11-18 of 18 results
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NSF Career Award: Effects of Magnetosheath properties on the dynamics and plasma transport produced by the Kelvin-Helmholtz Instability and on the Plasma Sheet Anisotropies
PI Heidi Nykyri
Project investigates impact of magnetosheath properties on Kelvin-Helmholtz instability
The magnetosheath processes will be studied by doing a statistical study of the magnetosheath properties using THEMIS data and by utilizing global hybrid (fluid electrons, particle ions) simulations. In addition, the MHD-scale KHI will be compared with hybrid and particle simulations of the instability.
Categories: Faculty-Staff
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Turbulence and Structure in the Magnetospheric Cusps: Cluster spacecraft observations
PI Heidi Nykyri
Project analyzes the structure, origin of fluctuations and high-energy particles in the high-altitude cusp regions
Project uses Cluster data and high-resolution local 3-D MHD simulations with test particles to determine the structure and origin of high-energy particles in the high-altitude cuspCategories: Faculty-Staff
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Magnetospheric Multi-Scale (MMS) Observations and simulations of high-energy electrons in the dayside magnetosheath
PI Heidi Nykyri
CO-I Brandon Burkholder
CO-I Xuanye Ma
The key objective of this study is to better understand the source and cause of high-energy electrons observed by the MMS in the dayside magnetosheath.
The key objective of this study is to better understand the source and cause of high-energy electrons observed by the MMS in the dayside magnetosheath. The Magnetospheric Multi-Scale (MMS) mission is a four-spacecraft constellation orbiting in formation around Earth with a main goal to study the microphysics of magnetic reconnection at the dayside magnetopause. Recent MMS observations showed high energy (40 keV) electrons leaking into the magnetosheath. However, the dominant leaking mechanism has not been fully understood. Global Lyon-Fedder-Mobarry (LFM) with test particle simulations suggest that low latitude reconnection and the nonlinear Kelvin-Helmholtz (KH) instability can cause the leak of high energy electrons into the magnetosheath. But it is important to notice that many of the electrons leaking events were observed close to Fall Equinox when the MMS orbit has a significant y-component and the z_GSM coordinate can be substantial (up to ~7 R_E). Therefore, MMS high-energy electron events may have a high-latitude source. For instance, it is well demonstrated that magnetic reconnection between the Interplanetary Magnetic Field (IMF) and Earth's magnetic field surrounding the cusps can lead to the formation of cusp diamagnetic cavities (Nykyri et al., JGR 2011a,b; Adamson et al., angeo 2011), extended regions of decreased magnetic field, which can be filled with higher energy (>30 keV) electrons, protons and O+ ions. Cluster observations revealed 90-degree pitch angle electrons in the cavity, strongly suggestive of a local acceleration mechanism (Walsh, angeo 2010; Nykyri et al, JASTP 2012). Test particle simulations in a high-resolution 3D cusp model uncovered that trapped particles in the diamagnetic cavities can be accelerated when their drift paths go through regions of "reconnection quasi-potential" (Nykyri et al, JASTP 2012). Once the IMF orientation changes it is possible for trapped particles in the cavity to end up into the loss cone and "leak out" of the cavity. A systematic approach to our science objective addresses the following compelling science questions by synergy using MMS observational data and numerical simulation.
Categories: Faculty-Staff
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Science and engineering proof of concept study for the Next generation Space Weather Prediction mission and space weather model development
PI Heidi Nykyri
Project analyzes astrodynamics (transfer trajectories) and spacecraft constellation stability about all Lagrange points for Mercury, Venus, Earth, Mars system for the "next generation" space weather prediction mission, and develops a solar wind model which will use data from this mission
Project analyzes astrodynamics and constellation stability for the "next generation" space weather prediction mission, and develops a solar wind model which will use data from this missionCategories: Faculty-Staff
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On The Origin and Transport of Energetic Particles
PI Heidi Nykyri
CO-I Xuanye Ma
Understanding the properties, origin and dynamics of energetic particles in the solar wind and magnetosphere is crucial for safe unmanned and manned space operations. This project will unravel the birth-mechanism of the source population of the Earth's radiation belts.
Understanding the properties, origin and dynamics of energetic particles in the solar wind and magnetosphere is crucial for safe unmanned and manned space operations. Therefore, energetic particles have attracted attention from the space physics community for decades. However, different regions and energy ranges of energetic particles may have their own unique origin and role for magnetospheric dynamics, which have not been fully explored and deserve to be investigated case by case. For instance, MMS recently observed dispersionless micro-injections in the 30-300 keV electrons accompanied by strong anisotropic ion temperature at the high-latitude magnetospheric boundary layer in the vicinity of the exterior southern cusp. Due to the different magnetic field geometry, these high-latitude microinjections could have a totally different origin than the typical low-latitude microinjections. Because this region is close to the radiation belts, ionosphere, and magnetosheath, these high-latitude microinjections could be the ~ tens to hundreds of keV seed population of the radiation belts, as well as leak into the ionosphere or into the magnetosheath. This project will unravel the birth-mechanism of the source population of the Earth's radiation belts.Categories: Faculty-Staff
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Experimental Identification of Plasma Wave Modes
PI Heidi Nykyri
CO-I Rachel Rice
Project uses MMS data to identify plasma wave modes contributing to the heating of the magnetospheric boundary layer
Projects uses single and multi-spacecraft data-analysis techniques to experimentally identify various plasma modes at different frequencies and assess their contribution to plasma heatingCategories: Faculty-Staff
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Bayesian Analysis of Stellar Evolution
PI Theodore von Hippel
Bayesian Analysis of Stellar Evolution is an international collaboration studying stellar evolution with an emphasis on stellar ages. We also develop and support a Bayesian software suite that recovers star cluster and stellar parameters from photometry, currently called BASE-9.
BASE-9 is useful for analyzing single-age, single-metallicity star clusters, binaries, or single stars, and for simulating such systems. BASE9 uses Markov chain Monte Carlo to estimate the posterior probability distribution for the age, metallicity, distance modulus, and line-of-sight absorption for a cluster, and for the mass, binary mass ratio, and cluster membership probability for every cluster member.Categories: Faculty-Staff
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Large Amplitude Electromagnetic Waves in the Radiation Belt
CO-I Miles Bengtson
CO-I Anatoly Streltsov
When the first American satellite, Explorer I, was launched into space it inadvertently discovered one of the most significant features of our local space environment: the Van Allen Radiation Belts. This region contains highly energetic particles that are hazardous. This research involves one promising remediation mechanism based on interactions between these particles and very-low frequency electromagnetic waves known as whistlers.
The Van Allen Radiation Belt is a region in the near-Earth space populated with high-energy, electrically charged particles. Because of their very high energy, these particles present a significant threat to low-Earth orbiting satellites, the International Space Station, and its human crew. The radiation damage to satellite electronics increases when the amount of energetic particles in the radiation belt increases by a factor of 10 or 100 due to the plasma eruptions on the Sun or the high-altitude nuclear explosions. Results from high-altitude nuclear tests produced in 1968 combined with modern computer simulations demonstrate that even a relatively "modest" nuclear explosion (equivalent to a few tenths of kilotons in TNT) in the upper atmosphere can reduce the lifetime of many very important and expensive commercial, military, intelligence, and communication satellites from years to months. Therefore, it is a matter of national security to develop a solid understanding of the basic physics of remediation of energetic particles from the space. One possible way to achieve this goal is to use large amplitude electromagnetic waves. They can efficiently interact with energetic particles and precipitate them from the magnetosphere into the atmosphere. We will study the observations of large-amplitude whistlers detected by the Van Allen Probes satellites in the radiation belt. We also will model these waves with comprehensive numerical models and compare the numerical results with the observed wave dynamics in the magnetosphere. The results from this project are very important for future experiments including launching waves into the radiation belt from ground antennas (like HAARP and Arecibo) or from space platforms.Categories: Undergraduate
11-18 of 18 results