Search Publications
Detection of B-Mode Polarization in the Cosmic Microwave Background with Data from the South Pole Telescope
Ade, P. A. R.; Bock, J. J.; Chiang, H. C. +65 more
Gravitational lensing of the cosmic microwave background generates a curl pattern in the observed polarization. This “B-mode” signal provides a measure of the projected mass distribution over the entire observable Universe and also acts as a contaminant for the measurement of primordial gravity-wave signals. In this Letter we present the first det…
Regimes of the Electron Diffusion Region in Magnetic Reconnection
Egedal, J.; Daughton, W.; Karimabadi, H. +3 more
The electron diffusion region during magnetic reconnection lies in different regimes depending on the pressure anisotropy, which is regulated by the properties of thermal electron orbits. In kinetic simulations at the weakest guide fields, pitch angle mixing in velocity space causes the outflow electron pressure to become nearly isotropic. Above a…
Bifurcated Structure of the Electron Diffusion Region in Three-Dimensional Magnetic Reconnection
Li, H.; Daughton, W.; Karimabadi, H. +2 more
Three-dimensional kinetic simulations of magnetic reconnection reveal that the electron diffusion region is composed of two or more current sheets in regimes with weak magnetic shear angles ϕ≲80°. This new morphology is explained by oblique tearing modes which produce flux ropes while simultaneously driving enhanced current at multiple resonance s…
Energy Partition in Magnetic Reconnection in Earth's Magnetotail
Eastwood, J. P.; Lavraud, B.; Phan, T. D. +4 more
The partition of energy flux in magnetic reconnection is examined experimentally using Cluster satellite observations of collisionless reconnection in Earth’s magnetotail. In this plasma regime, the dominant component of the energy flux is ion enthalpy flux, with smaller contributions from the electron enthalpy and heat flux and the ion kinetic en…
Limits on the Dependence of the Fine-Structure Constant on Gravitational Potential from White-Dwarf Spectra
Barstow, M. A.; Holberg, J. B.; Webb, J. K. +5 more
We propose a new probe of the dependence of the fine-structure constant α on a strong gravitational field using metal lines in the spectra of white-dwarf stars. Comparison of laboratory spectra with far-UV astronomical spectra from the white-dwarf star G191-B2B recorded by the Hubble Space Telescope Imaging Spectrograph gives limits of Δα/α=(4.2±1…
Stochastic Acceleration by Multi-Island Contraction during Turbulent Magnetic Reconnection
Kontar, Eduard P.; Bian, Nicolas H.
The acceleration of charged particles in magnetized plasmas is considered during turbulent multi-island magnetic reconnection. The particle acceleration model is constructed for an ensemble of islands which produce adiabatic compression of the particles. The model takes into account the statistical fluctuations in the compression rate experienced …
New Constraints on the Early Expansion History of the Universe
Hojjati, Alireza; Samsing, Johan; Linder, Eric V.
Cosmic microwave background measurements have pushed to higher resolution, lower noise, and more sky coverage. These data enable a unique test of the early Universe’s expansion rate and constituents such as effective number of relativistic degrees of freedom and dark energy. Using the most recent data from Planck and WMAP9, we constrain the expans…