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Articles 1 - 12 of 12
Full-Text Articles in Physical Sciences and Mathematics
Are Periodic Solar Wind Number Density Structures Formed In The Solar Corona?, N. M. Viall, Harlan E. Spence, J. Kasper
Are Periodic Solar Wind Number Density Structures Formed In The Solar Corona?, N. M. Viall, Harlan E. Spence, J. Kasper
Physics & Astronomy
[1] We present an analysis of the alpha to proton solar wind abundance ratio (AHe) during a period characterized by significant large size scale density fluctuations, focusing on an event in which the proton and alpha enhancements are anti-correlated. In a recent study using 11 years (1995–2005) of solar wind observations from the Wind spacecraft, N. M. Viall et al. [2008] showed that periodic proton density structures occurred at particular radial length-scales more often than others. The source of these periodic density structures is a significant and outstanding question. Are they generated in the interplanetary medium, or are they a …
Ion Observations From Geosynchronous Orbit As A Proxy For Ion Cyclotron Wave Growth During Storm Times, L. W. Blum, E. A. Macdonald, S. P. Gary, M. F. Thomsen, Harlan E. Spence
Ion Observations From Geosynchronous Orbit As A Proxy For Ion Cyclotron Wave Growth During Storm Times, L. W. Blum, E. A. Macdonald, S. P. Gary, M. F. Thomsen, Harlan E. Spence
Physics & Astronomy
[1] There is still much to be understood about the processes contributing to relativistic electron enhancements and losses in the radiation belts. Wave particle interactions with both whistler and electromagnetic ion cyclotron (EMIC) waves may precipitate or accelerate these electrons. This study examines the relation between EMIC waves and resulting relativistic electron flux levels after geomagnetic storms. A proxy for enhanced EMIC waves is developed using Los Alamos National Laboratory Magnetospheric Plasma Analyzer plasma data from geosynchronous orbit in conjunction with linear theory. In a statistical study using superposed epoch analysis, it is found that for storms resulting in net …
Observation Of Giant Positive Magnetoresistance In A Cooper Pair Insulator., H Q. Nguyen, Shawna M. Hollen, M D. Stewart Jr, J Shainline, Aijun Yin, J M. Xu, J M. Valles
Observation Of Giant Positive Magnetoresistance In A Cooper Pair Insulator., H Q. Nguyen, Shawna M. Hollen, M D. Stewart Jr, J Shainline, Aijun Yin, J M. Xu, J M. Valles
Physics & Astronomy
Ultrathin amorphous Bi films, patterned with a nanohoneycomb array of holes, can exhibit an insulating phase with transport dominated by the incoherent motion of Cooper pairs (CP) of electrons between localized states. Here, we show that the magnetoresistance (MR) of this Cooper pair insulator (CPI) phase is positive and grows exponentially with decreasing temperature T, for T well below the pair formation temperature. It peaks at a field estimated to be sufficient to break the pairs and then decreases monotonically into a regime in which the film resistance assumes the T dependence appropriate for weakly localized single electron transport. We …
Energy Dissipation And Ion Heating At The Heliospheric Termination Shock, P. Wu, D. Winske, S. P. Gary, Nathan A. Schwadron, Martin A. Lee
Energy Dissipation And Ion Heating At The Heliospheric Termination Shock, P. Wu, D. Winske, S. P. Gary, Nathan A. Schwadron, Martin A. Lee
Physics & Astronomy
The Los Alamos hybrid simulation code is used to examine heating and the partition of dissipation energy at the perpendicular heliospheric termination shock in the presence of pickup ions. The simulations are one-dimensional in space but three-dimensional in field and velocity components, and are carried out for a range of values of pickup ion relative density. Results from the simulations show that because the solar wind ions are relatively cold upstream, the temperature of these ions is raised by a relatively larger factor than the temperature of the pickup ions. An analytic model for energy partition is developed on the …
Near-Infrared Photoabsorption By C(60) Dianions In A Storage Ring, U. Kadhane, J. U. Andersen, E. Bonderup, B. Concina, P. Hvelplund, M. Kirketerp, B. Suhr, B. Liu, S. Bronsted Nielsen, S. Panja, J. Rangama, K. Stochkel, S. Tomita
Near-Infrared Photoabsorption By C(60) Dianions In A Storage Ring, U. Kadhane, J. U. Andersen, E. Bonderup, B. Concina, P. Hvelplund, M. Kirketerp, B. Suhr, B. Liu, S. Bronsted Nielsen, S. Panja, J. Rangama, K. Stochkel, S. Tomita
Physics & Astronomy
We present a detailed study of the electronic structure and the stability of C(60) dianions in the gas phase. Monoanions were extracted from a plasma source and converted to dianions by electron transfer in a Na vapor cell. The dianions were then stored in an electrostatic ring, and their near-infrared absorption spectrum was measured by observation of laser induced electron detachment. From the time dependence of the detachment after photon absorption, we conclude that the reaction has contributions from both direct electron tunneling to the continuum and vibrationally assisted tunneling after internal conversion. This implies that the height of the …
Multipoint, High Time Resolution Galactic Cosmic Ray Observations Associated With Two Interplanetary Coronal Mass Ejections, Andrew P. Jordan, Harlan E. Spence, J. B. Blake, T. Mulligan, D. N. A. Shaul, M. Galametz
Multipoint, High Time Resolution Galactic Cosmic Ray Observations Associated With Two Interplanetary Coronal Mass Ejections, Andrew P. Jordan, Harlan E. Spence, J. B. Blake, T. Mulligan, D. N. A. Shaul, M. Galametz
Physics & Astronomy
[1] Galactic cosmic rays (GCRs) play an important role in our understanding of the interplanetary medium (IPM). The causes of their short timescale variations, however, remain largely unexplored. In this paper, we compare high time resolution, multipoint space-based GCR data to explore structures in the IPM that cause these variations. To ensure that features we see in these data actually relate to conditions in the IPM, we look for correlations between the GCR time series from two instruments onboard the Polar and INTEGRAL (International Gamma Ray Astrophysical Laboratory) satellites, respectively inside and outside Earth's magnetosphere. We analyze the period of …
A Novel Metric For Coronal Mhd Models, D. J. Schmit, S. Gibson, G. De Toma, M. Wiltberger, W. J. Hughes, Harlan E. Spence, P. Riley, J. A. Linker, Z. Mikic
A Novel Metric For Coronal Mhd Models, D. J. Schmit, S. Gibson, G. De Toma, M. Wiltberger, W. J. Hughes, Harlan E. Spence, P. Riley, J. A. Linker, Z. Mikic
Physics & Astronomy
[1] In the interest of quantitatively assessing the capabilities of coronal MHD models, we have developed a metric that compares the structures of the white light corona observed with SOHO LASCO C2 to model predictions. The MAS model is compared to C2 observations from two Carrington rotations during solar cycle 23, CR1913 and CR1984, which were near the minimum and maximum of solar activity, respectively, for three radial heights, 2.5 R⊙, 3.0 R⊙, and 4.5 R⊙. In addition to simulated polarization brightness images, we create a synthetic image based on the field topology along the line of sight in the …
Assessing Access Of Galactic Cosmic Rays At Moon's Orbit, Chia-Lin L. Huang, Harlan E. Spence, B. T. Kress
Assessing Access Of Galactic Cosmic Rays At Moon's Orbit, Chia-Lin L. Huang, Harlan E. Spence, B. T. Kress
Physics & Astronomy
[1] Characterizing the lunar radiation environment is essential for preparing future robotic and human explorations on lunar bases. Galactic cosmic rays (GCR) represent one source of ionizing radiation at the Moon that poses a biological risk. Because GCR are charged particles, their paths are affected by the magnetic fields along their trajectories. Unlike the Earth, the Moon has no strong, shielding magnetic field of its own. However, as it orbits Earth, the Moon traverses not only the weak interplanetary magnetic field but also the distant magnetic tail of Earth's magnetosphere. We combine an empirical magnetic field model of Earth's magnetosphere …
Superconductor-Insulator Transitions In Films Patterned With A Disordered Nanohoneycomb Hole Array, H Q. Nguyen, Shawna M. Hollen, M D. Stewart Jr, Aijun Yin, J Shainline, J M. Xu, J M. Valles Jr.
Superconductor-Insulator Transitions In Films Patterned With A Disordered Nanohoneycomb Hole Array, H Q. Nguyen, Shawna M. Hollen, M D. Stewart Jr, Aijun Yin, J Shainline, J M. Xu, J M. Valles Jr.
Physics & Astronomy
No abstract provided.
High Field Magnetoresistance Peak Near The Superconductor Insulator Transition In Amorphous Bi Films Patterned With A Nanohoneycomb Array Of Holes, Shawna M. Hollen, H Q. Nguyen, M D. Stewart Jr, J Shainline, Aijun Yin, J M. Xu, J M. Valles Jr.
High Field Magnetoresistance Peak Near The Superconductor Insulator Transition In Amorphous Bi Films Patterned With A Nanohoneycomb Array Of Holes, Shawna M. Hollen, H Q. Nguyen, M D. Stewart Jr, J Shainline, Aijun Yin, J M. Xu, J M. Valles Jr.
Physics & Astronomy
No abstract provided.
Scale-Dependent Angle Of Alignment Between Velocity And Magnetic Field Fluctuations In Solar Wind Turbulence, J. J. Podesta, Benjamin D.G. Chandran, A. Bhattacharjee, D. A. Roberts, M. L. Goldstein
Scale-Dependent Angle Of Alignment Between Velocity And Magnetic Field Fluctuations In Solar Wind Turbulence, J. J. Podesta, Benjamin D.G. Chandran, A. Bhattacharjee, D. A. Roberts, M. L. Goldstein
Physics & Astronomy
Under certain conditions, freely decaying magnetohydrodynamic (MHD) turbulence evolves in such a way that velocity and magnetic field fluctuations delta v and delta B approach a state of alignment in which delta v proportional to delta B. This process is called dynamic alignment. Boldyrev has suggested that a similar kind of alignment process occurs as energy cascades from large to small scales through the inertial range in strong incompressible MHD turbulence. In this study, plasma and magnetic field data from the Wind spacecraft, data acquired in the ecliptic plane near 1 AU, are employed to investigate the angle theta(tau) between …
Relative Occurrence Rates And Connection Of Discrete Frequency Oscillations In The Solar Wind Density And Dayside Magnetosphere, N. M. Viall, L. Kepko, Harlan E. Spence
Relative Occurrence Rates And Connection Of Discrete Frequency Oscillations In The Solar Wind Density And Dayside Magnetosphere, N. M. Viall, L. Kepko, Harlan E. Spence
Physics & Astronomy
[1] We present an analysis of the occurrence distributions of statistically significant apparent frequencies of periodic solar wind number density structures and dayside magnetospheric oscillations in the f = 0.5–5.0 mHz range. Using 11 years (1995–2005) of solar wind data, we identified all spectral peaks that passed both an amplitude test and a harmonic F test at the 95% confidence level in 6-hour data segments. We find that certain discrete frequencies, specifically f = 0.7, 1.4, 2.0, and 4.8 mHz, occur more often than do other frequencies over those 11 years. We repeat the analysis on discrete oscillations observed in …