A multi-institutional, multi-national science team will soon submit a NASA proposal to build a constellation of spacecraft to fly into the near-Earth solar wind in a swarm spanning a multitude of scales in order to obtain critically... more
A multi-institutional, multi-national science team will soon submit a NASA proposal to build a constellation of spacecraft to fly into the near-Earth solar wind in a swarm spanning a multitude of scales in order to obtain critically needed measurements that will reveal the underlying dynamics of magnetized turbulence. This white paper, submitted to the Plasma 2020 Decadal Survey Committee, provides a brief overview of turbulent systems that constitute an area of compelling plasma physics research, including why this mission is needed, and how this mission will achieve the goal of revealing how energy is transferred across scales and boundaries in plasmas throughout the universe.
This white paper submitted for 2020 Decadal Assessment of Plasma Science concerns the importance of multi-spacecraft missions to address fundamental questions concerning plasma turbulence. Plasma turbulence is ubiquitous in the universe,... more
This white paper submitted for 2020 Decadal Assessment of Plasma Science concerns the importance of multi-spacecraft missions to address fundamental questions concerning plasma turbulence. Plasma turbulence is ubiquitous in the universe, and it is responsible for the transport of mass, momentum, and energy in such diverse systems as the solar corona and wind, accretion discs, planet formation, and laboratory fusion devices. Turbulence is an inherently multi-scale and multi-process phenomenon, coupling the largest scales of a system to sub-electron scales via a cascade of energy, while simultaneously generating reconnecting current layers, shocks, and a myriad of instabilities and waves. The solar wind is humankind's best resource for studying the naturally occurring turbulent plasmas that permeate the universe. Since launching our first major scientific spacecraft mission, Explorer 1, in 1958, we have made significant progress characterizing solar wind turbulence. Yet, due to th...
We present a comparison of statistical analyses of flow patterns in the near-earth plasma sheet of the geomagnetic tail, and in the near-earth simulation domain of global MHD simulations of the magnetosphere. To ensure a valid data/model... more
We present a comparison of statistical analyses of flow patterns in the near-earth plasma sheet of the geomagnetic tail, and in the near-earth simulation domain of global MHD simulations of the magnetosphere. To ensure a valid data/model comparison, we include in the investigation only subsets of both datasets with similar solar wind input conditions. Statistical earthward flow patterns in the
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On 23 November 2012, a sudden dropout of the relativistic electron flux was observed after an interplanetary shock arrival. The dropout peaks at ∼1 MeV and more than 80% of the electrons disappeared from the drift shell. Van Allen twin... more
On 23 November 2012, a sudden dropout of the relativistic electron flux was observed after an interplanetary shock arrival. The dropout peaks at ∼1 MeV and more than 80% of the electrons disappeared from the drift shell. Van Allen twin Probes observed a sharp electron flux dropout with clear energy dispersion signals. The repeating flux dropout and recovery signatures, or " dropout echoes " , constitute a new phenomenon referred to as a " drifting electron dropout " with a limited initial spatial range. The azimuthal range of the dropout is estimated to be on the duskside, from ∼1300 to 0100 LT. We conclude that the shock-induced electron dropout is not caused by the magnetopause shadowing. The dropout and consequent echoes suggest that the radial migration of relativistic electrons is induced by the strong dusk-dawn asymmetric interplanetary shock compression on the magnetosphere.
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Research Interests: Geology and Geophysical
Great progress has been made in understanding the composition and sources of variation in the radiation environment of the inner heliosphere A fundamental step in translating the primary spectrum of radiation into biological and hardware... more
Great progress has been made in understanding the composition and sources of variation in the radiation environment of the inner heliosphere A fundamental step in translating the primary spectrum of radiation into biological and hardware effects is understanding the evolution of the linear energy transfer LET of these particles as they pass through matter At high energies this process is complicated by uncertainties in our knowledge of nuclear fragmentation cross sections and in the limitations of modern propagation codes We present the design of the Cosmic Ray Telescope for the Effects of Radiation an instrument selected for flight on the Lunar Reconnaissance Orbiter LRO spacecraft LRO is the first mission in the NASA Robotic Lunar Exploration Program and is planned for launch in late 2008 The overall mission objective is to prepare for and to support future human exploration of the moon To achieve that objective LRO includes investigations that will characterize the lunar radiatio...
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In this paper we investigate the scattering of relativistic electrons in the nightside outer radiation belt (around the geostationary orbit). We consider the particular case of low geomagnetic activity (|Dst|<20 nT), quiet conditions... more
In this paper we investigate the scattering of relativistic electrons in the nightside outer radiation belt (around the geostationary orbit). We consider the particular case of low geomagnetic activity (|Dst|<20 nT), quiet conditions in the solar wind, and absence of whistler wave emissions. For such conditions we find several events of Van Allen probe observations of butterfly pitch angle distributions of relativistic electrons (energies about 1–3 MeV). Many previous publications have described such pitch angle distributions over a wide energy range as due to the combined effect of outward radial diffusion and magnetopause shadowing. In this paper we discuss another mechanism that produces butterfly distributions over a limited range of electron energies. We suggest that such distributions can be shaped due to relativistic electron scattering in the equatorial plane of magnetic field lines that are locally deformed by currents of hot ions injected into the inner magnetosphere. A...
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The twin Van Allen Probes spacecraft witnessed a series of lobe encounters between 0200 and 0515 UT on November 14th 2012. Although lobe entry had been observed previously by the other spacecraft, the two Van Allen Probe spacecraft allow... more
The twin Van Allen Probes spacecraft witnessed a series of lobe encounters between 0200 and 0515 UT on November 14th 2012. Although lobe entry had been observed previously by the other spacecraft, the two Van Allen Probe spacecraft allow us to observe the motion of the boundary for the first time. Moreover, this event is unique in that it consists of a series of six quasi-periodic lobe entries. The events occurred on the dawn flank between 4 and 6.6 local time and at altitudes between 5.6 and 6.2 RE. During the events Dst dropped to less than -100nT with the IMF being strongly southward (Bz = −15nT) and eastward (By = 20 nT). Observations by LANL GEO spacecraft at geosynchronous orbit also show lobe encounters in the northern hemisphere and on the dusk flank. The two spacecraft configuration provides strong evidence that these periodic entries into the lobe are the result of local expansions of the OCB propagating from the tail and passing over the Van Allen Probes. Examination of p...
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Research Interests: Physics and Space Weather
Bursty energetic electron events with energies of about 20–400keV have been observed in the cusp region when the CLUSTER S/C were travelling outbound on 5 April 2001. These electron events are characterized by strong impulsive increases... more
Bursty energetic electron events with energies of about 20–400keV have been observed in the cusp region when the CLUSTER S/C were travelling outbound on 5 April 2001. These electron events are characterized by strong impulsive increases in the flux whereas energetic ions (&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt;30keV) show no obvious changes. The enhanced energetic electron flux is more than 10 times higher than the
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Metrics and model validation represent two key elements upon which the success of the Center for Integrated Space Weather Modeling (CISM) hinges. The routine calculation of important operationally-and scientifically-motivated metrics... more
Metrics and model validation represent two key elements upon which the success of the Center for Integrated Space Weather Modeling (CISM) hinges. The routine calculation of important operationally-and scientifically-motivated metrics permits us to objectively measure and ...
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We present a comparison of statistical analyses of flow patterns in the near-earth plasma sheet of the geomagnetic tail, and in the near-earth simulation domain of global MHD simulations of the magnetosphere. To ensure a valid data/model... more
We present a comparison of statistical analyses of flow patterns in the near-earth plasma sheet of the geomagnetic tail, and in the near-earth simulation domain of global MHD simulations of the magnetosphere. To ensure a valid data/model comparison, we include in the investigation only subsets of both datasets with similar solar wind input conditions. Statistical earthward flow patterns in the
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The solar wind flow ultimately provides energy to the magnetosphere through a variety of different processes. One of these energy transfer paths is via the excitation of magnetospheric ULF waves. Recent studies (Kepko et al., 2002; Kepko... more
The solar wind flow ultimately provides energy to the magnetosphere through a variety of different processes. One of these energy transfer paths is via the excitation of magnetospheric ULF waves. Recent studies (Kepko et al., 2002; Kepko and Spence, 2003) have identified a subset of global ULF waves (multiple, discrete-frequency &amp;amp;amp;amp;lt;3 mHz), driven directly by density structures in the solar
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We present a statistical comparison of the near-earth central plasma sheet properties derived from Geotail observations and MHD simulations. We bin Geotail observations from 1995 to mid-1998 in the XYGSM plane and compare them with binned... more
We present a statistical comparison of the near-earth central plasma sheet properties derived from Geotail observations and MHD simulations. We bin Geotail observations from 1995 to mid-1998 in the XYGSM plane and compare them with binned parameters from a 2 month simulation of the Lyon-Fedder-Mobarry (LFM) model. The distributions of solar wind inputs driving the simulation are statistically similar to
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Center for Integrated Space Weather Modeling • Annual Site Visit • 13 June 2005 Abstract The coupled thermosphere-ionosphere magnetosphere (CMIT) and thermosphere ionosphere nested grid (TING) models have been run for the May 15, 1997... more
Center for Integrated Space Weather Modeling • Annual Site Visit • 13 June 2005 Abstract The coupled thermosphere-ionosphere magnetosphere (CMIT) and thermosphere ionosphere nested grid (TING) models have been run for the May 15, 1997 CME. Initial validation using middle latitude ionosondes is shown here. The quality of agreement between data and model varies from stations-to-station, with the agreement ranging from good at some stations and times to poor at others. Some reasons for this agreement and disagreement are discussed in the conclusions.
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We have developed a 3D Hall magnetohydrodynamic (MHD) model with the goal of embedding this high-resolution module into the plasma sheet region of the Lyon-Fedder-Mobarry global MHD model. We intend to investigate the effect of the Hall... more
We have developed a 3D Hall magnetohydrodynamic (MHD) model with the goal of embedding this high-resolution module into the plasma sheet region of the Lyon-Fedder-Mobarry global MHD model. We intend to investigate the effect of the Hall term on the size and structure of fast flow channels observed in the plasma sheet. Owing to insufficient spatial spacecraft coverage of plasma
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Accurate knowledge of the time-dependent magnetic field in the inner magnetosphere is an important factor needed to simulate correctly the radiation belt environment. The dramatic change of magnetic field configuration in the inner... more
Accurate knowledge of the time-dependent magnetic field in the inner magnetosphere is an important factor needed to simulate correctly the radiation belt environment. The dramatic change of magnetic field configuration in the inner magnetosphere, especially during magnetic storm time, could significantly alter radiation belt model predictions. Reproducing storm time magnetic field in the inner magnetosphere remains a challenge for both
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The physics-based Lyon-Fedder-Mobarry (LFM) model simulates magnetospheric configuration and dynamics, but observational comparisons are needed because they can reveal possible limitations of the model and suggest ways for improvements.... more
The physics-based Lyon-Fedder-Mobarry (LFM) model simulates magnetospheric configuration and dynamics, but observational comparisons are needed because they can reveal possible limitations of the model and suggest ways for improvements. Here we present a study that compares the global LFM MHD simulation to two semi-empirical magnetic field models (Tsyganenko 1996 and 2001) and geosynchronous magnetic field measurements from GOES 8, 9
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Metrics and model validation represent two key elements upon which the success of the Center for Integrated Space Weather Modeling (CISM) hinges. The routine calculation of important operationally-and scientifically-motivated metrics... more
Metrics and model validation represent two key elements upon which the success of the Center for Integrated Space Weather Modeling (CISM) hinges. The routine calculation of important operationally-and scientifically-motivated metrics permits us to objectively measure and ...
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We are preparing to return humans to the Moon and setting the stage for exploration to Mars and beyond. However, it is unclear if long missions outside of Low-Earth Orbit (LEO) can be accomplished with acceptable risk. The central... more
We are preparing to return humans to the Moon and setting the stage for exploration to Mars and beyond. However, it is unclear if long missions outside of Low-Earth Orbit (LEO) can be accomplished with acceptable risk. The central objective of our project, the Earth-Moon-Mars Radiation Exposure Module (EMMREM), is to develop and validate a numerical module for completely characterizing time-dependent radiation exposure in the Earth-Moon-Mars and Interplanetary space environments. EMMREM will provide the ability to predict radiation exposure on the surface or atmosphere of Earth, on the Moon, Mars, and in interplanetary space between Earth and Mars. EMMREM is being designed for broad use by researchers to predict radiation exposure by integrating over almost any incident particle distribution from interplanetary space. EMMREM is being developed using contemporary state-of-the-art particle radiation models. Beyond this, it will have the capability to incorporate new and improving mode...
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The Helium, Oxygen, Proton, &amp;amp;amp;amp;amp;amp; Electron (HOPE) mass spectrometer for the Energetic Particle, Composition and Thermal Plasma (ECT) investigation on the Radiation Belt Storm Probe (RBSP) mission will measure... more
The Helium, Oxygen, Proton, &amp;amp;amp;amp;amp;amp; Electron (HOPE) mass spectrometer for the Energetic Particle, Composition and Thermal Plasma (ECT) investigation on the Radiation Belt Storm Probe (RBSP) mission will measure plasma ions and electrons from eV energies to ˜40 keV/q. Ion mass will be obtained using carbon foil-based, linear time-of-flight (TOF), which also signifi- cantly enhances the signal-to-noise of both ion