Bulletin of the American Physical Society
58th Annual Meeting of the APS Division of Plasma Physics
Volume 61, Number 18
Monday–Friday, October 31–November 4 2016; San Jose, California
Session NM9: Mini-Conference: Physics of the Radiation Belts: Collaboration between Laboratory, Theory and Satellite Observations IMini-Conference
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Chair: Chris Crabtree, Naval Research Laboratory Room: 211 CD |
Wednesday, November 2, 2016 9:30AM - 9:55AM |
NM9.00001: Recent Science Highlights of the Van Allen Probes Mission. Aleksandr Ukhorskiy The morning of 30 August 2012 saw an Atlas 5 rocket launch NASA's second Living With a Star spacecraft mission, the twin Radiation Belt Storm Probes, into an elliptic orbit cutting through Earth's radiation belts. Renamed the Van Allen Probes soon after launch, the Probes are designed to determine how the highly variable populations of high-energy charged particles within the radiation belts, dangerous to astronauts and satellites, are created, respond to solar variations, and evolve in space environments. The Van Allen Probes mission extends beyond the practical considerations of the hazard's of Earth's space environment. Twentieth century observations of space and astrophysical systems throughout the solar system and out into the observable universe have shown that the processes that generate intense particle radiation within magnetized environments such as Earth's are universal. During its mission the Van Allen Probes verified and quantified previously suggested energization processes, discovered new energization mechanisms, revealed the critical importance of dynamic plasma injections into the innermost magnetosphere, and used uniquely capable instruments to reveal inner radiation belt features that were all but invisible to previous sensors. This paper gives a brief overview of the mission, presents some recent science highlights, and discusses plans for the extended mission. [Preview Abstract] |
Wednesday, November 2, 2016 9:55AM - 10:20AM |
NM9.00002: 3D Evolution of Lower Hybrid Turbulence in the Ionosphere. Gurudas Ganguli, Chris Crabtree, Leonid Rudakov Three-dimensional evolution of the lower hybrid turbulence driven by a spatially localized ion ring beam perpendicular to the ambient magnetic field in space plasmas is considered. It is shown that the quasi-linear saturation model breaks down when the nonlinear rate of scattering by thermal electron is larger than linear damping rates, which can occur even for low wave amplitudes. The evolution is found to be essentially a three-dimensional phenomenon, which cannot be accurately explained by two-dimensional simulations. An important feature missed in previous studies of this phenomenon is the nonlinear conversion of electrostatic lower hybrid waves into electromagnetic whistler and magnetosonic waves and the consequent energy loss due to radiation from the source region that can result in unique low-amplitude saturation with extended saturation time. It is shown that when the realistic nonlinear effects are considered the net energy that can be permanently extracted from the ring beam is larger. The results are applied to anticipate the outcome of a planned experiment that will seed lower hybrid turbulence in the ionosphere and monitor its evolution. [Preview Abstract] |
Wednesday, November 2, 2016 10:20AM - 10:45AM |
NM9.00003: Measurement of Ion Energization in Laboratory Plasmas Earl Scime Ion energization processes in space plasmas occur over a broad spectrum of spatial and temporal scales and once energized, such ions may trigger instabilities, drive turbulence, and alter pressure balance in MHD systems. Many of these ion energization processes can be investigated under controlled laboratory conditions, e.g., chorus energization of electrons in the radiation belts, ion temperature anisotropy driven instabilities, ion acceleration in double layers, ion beam structures created only in magnetic reconnection exhausts, Alfv\'{e}n wave heating of ions, and ion flows along and across magnetic fields oblique to boundaries. I will review a few laboratory studies of ion energization and their relevance to space plasma phenomena. [Preview Abstract] |
Wednesday, November 2, 2016 10:45AM - 11:10AM |
NM9.00004: Observations of Quasi-Periodic Whistler Mode Waves by the Van Allen Probes George Hospodarsky, Darrelle Wilkinson, William Kurth, Craig Kletzing, Ondrej Santolik Observed in Earth's inner magnetosphere, quasi-periodic whistler mode emissions (QP) are electromagnetic waves in the frequency range from a few hundred Hz to a few kHz that exhibit a periodic modulation (typically a few minutes) of their wave intensity. These waves were first detected at high latitude ground stations, but more recently have been observed by a number of spacecraft, including the twin Van Allen Probes. The Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) instrument simultaneously measures the vector wave magnetic field and electric field, allowing wave propagation parameters, such as wave normal angle and Poynting vector, to be obtained. Almost four years of Van Allen Probes data have been examined and a statistical survey of the occurrence and properties of the QP emissions has been performed. The QP emissions were found to have periods ranging from ~1 to 16 minutes with events lasting from less than 1 hour up to ~6 hours. Some events were detected on successive orbits and a number of events were simultaneously detected by both spacecraft, even during large spacecraft separations, providing an opportunity to investigate the source and propagation properties of these waves. [Preview Abstract] |
Wednesday, November 2, 2016 11:10AM - 11:35AM |
NM9.00005: Generation of VLF Waves to Provide Efficient Interaction with Energetic Electrons in a Radiation Belt V. Sotnikov, J. Caplinger, T. Kim, E. Mishin, N. Gershenzon, D. Main Whistler waves interact with radiation belt (RB) electrons via cyclotron resonance. This interaction leads to enhanced pitch angle diffusion and shifting energetic electrons towards the loss cone. In order for this interaction to be efficient it is necessary to create curtain level of finite amplitude VLF electromagnetic whistler waves in the interaction region. We will examine different sources for VLF whistler wave excitation including conventional loop antennas and parametric antennas. In the case of conventional sources a great deal of the source power is radiated not as a whistler wave but as a quasi-electrostatic low oblique resonance (LOR) mode which does not propagate on great distances from the source region. Only a small percentage of the power is radiated as the electromagnetic whistler wave. We present results on parametric interaction of LOR waves with ion acoustic (IA) waves and extremely low frequency (ELF) waves to demonstrate the possibility to overcome this difficulty. Additionally, particle-in-cell (PIC) simulations, which demonstrate the excitation and spatial structure of VLF waves excited by conventional and parametric antennas are presented. [Preview Abstract] |
Wednesday, November 2, 2016 11:35AM - 12:00PM |
NM9.00006: High beta plasma observations in Earth’s inner magnetosphere: Waves and particle oscillations, and drift-mirror instability. A. Rualdo Soto Chavez, Louis J. Lanzerotti, Ross Cohen, Andrew Gerrard, Jerry W. Manweiler We report on high beta ( $>$ 1) plasma observations made by the RBSPICE instruments onboard the Van Allen Probes spacecraft. The data presented covers almost two years of continuous measurements (March 9, 2013 to December 31, 2014). This coverage provides an unprecedented opportunity to identify and characterize high-beta plasma occurrences in the inner magnetosphere and their characteristics. It is known that high-beta events involve complex plasma physics dynamics. These events can also have global effects on Earth’s magnetosphere. Here we show that on July 6, 2013 (one of many high-beta events) a Pc5 ($\sim$ 2.5 min period) wave was locally generated in the magnetosphere through the drift-mirror instability. We describe the wave characteristics and its effects on particle modulations, specifically ring current ions ($\sim$ 50-500 keV). [Preview Abstract] |
Wednesday, November 2, 2016 12:00PM - 12:25PM |
NM9.00007: Kinetic Alfv\'{e}n Eigenmodes and Particle Acceleration in Near-Earth Space Christopher Chaston We present observations of filamentary electromagnetic structures in Earth's inner magnetosphere. These structures have the characteristics of Alfv\'{e}nic eigen-modes of the geomagnetic field on scales comparable to the average ion-gyro-radii of the supporting plasma. It is shown how these field structures extract ions from the ionosphere and drive them into the magnetosphere with energies orders of magnitude larger than that their ionospheric source. These features are observed nearly continuously during intervals of enhanced geomagnetic activity known as geomagnetic storms. As the ions accelerated in these waves gradient/curvature drift in the geomagnetic field they will make a substantial contribution to global magnetospheric plasma pressure and alter the drift paths of all inner magnetospheric plasmas. These waves may therefore be a heretofore unknown controller of the magnetospheric response to space weather events. [Preview Abstract] |
Wednesday, November 2, 2016 12:25PM - 12:50PM |
NM9.00008: Plasma waves and electrostatic structures near propagating boundary layers in the inner terrestrial magnetosphere: Van Allen Probes and THEMIS observations David Malaspina, John Wygant, Robert Ergun, Geoff Reeves, Ruth Skoug, Brian Larsen A broad range of plasma wave phenomena, only recently reported in the near-equatorial inner terrestrial magnetosphere, have been detected using the Van Allen Probes. These phenomena include electrostatic structures, such as double layers and phase space holes, as well as plasma wave modes including nonlinearly steepened whistler waves and kinetic Alfv\'{e}n waves. The ubiquity of these structures is now confirmed, but it is not understood what role these structures and waves play in the dynamics of the inner magnetosphere and radiation belts. To quantify their importance, it is necessary to understand their distribution, generation, and impact on particle populations. In this study, we demonstrate a strong correlation between the occurrence of these phenomena and plasma boundaries, including the inner edge of the plasma sheet, propagating injection fronts, and the plasmapause. Further, we find that these structures and waves are continually generated as these boundaries propagate through the inner magnetosphere. Understanding the generation mechanisms of these structures and waves, as well as their impact on particle populations stands to benefit significantly from careful theoretical treatment, numerical simulation, and laboratory experiments. [Preview Abstract] |
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