Search Publications
Ion Charge States in the Fast Solar Wind: New Data Analysis and Theoretical Refinements
Laming, J. Martin; Lepri, Susan T.
We present a further investigation into the increased ionization observed in element charge states in the fast solar wind compared to its coronal hole source regions. Once ions begin to be perpendicularly heated by ion cyclotron waves and execute large gyro-orbits, density gradients in the flow can excite lower hybrid waves that then damp by heati…
Solar Models with Revised Abundances and Opacities
Yang, W. M.; Bi, S. L.
Using reconstructed opacities, we construct solar models with low heavy-element abundance. Rotational mixing and enhanced diffusion of helium and heavy elements are used to reconcile the recently observed abundances with helioseismology. The sound speed and density of models in which the relative and absolute diffusion coefficients for helium and …
Flux Pile-up Magnetic Reconnection in the Solar Photosphere
Chae, Jongchul; Litvinenko, Yuri E.; Park, So-Young
Magnetic reconnection in the temperature minimum region of the solar photosphere, observationally manifested as canceling magnetic features, is considered. Flux pile-up reconnection in the Sweet-Parker current sheet is analyzed. It is shown that the standard Sweet-Parker reconnection rate in the photosphere is too slow to explain the observed canc…
Effect of Suppressed Excitation on the Amplitude Distribution of 5 Minute Oscillations in Sunspots
Kosovichev, A. G.; Parchevsky, K. V.
Five minute oscillations on the Sun (acoustic and surface gravity waves) are excited by subsurface turbulent convection. However, in sunspots the excitation is suppressed because a strong magnetic field inhibits convection. We use three-dimensional simulations to investigate how the suppression of excitation sources affects the distribution of the…
Dynamical Constraints on the Component Masses of the Cataclysmic Variable WZ Sagittae
Howell, Steve B.; Sion, Edward M.; Gänsicke, Boris T. +3 more
We present phase-resolved spectroscopy of the short-period cataclysmic variable WZ Sge obtained with the Hubble Space Telescope. We were able to resolve the orbital motion of a number of absorption lines that likely probe the environment near the accreting white dwarf. The radial velocities derived from simultaneous fits to 13 absorption lines ind…
A Strong-Lens Survey in AEGIS: The Influence of Large-Scale Structure
Davis, Marc; Willmer, Christopher N. A.; Coil, Alison L. +10 more
We report on a visual search for galaxy-scale strong gravitational lenses over 650 arcmin2 of HST ACS (V606 and I814) imaging in the DEEP2 Extended Groth Strip. This field has Keck DEIMOS spectroscopy of ~14,000 galaxies (~75% complete to RAB<24.1). We identify three strong galaxy-galaxy lenses: HST J…
Vector Magnetic Fields of Moving Magnetic Features and Flux Removal from a Sunspot
Kubo, M.; Tsuneta, S.; Shimizu, T.
Moving magnetic features (MMFs) are small photospheric magnetic elements moving outward in the zone (moat region) surrounding mature sunspots. Vector magnetic fields and horizontal motion of the classical MMFs (called isolated MMFs hereafter) are investigated using coordinated ASP and MDI observations. Their magnetic and velocity properties are co…
Optical Studies of the Ultraluminous X-Ray Source NGC 1313 X-2
Kaaret, Philip; Miller, Jon; Liu, Ji-Feng +1 more
NGC 1313 X-2 was among the first ultraluminous X-ray sources discovered, and has been a frequent target of X-ray and optical observations. Using the HST ACS multiband observations, this source is identified with a unique counterpart within an error circle of 0.2". The counterpart is a blue star on the edge of a young cluster of <=107…
Nonlinear Interaction of Minor Heavy Ions with Kinetic Alfvén Waves and Their Anisotropic Energization in Coronal Holes
Wu, D. J.; Yang, L.
Some recent observations of the solar corona suggest that minor heavy ions undergo an anisotropic and mass-charge dependent energization in the extended corona. In this paper we investigate the nonlinear interaction of minor heavy ions with kinetic Alfvén waves (KAWs) in the extended corona where plasma is low-β, in particular the ion energization…
How Hot is the Wind from TW Hydrae?
Herczeg, Gregory J.; Johns-Krull, Christopher M.
It has recently been suggested that the winds from classical T Tauri stars in general, and the wind from TW Hya in particular, reaches temperatures of 300,000 K while maintaining a mass-loss rate of ~10-11 Msolar yr-1 or larger. If confirmed, this would place strong new requirements on wind launching and heating mo…