Defense Meteorological Satellite Program Research Articles

Tracking the Development of Lit Fisheries by Using DMSP/OLS Data in the Open South China Sea

Nightly images offer a special data source for monitoring fishing activities. This study used images from the Defense Meteorological Satellite Program (DMSP)/Operational Linescan System (OLS) to analyze the early development of lit fisheries in the open South China Sea (SCS), which mainly occurred around the Zhong Sha and Xi Sha Islands. Based on peak detection and a fixed threshold, lit fishing positions were extracted well from filtered, high-quality DMSP/OLS images. The results indicated that fisheries experienced an apparent rise and fall from 2005 to 2012, with the numbers of lit fishing boats rising to a maximum of ~60 from 2005 to 2008, almost disappearing in 2009, peaking at ~130 from 2010 to 2011, and starting to decline in 2012. The fish price of major fishing targets declined by ~60% in 2009, which obviously impacted the year’s fishing operations. The reason for declined fishing operations in 2012 was that most of the lit fishing operations shifted farther south to fishing grounds around the Nan Sha Islands. We also explored factors shaping the distribution patterns of lit fisheries by using MaxEnt models to relate fishing positions to environmental variables. Major environmental factors influencing the distribution of lit fishing boats varied with years, of which water depth was the most important factor across years, with an optimal depth range of 1000–2000 m. In addition to depth, the distribution of lit fisheries was also influenced by SST, especially for the years 2005–2008, and a suitable SST was found between 26 and 28 °C. This study fills the knowledge gaps of the inception of lit fisheries and their dynamic changes in the SCS.

Different Origin Field‐Aligned Currents and Their Relationship With Auroral Intensity

AbstractThe ionospheric field‐aligned current (FAC) consists of three components related to ionospheric vortices and gradients of Pedersen and Hall conductances, with the first term being of magnetospheric origin and the latter two being of ionospheric origin (Eq. 1). We calculate each of them between 2010 and 2016 using line‐of‐sight velocity data from the Super Dual Auroral Radar Network radar and auroral electron precipitation data from the Defense Meteorological Satellite Program. Then, we investigate the contribution of each FAC component, as well as the relationship between each FAC component and auroral activity. Our result shows that ionospheric‐origin FACs contribute up to 54% (dawn) and 42% (dusk) within the auroral oval. Both magnetospheric‐origin FACs and ionospheric‐origin FACs initially increase and then stabilize as the SuperMAG electrojet (SME) index increases. After stabilization, these two currents have almost equally important roles, with an average contribution rate of 56% and 44%, respectively. Additionally, the ionospheric‐origin FACs are found to have a higher dependency on auroral intensity. We also find that magnetospheric‐origin FACs exhibit distribution patterns similar to the R1/R2 FAC systems because their directions are determined by vorticities. When the SME index exceeds 200 nT, the contribution from the Pedersen conductance gradient consistently exhibits downward currents near 70° magnetic latitude in the dusk and predawn sectors due to the combined effects of velocities and Pedersen conductance gradients. However, the distribution pattern from the Hall conductance gradient is not so clear due to the uncertainty in the angle between velocity and Hall conductance gradient.

Impact of Interplanetary Shock on Thermospheric Cooling Emission: A Case Study

AbstractInterplanetary (IP) shock is one of the most common phenomena that controls the shape and size of the magnetosphere. It affects the whole magnetosphere‐ionosphere‐thermosphere (MIT) system. We utilized the NO 5.3 m radiative emission, as observed by SABER (Sounding of the Atmosphere using Broadband Emission Radiometry) onboard NASA's TIMED (Thermosphere Ionosphere Mesosphere Energetics Dynamics) satellite, to investigate its response to fast forward shock during 26 January 2017. The high latitude NO emission exhibits a strong enhancement (three times with respect to pre‐event value) during IP shock within 5 hr of onset. We analyzed both the energy dissipation sources and subsequent chemical mechanisms. The Field‐Aligned‐Current observations from Active Magnetosphere and Planetary Response Experiment (AMPERE), EISCAT measurements of Pederson conductivity and the defense Meteorological Satellite Program (DMSP F18) calculated hemispheric power demonstrate a strong intensification. The low energy particle precipitation from DMSP F18 spacecraft shows an early enhancement for energy less than 1 keV. The particle flux of higher energy responds later which remained elevated for longer duration. The thermospheric density and temperature also experience significant variation during IP shock. The NO molecule and temperature displayed an early enhancement. NO density increased by an order of magnitude with respect to the pre‐event value. About 20 increase is noticed in the temperature variation. The atomic oxygen and atomic nitrogen illustrate an early depletion during IP event. The enhanced response of NO cooling to IP shock can be attributed to the combined effects of energy input and subsequent chemical mechanisms.

Outdoor light at night is a modifiable environmental factor for metabolic syndrome: The 33 Communities Chinese Health Study (33CCHS)

Metabolic syndrome (MetS) is a significant public health problem and presents an escalating clinical challenge globally. To combat this problem effectively, urgent measures including identify some modifiable environmental factors are necessary. Outdoor artificial light at night (LAN) exposure garnered much attention due to its impact on circadian rhythms and metabolic process. However, epidemiological evidence on the association between outdoor LAN exposure and MetS remains limited. To determine the relationship between outdoor LAN exposure and MetS, 15,477 adults participated the 33 Communities Chinese Health Study (33CCHS) in 2009 were evaluated. Annual levels of outdoor LAN exposure at participants' residential addresses were assessed using satellite data from the Defense Meteorological Satellite Program (DMSP) Operational Linescan System (OLS). Generalized linear mixed effect models were utilized to assess the association of LAN exposure with MetS and its components, including elevated waist circumference (WC), triglycerides (TG), blood pressure (BP), fasting blood glucose (FBG), and reduced high-density lipoprotein cholesterol (HDL-C). Effect modification by various social demographic and behavior factors was also examined. Overall, 4701 (30.37 %) participants were defined as MetS. The LAN exposure ranged from 6.03 to 175.00 nW/cm2/sr. The adjusted odds ratio (OR) of MetS each quartile increment of LAN exposure were 1.43 (95 % CI: 1.21–1.69), 1.44 (95 % CI: 1.19–1.74) and 1.52 (95 % CI: 1.11–2.08), respectively from Q2–Q4. Similar adverse associations were also found for the components of MetS, especially for elevated BP, TG and FBG. Interaction analyses indicated that the above associations were stronger in participants without habitual exercise compared with those with habitual exercise (e.g. OR were 1.52 [95 % CI: 1.28–1.82] vs. 1.27 [95 % CI, 1.04–1.55], P-interaction = 0.042 for MetS). These findings suggest that long-term exposure to LAN can have a significant deleterious effect on MetS, potentially making LAN an important modifiable environmental factor to target in future preventive strategies.

Which Nighttime Lights Data Better Represent India’s Economic Activities and Regional Inequality?

This paper demonstrates how the estimation of economic activities and inequality for the Indian economy based on nighttime lights data from the Visible Infrared Imaging Radiometer Suite (VIIRS) satellite outperforms those obtained using traditional Defense Meteorological Satellite Program Operational Line-Scan System (DMSP-OLS) sources. In the extant literature, nighttime lights data have been frequently used as a proxy for economic activities, especially at granular geographical levels where gross domestic product data are otherwise unavailable. Since the traditional DMSP-OLS-based nighttime lights data suffer from measurement errors due to blurring and top coding, VIIRS-based nighttime lights data, which are devoid of such limitations, are gaining popularity. We show that at the subnational or district level in India, VIIRS satellite-based nighttime lights data are indeed a better proxy for economic activities and inequality. Our robust findings imply that all future scholarly works that employ nighttime lights data for the Indian economy should use VIIRS-based data for greater accuracy compared to other similar data sources.

Developing an annual global Sub-National scale economic data from 1992 to 2021 using nighttime lights and deep learning

The Gross Domestic Product (GDP) per capita is one of the most widely used socioeconomic indicators, serving as an integral component for climate change impact analysis. However, a national scale assessment may induce considerable bias because it conceals any internal variations within a country. The lack of a long-term sub-national scale GDP data is a substantive hinderance. Leveraging the close relationship between nighttime lights and GDP, we address this gap by developing a novel methodological framework in two steps. First, under the modeling philosophy of spatial statistics, we developed a novel approach based on deep and machine learning techniques to establish a complex mapping between two inconsistent nighttime lights (NTL) datasets: the Defense Meteorological Satellite Program’s Operational Linescan System (DMSP) and the National Polar-Orbiting Partnership’s Visible Infrared Imaging Radiometer Suite (VIIRS). The models achieve accuracies ranging from 0.945 to 0.980 (correlation coefficients). By taking the estimations ensemble of the two techniques, the time series of DMSP data was extended to 2021. Next, a novel modeling strategy based on multi-layer perceptron was developed to derive the non-linear relationship between NTL and GDP per capita at sub-national scale to alleviate scale effects at this granularity, while explicitly capturing regional heterogeneity effect. The trained models achieve average accuracies of 0.967, 0.959, and 0.959 on the training, validation, and test sets, respectively. We evaluate the developed dataset at the global, national, and sub-national scales from various perspective, and the results offer solid evidence on the reliability of the estimated economic data. By linking to historical global climate change data, we quantify global economic losses attributed to extreme heat to demonstrate how the estimated GDP data can be useful in the climate change impact analysis.

Latitudinal Characteristics of Nighttime Electron Temperature in the Topside Ionosphere and Its Dependence on Solar and Geomagnetic Activities

This study investigates the latitudinal characteristics of the nighttime electron temperature, as observed by the Defense Meteorological Satellite Program F16 satellite, and its dependence on solar and geomagnetic activities between 2013 and 2022 in the topside ionosphere, only for the winter hemispheres. The electron temperature in both hemispheres exhibited a low-temperature zone at the equator and a double high-temperature zone at the sub-auroral and auroral latitudes along the magnetic latitude. In addition, we further studied the temperature crest/trough positions in the temperature zone at different latitudes. As the solar activity intensity decreased (increased), the temperature trough position at the equator shifted from the Southern (Northern) to the Northern (Southern) Hemisphere, and the temperature double-crest positions at the sub-auroral and auroral latitudes gradually approached (moved away from) each other. Furthermore, during the geomagnetic disturbance time, the temperature double-crest positions both moved toward lower latitudes, but the temperature trough position was not sensitive to geomagnetic activity. Our analysis demonstrates that the values and correlations of the electron temperature and density varied in different temperature characteristic zones (the temperature crest/trough positions ±2°), possibly due to the different energy control factors of the electrons at different latitudes. This may also indirectly indicate the energy coupling process between the topside ionosphere and different regions at different latitudes.

Impact of interplanetary shock on nitric oxide cooling emission: A superposed epoch study

The impact of interplanetary (IP) shock on Nitric Oxide (NO) 5.3 µm cooling emission is studied during geomagnetic quiet periods. The Active Magnetosphere and Planetary Electrodynamics Response Experiment measurements of field-aligned-currents intensify during IP shock with a relatively higher magnitude in southern hemisphere as compared to the northern hemispheric counterpart. The Defense Meteorological Satellite Program spacecraft observations displayed an early and strong enhancement in the precipitating particle flux of energy less than 1 keV. The particle flux of higher energy responds at later time. The NO density exhibited a significant, pre-event increase by an order of magnitude due to low-energy particle precipitation. The thermospheric temperature increased by about 100 K at 400 km. The superposed epoch analysis study revealed a linear enhancement in SABER (Sounding of the Atmosphere using Broadband Emission Radiometry) measurements of NO cooling emission onboard the TIMED (Thermosphere Ionosphere Mesosphere Energetics Dynamics) satellite due to the prompt increase in particle precipitations and thermospheric temperature triggered by IP shock.

Nightside Detached Auroras Associated With Expanding Auroral Oval During the Main and Recovery Phases of a Magnetic Storm

AbstractDetached subauroral proton arcs are commonly observed during the recovery phase of geomagnetic storms, and have been extensively investigated. However, there is limited study on their occurrence during the main phase of storms. This study investigated nightside detached auroras (NDAs) observed by the far‐ultraviolet imager onboard the Defense Meteorological Satellite Program spacecraft. The NDAs occurred in the nightside sector, separated from the equatorward boundary of the auroral oval, and were observed during the main and recovery phases of the geomagnetic storm on 02 October 2013. The occurrence of the NDAs appears to correlate with the expanding auroral oval toward lower latitudes, and is independent of the polarity change in the interplanetary magnetic field Bz component. Particle measurements indicate that the NDAs were generated by energetic protons, primarily above 10 keV, originating from the ring current. These precipitating proton fluxes, predominantly anisotropic, were observed to be detached from the isotropic boundary within the auroral oval. Analysis of Pc1 data obtained by ground stations suggests that electromagnetic ion cyclotron waves account for the generation of the NDAs. The limited latitudinal distribution of the NDAs indicates the wave activity in the magnetospheric source region within a narrow L‐shell region. The observations presented in this study would contribute to our understanding of the coupling processes between the magnetosphere and ionosphere within the subauroral region.

Effect of Polar Cap Patches on the High‐Latitude Upper Thermospheric Winds

AbstractThis study focuses on the poorly known effect of polar cap patches (PCPs) on the ion‐neutral coupling in the F‐region. The PCPs were identified by total electron content measurements from the Global Navigation Satellite System (GNSS) and the ionospheric parameters from the Defense Meteorological Satellite Program spacecraft. The EISCAT incoherent scatter radars on Svalbard and at Tromsø, Norway observed that PCPs entered the nightside auroral oval from the polar cap and became plasma blobs. The ionospheric convection further transported the plasma blobs to the duskside. Simultaneously, long‐lasting strong upper thermospheric winds were detected in the duskside auroral oval by a Fabry‐Perot Interferometer (FPI) at Tromsø and in the polar cap by the Gravity Recovery and Climate Experiment satellite. Using EISCAT ion velocities and plasma parameters as well as FPI winds, the ion drag acting on neutrals and the time constant for the ion drag could be estimated. Due to the arrival of PCPs/blobs and the accompanied increase in the F‐region electron densities, the ion drag is enhanced between about 220 and 500 km altitudes. At the F peak altitudes near 300 km, the median ion drag acceleration affecting neutrals more than doubled and the associated median e‐folding time decreased from 4.4 to 2 hr. The strong neutral wind was found to be driven primarily by the ion drag force due to large‐scale ionospheric convection. Our results provide a new insight into ionosphere‐thermosphere coupling in the presence of PCPs/blobs.

Observations of ionospheric disturbances associated with the 2020 Beirut explosion by Defense Meteorological Satellite Program and ground-based ionosondes

Abstract. A major explosion that released a significant amount of energy into the atmosphere occurred in Beirut on 4 August 2020. The energy released may have reached the upper atmosphere and generated some traveling ionospheric disturbances (TIDs), which can affect radio wave propagation. In this study, we used data from the Defense Meteorological Satellite Program (DMSP) and ground-based ionosondes in the Mediterranean region to investigate the ionospheric response to this historic explosion event. Our DMSP data analysis revealed a noticeable increase in the ionospheric electron density near the Beirut area following the explosion, accompanied by some wavelike disturbances. Some characteristic TID signatures were also identified in the shape of ionogram traces at several locations in the Mediterranean. This event occurred during a period of relatively quiet geomagnetic conditions, making the observed TIDs likely to have originated from the Beirut explosion, not from other sources such as auroral activities. These observational findings demonstrate that TIDs from the Beirut explosion were able to propagate over longer distances, beyond the immediate areas of Lebanon and Israel–Palestine, reaching the Mediterranean and eastern Europe.

Are Disaster Impact Estimates Distorted by Errors in Popular Night-Time Lights Data?

Satellite-detected night lights data are widely used to evaluate economic impacts of disasters. Growing evidence from elsewhere in applied economics suggests that impact estimates are potentially distorted when popular Defense Meteorological Satellite Program (DMSP) night lights data are used. The low resolution DMSP sensor provides blurred and top-coded images compared to those from the newer and more precise Visible Infrared Imaging Radiometer Suite (VIIRS) images. Despite this, some disaster impact studies continue to use DMSP data, which have also been given a new lease of life through the use of harmonized series linking DMSP and VIIRS data to provide a longer sample. We examine whether use of DMSP data affects evaluations, using expected typhoon damages in the Philippines from 2012–19 as our case study. With DMSP data, negative impacts on economic activity from expected damages at the municipality level appear over 50% larger than when the VIIRS data are used. The DMSP data give the appearance of greater spatial autocorrelation in luminosity and through this channel may tend to spread apparent spatial impacts of shocks. Harmonized data that adjust VIIRS images to be like the DMSP data also have this spurious autocorrelation so researchers should be cautious in using these data for disaster assessments.

Role of Subauroral Polarization Streams in Deep Injections of Energetic Electrons Into the Inner Magnetosphere

AbstractThe electric fields of subauroral polarization streams (SAPS) have been suggested to affect energetic charged particles' dynamics in the inner magnetosphere, though their role on radiation belt electrons has never been properly quantified. A moderate geomagnetic storm on 2015‐09‐07 caused the deep injection of 10–100s of keV electrons in Earth's inner magnetosphere to low L* (L* < 4). Using a 2‐D test particle tracer, we present the effects of electric fields given by the Volland‐Stern model, a SAPS (Goldstein et al., 2005, https://doi.org/10.1029/2005ja011135) model, and a modified SAPS model on the energetic electron deep injections. The modified SAPS model reflects the SAPS electric field observations by the Van Allen Probes and is supported by Defense Meteorological Satellite Program observations. Simulations suggest that the SAPS electric field pushes 10–20 MeV/G electrons Earthward to L* ∼ 2.7 in 2.5 hr, much deeper compared to the Volland‐Stern electric field.

Generation of monthly VIIRS nighttime lights time-series (1992–2013) images using deep learning (cGAN) technique

Satellite-based nighttime lights (NTL) are often used as indicators of the socioeconomic dynamics of an area. The Earth Observation Group at Colorado School of Mines provides monthly NTL products from the Day Night Band (DNB) sensor on board the Visible and Infrared Imaging Suite (VIIRS) satellite (April 2012 onwards) and from Operational Linescan System (OLS) sensor onboard the Defense Meteorological Satellite Program (DMSP) satellites (April 1992–December 2013). VIIRS-DNB (hereinafter referred to as VIIRS) and DMSP-OLS (hereinafter referred to as DMSP) NTL images have 15-arc second and 30-arc second spatial resolution, respectively. In the current study, an attempt has been made to generate synthetic (fine-resolution) monthly VIIRS-like products of 1992–2012 from (coarse-resolution) DMSP products, using a deep learning-based image translation network. Initially, the defects of the 216 monthly DMSP images (1992–2013) were corrected to remove geometric errors, background noise, and radiometric errors. Correction on monthly VIIRS imagery to remove background noise and ephemeral lights was done by thresholding. Improved monthly NTL images of DMSP-OLS and VIIRS from April 2012–December 2013 were used in a conditional generative adversarial network (cGAN) along with the land cover, as auxiliary input, to generate VIIRS-like monthly imagery from 1992 to 2012. The modelled imagery was aggregated annually, which showed an R2 of 0.94 with the results of other annual-scale VIIRS-like imagery products (2000–2020) over India; R2 of 0.85 w.r.t GDP; and R2 of 0.69 w.r.t population. Regression analysis of the generated VIIRS-like products with the actual VIIRS images for the years 2012 and 2013 over India indicated a good approximation with an R2 of 0.64 and 0.67 respectively, while the spatial density relation depicted an under-estimation of the brightness values by the model at extremely high radiance values with an R2 of 0.56 and 0.53 respectively. Qualitative analysis is also performed on both country and State scales. Visual analysis over 1992–2013 confirms a gradual increase in the brightness of the nighttime lights indicating that the cGAN model images closely represent the actual pattern followed by the nighttime lights. Finally, synthetically generated monthly VIIRS-like products are delivered to the research community which will be useful for studying the changes in socio-economic dynamics over time.

Estimation of Ionospheric Field‐Aligned Currents Using SuperDARN Radar and DMSP Observations

AbstractStudies commonly assumed that variations in ionospheric conductance were insignificant and proposed that vorticities can be a reliable proxy or diagnostic for ionospheric field‐aligned currents (FACs). We propose a complete method for measuring FACs using data from the Super Dual Auroral Radar Network radar and the Defense Meteorological Satellite Program. In our method, the FACs are determined by three terms. The first term is referred to as magnetospheric‐origin FACs, while the second and third terms are known as ionospheric‐origin FACs. This method incorporates height‐integrated conductances based on observational data, thereby addressing the limitation of assuming uniform conductances. Different from previous works, we can calculate FACs at a low altitude of 250 km and obtain high‐resolution measurements within observable areas. Another advantage of this method lies in its ability to directly calculate and analyze the impact of ionospheric vorticity and conductance on FACs. We apply this method to obtain FACs in the Northern Hemisphere from 2010 to 2016 and analyze the distributions of height‐integrated conductances and total FACs. Our analysis reveals that the average FACs clearly exhibit the large‐scale R1 and R2 FAC systems. We conduct statistical analysis on magnetospheric‐origin FACs and ionospheric‐origin FACs. Our findings show that within the auroral oval, ionospheric‐origin FACs reach a comparable level to magnetospheric‐origin FACs. However, ionospheric‐origin FACs are significantly minor and almost negligible in other regions. This implies that height‐integrated conductance gradients and vorticities play equally significant roles within the auroral oval, whereas vorticities dominate in other regions.

A Statistical Study of Space Hurricanes in the Southern Hemisphere

AbstractThe space hurricane is a large‐scale three‐dimensional magnetic vortex structure that can cause massive local energy injections in the polar cap. By analyzing Defense Meteorological Satellite Program (DMSP) F16–F19 satellite observations from 2005 to 2016, we found that the Southern Hemisphere space hurricane mainly occurs in summer under negative By dominated northward interplanetary magnetic field (IMF) conditions. In particular, the space hurricanes are more likely to occur in the dayside polar cap at magnetic latitude greater than 80°. The characteristics for the Southern Hemisphere are basically consistent with the characteristics of space hurricanes in the Northern Hemisphere. The different dependences of By component in different hemispheres supports the high‐latitude lobe reconnection as the formation mechanism. Plasma data from DMSP satellites in both hemispheres show that the appearance of the space hurricane greatly enhances the convection in the polar cap and the electron density on its dawn side. Within the space hurricane, electron temperatures typically increase significantly, accompanied by strong upward field‐aligned currents and electron precipitation. These results give us a better understanding of the solar wind‐magnetosphere‐polar ionosphere coupling process under northward IMF conditions.

GOLD Observations of Equatorial Plasma Bubbles Reaching Mid‐Latitudes During the 23 April 2023 Geomagnetic Storm

AbstractA coronal mass ejection erupted from the Sun on 21 April 2023 and created a G4 geomagnetic storm on 23 April. NASA's global‐scale observations of the limb and disk (GOLD) imager observed bright equatorial ionization anomaly (EIA) crests at ∼25° Mlat, ∼11° poleward from their average locations, computed by averaging the EIA crests during the previous geomagnetic quiet days (18–22 April) between ∼15°W and 5°W Glon. Reversed C‐shape equatorial plasma bubbles (EPBs) were observed reaching ∼±36° Mlat (∼40°N and ∼30°S Glat) with apex altitudes ∼4,000 km and large westward tilts of ∼52°. Using GOLD's observations EPBs zonal motions are derived. It is observed that the EPBs zonal velocities are eastward near the equator and westward at mid‐latitudes. Model‐predicted prompt penetration electric fields indicate that they may have affected the postsunset pre‐reversal enhancement at equatorial latitudes. Zonal ion drifts from a defense meteorological satellite program satellite suggest that westward neutral winds and perturbed westward ion drifts over mid‐latitudes contributed to the observed latitudinal shear in zonal drifts.

Ion precipitation in the cusp for northward IMF and its relationship with magnetosheath flow

If the interplanetary magnetic field (IMF) has a northward component, a portion of the solar wind ions flowing in the high-latitude magnetosheath drastically alters the flow direction owing to lobe reconnection and follows the Earth's magnetic field lines toward the low-altitude cusp. Partly because of this folded path, the relationship between the speed of ion flow in the magnetosheath and the energy of the precipitating ions in the low-altitude cusp remains unclarified. Herein, we examined particle data from 11 years of observations by Defense Meteorological Satellite Program satellites to obtain 1990 cases through an automated event identification of the cusp. This corresponds to the largest number of cusp ion events reported to date for a stable northward IMF. The results revealed a positive correlation between the energy of the precipitating ions and the estimated flow speed in the magnetosheath, which answers the question that has remained unexplained for decades: why is the brightness of the cusp proton aurora more strongly correlated with the solar wind dynamic pressure than with the solar wind number density? We suggest additional energizations of the exhausted ions from lobe reconnection in the outflow region because of the turbulent electric field formed by the opposite flow of two ion populations—one in the tailward-directed magnetosheath flow and the other in the earthward-directed outflow jet.Graphical

Global Distribution of EMIC Waves and Its Association to Subauroral Proton Precipitation During the 27 May 2017 Storm: Modeling and Multipoint Observations

AbstractRecent simulation studies using the RAM‐SCB model showed that proton precipitation contributes significantly to the total energy flux deposited into the subauroral ionosphere thereby affecting the magnetosphere‐ionosphere coupling. In this study, we use the BATS‐R‐US + RAM‐SCB model to understand the evolution of ElectroMagnetic Ion Cyclotron (EMIC) waves in the inner magnetosphere, their correspondence to the proton precipitation into the subauroral ionosphere, and to assess the performance of the model in reproducing the EMIC wave‐particle interactions. During the 27 May 2017 storm, Arase and RBSP‐A satellites observed typical signatures of EMIC waves in the inner magnetosphere. Within this interval, Defense Meteorological Satellite Program (DMSP) and National Oceanic and Atmospheric Administration (NOAA)/MetOp satellites observed significant proton precipitation in the dusk‐midnight sector. Simulation results show that H‐ and He‐band EMIC waves are excited within regions of strong temperature anisotropy near the plasmapause. The simulated growth rates of EMIC waves show a similar trend to that of the EMIC wave power observed by the Arase and RBSP‐A satellites, suggesting that the model can reproduce the EMIC wave activity qualitatively. The simulated H‐band waves in the dusk sector are stronger than He‐band waves possibly due to the presence of excess protons in the boundary conditions obtained from the BATS‐R‐US code. The precipitating proton fluxes reproduced by the simulation with EMIC waves are found to agree reasonably well with the DMSP and NOAA/MetOp satellite observations. It is suggested that EMIC wave scattering of ring current ions can account for proton precipitation observed by the DMSP and MetOp satellites during the 27 May 2017 storm.

Influence of Supraglacial Lakes on Accuracy of Inversion of Greenland Ice Sheet Surface Melt Data in Different Passive Microwave Bands

The occurrence of Supraglacial Lakes (SGLs) may influence the signals acquired with microwave radiometers, which may result in a degree of uncertainty when employing microwave radiometer data for the detection of surface melt. Accurate monitoring of surface melting requires a reasonable assessment of this uncertainty. However, there is a scarcity of research in this field. Therefore, in this study, we computed surface melt in the vicinity of Automatic Weather Stations (AWSs) by employing Defense Meteorological Satellite Program (DMSP) Ka-band data and Soil Moisture and Ocean Salinity (SMOS) satellite L-band data and extracted SGL pixels by utilizing Sentinel-2 data. A comparison between surface melt results derived from AWS air temperature estimates and those obtained with remote sensing inversion in the two different bands was conducted for sites below the mean snowline elevation during the summers of 2016 to 2020. Compared with sites with no SGLs, the commission error (CO) of DMSP morning and evening data at sites where these water bodies were present increased by 36% and 30%, respectively, and the number of days with CO increased by 12 and 3 days, respectively. The omission error (OM) of SMOS morning and evening data increased by 33% and 32%, respectively, and the number of days with OM increased by 17 and 21 days, respectively. Identifying the source of error is a prerequisite for the improvement of surface melt algorithms, for which this study provides a basis.