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C A Kletzing - One of the best experts on this subject based on the ideXlab platform.
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comparing simulated and observed Emic wave amplitudes using in situ van allen probes measurements
Journal of Atmospheric and Solar-Terrestrial Physics, 2018Co-Authors: Anthony A. Saikin, J C Zhang, C W Smith, Roy B. Torbert, C A Kletzing, V K Jordanova, H. E. Spence, B. A. Larsen, G D Reeves, Irina ZhelavskayaAbstract:Abstract We perform a statistical study calculating electromagnetic ion cyclotron (Emic) wave amplitudes based off in situ plasma measurements taken by the Van Allen Probes’ (1.1–5.8 Re) Helium, Oxygen, Proton, Electron (HOPE) instrument. Calculated wave amplitudes are compared to Emic waves observed by the Electric and Magnetic Field Instrument Suite and Integrated Science on board the Van Allen Probes during the same period. The survey covers a 22-month period (1 November 2012 to 31 August 2014), a full Van Allen Probe magnetic local time (MLT) precession. The linear theory proxy was used to identify Emic wave events with plasma conditions favorable for Emic wave excitation. Two hundred and thirty-two Emic wave events (103 H+-band and 129 He+-band) were selected for this comparison. Nearly all events selected are observed beyond L = 4. Results show that calculated wave amplitudes exclusively using the in situ HOPE measurements produce amplitudes too low compared to the observed Emic wave amplitudes. Hot proton anisotropy (Ahp) distributions are asymmetric in MLT within the inner (L
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statistical distribution of Emic wave spectra observations from van allen probes
Geophysical Research Letters, 2016Co-Authors: Xiaojia Zhang, C A Kletzing, J Bortnik, W Li, R M Thorne, V Angelopoulos, W S Kurth, G B HospodarskyAbstract:It has been known that electromagnetic ion cyclotron (Emic) waves can precipitate ultrarelativistic electrons through cyclotron resonant scattering. However, the overall effectiveness of this mechanism has yet to be quantified, because it is difficult to obtain the global distribution of Emic waves that usually exhibit limited spatial presence. We construct a statistical distribution of Emic wave frequency spectra and their intensities based on Van Allen Probes measurements from September 2012 to December 2015. Our results show that as the ratio of plasma frequency over electron gyrofrequency increases, Emic wave power becomes progressively dominated by the helium band. There is a pronounced dawn-dusk asymmetry in the wave amplitude and the frequency spectrum. The frequency spectrum does not follow the commonly used single-peak Gaussian function. Incorporating these realistic Emic wave frequency spectra into radiation belt models is expected to improve the quantification of Emic wave scattering effects in ultrarelativistic electron dynamics.
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direct evidence for Emic wave scattering of relativistic electrons in space
Journal of Geophysical Research, 2016Co-Authors: Xiaojia Zhang, C A Kletzing, J Bortnik, W Li, R M Thorne, V Angelopoulos, Lunjin Chen, W S Kurth, G B Hospodarsky, D N BakerAbstract:Electromagnetic ion cyclotron (Emic) waves have been proposed to cause efficient losses of highly relativistic (>1 MeV) electrons via gyroresonant interactions. Simultaneous observations of Emic waves and equatorial electron pitch angle distributions, which can be used to directly quantify the Emic wave scattering effect, are still very limited, however. In the present study, we evaluate the effect of Emic waves on pitch angle scattering of ultrarelativistic (>1 MeV) electrons during the main phase of a geomagnetic storm, when intense Emic wave activity was observed in situ (in the plasma plume region with high plasma density) on both Van Allen Probes. Emic waves captured by Time History of Events and Macroscale Interactions during Substorms (THEMIS) probes and on the ground across the Canadian Array for Real-time Investigations of Magnetic Activity (CARISMA) are also used to infer their magnetic local time (MLT) coverage. From the observed Emic wave spectra and local plasma parameters, we compute wave diffusion rates and model the evolution of electron pitch angle distributions. By comparing model results with local observations of pitch angle distributions, we show direct, quantitative evidence of Emic wave-driven relativistic electron losses in the Earth's outer radiation belt.
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the dependence on geomagnetic conditions and solar wind dynamic pressure of the spatial distributions of Emic waves observed by the van allen probes
Journal of Geophysical Research, 2016Co-Authors: Anthony A. Saikin, J C Zhang, C W Smith, Roy B. Torbert, H. E. Spence, C A KletzingAbstract:A statistical examination on the spatial distributions of electromagnetic ion cyclotron (Emic) waves observed by the Van Allen Probes against varying levels of geomagnetic activity (i.e., AE and SYM-H) and dynamic pressure has been performed. Measurements taken by the Electric and Magnetic Field Instrument Suite and Integrated Science for the first full magnetic local time (MLT) precession of the Van Allen Probes (September 2012–June 2014) are used to identify over 700 Emic wave events. Spatial distributions of Emic waves are found to vary depending on the level of geomagnetic activity and solar wind dynamic pressure. Emic wave events were observed under quiet (AE ≤ 100 nT, 325 wave events), moderate (100 nT 300 nT, 228 wave events) geomagnetic conditions and are primarily observed in the prenoon sector (~800 3 nPa) correlates to mostly afternoon Emic wave observations.
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high resolution in situ observations of electron precipitation causing Emic waves
Geophysical Research Letters, 2015Co-Authors: Craig J Rodger, C A Kletzing, Aaron T Hendry, Mark A Clilverd, J B Brundell, Geoffrey D. ReevesAbstract:Electromagnetic ion cyclotron (Emic) waves are thought to be important drivers of energetic electron losses from the outer radiation belt through precipitation into the atmosphere. While the theoretical possibility of pitch angle scattering-driven losses from these waves has been recognized for more than four decades, there have been limited experimental precipitation observations to support this concept. We have combined satellite-based observations of the characteristics of Emic waves, with satellite and ground-based observations of the Emic-induced electron precipitation. In a detailed case study, supplemented by an additional four examples, we are able to constrain for the first time the location, size, and energy range of Emic-induced electron precipitation inferred from coincident precipitation data and relate them to the Emic wave frequency, wave power, and ion band of the wave as measured in situ by the Van Allen Probes. These observations will better constrain modeling into the importance of Emic wave-particle interactions.
J C Zhang - One of the best experts on this subject based on the ideXlab platform.
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comparing simulated and observed Emic wave amplitudes using in situ van allen probes measurements
Journal of Atmospheric and Solar-Terrestrial Physics, 2018Co-Authors: Anthony A. Saikin, J C Zhang, C W Smith, Roy B. Torbert, C A Kletzing, V K Jordanova, H. E. Spence, B. A. Larsen, G D Reeves, Irina ZhelavskayaAbstract:Abstract We perform a statistical study calculating electromagnetic ion cyclotron (Emic) wave amplitudes based off in situ plasma measurements taken by the Van Allen Probes’ (1.1–5.8 Re) Helium, Oxygen, Proton, Electron (HOPE) instrument. Calculated wave amplitudes are compared to Emic waves observed by the Electric and Magnetic Field Instrument Suite and Integrated Science on board the Van Allen Probes during the same period. The survey covers a 22-month period (1 November 2012 to 31 August 2014), a full Van Allen Probe magnetic local time (MLT) precession. The linear theory proxy was used to identify Emic wave events with plasma conditions favorable for Emic wave excitation. Two hundred and thirty-two Emic wave events (103 H+-band and 129 He+-band) were selected for this comparison. Nearly all events selected are observed beyond L = 4. Results show that calculated wave amplitudes exclusively using the in situ HOPE measurements produce amplitudes too low compared to the observed Emic wave amplitudes. Hot proton anisotropy (Ahp) distributions are asymmetric in MLT within the inner (L
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Emic waves and associated relativistic electron precipitation on 25 26 january 2013
Journal of Geophysical Research, 2016Co-Authors: J C Zhang, Brian A. Larsen, Geoffrey D. Reeves, Robyn M. Millan, Chia-lin Huang, Anthony A. Saikin, Harlan E Spence, A J Halford, C W SmithAbstract:Using measurements from the Van Allen Probes and the Balloon Array for RBSP Relativistic Electron Losses (BARREL), we perform a case study of electromagnetic ion cyclotron (Emic) waves and associated relativistic electron precipitation (REP) observed on 25 – 26 January 2013. Among all the Emic wave and REP events from the two missions, the pair of the events is the closest both in space and time. The Van Allen Probe-B detected significant Emic waves at L = 2.1 – 3.9 and MLT = 21.0 – 23.4 for 53.5 minutes from 2353:00 UT, 25 January 2013. Meanwhile, BARREL-1 T observed clear precipitation of relativistic electrons at L = 4.2 – 4.3 and MLT = 20.7 – 20.8 for 10.0 minutes from 2358 UT, 25 January 2013. Local plasma and field conditions for the excitation of the Emic waves, wave properties, electron minimum resonant energy Emin, and electron pitch angle diffusion coefficient Dαα of a sample Emic wave packet are examined along with solar wind plasma and interplanetary magnetic field (IMF) parameters, geomagnetic activity, and results from the spectral analysis of the BARREL balloon observations to investigate the two types of events. The events occurred in the early main phase of a moderate storm (min. Dst* = -51.0 nT). The Emic wave event consists of two parts. Unlike the first part, the second part of the Emic wave event was locally generated and still in its source region. It is found that the REP event is likely associated with the Emic wave event.
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the dependence on geomagnetic conditions and solar wind dynamic pressure of the spatial distributions of Emic waves observed by the van allen probes
Journal of Geophysical Research, 2016Co-Authors: Anthony A. Saikin, J C Zhang, C W Smith, Roy B. Torbert, H. E. Spence, C A KletzingAbstract:A statistical examination on the spatial distributions of electromagnetic ion cyclotron (Emic) waves observed by the Van Allen Probes against varying levels of geomagnetic activity (i.e., AE and SYM-H) and dynamic pressure has been performed. Measurements taken by the Electric and Magnetic Field Instrument Suite and Integrated Science for the first full magnetic local time (MLT) precession of the Van Allen Probes (September 2012–June 2014) are used to identify over 700 Emic wave events. Spatial distributions of Emic waves are found to vary depending on the level of geomagnetic activity and solar wind dynamic pressure. Emic wave events were observed under quiet (AE ≤ 100 nT, 325 wave events), moderate (100 nT 300 nT, 228 wave events) geomagnetic conditions and are primarily observed in the prenoon sector (~800 3 nPa) correlates to mostly afternoon Emic wave observations.
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the occurrence and wave properties of h he and o band Emic waves observed by the van allen probes
Journal of Geophysical Research, 2015Co-Authors: Anthony A. Saikin, J C Zhang, R C Allen, C W Smith, Lynn M. Kistler, Harlan E Spence, Roy B. Torbert, C A Kletzing, V K JordanovaAbstract:We perform a statistical study of electromagnetic ion cyclotron (Emic) waves detected by the Van Allen Probes mission to investigate the spatial distribution of their occurrence, wave power, ellipticity, and normal angle. The Van Allen Probes have been used which allow us to explore the inner magnetosphere (1.1 to 5.8 RE). Magnetic field measurements from the Electric and Magnetic Field Instrument Suite and Integrated Science on board the Van Allen Probes are used to identify Emic wave events for the first 22 months of the mission operation (8 September 2012 to 30 June 2014). Emic waves are examined in H+, He+, and O+ bands. Over 700 Emic wave events have been identified over the three different wave bands (265 H+-band events, 438 He+-band events, and 68 O+-band events). Emic wave events are observed between L = 2–8, with over 140 Emic wave events observed below L = 4. Results show that H+-band Emic waves have two peak magnetic local time (MLT) occurrence regions: prenoon (09:00 0.1 nT2/Hz), especially in the afternoon sector. Ellipticity observations reveal that linearly polarized Emic waves dominate in lower L shells.
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resonant scattering of outer zone relativistic electrons by multiband Emic waves and resultant electron loss time scales
Journal of Geophysical Research, 2015Co-Authors: Binbin Ni, J C Zhang, J Bortnik, Xudong Gu, Chen Zhou, Song Fu, Zhengyu ZhaoAbstract:To improve our understanding of the role of electromagnetic ion cyclotron (Emic) waves in radiation belt electron dynamics, we perform a comprehensive analysis of Emic wave-induced resonant scattering of outer zone relativistic (>0.5 MeV) electrons and resultant electron loss time scales with respect to Emic wave band, L shell, and wave normal angle model. The results demonstrate that while H+-band Emic waves dominate the scattering losses of ~1–4 MeV outer zone relativistic electrons, it is He+-band and O+-band waves that prevail over the pitch angle diffusion of ultrarelativistic electrons at higher energies. Given the wave amplitude, Emic waves at higher L shells tend to resonantly interact with a larger population of outer zone relativistic electrons and drive their pitch angle scattering more efficiently. Obliquity of Emic waves can reduce the efficiency of wave-induced relativistic electron pitch angle scattering. Compared to the frequently adopted parallel or quasi-parallel model, use of the latitudinally varying wave normal angle model produces the largest decrease in H+-band Emic wave scattering rates at pitch angles ~5 MeV. At a representative nominal amplitude of 1 nT, Emic wave scattering produces the equilibrium state (i.e., the lowest normal mode under which electrons at the same energy but different pitch angles decay exponentially on the same time scale) of outer belt relativistic electrons within several to tens of minutes and the following exponential decay extending to higher pitch angles on time scales from <1 min to ~1 h. The electron loss cone can be either empty as a result of the weak diffusion or heavily/fully filled due to approaching the strong diffusion limit, while the trapped electron population at high pitch angles close to 90° remains intact because of no resonant scattering. In this manner, Emic wave scattering has the potential to deepen the anisotropic distribution of outer zone relativistic electrons by reshaping their pitch angle profiles to “top-hat.” Overall, H+-band and He+-band Emic waves are most efficient in producing the pitch angle scattering loss of relativistic electrons at ~1–2 MeV. In contrast, the presence of O+-band Emic waves, while at a smaller occurrence rate, can dominate the scattering loss of 5–10 MeV electrons in the entire region of the outer zone, which should be considered in future modeling of the outer zone relativistic electron dynamics.
Anthony A. Saikin - One of the best experts on this subject based on the ideXlab platform.
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comparing simulated and observed Emic wave amplitudes using in situ van allen probes measurements
Journal of Atmospheric and Solar-Terrestrial Physics, 2018Co-Authors: Anthony A. Saikin, J C Zhang, C W Smith, Roy B. Torbert, C A Kletzing, V K Jordanova, H. E. Spence, B. A. Larsen, G D Reeves, Irina ZhelavskayaAbstract:Abstract We perform a statistical study calculating electromagnetic ion cyclotron (Emic) wave amplitudes based off in situ plasma measurements taken by the Van Allen Probes’ (1.1–5.8 Re) Helium, Oxygen, Proton, Electron (HOPE) instrument. Calculated wave amplitudes are compared to Emic waves observed by the Electric and Magnetic Field Instrument Suite and Integrated Science on board the Van Allen Probes during the same period. The survey covers a 22-month period (1 November 2012 to 31 August 2014), a full Van Allen Probe magnetic local time (MLT) precession. The linear theory proxy was used to identify Emic wave events with plasma conditions favorable for Emic wave excitation. Two hundred and thirty-two Emic wave events (103 H+-band and 129 He+-band) were selected for this comparison. Nearly all events selected are observed beyond L = 4. Results show that calculated wave amplitudes exclusively using the in situ HOPE measurements produce amplitudes too low compared to the observed Emic wave amplitudes. Hot proton anisotropy (Ahp) distributions are asymmetric in MLT within the inner (L
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Emic waves and associated relativistic electron precipitation on 25 26 january 2013
Journal of Geophysical Research, 2016Co-Authors: J C Zhang, Brian A. Larsen, Geoffrey D. Reeves, Robyn M. Millan, Chia-lin Huang, Anthony A. Saikin, Harlan E Spence, A J Halford, C W SmithAbstract:Using measurements from the Van Allen Probes and the Balloon Array for RBSP Relativistic Electron Losses (BARREL), we perform a case study of electromagnetic ion cyclotron (Emic) waves and associated relativistic electron precipitation (REP) observed on 25 – 26 January 2013. Among all the Emic wave and REP events from the two missions, the pair of the events is the closest both in space and time. The Van Allen Probe-B detected significant Emic waves at L = 2.1 – 3.9 and MLT = 21.0 – 23.4 for 53.5 minutes from 2353:00 UT, 25 January 2013. Meanwhile, BARREL-1 T observed clear precipitation of relativistic electrons at L = 4.2 – 4.3 and MLT = 20.7 – 20.8 for 10.0 minutes from 2358 UT, 25 January 2013. Local plasma and field conditions for the excitation of the Emic waves, wave properties, electron minimum resonant energy Emin, and electron pitch angle diffusion coefficient Dαα of a sample Emic wave packet are examined along with solar wind plasma and interplanetary magnetic field (IMF) parameters, geomagnetic activity, and results from the spectral analysis of the BARREL balloon observations to investigate the two types of events. The events occurred in the early main phase of a moderate storm (min. Dst* = -51.0 nT). The Emic wave event consists of two parts. Unlike the first part, the second part of the Emic wave event was locally generated and still in its source region. It is found that the REP event is likely associated with the Emic wave event.
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the dependence on geomagnetic conditions and solar wind dynamic pressure of the spatial distributions of Emic waves observed by the van allen probes
Journal of Geophysical Research, 2016Co-Authors: Anthony A. Saikin, J C Zhang, C W Smith, Roy B. Torbert, H. E. Spence, C A KletzingAbstract:A statistical examination on the spatial distributions of electromagnetic ion cyclotron (Emic) waves observed by the Van Allen Probes against varying levels of geomagnetic activity (i.e., AE and SYM-H) and dynamic pressure has been performed. Measurements taken by the Electric and Magnetic Field Instrument Suite and Integrated Science for the first full magnetic local time (MLT) precession of the Van Allen Probes (September 2012–June 2014) are used to identify over 700 Emic wave events. Spatial distributions of Emic waves are found to vary depending on the level of geomagnetic activity and solar wind dynamic pressure. Emic wave events were observed under quiet (AE ≤ 100 nT, 325 wave events), moderate (100 nT 300 nT, 228 wave events) geomagnetic conditions and are primarily observed in the prenoon sector (~800 3 nPa) correlates to mostly afternoon Emic wave observations.
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Emic waves and associated relativistic electron precipitation on 25–26 January 2013
Journal of Geophysical Research: Space Physics, 2016Co-Authors: Jichun Zhang, Alexa J. Halford, Brian A. Larsen, Geoffrey D. Reeves, Robyn M. Millan, Chia-lin Huang, Charles W. Smith, Anthony A. Saikin, Harlan E Spence, Roy B. TorbertAbstract:Using measurements from the Van Allen Probes and the Balloon Array for RBSP Relativistic Electron Losses (BARREL), we perform a case study of electromagnetic ion cyclotron (Emic) waves and associated relativistic electron precipitation (REP) observed on 25–26 January 2013. Among all the Emic wave and REP events from the two missions, the pair of the events is the closest both in space and time. The Van Allen Probe-B detected significant Emic waves at L=2.1–3.9 and magnetic local time (MLT)=21.0–23.4 for 53.5 min from 2353:00 UT, 25 January 2013. Meanwhile, BARREL-1T observed clear precipitation of relativistic electrons at L=4.2–4.3 and MLT=20.7–20.8 for 10.0 min from 2358 UT, 25 January 2013. Local plasma and field conditions for the excitation of the Emic waves, wave properties, electron minimum resonant energy Emin, and electron pitch angle diffusion coefficient Dαα of a sample Emic wave packet are examined along with solar wind plasma and interplanetary magnetic field parameters, geomagnetic activity, and results from the spectral analysis of the BARREL balloon observations to investigate the two types of events. The events occurred in the early main phase of a moderate storm (min. Dst*=?51.0 nT). The Emic wave event consists of two parts. Unlike the first part, the second part of the Emic wave event was locally generated and still in its source region. It is found that the REP event is likely associated with the Emic wave event
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the occurrence and wave properties of h he and o band Emic waves observed by the van allen probes
Journal of Geophysical Research, 2015Co-Authors: Anthony A. Saikin, J C Zhang, R C Allen, C W Smith, Lynn M. Kistler, Harlan E Spence, Roy B. Torbert, C A Kletzing, V K JordanovaAbstract:We perform a statistical study of electromagnetic ion cyclotron (Emic) waves detected by the Van Allen Probes mission to investigate the spatial distribution of their occurrence, wave power, ellipticity, and normal angle. The Van Allen Probes have been used which allow us to explore the inner magnetosphere (1.1 to 5.8 RE). Magnetic field measurements from the Electric and Magnetic Field Instrument Suite and Integrated Science on board the Van Allen Probes are used to identify Emic wave events for the first 22 months of the mission operation (8 September 2012 to 30 June 2014). Emic waves are examined in H+, He+, and O+ bands. Over 700 Emic wave events have been identified over the three different wave bands (265 H+-band events, 438 He+-band events, and 68 O+-band events). Emic wave events are observed between L = 2–8, with over 140 Emic wave events observed below L = 4. Results show that H+-band Emic waves have two peak magnetic local time (MLT) occurrence regions: prenoon (09:00 0.1 nT2/Hz), especially in the afternoon sector. Ellipticity observations reveal that linearly polarized Emic waves dominate in lower L shells.
Yuri Shprits - One of the best experts on this subject based on the ideXlab platform.
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hot plasma effects on the cyclotron resonant pitch angle scattering rates of radiation belt electrons due to Emic waves
Geophysical Research Letters, 2018Co-Authors: Binbin Ni, Yuri Shprits, Xudong Gu, Danny Summers, Song FuAbstract:To investigate the hot plasma effects on the cyclotron-resonant interactions between electromagnetic ion cyclotron (Emic) waves and radiation belt electrons in a realistic magnetospheric environment, calculations of the wave-induced bounce-averaged pitch angle diffusion coefficients are performed using both the cold and hot plasma dispersion relations. The results demonstrate that the hot plasma effects have a pronounced influence on the electron pitch angle scattering rates due to all three Emic emission bands (H+, He+, and O+) when the hot plasma dispersion relation deviates significantly from the cold plasma approximation. For a given wave spectrum, the modification of the dispersion relation by hot anisotropic protons can strongly increase the minimum resonant energy for electrons interacting with O+ band Emic waves, while the minimum resonant energies for H+ and He+ bands are not greatly affected. For H+ band Emic waves, inclusion of hot protons tends to weaken the pitch angle scattering efficiency of >5 MeV electrons. The most crucial differences introduced by the hot plasma effects occur for >3 MeV electron scattering rates by He+ band Emic waves. Mainly due to the changes of resonant frequency and wave group velocity when the hot protons are included, the difference in scattering rates can be up to an order of magnitude, showing a strong dependence on both electron energy and equatorial pitch angle. Our study confirms the importance of including hot plasma effects in modeling the scattering of ultra-relativistic radiation belt electrons by Emic waves.
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Emic wave parameterization in the long‐term VERB code simulation
Journal of Geophysical Research, 2017Co-Authors: A Drozdov, Yuri Shprits, Nikita Aseev, Maria Usanova, A C KellermanAbstract:Electromagnetic ion cyclotron (Emic) waves play an important role in the dynamics of ultrarelativistic electron population in the radiation belts. However, as Emic waves are very sporadic, developing a parameterization of such wave properties is a challenging task. Currently, there are no dynamic, activity-dependent models of Emic waves that can be used in the long-term (several months) simulations, which makes the quantitative modeling of the radiation belt dynamics incomplete. In this study, we investigate Kp, Dst, AE indices, solar wind speed and dynamic pressure as possible parameters of Emic wave presence. The Emic waves are included in the long-term simulations (one year, including different geomagnetic activity) performed with the Versatile Electron Radiation Belt (VERB) code, and we compare results of the simulation with the Van Allen Probes observations. The comparison shows that modeling with Emic waves, parameterized by solar wind dynamic pressure, provides a better agreement with the observations among considered parameterizations. The simulation with Emic waves improves the dynamics of ultrarelativistic fluxes and reproduces the formation of the local minimum in the phase space density profiles.
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Emic wave parameterization in the long term verb code simulation
Journal of Geophysical Research, 2017Co-Authors: A Drozdov, M Usanova, Yuri Shprits, Nikita Aseev, A C KellermanAbstract:Electromagnetic ion cyclotron (Emic) waves play an important role in the dynamics of ultrarelativistic electron population in the radiation belts. However, as Emic waves are very sporadic, developing a parameterization of such wave properties is a challenging task. Currently, there are no dynamic, activity-dependent models of Emic waves that can be used in the long-term (several months) simulations, which makes the quantitative modeling of the radiation belt dynamics incomplete. In this study, we investigate Kp, Dst, AE indices, solar wind speed and dynamic pressure as possible parameters of Emic wave presence. The Emic waves are included in the long-term simulations (one year, including different geomagnetic activity) performed with the Versatile Electron Radiation Belt (VERB) code, and we compare results of the simulation with the Van Allen Probes observations. The comparison shows that modeling with Emic waves, parameterized by solar wind dynamic pressure, provides a better agreement with the observations among considered parameterizations. The simulation with Emic waves improves the dynamics of ultrarelativistic fluxes and reproduces the formation of the local minimum in the phase space density profiles.
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rapid scattering of radiation belt electrons by storm time Emic waves
Geophysical Research Letters, 2010Co-Authors: A Y Ukhorskiy, Yuri Shprits, B J Anderson, K Takahashi, R M ThorneAbstract:[1] A storm main phase can produce a rapid depletion of electron fluxes in the Earth's outer radiation belt and the pitch-angle scattering by the electromagnetic ion cyclotron (Emic) waves is one mechanism that might account for the electron losses. To efficiently scatter the bulk of the electron population, below *1-2 MeV, the Emic waves would need to have significant power very near a heavy ion gyrofrequency. We present a wave event at the storm main phase and carefully examine the wave spectrum to identify the energy range of electrons scattered by the waves. The Emic waves exhibit power right below the He + gyrofrequency and we estimate that they can interact with electrons having energies as low as 400 keV producing rapid scattering at almost all pitch-angle values on the time scales of seconds. Our statistical analysis suggests that this event is not an exception; the majority of Emic waves can scatter electrons with energies under 2 MeV. Our results show that Emic waves can be one of the dominant radiation belt loss mechanisms during the storm main phase.
M Usanova - One of the best experts on this subject based on the ideXlab platform.
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Emic wave parameterization in the long term verb code simulation
Journal of Geophysical Research, 2017Co-Authors: A Drozdov, M Usanova, Yuri Shprits, Nikita Aseev, A C KellermanAbstract:Electromagnetic ion cyclotron (Emic) waves play an important role in the dynamics of ultrarelativistic electron population in the radiation belts. However, as Emic waves are very sporadic, developing a parameterization of such wave properties is a challenging task. Currently, there are no dynamic, activity-dependent models of Emic waves that can be used in the long-term (several months) simulations, which makes the quantitative modeling of the radiation belt dynamics incomplete. In this study, we investigate Kp, Dst, AE indices, solar wind speed and dynamic pressure as possible parameters of Emic wave presence. The Emic waves are included in the long-term simulations (one year, including different geomagnetic activity) performed with the Versatile Electron Radiation Belt (VERB) code, and we compare results of the simulation with the Van Allen Probes observations. The comparison shows that modeling with Emic waves, parameterized by solar wind dynamic pressure, provides a better agreement with the observations among considered parameterizations. The simulation with Emic waves improves the dynamics of ultrarelativistic fluxes and reproduces the formation of the local minimum in the phase space density profiles.
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observations of coincident Emic wave activity and duskside energetic electron precipitation on 18 19 january 2013
Geophysical Research Letters, 2015Co-Authors: L W Blum, Robyn M. Millan, J W Bonnell, M Usanova, A J Halford, G D Reeves, M J Engebretson, J Goldstein, M Ohnsted, H J SingerAbstract:Electromagnetic ion cyclotron (Emic) waves have been suggested to be a cause of radiation belt electron loss to the atmosphere. Here simultaneous, magnetically conjugate measurements are presented of Emic wave activity, measured at geosynchronous orbit and on the ground, and energetic electron precipitation, seen by the Balloon Array for Radiation belt Relativistic Electron Losses (BARREL) campaign, on two consecutive days in January 2013. Multiple bursts of precipitation were observed on the duskside of the magnetosphere at the end of 18 January and again late on 19 January, concurrent with particle injections, substorm activity, and enhanced magnetospheric convection. The structure, timing, and spatial extent of the waves are compared to those of the precipitation during both days to determine when and where Emic waves cause radiation belt electron precipitation. The conjugate measurements presented here provide observational support of the theoretical picture of duskside interaction of Emic waves and MeV electrons leading to radiation belt loss.
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spatial localization and ducting of Emic waves van allen probes and ground based observations
Geophysical Research Letters, 2014Co-Authors: I R Mann, C A Kletzing, M Usanova, J R Wygant, K R Murphy, Matthew Robertson, D K Milling, A Kale, S A Thaller, Tero RaitaAbstract:On 11 October 2012, during the recovery phase of a moderate geomagnetic storm, an extended interval (> 18 h) of continuous electromagnetic ion cyclotron (Emic) waves was observed by Canadian Array for Real-time Investigations of Magnetic Activity and Solar-Terrestrial Environment Program induction coil magnetometers in North America. At around 14:15 UT, both Van Allen Probes B and A (65° magnetic longitude apart) in conjunction with the ground array observed very narrow (ΔL ~ 0.1–0.4) left-hand polarized Emic emission confined to regions of mass density gradients at the outer edge of the plasmasphere at L ~ 4. Emic waves were seen with complex polarization patterns on the ground, in good agreement with model results from Woodroffe and Lysak (2012) and consistent with Earth's rotation sweeping magnetometer stations across multiple polarization reversals in the fields in the Earth-ionosphere duct. The narrow L-widths explain the relative rarity of space-based Emic occurrence, ground-based measurements providing better estimates of global Emic wave occurrence for input into radiation belt dynamical models.
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statistical analysis of Emic waves in plasmaspheric plumes from cluster observations
Journal of Geophysical Research, 2013Co-Authors: M Usanova, I R Mann, F Darrouzet, J BortnikAbstract:Recently, electromagnetic ion cyclotron (Emic) wave generation in plasmaspheric plumes has been the subject of extensive discussion. Theory predicts that regions of detached cold, dense plasma immersed in relatively low background magnetic field should aid Emic wave growth and may provide conditions for interaction between the Emic waves and relativistic (MeV) electrons, leading to energetic particle loss into the atmosphere. Since plasmaspheric plumes are specific to disturbed geomagnetic conditions, the link between Emic waves and plumes may be especially important for radiation belt dynamics during magnetic storms. In this work, we present an in situ survey of Emic waves in plasmaspheric plumes using data from the Cluster satellites and will address the question of whether plumes are important for Emic wave generation from a statistical perspective. We used a survey of plasmaspheric plumes between 2001 and 2006 identified from the Waves of High frequency and Sounder for Probing of Electron density by Relaxation (WHISPER) sounder measurements. We further identified Emic waves from simultaneous (with WHISPER) magnetic field measurements by the fluxgate magnetometer instruments and investigated the relationship between these two data sets. Only 10% of the time when Cluster-observed plumes along its orbit did we also observe Emic waves. The wave occurrence outside plumes is further significantly reduced and is ~20 times lower in immediately adjacent regions than inside plumes. We found that cold plasma density was not a good predictor of Emic occurrence inside the plumes and that the absolute density does not affect the Emic probability. On the other hand, enhanced solar wind dynamic pressure significantly increases Emic wave occurrence rate inside the plumes. Key Points We analyzed 6 years of the Cluster satellite data Emic waves were seen during 10% of the time when Cluster observed plumes Enhanced solar wind pressure controls Emic occurrence in plumes.
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conjugate ground and multisatellite observations of compression related Emic pc1 waves and associated proton precipitation
Journal of Geophysical Research, 2010Co-Authors: M Usanova, Z. C. Kale, I R Mann, Karl-heinz Glassmeier, R D Sydora, Marit Irene Sandanger, F Soraas, K H Fornacon, H Matsui, P A PuhlquinnAbstract:[1] We present coordinated ground satellite observations of solar wind compression-related dayside electromagnetic ion cyclotron (Emic) waves from 25 September 2005. On the ground, dayside structured Emic wave activity was observed by the CARISMA and STEP magnetometer arrays for several hours during the period of maximum compression. The Emic waves were also registered by the Cluster satellites for half an hour, as they consecutively crossed the conjugate equatorial plasmasphere on their perigee passes at L ∼ 5. Simultaneously, conjugate to Cluster, NOAA 17 passed through field lines supporting Emic wave activity and registered a localized enhancement of precipitating protons with energies >30 keV. Our observations suggest that generation of the Emic waves and consequent loss of energetic protons may last for several hours while the magnetosphere remains compressed. The Emic waves were confined to the outer plasmasphere region, just inside the plasmapause. Analysis of lower-frequency Pc5 waves observed both by the Cluster electron drift instrument (EDI) and fluxgate magnetometer (FGM) instruments and by the ground magnetometers show that the repetitive structure of Emic wave packets observed on the ground cannot be explained by the ultra low frequency (ULF) wave modulation theory. However, the Emic wave repetition period on the ground was close to the estimated field-aligned Alfvenic travel time. For a short interval of time, there was some evidence that Emic wave packet repetition period in the source region was half of that on the ground, which further suggests bidirectional propagation of wave packets.
