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M Spasojevic - One of the best experts on this subject based on the ideXlab platform.
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electromagnetic ion cyclotron Wave modeling during the geospace environment modeling challenge event
2014Co-Authors: Lunjin Chen, V K Jordanova, M Spasojevic, R M Thorne, Richard B HorneAbstract:We investigate the temporal evolution and the spatial Distribution of electromagnetic ion cyclotron (EMIC) Waves during the 8–11 June 2001 geomagnetic storm, one of the storms selected for study by the Geospace Environment Modeling program. Generations of EMIC Waves in the H+, He+, and O+ bands are simulated using the kinetic ring current-atmosphere interactions model with a self-consistent magnetic field and a ray tracing code. Simulations show that strong Wave gain occurs in the afternoon sector at L > 5 and overlaps with a high-density plasmaspheric drainage plume. EMIC Wave gain maximizes during the main phase and decreases in the recovery phase. We find that EMIC Wave gain is stronger in the He+ band than in the other two bands in the inner magnetosphere, except the region of low L (< 3) where the H+ band is dominant due to an enhancement in the ring current anisotropy. Little Wave gain is obtained for the O+ band. Comparison with in situ EMIC events and EMIC event proxies at five geosynchronous satellites shows consistence in the temporal and local time evolution of the Wave Distribution. Our simulations of the EMIC Wave Distribution also agree with proton aurora at subauroral latitudes observed from the Imager for Magnetopause-to-Aurora Global Exploration satellite.
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correspondence between a plasma based emic Wave proxy and subauroral proton precipitation
2011Co-Authors: M Spasojevic, L W Blum, E Macdonald, S A Fuselier, D I GoldenAbstract:[1] The loss of relativistic electrons from the Earth's radiation belts as a result of resonant interactions with electromagnetic ion cyclotron Waves (EMIC) Waves has yet to be fully quantified, in part, due to the lack of global measurements of the Wave Distribution during individual storm events. Recent work has focused on augmenting direct Wave measurements with proxy Wave indicators. Here we compare two different techniques for inferring the presence of EMIC Waves: 1) a Wave-growth proxy and amplitude estimate based on in situ plasma measurements of the cold and hot ion Distributions, and 2) FUV observations of subauroral proton precipitation, which is thought to result from interactions with EMIC Waves. For two event intervals, we show good correspondence between proxy predictions of Wave growth, calculated using measurements from geostationary spacecraft, and precipitation observed at the northern hemisphere ionospheric footprint. Further, for times when the proxy is positive, we observe a moderate positive correlation (r = 0.56) between the predicted Wave amplitude and the mean FUV brightness in a 300-km circle about the footprint. Further development and verification of these techniques will enhance our ability to infer the global Distribution of EMIC Waves when direct measurements are not available.
George B. Hospodarsky - One of the best experts on this subject based on the ideXlab platform.
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Quantitative Evaluation of Radial Diffusion and Local Acceleration Processes During GEM Challenge Events
2018Co-Authors: Jacob Bortnik, Richard M. Thorne, Geoffrey D. Reeves, Craig Kletzing, Xiangning Chu, Louis G. Ozeke, William S. Kurth, George B. HospodarskyAbstract:We simulate the radiation belt electron flux enhancements during selected Geospace Environment Modeling (GEM) challenge events to quantitatively compare the major processes involved in relativistic electron acceleration under different conditions. Van Allen Probes observed significant electron flux enhancement during both the storm time of 17–18 March 2013 and non–storm time of 19–20 September 2013, but the Distributions of plasma Waves and energetic electrons for the two events were dramatically different. During 17–18 March 2013, the SYM-H minimum reached −130 nT, intense chorus Waves (peak Bw ~140 pT) occurred at 3.5 5.5, and electron fluxes at energies up to 3 MeV increased by a factor of ~5 at L > 5.5. The two electron flux enhancement events were simulated using the available Wave Distribution and diffusion coefficients from the GEM focus group Quantitative Assessment of Radiation Belt Modeling. By comparing the individual roles of local electron heating and radial transport, our simulation indicates that resonant interaction with chorus Waves is the dominant process that accounts for the electron flux enhancement during the storm time event particularly near the flux peak locations, while radial diffusion by ultralow-frequency Waves plays a dominant role in the enhancement during the non–storm time event. Incorporation of both processes reasonably reproduces the observed location and magnitude of electron flux enhancement.
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electron scattering by magnetosonic Waves in the inner magnetosphere
2016Co-Authors: R M Thorne, Jacob Bortnik, Craig Kletzing, W S Kurth, George B. HospodarskyAbstract:PUBLICATIONS Journal of Geophysical Research: Space Physics RESEARCH ARTICLE 10.1002/2015JA021992 Key Points: • A new statistics of magnetosonic Waves is performed • Magnetosonic Waves can lead to the butterfly Distributions of energetic electrons • Typical acceleration of electrons by magnetosonic Waves is slower than energization by chorus Correspondence to: Q. Ma, qianlima@atmos.ucla.edu Citation: Ma, Q., W. Li, R. M. Thorne, J. Bortnik, C. A. Kletzing, W. S. Kurth, and G. B. Hospodarsky (2016), Electron scattering by magnetosonic Waves in the inner magnetosphere, J. Geophys. Res. Space Physics, 121, 274–285, doi:10.1002/2015JA021992. Received 4 OCT 2015 Accepted 21 DEC 2015 Accepted article online 28 DEC 2015 Published online 20 JAN 2016 Electron scattering by magnetosonic Waves in the inner magnetosphere Qianli Ma 1 , Wen Li 1 , Richard M. Thorne 1 , Jacob Bortnik 1 , C. A. Kletzing 2 , W. S. Kurth 2 , and G. B. Hospodarsky 2 Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles, California, USA, 2 Department of Physics and Astronomy, University of Iowa, Iowa City, Iowa, USA Abstract We investigate the importance of electron scattering by magnetosonic Waves in the Earth’s inner magnetosphere. A statistical survey of the magnetosonic Wave amplitude and Wave frequency spectrum, as a function of geomagnetic activity, is performed using the Van Allen Probes Wave measurements and is found to be generally consistent with the Wave Distribution obtained from previous spacecraft missions. Outside the plasmapause the statistical frequency Distribution of magnetosonic Waves follows the variation of the lower hybrid resonance frequency, but this trend is not observed inside the plasmasphere. Drift and bounce averaged electron diffusion rates due to magnetosonic Waves are calculated using a recently developed analytical formula. The resulting timescale of electron energization during disturbed conditions (when AE* > 300 nT) is more than 10 days. We perform a 2-D simulation of the electron phase space density evolution due to magnetosonic Wave scattering during disturbed conditions. Outside the plasmapause, the Waves accelerate electrons with pitch angles between 50° and 70° and form butterfly pitch angle Distributions at energies from ~100 keV to a few MeV over a timescale of several days; whereas inside the plasmapause, the electron acceleration is very weak. Our study suggests that intense magnetosonic Waves may cause the butterfly Distribution of radiation belt electrons especially outside the plasmapause, but electron acceleration due to magnetosonic Waves is generally not as effective as chorus Wave acceleration. 1. Introduction Fast magnetosonic Waves are highly oblique whistler-mode electromagnetic emissions generated in the frequency range between the local proton gyrofrequency (f cp ) and the lower hybrid resonance frequency (f LHR ) [e.g., Perraut et al., 1982; Laakso et al., 1990; Santolik et al., 2002] and are primarily observed by spacecraft within 5° of the Earth’s magnetic equator [Russell and Holzer, 1970; Němec et al., 2005, 2006; Pokhotelov et al., 2008; Santolik et al., 2004]. The Waves occur over a broad spatial region between 2 R E and 8 R E both inside and outside the plasmapause, with highest Wave intensities observed near the dayside during geomagnetically disturbed conditions [Meredith et al., 2008; Ma et al., 2013; Němec et al., 2015]. Ion ring Distributions provide free energy for the local excitation of magnetosonic Waves when the ion ring energy is close to the local Alfven energy and typically occur over a broad region outside the plasmapause and near the outer edge of the plasmasphere [Chen et al., 2010; Jordanova et al., 2012; Ma et al., 2014a]. The injected ion populations may account for the excitation of magnetosonic Waves especially on the dayside outside the plasmapause [Boardsen et al., 1992; Chen et al., 2011; Thomsen et al., 2011; Xiao et al., 2013], and the excited Waves then propagate in both radial and azimuthal directions [e.g., Xiao et al., 2012]. Magnetosonic Waves propagate nearly perpendicularly to the background magnetic field near the equatorial plane [Kasahara et al., 1994; Chen and Thorne, 2012], and the Waves inside the plasmapause may become naturally trapped within the plasmasphere [Ma et al., 2014b]. ©2015. American Geophysical Union. All Rights Reserved. MA ET AL. The energetic electron populations in the Earth’s outer radiation belt can experience diffusive scattering by various plasma Waves [Kennel and Engelmann, 1966; Lyons, 1974a, 1974b]. Two important magnetospheric Waves that cause local electron acceleration in the radiation belts are whistler-mode chorus and magnetosonic Waves [Thorne, 2010]. The Van Allen Probes observations and their related simulation studies have confirmed that whistler-mode chorus Waves provide sufficient local heating of energetic electrons in the heart of radiation belts during geomagnetic storm periods [Reeves et al., 2013; Thorne et al., 2013; Foster et al., 2014; Li et al., 2014b]. On the other hand, intense magnetosonic Wave events are observed by the spacecraft in the inner magnetosphere and could have a potential role in electron acceleration via Landau resonance and transit-time scattering effects [Horne et al., 2007; Bortnik and Thorne, 2010; Li et al., 2014a]. During Landau resonant ELECTRON SCATTERING BY MS WaveS
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analysis of plasmaspheric hiss Wave amplitudes inferred from low altitude poes electron data validation with conjunctive van allen probes observations
2015Co-Authors: Jacob Bortnik, Craig Kletzing, R M Thorne, M De Soriasantacruz, W S Kurth, George B. HospodarskyAbstract:©2015. American Geophysical Union. All Rights Reserved. Plasmaspheric hiss plays an important role in controlling the overall structure and dynamics of the Earth's radiation belts. The interaction of plasmaspheric hiss with radiation belt electrons is commonly evaluated using diffusion codes, which rely on statistical models of Wave observations that may not accurately reproduce the instantaneous global Wave Distribution or the limited in situ satellite Wave measurements. This paper evaluates the performance and limitations of a novel technique capable of inferring Wave amplitudes from low-altitude electron flux observations from the Polar Orbiting Environmental Satellites (POES), which provide extensive coverage in shell and magnetic local time (MLT). We found that, within its limitations, this technique could potentially be used to build a dynamic global model of the plasmaspheric hiss Wave intensity. The technique is validated by analyzing the conjunctions between the POES spacecraft and the Van Allen Probes from September 2012 to June 2014. The technique performs well for moderate-to-strong hiss activity (≥30 pT) with sufficiently high electron fluxes. The main source of these limitations is the number of counts of energetic electrons measured by the POES spacecraft capable of resonating with hiss Waves. For moderate-to-strong hiss events, the results show that the Wave amplitudes from the EMFISIS instruments on board the Van Allen Probes are well reproduced by the POES technique, which provides more consistent estimates than the parameterized statistical hiss Wave model based on CRRES data.
R M Thorne - One of the best experts on this subject based on the ideXlab platform.
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electron scattering by magnetosonic Waves in the inner magnetosphere
2016Co-Authors: R M Thorne, Jacob Bortnik, Craig Kletzing, W S Kurth, George B. HospodarskyAbstract:PUBLICATIONS Journal of Geophysical Research: Space Physics RESEARCH ARTICLE 10.1002/2015JA021992 Key Points: • A new statistics of magnetosonic Waves is performed • Magnetosonic Waves can lead to the butterfly Distributions of energetic electrons • Typical acceleration of electrons by magnetosonic Waves is slower than energization by chorus Correspondence to: Q. Ma, qianlima@atmos.ucla.edu Citation: Ma, Q., W. Li, R. M. Thorne, J. Bortnik, C. A. Kletzing, W. S. Kurth, and G. B. Hospodarsky (2016), Electron scattering by magnetosonic Waves in the inner magnetosphere, J. Geophys. Res. Space Physics, 121, 274–285, doi:10.1002/2015JA021992. Received 4 OCT 2015 Accepted 21 DEC 2015 Accepted article online 28 DEC 2015 Published online 20 JAN 2016 Electron scattering by magnetosonic Waves in the inner magnetosphere Qianli Ma 1 , Wen Li 1 , Richard M. Thorne 1 , Jacob Bortnik 1 , C. A. Kletzing 2 , W. S. Kurth 2 , and G. B. Hospodarsky 2 Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles, California, USA, 2 Department of Physics and Astronomy, University of Iowa, Iowa City, Iowa, USA Abstract We investigate the importance of electron scattering by magnetosonic Waves in the Earth’s inner magnetosphere. A statistical survey of the magnetosonic Wave amplitude and Wave frequency spectrum, as a function of geomagnetic activity, is performed using the Van Allen Probes Wave measurements and is found to be generally consistent with the Wave Distribution obtained from previous spacecraft missions. Outside the plasmapause the statistical frequency Distribution of magnetosonic Waves follows the variation of the lower hybrid resonance frequency, but this trend is not observed inside the plasmasphere. Drift and bounce averaged electron diffusion rates due to magnetosonic Waves are calculated using a recently developed analytical formula. The resulting timescale of electron energization during disturbed conditions (when AE* > 300 nT) is more than 10 days. We perform a 2-D simulation of the electron phase space density evolution due to magnetosonic Wave scattering during disturbed conditions. Outside the plasmapause, the Waves accelerate electrons with pitch angles between 50° and 70° and form butterfly pitch angle Distributions at energies from ~100 keV to a few MeV over a timescale of several days; whereas inside the plasmapause, the electron acceleration is very weak. Our study suggests that intense magnetosonic Waves may cause the butterfly Distribution of radiation belt electrons especially outside the plasmapause, but electron acceleration due to magnetosonic Waves is generally not as effective as chorus Wave acceleration. 1. Introduction Fast magnetosonic Waves are highly oblique whistler-mode electromagnetic emissions generated in the frequency range between the local proton gyrofrequency (f cp ) and the lower hybrid resonance frequency (f LHR ) [e.g., Perraut et al., 1982; Laakso et al., 1990; Santolik et al., 2002] and are primarily observed by spacecraft within 5° of the Earth’s magnetic equator [Russell and Holzer, 1970; Němec et al., 2005, 2006; Pokhotelov et al., 2008; Santolik et al., 2004]. The Waves occur over a broad spatial region between 2 R E and 8 R E both inside and outside the plasmapause, with highest Wave intensities observed near the dayside during geomagnetically disturbed conditions [Meredith et al., 2008; Ma et al., 2013; Němec et al., 2015]. Ion ring Distributions provide free energy for the local excitation of magnetosonic Waves when the ion ring energy is close to the local Alfven energy and typically occur over a broad region outside the plasmapause and near the outer edge of the plasmasphere [Chen et al., 2010; Jordanova et al., 2012; Ma et al., 2014a]. The injected ion populations may account for the excitation of magnetosonic Waves especially on the dayside outside the plasmapause [Boardsen et al., 1992; Chen et al., 2011; Thomsen et al., 2011; Xiao et al., 2013], and the excited Waves then propagate in both radial and azimuthal directions [e.g., Xiao et al., 2012]. Magnetosonic Waves propagate nearly perpendicularly to the background magnetic field near the equatorial plane [Kasahara et al., 1994; Chen and Thorne, 2012], and the Waves inside the plasmapause may become naturally trapped within the plasmasphere [Ma et al., 2014b]. ©2015. American Geophysical Union. All Rights Reserved. MA ET AL. The energetic electron populations in the Earth’s outer radiation belt can experience diffusive scattering by various plasma Waves [Kennel and Engelmann, 1966; Lyons, 1974a, 1974b]. Two important magnetospheric Waves that cause local electron acceleration in the radiation belts are whistler-mode chorus and magnetosonic Waves [Thorne, 2010]. The Van Allen Probes observations and their related simulation studies have confirmed that whistler-mode chorus Waves provide sufficient local heating of energetic electrons in the heart of radiation belts during geomagnetic storm periods [Reeves et al., 2013; Thorne et al., 2013; Foster et al., 2014; Li et al., 2014b]. On the other hand, intense magnetosonic Wave events are observed by the spacecraft in the inner magnetosphere and could have a potential role in electron acceleration via Landau resonance and transit-time scattering effects [Horne et al., 2007; Bortnik and Thorne, 2010; Li et al., 2014a]. During Landau resonant ELECTRON SCATTERING BY MS WaveS
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analysis of plasmaspheric hiss Wave amplitudes inferred from low altitude poes electron data validation with conjunctive van allen probes observations
2015Co-Authors: Jacob Bortnik, Craig Kletzing, R M Thorne, M De Soriasantacruz, W S Kurth, George B. HospodarskyAbstract:©2015. American Geophysical Union. All Rights Reserved. Plasmaspheric hiss plays an important role in controlling the overall structure and dynamics of the Earth's radiation belts. The interaction of plasmaspheric hiss with radiation belt electrons is commonly evaluated using diffusion codes, which rely on statistical models of Wave observations that may not accurately reproduce the instantaneous global Wave Distribution or the limited in situ satellite Wave measurements. This paper evaluates the performance and limitations of a novel technique capable of inferring Wave amplitudes from low-altitude electron flux observations from the Polar Orbiting Environmental Satellites (POES), which provide extensive coverage in shell and magnetic local time (MLT). We found that, within its limitations, this technique could potentially be used to build a dynamic global model of the plasmaspheric hiss Wave intensity. The technique is validated by analyzing the conjunctions between the POES spacecraft and the Van Allen Probes from September 2012 to June 2014. The technique performs well for moderate-to-strong hiss activity (≥30 pT) with sufficiently high electron fluxes. The main source of these limitations is the number of counts of energetic electrons measured by the POES spacecraft capable of resonating with hiss Waves. For moderate-to-strong hiss events, the results show that the Wave amplitudes from the EMFISIS instruments on board the Van Allen Probes are well reproduced by the POES technique, which provides more consistent estimates than the parameterized statistical hiss Wave model based on CRRES data.
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electromagnetic ion cyclotron Wave modeling during the geospace environment modeling challenge event
2014Co-Authors: Lunjin Chen, V K Jordanova, M Spasojevic, R M Thorne, Richard B HorneAbstract:We investigate the temporal evolution and the spatial Distribution of electromagnetic ion cyclotron (EMIC) Waves during the 8–11 June 2001 geomagnetic storm, one of the storms selected for study by the Geospace Environment Modeling program. Generations of EMIC Waves in the H+, He+, and O+ bands are simulated using the kinetic ring current-atmosphere interactions model with a self-consistent magnetic field and a ray tracing code. Simulations show that strong Wave gain occurs in the afternoon sector at L > 5 and overlaps with a high-density plasmaspheric drainage plume. EMIC Wave gain maximizes during the main phase and decreases in the recovery phase. We find that EMIC Wave gain is stronger in the He+ band than in the other two bands in the inner magnetosphere, except the region of low L (< 3) where the H+ band is dominant due to an enhancement in the ring current anisotropy. Little Wave gain is obtained for the O+ band. Comparison with in situ EMIC events and EMIC event proxies at five geosynchronous satellites shows consistence in the temporal and local time evolution of the Wave Distribution. Our simulations of the EMIC Wave Distribution also agree with proton aurora at subauroral latitudes observed from the Imager for Magnetopause-to-Aurora Global Exploration satellite.
F Gardner - One of the best experts on this subject based on the ideXlab platform.
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linear pm generator system for Wave energy conversion in the aws
2004Co-Authors: H Polinder, M Damen, F GardnerAbstract:The Archimedes Wave Swing is a system that converts ocean Wave energy into electric energy. A pilot plant of this system has been built. The generator system consists of a permanent-magnet linear synchronous generator with a current source inverter (CSI). The correlation between the measured and the calculated parameters of the designed generator is reasonable. The annual energy yield of the pilot plant is calculated from the Wave Distribution as 1.64 GWh. Using a voltage source inverter instead of a CSI improves the power factor, the current Waveforms, the efficiency and the generator force, so that the annual energy yield increases with 18%.
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linear pm generator for Wave energy conversion in the aws
2000Co-Authors: H Polinder, F Gardner, B VriesemaAbstract:The Archimedes Wave Swing (AWS) is a system which converts ocean Wave energy into electric energy. It is planned to install a pilot plant of the AWS at the coast of Portugal to prove the survivability of the system. The AWS is an air-filled chamber of which the lid is moved up and down by the Waves. This paper focusses on the energy yield and the generator system. From the linear motion, energy is extracted by means of a linear permanent-magnet (PM) generator, the design of which is described. The generator is connected to the utility grid via an umbilical and a voltage source inverter. The peak power of the system is 4 MW. From the Wave Distribution, the annual energy yield is calculated as 2.1 GWh. To make the system economically viable, the stroke and the diameter must be increased. (orig.)
Richard B Horne - One of the best experts on this subject based on the ideXlab platform.
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electromagnetic ion cyclotron Wave modeling during the geospace environment modeling challenge event
2014Co-Authors: Lunjin Chen, V K Jordanova, M Spasojevic, R M Thorne, Richard B HorneAbstract:We investigate the temporal evolution and the spatial Distribution of electromagnetic ion cyclotron (EMIC) Waves during the 8–11 June 2001 geomagnetic storm, one of the storms selected for study by the Geospace Environment Modeling program. Generations of EMIC Waves in the H+, He+, and O+ bands are simulated using the kinetic ring current-atmosphere interactions model with a self-consistent magnetic field and a ray tracing code. Simulations show that strong Wave gain occurs in the afternoon sector at L > 5 and overlaps with a high-density plasmaspheric drainage plume. EMIC Wave gain maximizes during the main phase and decreases in the recovery phase. We find that EMIC Wave gain is stronger in the He+ band than in the other two bands in the inner magnetosphere, except the region of low L (< 3) where the H+ band is dominant due to an enhancement in the ring current anisotropy. Little Wave gain is obtained for the O+ band. Comparison with in situ EMIC events and EMIC event proxies at five geosynchronous satellites shows consistence in the temporal and local time evolution of the Wave Distribution. Our simulations of the EMIC Wave Distribution also agree with proton aurora at subauroral latitudes observed from the Imager for Magnetopause-to-Aurora Global Exploration satellite.
