Pub Date : 2021-08-09DOI: 10.23919/USNC-URSIRSM52661.2021.9552374
M. Usanova, L. Blum
Electromagnetic ion cyclotron (EMIC) waves are transverse electromagnetic waves typically generated in the equatorial magnetosphere by anisotropic proton distributions. These waves can resonantly interact with multiple particle populations in the inner magnetosphere believed to be an important loss mechanism for both ring current ions and radiation belt electrons, as well as a cold plasma heating source. The spatiotemporal extent of wave activity is one of the key parameters used to quantify the effects of EMIC waves on magnetospheric plasma populations. However, from single-point spacecraft measurements or ground based observations alone, it is challenging to get the full picture of wave occurrence distributions. Due to a number of processes, ground and in situ observations of EMIC wave activity, specifically, its global occurrence, duration, and frequency often exhibit noticeable variations [1]. In particular, EMIC waves in the H+ frequency band are not always seen on the ground conjugately to locations of space observations [2]. In addition, ground and space EMIC wave distributions have different dependencies on local time, L shell, and geomagnetic activity, adding to the challenge of comparing measurements across these platforms [3]. Here we address this challenge by examining the relationship between EMIC wave occurrence and power on the Van Allen Probes and conjugate CARISMA ground magnetometer stations in the Canadian sector. We apply an automated wave detection algorithm to magnetometer data [4]. We present an analysis of long-term simultaneous EMIC wave observations in space and on the ground, and study wave propagation characteristics in the He+ and H+ frequency bands during different geomagnetic conditions.
{"title":"Analysis of Conjugate Satellite and Ground EMIC Wave Observations","authors":"M. Usanova, L. Blum","doi":"10.23919/USNC-URSIRSM52661.2021.9552374","DOIUrl":"https://doi.org/10.23919/USNC-URSIRSM52661.2021.9552374","url":null,"abstract":"Electromagnetic ion cyclotron (EMIC) waves are transverse electromagnetic waves typically generated in the equatorial magnetosphere by anisotropic proton distributions. These waves can resonantly interact with multiple particle populations in the inner magnetosphere believed to be an important loss mechanism for both ring current ions and radiation belt electrons, as well as a cold plasma heating source. The spatiotemporal extent of wave activity is one of the key parameters used to quantify the effects of EMIC waves on magnetospheric plasma populations. However, from single-point spacecraft measurements or ground based observations alone, it is challenging to get the full picture of wave occurrence distributions. Due to a number of processes, ground and in situ observations of EMIC wave activity, specifically, its global occurrence, duration, and frequency often exhibit noticeable variations [1]. In particular, EMIC waves in the H+ frequency band are not always seen on the ground conjugately to locations of space observations [2]. In addition, ground and space EMIC wave distributions have different dependencies on local time, L shell, and geomagnetic activity, adding to the challenge of comparing measurements across these platforms [3]. Here we address this challenge by examining the relationship between EMIC wave occurrence and power on the Van Allen Probes and conjugate CARISMA ground magnetometer stations in the Canadian sector. We apply an automated wave detection algorithm to magnetometer data [4]. We present an analysis of long-term simultaneous EMIC wave observations in space and on the ground, and study wave propagation characteristics in the He+ and H+ frequency bands during different geomagnetic conditions.","PeriodicalId":365284,"journal":{"name":"2021 USNC-URSI Radio Science Meeting (USCN-URSI RSM)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116224425","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-08-09DOI: 10.23919/USNC-URSIRSM52661.2021.9552364
D. Turner, C. Wilkins, Wen Li, V. Angelopoulos
The Electron Losses and Fields Investigation (ELFIN) is a satellite mission 1 launched in 2018 consisting of two, identical 3U CubeSats in circular, polar LEO orbit at altitudes ~450 km. Onboard each spacecraft, the ELFIN prime payloads consist of energetic particle telescopes and boom-deployed fluxgate magnetometers. Each orbit, ELFIN observes energetic electrons ranging from 50 keV to 7 MeV precipitating from Earth's radiation belts, and ELFIN presents the opportunity to study such radiation belt losses in unprecedented energy resolution with multipoint observations that enable some disambiguation of spatiotemporal evolution. Furthermore, the ELFIN spacecraft are spinners, revealing for the first time details of electron pitch angle distributions within the atmospheric loss cones. In this talk, we will introduce the ELFIN mission and system and payloads. Next, we present new results from ELFIN highlighting several enlightening features of outer radiation belt precipitation, including: energy spectra of> 1 MeV precipitation events and microbursts; spatial structure and temporal evolution of precipitation bands; evidence of localized regions of enhanced precipitation, presumably from chorus wave activity just outside the plasmapause; quantification of steady “drizzle” of electrons into the atmospheric loss cones vs. enhanced, time-limited microbursts and precipitation bands; and quantification of atmospheric backscatter of precipitating electrons. All of these are new insights enabled by the unique observations made possible from the multipoint ELFIN mission.
{"title":"New perspectives on radiation belt precipitation from the ELFIN CubeSats","authors":"D. Turner, C. Wilkins, Wen Li, V. Angelopoulos","doi":"10.23919/USNC-URSIRSM52661.2021.9552364","DOIUrl":"https://doi.org/10.23919/USNC-URSIRSM52661.2021.9552364","url":null,"abstract":"The Electron Losses and Fields Investigation (ELFIN) is a satellite mission 1 launched in 2018 consisting of two, identical 3U CubeSats in circular, polar LEO orbit at altitudes ~450 km. Onboard each spacecraft, the ELFIN prime payloads consist of energetic particle telescopes and boom-deployed fluxgate magnetometers. Each orbit, ELFIN observes energetic electrons ranging from 50 keV to 7 MeV precipitating from Earth's radiation belts, and ELFIN presents the opportunity to study such radiation belt losses in unprecedented energy resolution with multipoint observations that enable some disambiguation of spatiotemporal evolution. Furthermore, the ELFIN spacecraft are spinners, revealing for the first time details of electron pitch angle distributions within the atmospheric loss cones. In this talk, we will introduce the ELFIN mission and system and payloads. Next, we present new results from ELFIN highlighting several enlightening features of outer radiation belt precipitation, including: energy spectra of> 1 MeV precipitation events and microbursts; spatial structure and temporal evolution of precipitation bands; evidence of localized regions of enhanced precipitation, presumably from chorus wave activity just outside the plasmapause; quantification of steady “drizzle” of electrons into the atmospheric loss cones vs. enhanced, time-limited microbursts and precipitation bands; and quantification of atmospheric backscatter of precipitating electrons. All of these are new insights enabled by the unique observations made possible from the multipoint ELFIN mission.","PeriodicalId":365284,"journal":{"name":"2021 USNC-URSI Radio Science Meeting (USCN-URSI RSM)","volume":"41 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123844696","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-08-09DOI: 10.23919/USNC-URSIRSM52661.2021.9552343
Mohsen Sabbaghi, Jun Zhang, G. Hanson
Here, we showcase an application of neural networks (NNs) to solve an inverse problem in electromagnetics. Wires are randomly distributed into an area of known dimensions. The wires are then illuminated with a monochromatic plane wave (PW) at a certain angle of incidence, and the electromagnetic (EM) field measured at a finite number of points along the perimeter of the area is then fed into a convolutional neural network (CNN) designed to predict either (i) the number of the wires or (ii) the location of the wires.
{"title":"Target counting and location detection in electromagnetics using convolutional neural networks","authors":"Mohsen Sabbaghi, Jun Zhang, G. Hanson","doi":"10.23919/USNC-URSIRSM52661.2021.9552343","DOIUrl":"https://doi.org/10.23919/USNC-URSIRSM52661.2021.9552343","url":null,"abstract":"Here, we showcase an application of neural networks (NNs) to solve an inverse problem in electromagnetics. Wires are randomly distributed into an area of known dimensions. The wires are then illuminated with a monochromatic plane wave (PW) at a certain angle of incidence, and the electromagnetic (EM) field measured at a finite number of points along the perimeter of the area is then fed into a convolutional neural network (CNN) designed to predict either (i) the number of the wires or (ii) the location of the wires.","PeriodicalId":365284,"journal":{"name":"2021 USNC-URSI Radio Science Meeting (USCN-URSI RSM)","volume":"123 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123997842","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-08-09DOI: 10.23919/USNC-URSIRSM52661.2021.9552344
Allison N. Javnes, Jayasri Joseph, Joshua Doucette, D. Baker, Xinlin Li, S. Kanekal
High-energy electron populations within the Van Allen radiation belts are highly dynamic, and seen to increase and decrease on timescales as short as hours. One of the lingering questions about radiation belt dynamics overall is which types of plasma waves are responsible for the various changes we observe. Here, we present two studies that illuminate how ULF waves shape the boundaries and enhancements of relativistic electrons. One result, using seven years of Van Allen Probes satellite data, shows that ULF waves can create multi-MeV flux enhancements following geomagnetically active periods. Thus, ULF-driven radial diffusion can often be the dominant mechanism behind ultrarelativistic electron enhancements; although high populations of lower energies, likely produced by VLF interactions, are a necessary precondition. A second analysis, looking at decades of POES data, shows that relativistic breaches of the lower boundary of the outer belt happen in concert with elevated ULF wave power yet are not associated with particular type of solar driving. How relativistic electrons can cross this barrier and enter into the slot region and inner zone is crucial for understanding the radiation environment in this regime closest to Earth.
{"title":"Boundaries and enhancements: ULF wave-driven dynamics of energetic particles in the Van Allen belts","authors":"Allison N. Javnes, Jayasri Joseph, Joshua Doucette, D. Baker, Xinlin Li, S. Kanekal","doi":"10.23919/USNC-URSIRSM52661.2021.9552344","DOIUrl":"https://doi.org/10.23919/USNC-URSIRSM52661.2021.9552344","url":null,"abstract":"High-energy electron populations within the Van Allen radiation belts are highly dynamic, and seen to increase and decrease on timescales as short as hours. One of the lingering questions about radiation belt dynamics overall is which types of plasma waves are responsible for the various changes we observe. Here, we present two studies that illuminate how ULF waves shape the boundaries and enhancements of relativistic electrons. One result, using seven years of Van Allen Probes satellite data, shows that ULF waves can create multi-MeV flux enhancements following geomagnetically active periods. Thus, ULF-driven radial diffusion can often be the dominant mechanism behind ultrarelativistic electron enhancements; although high populations of lower energies, likely produced by VLF interactions, are a necessary precondition. A second analysis, looking at decades of POES data, shows that relativistic breaches of the lower boundary of the outer belt happen in concert with elevated ULF wave power yet are not associated with particular type of solar driving. How relativistic electrons can cross this barrier and enter into the slot region and inner zone is crucial for understanding the radiation environment in this regime closest to Earth.","PeriodicalId":365284,"journal":{"name":"2021 USNC-URSI Radio Science Meeting (USCN-URSI RSM)","volume":"19 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122051012","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-08-09DOI: 10.23919/USNC-URSIRSM52661.2021.9552359
C. Suer, D. Breton, C. Haedrich, R. Lang
Bistatic scattering coefficients are computed for a site on a tree covered mountainside at L Band. The layer which consists of inclined trees is modeled by discrete scatterers consisting of trunks, branches, needles and leaves with varying orientations and dimensions. Due to the sloped nature of the terrain, azimuthal asymmetry occurs and this causes mixing of polarizations of the incident and scattered waves. The mean equation is solved to acquire the propagation constants inside the layer. Direct (volume) scattering is found to be the dominant scattering mechanism for the modeled layer at L band. Ground truth measurement data is used to simulate the attenuations. Further study shall be done to compare the bistatic scattering results with the ground truth measurements to be made in July 2021.
{"title":"Bistatic Scattering Coefficients of a Tree Covered Mountainside at L Band","authors":"C. Suer, D. Breton, C. Haedrich, R. Lang","doi":"10.23919/USNC-URSIRSM52661.2021.9552359","DOIUrl":"https://doi.org/10.23919/USNC-URSIRSM52661.2021.9552359","url":null,"abstract":"Bistatic scattering coefficients are computed for a site on a tree covered mountainside at L Band. The layer which consists of inclined trees is modeled by discrete scatterers consisting of trunks, branches, needles and leaves with varying orientations and dimensions. Due to the sloped nature of the terrain, azimuthal asymmetry occurs and this causes mixing of polarizations of the incident and scattered waves. The mean equation is solved to acquire the propagation constants inside the layer. Direct (volume) scattering is found to be the dominant scattering mechanism for the modeled layer at L band. Ground truth measurement data is used to simulate the attenuations. Further study shall be done to compare the bistatic scattering results with the ground truth measurements to be made in July 2021.","PeriodicalId":365284,"journal":{"name":"2021 USNC-URSI Radio Science Meeting (USCN-URSI RSM)","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128873023","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-08-09DOI: 10.23919/USNC-URSIRSM52661.2021.9552349
Xu Liu, W. Gu, Z. Xia, Lunjin Chen, R. Horne
The plasmasphere is a vast torus shape region of the inner magnetosphere, filled with dense $left(sim 1-10^{6} # / text{cm}^{-3}right)$ and cold (less than $10 text{eV})$ ions and electrons. The outer boundary of the plasmasphere, called plasmapause, is a sharp plasma density boundary that separates closed and open drift paths for cold plasmas. Distinct plasmapause with sharp density variations are only 16% of the observed plasmapause and are preferred to occur at the post-midnight and dawnside than the duskside. Most of the plasmapause, however, is accompanied by significant density irregularities. These density irregularities are thought to play an important role in wave excitation and propagation, such as the excitation of the electromagnetic ion cyclotron (EMIC) waves and magnetosonic (MS) waves, and the propagation of EMIC wave and MS waves.
等离子层是内磁层的一个巨大的环状区域，充满了密集的$left(sim 1-10^{6} # / text{cm}^{-3}right)$和冷的(小于$10 text{eV})$)离子和电子。等离子体层的外边界，称为等离子体顶，是一个尖锐的等离子体密度边界，它将冷等离子体的封闭和开放漂移路径分开。具有明显密度变化的等离子体ause只有16个% of the observed plasmapause and are preferred to occur at the post-midnight and dawnside than the duskside. Most of the plasmapause, however, is accompanied by significant density irregularities. These density irregularities are thought to play an important role in wave excitation and propagation, such as the excitation of the electromagnetic ion cyclotron (EMIC) waves and magnetosonic (MS) waves, and the propagation of EMIC wave and MS waves.
{"title":"Two Whistler-Mode Waves Modulation By Background-Level Density Irregularity During The Recovery Phase of A Geomagnetic Storm","authors":"Xu Liu, W. Gu, Z. Xia, Lunjin Chen, R. Horne","doi":"10.23919/USNC-URSIRSM52661.2021.9552349","DOIUrl":"https://doi.org/10.23919/USNC-URSIRSM52661.2021.9552349","url":null,"abstract":"The plasmasphere is a vast torus shape region of the inner magnetosphere, filled with dense $left(sim 1-10^{6} # / text{cm}^{-3}right)$ and cold (less than $10 text{eV})$ ions and electrons. The outer boundary of the plasmasphere, called plasmapause, is a sharp plasma density boundary that separates closed and open drift paths for cold plasmas. Distinct plasmapause with sharp density variations are only 16% of the observed plasmapause and are preferred to occur at the post-midnight and dawnside than the duskside. Most of the plasmapause, however, is accompanied by significant density irregularities. These density irregularities are thought to play an important role in wave excitation and propagation, such as the excitation of the electromagnetic ion cyclotron (EMIC) waves and magnetosonic (MS) waves, and the propagation of EMIC wave and MS waves.","PeriodicalId":365284,"journal":{"name":"2021 USNC-URSI Radio Science Meeting (USCN-URSI RSM)","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126614878","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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