Bulletin of the American Physical Society
56th Annual Meeting of the APS Division of Plasma Physics
Volume 59, Number 15
Monday–Friday, October 27–31, 2014; New Orleans, Louisiana
Session PM10: Mini-Conference: Nonlinear Effects in Geospace Plasmas II |
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Chair: Evgeny Mishin, Air Force Research Laboratory Room: Salon FGH |
Wednesday, October 29, 2014 2:00PM - 2:12PM |
PM10.00001: Demonstration of anisotropic fluid closure capturing the kinetic structure of magnetic reconnection Obioma Egedal, Jan Egedal, Vyacheslav Lukin, William Daughton Weakly-collisional magnetic reconnection, a process linked to solar flares, coronal mass ejections, and magnetic substorms, has been widely studied through fluid and kinetic simulations. While two-fluid models often reproduce the fast reconnection rate of kinetic simulations, significant differences are observed in the structure of the reconnection regions [1]. Recently, new equations of state that accurately account for the development of anisotropic electron pressure due to the electric and magnetic trapping of electrons have been developed [2]. Using these equations of state, guide-field fluid simulations have been shown to reproduce the detailed reconnection region observed in kinetic simulations [3]. Implementing this two-fluid simulation using the HiFi framework [4], we study the force balance of the electron layers in guide-field reconnection and derive scaling laws for the heating observed in these layers.\\[1ex] [1] Daughton W et al., Phys. Plasmas 13, 072101 (2006).\\[0ex] [2] Le A et al., Phys. Rev. Lett. 102, 085001 (2009).\\[0ex] [3] Ohia O, et al., Phys. Rev. Lett. In Press (2012).\\[0ex] [4] Lukin VS, Linton MG, Nonlinear Proc. Geoph. 18, 871 (2011) [Preview Abstract] |
Wednesday, October 29, 2014 2:12PM - 2:24PM |
PM10.00002: In situ evidence of new magnetotail reconnection regime with embedded current layers and anisotropic exhaust electrons John Boguski, Jan Egedal, William Daughton Using kinetic simulations a new regime of magnetic reconnection has been discovered in parameter ranges similar to those found in the Earth's magnetotail [1]. The regime is closely related to the dynamics of magnetized trapped electrons causing strong electron pressure anisotropy which reaches the firehose condition and has the ability to drive current layers in the reconnection exhaust [2]. As part of an endeavor to conclusively verify the existence of the new reconnection regime in Earth's magnetotail, a systematic analysis of the 2002-08-28 reconnection event first identified by A.L. Borg [3] is performed. In particular we assess the pressure anisotropy, the satisfaction of the firehose condition, and the agreement of pressure measurements to those predicted from theory. The analysis of this event and comparison to simulation results document the importance of the new regime to reconnection in the Earth magnetosphere. \\[1ex] [1] A. Le et al., PRL 110, 135004, 2013. \\[0ex] [2] A. Le et al., PRL 102, 085001, 2009. \\[0ex] [3] A.L. Borg et al., Annales Geophysicae, 30(1):109-117, 2012. [Preview Abstract] |
Wednesday, October 29, 2014 2:24PM - 2:36PM |
PM10.00003: Unifying the Parker and the Turbulence Models of Solar Coronal Heating C.S. Ng, T.J. Dennis We present results from a series of three-dimensional simulations investigating heating in coronal loops of various lengths, based on the equations of reduced magnetohydrodynamics, following up on our recent simulations of the Parker model of coronal heating [Ng et al., Astrophys. J. {\bf 747} 109, 2012]. We study the time-averaged energy dissipation rate $\langle W \rangle$ as a function of the length of the loop $L$. We confirm that in the limit of small $L$ ($L \ll V_A \tau_c$, where $V_A$ is the Alfv\'en speed based on the parallel magnetic field and $\tau_c$ is the correlation time of the random photospheric motions), $\langle W \rangle$ agrees well with the scaling derived from the Parker model. In the other limit of $L \gg V_A \tau_c$, we show that $\langle W \rangle$ is given by the photospheric Poynting flux required to launch Alfv\'en waves. In the intermediate range of $L \sim V_A \tau_c$, $\langle W \rangle$ is well described by a scaling based on the Kolmogorov turbulence energy cascade, rather than the Iroshnikov-Kraichnan cascade. We also show that $\langle W \rangle$ can be modeled by combining the Parker heating and the Alfv\'en wave launching power for all range of $L$. [Preview Abstract] |
Wednesday, October 29, 2014 2:36PM - 2:48PM |
PM10.00004: Nonlinear Plasma Experiments in Geospace with Gigawatts of RF Power at HAARP J.P. Sheerin, N. Rayyan, B.J. Watkins, W.A. Bristow, P.A. Bernhardt The HAARP phased-array HF transmitter at Gakona, AK delivers up to 3.6 GW (ERP) of HF power in the range of 2.8 -- 10 MHz to the ionosphere with millisecond pointing, power modulation, and frequency agility. HAARP's unique features have enabled the conduct of a number of nonlinear plasma experiments in the interaction region of overdense ionospheric plasma including stimulated electromagnetic emissions (SEE), artificial aurora, artificial ionization layers, VLF wave-particle interactions in the magnetosphere, strong Langmuir turbulence (SLT) and suprathermal electron acceleration. Diagnostics include the Modular UHF Ionospheric Radar (MUIR) sited at HAARP, the SuperDARN-Kodiak HF radar, spacecraft radio beacons, HF receivers to record stimulated electromagnetic emissions (SEE) and telescopes and cameras for optical emissions. We report on short timescale ponderomotive overshoot effects, artificial field-aligned irregularities (AFAI), the aspect angle dependence of the intensity of the plasma line, and suprathermal electrons. Applications are made to the study and control of irregularities affecting spacecraft communication and navigation systems. [Preview Abstract] |
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