Bulletin of the American Physical Society
53rd Annual Meeting of the APS Division of Plasma Physics
Volume 56, Number 16
Monday–Friday, November 14–18, 2011; Salt Lake City, Utah
Session BM10: Mini-conference on Nonlinear Effects in Geospace Plasmas I |
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Chair: Evgeny Mishin, Air Force Research Laboratory Room: 151 ABCG |
Monday, November 14, 2011 9:30AM - 10:10AM |
BM10.00001: Space as an open plasma laboratory Konstantinos Papadopoulos Ionospheric heaters supplemented by ground and space based diagnostic instruments have for a long time being used to conduct plasma physics, geophysical and radio science investigations. The recently completed HF transmitter associated with the High Frequency Active Ionospheric Research Program (HAARP), far exceeds the capabilities of previous ionospheric heaters and allows for new frontier research in plasma physics, geophysics and radio science. The transmitter radiates 3.6 MW of HF power in the 2.8-10.0 MHz frequency range. The beam-width varies from 15-5 degrees, corresponding to 20-30 dB gain and resulting in Effective Radiating Power (ERP) between .36 -- 4.0 GW. The antenna can point to any direction in a cone of 30 degrees from the vertical, with a reposition time of 15 degrees in 15 microseconds resulting in super-luminous scanning speeds. The transmitter can synthesize essentially any desired waveform in linear and circular polarization. We present a number of HAARP experiments that used space as an open plasma laboratory. The experiments cover the areas of (i) Artificial ULF/ELF/VLF generation and injection in the magnetosphere (ii) Studies of wave-particle interactions in the magnetosphere (iii) Langmuir turbulence, parametric instabilities, electron acceleration and optical emissions (iv) Artificial ionization. Work supported by MURI ONR N00140710789 and DARPA-DSO HR0011-09-C-0099. [Preview Abstract] |
Monday, November 14, 2011 10:10AM - 10:50AM |
BM10.00002: 3D Modeling of Equatorial Plasma Bubbles Joseph Huba, Glenn Joyce, Jonathan Krall Post-sunset ionospheric irregularities in the equatorial F region were first observed by Booker and Wells (1938) using ionosondes. This phenomenon has become known as equatorial spread F (ESF). During ESF the equatorial ionosphere becomes unstable because of a Rayleigh-Taylor-like instability: large scale (10s km) electron density ``bubbles'' can develop and rise to high altitudes (1000 km or greater at times). Understanding and modeling ESF is important because of its impact on space weather: it causes radio wave scintillation that degrades communication and navigation systems. In fact, it is the focus of of the Air Force Communications/Navigation Outage Forecast Satellite (C/NOFS) mission. We will describe 3D simulation results from the NRL ionosphere models SAMI3 and SAMI3/ESF of this phenomenon. In particular, we will examine the causes of the day-to-day ariability of ESF which is an unresolved problem at this time. \medskip \\ Booker, H.G. and H.G. Wells, {\it Terr. Mag. Atmos. Elec. 43}, 249, 1938. [Preview Abstract] |
Monday, November 14, 2011 10:50AM - 11:30AM |
BM10.00003: Double Layers and Electron Holes in Space Plasmas Nagendra Singh Electron holes are highly nonlinear structures in plasmas. Since electron holes require electron beams for their formation, they are intimately related to double layers in plasmas; they are a dominant feature of the plasma on the high potential side of a double layer. We will briefly review theory, simulations, satellite observations and laboratory studies on electron holes. Their relationship with double layers as seen in simulations and satellite observations will be confirmed. Their shape and size as found in simulations, observations and recent laboratory experiments will be discussed. The detection of electron holes and double layers driven by magnetic flux ropes, depolarization events, bursty bulk flows, and magnetic reconnection in the Earth's magneto-tail will be discussed. The dissipation of magnetic energy and currents in the large-scale magnetic structures by electron holes and double layers will be highlighted. [Preview Abstract] |
Monday, November 14, 2011 11:30AM - 12:00PM |
BM10.00004: Large scale electron acceleration by parallel electric fields during magnetic reconnection J. Egedal, A. Le, W. Daughton Magnetic reconnection is an ubiquitous phenomenon in plasmas. It permits an explosive release of energy through changes in the magnetic field line topology. In the Earth's magnetotail, reconnection energizes electrons up to hundreds of keV and solar flares events can channel up to 50\% of the magnetic energy into the electrons resulting in superthermal populations. Electron energization is also fundamentally important to astrophysical applications, where X-rays generated by relativistic electrons provide a unique window into the extreme environments. Here we show that during reconnection powerful energization of electrons by $E_{\parallel}$ can occur over spatial scales which hugely exceed what previously thought possible. Thus, our results are contrary to a fundamental assumption that a hot plasma -- a highly conducting medium for electrical current -- cannot support any significant $E_{\parallel}$ over length scales large compared to the small electron inertial length $d_e=c/\omega_{pe}$. In our model $E_{\parallel}$ is supported by strongly anisotropic features in the electron distributions not permitted in standard fluid formulations, but routinely observed by spacecraft in the Earth's magnetosphere. This allows for electron energization in spatial regions that exceed the regular $d_e$ scale electron diffusion region by at least three orders of magnitude. [Preview Abstract] |
Monday, November 14, 2011 12:00PM - 12:30PM |
BM10.00005: Quasilinear Evolution from KAW Turbulence and Perpendicular Ion Heating in the Solar Wind Leonid Rudakov, Manish Mithaiwala, Gurudas Ganguli, Chris Crabtree The electron and ion distribution functions resulting from
quasi-linear
diffusion in the turbulent solar wind plasma is calculated using the
measured spectrum of the kinetic Alfven wave (KAW) fluctuations.
Quasi-linear diffusion establishes a step-like profile on the
distribution
function over parallel velocity [1]. The size of ``plateau'' $v_m
$, which
can be created within the time of travel of solar wind plasma to
the Earth
$\sim $ 10$^{5}$ s, is estimated for electrons as $v_{me} /v_{te}
\sim
(10^{-7}t)^{1/6}\sim 0.5$, while for ions $v_{mi} /v_{ti} \sim
(10^{-2}t)^{1/7}\sim 3$. In this case the evolution of the ion tail
distribution function can be approximated as$f_{tail} \sim
t^{-1/7}\exp
(-\vert v_z \vert ^7/v_{mi}^7 )$. As a result, the Landau damping
of KAW and
whistlers in the high beta solar wind plasma is strongly
diminished for
$\omega |
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