Open Access. Powered by Scholars. Published by Universities.®
- Discipline
- Keyword
-
- Amplitudes (1)
- Atmospheric precipitation (1)
- Birkeland current (1)
- Condensed matter (1)
- Convection (1)
-
- Convection currents (1)
- Convection flow (1)
- Decay (1)
- Digital simulation (1)
- Electric potential (1)
- Electromagnetic power (1)
- Electron precipitation (1)
- Electron temperature (1)
- Energy deposition (1)
- Energy transfer (1)
- Field potential (1)
- Fluctuations (1)
- Fluid dynamics (1)
- Forcing (1)
- Geophysics (1)
- Height (1)
- Inflationary universe (1)
- Ion conic (1)
- Ion precipitation (1)
- Ionosphere magnetosphere coupling (1)
- Ionospheric current (1)
- Ionospheric disturbance (1)
- MHD model (1)
- Magnetosphere (1)
- Magnetospheric physics (Magnetosphere- ionosphere interactions (1)
Articles 1 - 9 of 9
Full-Text Articles in Physics
Auroral Ion Outflow: Low Altitude Energization, Kristina A. Lynch, J. L. Semeter, M. Zettergren, P. Kintner, R. Arnoldy, E. Klatt, J. Labelle, R. G. Michell
Auroral Ion Outflow: Low Altitude Energization, Kristina A. Lynch, J. L. Semeter, M. Zettergren, P. Kintner, R. Arnoldy, E. Klatt, J. Labelle, R. G. Michell
Dartmouth Scholarship
The SIERRA nightside auroral sounding rocket made observations of the origins of ion upflow, at topside F-region altitudes (below 700 km), comparatively large topside plasma densities (above 20 000/cc), and low energies (10 eV). Upflowing ions with bulk velocities up to 2 km/s are seen in conjunction with the poleward edge of a nightside substorm arc. The upflow is limited within the poleward edge to a region (a) of northward convection, (b) where Alfvenic ´ and Pedersen conductivities are well-matched, leading to good ionospheric transmission of Alfvenic power, and (c) of ´ soft electron precipitation (below 100 eV). Models of …
Hydrodynamic And Magnetohydrodynamic Computations Inside A Rotating Sphere, P. D. Mininni, D. C. Montgomery, L. Turner
Hydrodynamic And Magnetohydrodynamic Computations Inside A Rotating Sphere, P. D. Mininni, D. C. Montgomery, L. Turner
Dartmouth Scholarship
Numerical solutions of the incompressible magnetohydrodynamic (MHD) equations are reported for the interior of a rotating, perfectly-conducting, rigid spherical shell that is insulator-coated on the inside. A previously-reported spectral method is used which relies on a Galerkin expansion in Chandrasekhar–Kendall vector eigenfunctions of the curl. The new ingredient in this set of computations is the rigid rotation of the sphere. After a few purely hydrodynamic examples are sampled (spin down, Ekman pumping, inertial waves), attention is focused on selective decay and the MHD dynamo problem. In dynamo runs, prescribed mechanical forcing excites a persistent velocity field, usually turbulent at modest …
Displacement Detection With A Vibrating Rf Superconducting Interference Device: Beating The Standard Linear Limit, Eyal Buks, Stav Zaitsev, Eran Segev, Baleegh Abdo, M. P. Blencowe
Displacement Detection With A Vibrating Rf Superconducting Interference Device: Beating The Standard Linear Limit, Eyal Buks, Stav Zaitsev, Eran Segev, Baleegh Abdo, M. P. Blencowe
Dartmouth Scholarship
We study a configuration for displacement detection consisting of a nanomechanical resonator coupled to both a radio frequency superconducting interference device and to a superconducting stripline resonator. We employ an adiabatic approximation and rotating wave approximation and calculate the displacement sensitivity. We study the performance of such a displacement detector when the stripline resonator is driven into a region of nonlinear oscillations. In this region the system exhibits noise squeezing in the output signal when homodyne detection is employed for readout. We show that displacement sensitivity of the device in this region may exceed the upper bound imposed upon the …
Bubbling The False Vacuum Away, M. Gleiser, B. Rogers, J. Thorarinson
Bubbling The False Vacuum Away, M. Gleiser, B. Rogers, J. Thorarinson
Dartmouth Scholarship
We investigate the role of nonperturbative, bubble-like inhomogeneities on the decay rate of false- vacuum states in two and three-dimensional scalar field theories. The inhomogeneities are induced by setting up large-amplitude oscillations of the field about the false vacuum as, for example, after a rapid quench or in certain models of cosmological inflation. We show that, for a wide range of parameters, the presence of large-amplitude bubble-like inhomogeneities greatly accelerates the de- cay rate, changing it from the well-known exponential suppression of homogeneous nucleation to a power-law suppression. It is argued that this fast, power-law vacuum decay – known as …
Quantum Analysis Of A Linear Dc Squid Mechanical Displacement Detector, M. P. Blencowe, E. Buks
Quantum Analysis Of A Linear Dc Squid Mechanical Displacement Detector, M. P. Blencowe, E. Buks
Dartmouth Scholarship
We provide a quantum analysis of a dc SQUID mechanical displacement detector within the subcritical Josephson current regime. A segment of the SQUID loop forms the mechanical resonator and motion of the latter is transduced inductively through changes in the flux threading the loop. Expressions are derived for the detector signal response and noise, which are used to evaluate the position and force detection sensitivity. We also investigate cooling of the mechanical resonator due to detector back reaction.
A Global Mhd Simulation Of An Event With A Quasi-Steady Northward Imf Component, V G. Merkin, J G. Lyon, B J. Anderson, H Korth, C C. Goodrich, K Papadopoulos
A Global Mhd Simulation Of An Event With A Quasi-Steady Northward Imf Component, V G. Merkin, J G. Lyon, B J. Anderson, H Korth, C C. Goodrich, K Papadopoulos
Dartmouth Scholarship
We show results of the Lyon-Fedder-Mobarry (LFM) global MHD simulations of an event previously ex- amined using Iridium spacecraft observations as well as DMSP and IMAGE FUV data. The event is chosen for the steady northward IMF sustained over a three-hour pe- riod during 16 July 2000. The Iridium observations showed very weak or absent Region 2 currents in the ionosphere, which makes the event favorable for global MHD model- ing. Here we are interested in examining the model’s per- formace during weak magnetospheric forcing, in particular, its ability to reproduce gross signatures of the ionospheric currents and convection pattern …
Dynamical Control Of Electron Spin Coherence In A Quantum Dot: A Theoretical Study, Wenxian Zhang, V. V. Dobrovitski, Lea F. Santos, Lorenza Viola, B. N. Harmon
Dynamical Control Of Electron Spin Coherence In A Quantum Dot: A Theoretical Study, Wenxian Zhang, V. V. Dobrovitski, Lea F. Santos, Lorenza Viola, B. N. Harmon
Dartmouth Scholarship
We investigate the performance of dynamical decoupling methods at suppressing electron spin decoherence from a low-temperature nuclear spin reservoir in a quantum dot. The controlled dynamics is studied through exact numerical simulation, with emphasis on realistic pulse delays and the long-time limit. Our results show that optimal performance for this system is attained by a periodic protocol exploiting concatenated design, with control rates substantially slower than expected from the upper spectral cutoff of the bath. For a known initial electron spin state, coherence can saturate at long times, signaling the creation of a stable “spin-locked” decoherence-free subspace. Analytical insight into …
Generalized Coherent States As Preferred States Of Open Quantum Systems, S Boixo, L Viola, G Ortiz
Generalized Coherent States As Preferred States Of Open Quantum Systems, S Boixo, L Viola, G Ortiz
Dartmouth Scholarship
We investigate the connection between quasi-classical (pointer) states and generalized coherent states (GCSs) within an algebraic approach to Markovian quantum systems (including bosons, spins, and fermions). We establish conditions for the GCS set to become most robust by relating the rate of purity loss to an invariant measure of uncertainty derived from quantum Fisher information. We find that, for damped bosonic modes, the stability of canonical coherent states is confirmed in a variety of scenarios, while for systems described by (compact) Lie algebras, stringent symmetry constraints must be obeyed for the GCS set to be preferred. The relationship …
Continuous Measurement Of The Energy Eigenstates Of A Nanomechanical Resonator Without A Nondemolition Probe, Kurt Jacobs, Pavel Lougovski, Miles Blencowe
Continuous Measurement Of The Energy Eigenstates Of A Nanomechanical Resonator Without A Nondemolition Probe, Kurt Jacobs, Pavel Lougovski, Miles Blencowe
Dartmouth Scholarship
We show that it is possible to perform a continuous measurement that continually projects a nanoresonator into its energy eigenstates by employing a linear coupling with a two-state system. This technique makes it possible to perform a measurement that exposes the quantum nature of the resonator by coupling it to a Cooper-pair box and a superconducting transmission line resonator.