAA ion fluxes decrease westward of 2000 magnetic local time. The TWINS‐NOAA comparison indicates that the global ion precipitation oval comprises multiple smaller‐scale (3–5° of latitude) structures.

Tomographic reconstruction of storm time RC ion distribution from ENA images on board multiple spacecraft

AbstractA quantitative retrieval of 3‐D distribution of energetic ions as energetic neutral atoms (ENA) sources is a challenging task. In this paper the voxel computerized tomography (CT) method is initially applied to reconstruct the 3‐D distribution of energetic ions in the magnetospheric ring current (RC) region from ENA emission images on board multiple spacecraft. To weaken the influence of low‐altitude emission (LAE) on the reconstruction, the LAE‐associated ENA intensities are corrected by invoking the thick‐target approximation. To overcome the divergence in iteration due to discordant instrument biases, a differential ENA voxel CT method is developed. The method is proved reliable and advantageous by numerical simulation for the case of constant bias independent of viewing angle. Then this method is implemented with ENA data measured by the Two Wide‐angle Imaging Neutral‐atom Spectrometers mission which performs stereoscopic ENA imaging. The 3‐D spatial distributions and energy spectra of RC ion flux intensity are reconstructed for energies of 4–50 keV during the main phase of a major magnetic storm. The retrieved ion flux distributions seem to correspond to an asymmetric partial RC, located mainly around midnight favoring the postmidnight with L = 3.5–7.0 in the equatorial plane. The RC ion distributions with magnetic local time depend on energy, with major equatorial flux peak for lower energy located east of that for higher energy. In comparison with the ion energy spectra measured by Time History of Events and Macroscale Interactions during Substorms‐D satellite flying in the RC region, the retrieved spectrum from remotely sensed ENA images are well matched with the in situ measurements.

MAGNETIC PAIR CREATION TRANSPARENCY IN GAMMA-RAY PULSARS

Magnetic pair creation $\gamma \to e^+e^-$ has been at the core of radio pulsar paradigms and central to polar cap models of gamma-ray pulsars for over three decades. The Fermi gamma-ray pulsar population now exceeds 140 sources and has defined an important part of Fermi's science legacy. Among the population characteristics well established is the common occurrence of exponential turnovers in their spectra in the 1--10 GeV range. These turnovers are too gradual to arise from magnetic pair creation in the strong magnetic fields of pulsar inner magnetospheres. By demanding insignificant photon attenuation precipitated by such single-photon pair creation, the energies of these turnovers for Fermi pulsars can be used to compute lower bounds for the typical altitude of GeV band emission. This paper explores such pair transparency constraints below the turnover energy, and updates earlier altitude bound determinations of that have been deployed in various Fermi pulsar papers. For low altitude emission locales, general relativistic influences are found to be important. Rotational aberration influences are also explored, and are found to be small at low altitudes, except near the magnetic pole. The altitude bounds are typically in the range of 2-7 stellar radii for the young Fermi pulsar population, and provide key information on the emission altitude in radio quiet pulsars that do not possess double-peaked pulse profiles. The bound for the Crab pulsar is at a much higher altitude, with the putative detection by MAGIC out to 350-400 GeV implying a lower bound of 310km to the emission region, i.e., approximately 20% of the light cylinder radius. These results are also extended to the super-critical field domain, where it is found that emission in magnetars originating below around 10 stellar radii will not appear in the Fermi-LAT band.

Stokes tomography of a radio pulsar with an offset magnetic dipole

Stokes tomography reveals that ≳60 per cent of radio pulsars with superficially dipole-like characteristics (e.g. S-shaped position angle swing; pulse width-period relation) exhibit Q - U phase portraits inconsistent with low-altitude emission in the rotating vector model. It is shown that an offset dipole offers one way to account for the discrepancy for a range of dipole displacement vectors without distorting greatly the pulse shape and position angle swing. © 2014 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.

Local‐time‐dependent low‐altitude ion spectra deduced from TWINS ENA images

In this paper, we analyze Two Wide‐angle Imaging Neutral‐atom Spectrometers (TWINS) stereo observations of energetic neutral atoms (ENAs) produced from the low altitude emission (LAE) region during the interval 1130–1146 UT on 6 April 2010. Geometrical calculations determine the geophysical locations of pixels at or near the LAE limb and the associated uncertainties. For our event, the two TWINS imagers observed a broad (8.4–9.2 h wide in magnetic local time (MLT)) region of LAEs on the opposing limb, possibly containing an ion boundary near dusk. The most intense LAEs were detected in a narrow range of magnetic latitude (67°–74°) and pitch angle (112°–116°). We implement a simplified thick‐target approximation (TTA) to obtain ion spectra from TWINS LAEs and perform a validation study using a conjunction of the TWINS‐observed LAE crescents with a simultaneous NOAA 17 polar‐orbit pass slightly west of the TWINS LAEs. Since TTA is limited to the brightest portion of LAEs, we apply our analysis for pixels with at least 30% of the peak value. TWINS ion spectra are calculated for individual pixels spanning several hours of MLT. The spectra exhibit a pronounced local time dependence. For more westward MLT (and more equatorward latitude), there is a shift toward spectra that are more energetic and peaked. This spatial dependence is consistent with ion drift theory and previous observations. The peaked LAE‐derived ion spectra of 6 April 2010 are notably different than those observed during much weaker disturbances, but are consistent with LAE observations from similar activity levels. These results demonstrate that with proper caution in interpreting the results, TWINS ENA imaging resolves MLT‐dependent (and to a limited extent, latitude‐dependent) low‐altitude ion spectral shape information, simultaneously across a broad range of MLT. This study advances previous results that considered much coarser MLT structure in LAEs and augments previous statistical spectral analysis of in situ data.

Oxygen‐hydrogen differentiated observations from TWINS: The 22 July 2009 storm

The 22 July 2009 magnetic storm is the first significant storm during the emergence of the recent prolonged solar cycle minimum. This moderate storm (minimum Dst approximately ≤ −78 nT) has received a good deal of attention in the community. We present here global observations of the H and O populations in the inner magnetosphere using Energetic Neutral Atom (ENA) observations from the TWINS mission. We develop and provide the methodology for separating H and O ENAs, based on mass dependent differences in the pulse height distributions of the microchannel plate (MCP) based detectors. We present the first composition separated H and O ENA images at central energies of 16 and 32 keV. We also show that TWINS has sufficient angular resolution to separate the High Altitude Emissions (HAEs) from the Low Altitude Emissions (LAEs). We observe that all ENA emissions in this energy range quickly rise, but the O ENAs have a larger relative increase, and stay at elevated levels much longer, well into the recovery phase.

Comparative analysis of low‐altitude ENA emissions in two substorms

AbstractWe report on the dynamics of low‐altitude energetic neutral atom (ENA) emissions during two substorms that occurred during the main phases of two storms: (1) a CIR‐driven storm on 11 October 2008 and (2) a coronal mass ejection (CME)‐driven storm on 5 April 2010. For both of these storms, we have complementary spacecraft and ground‐based observations. The dual‐spacecraft Two Wide‐angle Imaging Neutral‐atom Spectrometers (TWINS) mission obtained ENA images containing low‐altitude emissions (LAEs). Substorm dynamics is inferred from THEMIS all‐sky imagers. TWINS‐observed LAEs are compared with trapped/loss cone proton fluxes from the low‐altitude NOAA/MetOp spacecraft constellation. We find that the timing and intensity profiles of LAEs are different for the two selected events. For the 11 October 2008 event, the LAEs rise during substorm recovery phase and storm main phase. On 5 April 2010, the LAEs tend to peak near substorm onset. We argue that the different LAE behavior results from different pitch‐angle distributions (PADs) of the ion source population. Ion PADs are isotropic during substorm recovery phase for the 11 October 2008 event and have empty loss cone for the 5 April 2010 event. For both cases, LAE intensification marks the onset of activity in the magnetotail and precedes the large substorm onset. We conclude that the LAE production starts in the transition region between the magnetotail and ring current and may expand/move into the inner magnetosphere together with ring current formation.

Evolution of ring current ion energy spectra during the storm recovery phase: Implication for dominant ion loss processes

[1] We examine the temporal evolution of spatially averaged energy spectra of ring current ions (27–120 keV for H+, 79–264 keV for O+) during the recovery phase of three magnetic storms. The energy spectra are derived from energetic neutral atom (ENA) imaging provided by the High Energy Neutral Atom (HENA) imager on board the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) satellite; ENAs generated within HENA lines of sight passing by close to the Earth are excluded in order to distinguish high-altitude emissions from low-altitude emissions. We confirm, by performing a simple model of ENA production, that the retrieved spectra are a good indication of those at 3.5 60 keV H+ was higher than the prestorm level. It is likely that the contribution from >60 keV H+ to the ring current intensity (and H+ pressure) increases as a storm recovers. We suggest that the ring current intensity is dominated by higher-energy (>60 keV) H+ during the late recovery phase.

Evolution of low‐altitude and ring current ENA emissions from a moderate magnetospheric storm: Continuous and simultaneous TWINS observations

The moderate storm of 22 July 2009 is the largest measured during the extended solar minimum between December 2006 and March 2010. We present observations of this storm made by the two wide‐angle imaging neutral‐atom spectrometers (TWINS) mission. The TWINS mission measures energetic neutral atoms (ENAs) using sensors mounted on two separate spacecrafts. Because the two spacecrafts' orbital planes are significantly offset, the pair provides a nearly optimal combination of continuous magnetospheric observations from at least one of the TWINS platforms with several hours of simultaneous, dual‐platform viewing over each orbit. The ENA imaging study presented in this paper is the first reported magnetospheric storm for which both continuous coverage and stereoscopic imaging were available. Two populations of ENAs are observed during this storm. The first are emissions from the ring current and come from a parent population of trapped ions in the inner magnetosphere. The second, low‐altitude emissions (LAEs), are the result of precipitating ions which undergo multiple charge exchange and stripping collisions with the oxygen exosphere. The temporal evolution of this storm shows that the LAEs begin earlier and are the brightest emissions seen during the main phase, while later, during the recovery, the LAE is only as bright as the bulk ring current emissions.

Comparison of TWINS images of low‐altitude emission of energetic neutral atoms with DMSP precipitating ion fluxes

The brightest energetic neutral atom (ENA) intensity viewed by spacecraft in high‐inclination Earth orbit is from low‐altitude emission (LAE). It is a prominent feature in the stereo ENA images obtained by cameras on the NASA TWINS 1/2 Mission of Opportunity. This emission is produced by energetic magnetospheric ions precipitating into the atomic oxygen exosphere at latitudes near the auroral zones at altitudes ∼300 km. The ions undergo multiple atomic collisions including charge exchange of ions and stripping of the resulting neutrals. Consequently, this is a “thick target” process. We introduce a “thick‐target” approximation that allows us to extract the shape of the spatially averaged spectra of the precipitating ions from the ENA spectra in the TWINS 1/2 pixels viewing the LAE from near their orbital apogees. These ENA‐extracted ion spectra are compared with in situ precipitating ion spectra measured concurrently by DMSP satellites (F15 and F16) at ∼825 km altitude, while they are passing directly over the LAE regions in the TWINS 1/2 images. We obtain good agreement between the shape of the ENA‐extracted and in situ ion spectra from three distinct precipitation regions over energies from 2 to 32 keV (assuming precipitating protons). The absolute normalization of the ENA‐extracted and in situ spectra depends upon the TWINS viewing geometry because the ENA LAE source is not resolved by the imager. None of the spectral shapes obtained is consistent with a simple thermal intensity spectrum with kT = 5 keV.

Passive Atmospheric Diffusion With Gaussian Fragmentation

Events such as atmospheric gas dispersion by industrial accidents or processes are generally predicted with Gaussian plumes, coupled with local models of gas emission. In this contribution we investigate the association of integral models of instantaneous emission with Gaussian dispersion processes for predicting the progression of potentially hazardous low-altitude emissions over sensitive or populated areas. We develop a novel, more accurate approach suitable for dynamic, high spatial resolution atmospheric conditions by means of gas plume fragmentation and parallel estimation of extent and concentration.

The contributions of high- and low altitude emission sources to the near ground concentrations of air pollutants

The scale of transport through the atmosphere depends on the effective height of an emission source, the meteorological conditions and the physico-chemical characteristics of the pollutants. Atmospheric surface temperature inversions play a significant role in the problem of air pollution since their upper edge acts as a natural barrier to the vertical dispersion of pollutants. When the altitude of an emission source is lower than the edge of the boundary layer, the pollution remains below the upper edge and spreads by advection inside the lower layer towards the ground. However, if the altitude of the emission source is higher than the edge of the boundary layer, then the pollution spreads above the barrier. An analysis of a pollution episode during one month (August 2004) in an urban atmosphere of industrial city, using results of continuous monitoring of minute-by-minute fluctuations of the pollutants' concentrations, is presented. Region of a developed industrial town as a model was investigated. The investigated region is characterized by maximum number of surface temperature inversions during the nights in August and their furlough during the day time. With a combination of local meteorological information, that is the number of surface temperature inversions of the atmosphere, the results showed that the concentrations of pollutants originating from low altitude emission sources, e.g. organic pollutants, were higher at night. The near ground concentrations of SO 2, originating from high-(industrial stacks) and low altitude (traffic) sources, and the PM 10 originating from various sources i.e. from complex mechanisms of formation e.g. traffic emissions, SOA mechanisms and re-suspensions, were the same during the night and during the day. However, concentrations of NH 3 from high altitude sources (fertilizer plant) were higher during the day. Cluster Analysis and Principal Component Analysis showed associations of highest correlation between pollutants, which are constituents of non-methane volatile organic compounds (NMVOCs), which signify strong influences of emission from low altitude sources e.g. oil pollutants from near industrial zone.

Storm‐time plasma signatures observed by IMAGE/MENA and comparison with a global physics‐based model

We present energetic neutral atom (ENA) fluxes measured by the medium energy neutral atom (MENA) imager onboard the IMAGE satellite for the geomagnetic storm of 21 October 2001 at energies of 6 and 12 keV. The fluxes indicate strong low altitude emissions close to the Earth and a nightside peak close to local midnight. The fluxes are compared with theoretical ENA fluxes calculated using the ring current‐atmosphere interaction model (RAM). We find good quantitative agreement between MENA data and RAM results, both of which indicate a peak in ENA emissions on the nightside, close to local midnight which varies in radial location between ∼2 and ∼5 Re during the period of study. We demonstrate the validity of comparing RAM results with MENA data and pave the way for further study of plasma sheet entry to the inner magnetosphere during storm‐times.