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Aerospace, Physics, and Space Science Faculty Publications

Series

2004

Articles 1 - 9 of 9

Full-Text Articles in Physical Sciences and Mathematics

Nonlinear Parallel And Perpendicular Diffusion Of Charged Cosmic Rays In Weak Turbulence, Andreas Schalchi, John William Bieber, William H. Matthaeus, Gang Qin Nov 2004

Nonlinear Parallel And Perpendicular Diffusion Of Charged Cosmic Rays In Weak Turbulence, Andreas Schalchi, John William Bieber, William H. Matthaeus, Gang Qin

Aerospace, Physics, and Space Science Faculty Publications

The problem of particle transport perpendicular to a magnetic background field is well known in cosmic-ray astrophysics. Whereas it is widely accepted that quasi-linear theory (QLT) of particle transport does not provide the correct results for perpendicular diffusion, it was assumed for a long time that QLT is the correct theory for parallel diffusion. In the current paper we demonstrate that QLT is in general also incorrect for parallel particle transport if we consider composite turbulence geometry. Motivated through the recent success of the so-called nonlinear guiding center theory of perpendicular diffusion, we present a new theory for parallel and …

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Spectral Properties Of Heavy Ions Associated With The Passage Of Interplanetary Shocks At 1 Au, Mihir I. Desai, Joseph R. Dwyer Aug 2004

Spectral Properties Of Heavy Ions Associated With The Passage Of Interplanetary Shocks At 1 Au, Mihir I. Desai, Joseph R. Dwyer

Aerospace, Physics, and Space Science Faculty Publications

We have surveyed the energy spectra of ∼0.1-100 MeV nucleonˉ¹ C, O, and Fe nuclei associated with the passage of 72 interplanetary (IP) shocks observed on board the ACE spacecraft during the period 1997 October-2002 October. Our main results are as follows: (1) The spectral fit parameters are independent of the local shock properties. (2) About 7% of the events exhibit increasing Fe/O ratios with energy; the remaining events have Fe/O ratios that either remain constant or decrease with energy. (3) The Fe/O ratio in the shock-associated particles is typically ∼30% lower than in the ambient population. (4) The fractionation …

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Interplanetary Transport Mechanisms Of Solar Energetic Particles, Gang Qin, Ming Zhang, Joseph R. Dwyer, Hamid K. Rassoul Jul 2004

Interplanetary Transport Mechanisms Of Solar Energetic Particles, Gang Qin, Ming Zhang, Joseph R. Dwyer, Hamid K. Rassoul

Aerospace, Physics, and Space Science Faculty Publications

Numerical simulations of charged particle trajectories in a Parker field with model turbulence are used to study the transport mechanisms of solar energetic particles (SEPs): magnetic focusing, pitch-angle diffusive transport due to magnetic fluctuations, and adiabatic cooling. The results of the simulations are compared with analytical formulae for the transport effects. We find that adiabatic cooling is significant for SEPs traveling from the Sun to 1 AU. The simulation results agree much better with the anisotropic adiabatic cooling effect theory than with the isotropic one. Also, we show that the simulation results agree well with the theory of magnetic focusing …

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Spectroscopic And Photometric Analysis Of Hs 1136+6646: A Hot Young Dao+K7 V Post-Common-Envelope, Pre-Cataclysmic Variable Binary, David K. Sing, Terry D. Oswalt, Mark J. Rudkin, K Johnston, S Rafferty May 2004

Spectroscopic And Photometric Analysis Of Hs 1136+6646: A Hot Young Dao+K7 V Post-Common-Envelope, Pre-Cataclysmic Variable Binary, David K. Sing, Terry D. Oswalt, Mark J. Rudkin, K Johnston, S Rafferty

Aerospace, Physics, and Space Science Faculty Publications

Extensive photometric and spectroscopic observations have been obtained for HS 1136+6646. The observations reveal a newly formed post–common-envelope binary system containing a hot ~DAO.5 primary and a highly irradiated secondary. HS 1136+6646 is the most extreme example yet of a class of short-period hot H-rich white dwarfs with K–M companion systems such as V471 Tau and Feige 24. HS 1136+6646 is a double-line spectroscopic binary showing emission lines of H I, He II, C II, Ca II, and Mg II, due in part to irradiation of the K7 V secondary by the hot white dwarf. Echelle spectra reveal the hydrogen …

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Abundances Of Heavy And Ultraheavy Ions In ³He-Rich Solar Flares, Glenn M. Mason, Joseph E. Mazur, Joseph R. Dwyer, Jack Randy Jokipii, Robert E. Gold, Stamatios M. Krimigis May 2004

Abundances Of Heavy And Ultraheavy Ions In ³He-Rich Solar Flares, Glenn M. Mason, Joseph E. Mazur, Joseph R. Dwyer, Jack Randy Jokipii, Robert E. Gold, Stamatios M. Krimigis

Aerospace, Physics, and Space Science Faculty Publications

We have surveyed ³He-rich solar energetic particle (SEP) events over the period 1997 September-2003 April in order to characterize abundances of heavy ions near 400 keV nucleonˉ¹. The first part of the study focuses on 20 distinct SEP events that show the previously observed pattern in which, relative to O, heavy ions through Fe are enriched, with the enrichment increasing with mass. We find that these enrichments are well correlated such that ³He-rich SEP events with high Fe/C also show larger enrichments in other heavy ions. Ultraheavy (UH; taken as 78-220 amu) ions are routinely seen in these events with …

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The Nonlinear Coupling Of Electromagnetic Ion Cyclotron And Lower Hybrid Waves In The Ring Current Region: The Magnetic Storm 1–7 May 1998, G. V. Khazanov, E. N. Krivorutsky, K. V. Gamayunov, L. A. Avanov Jan 2004

The Nonlinear Coupling Of Electromagnetic Ion Cyclotron And Lower Hybrid Waves In The Ring Current Region: The Magnetic Storm 1–7 May 1998, G. V. Khazanov, E. N. Krivorutsky, K. V. Gamayunov, L. A. Avanov

Aerospace, Physics, and Space Science Faculty Publications

The excitation of lower hybrid waves (LHWs) is a widely discussed mechanism of interaction between plasma species in space, and is one of the unresolved questions of magnetospheric multi-ion plasmas. In this paper we present the morphology, dynamics, and level of LHWactivity generated by electromagnetic ion cyclotron (EMIC) waves during the 2–7 May 1998 storm period on the global scale. The LHWs were calculated based on a newly developed selfconsistent model (Khazanov et. al., 2002) that couples the system of two kinetic equations: one equation describes the ring current (RC) ion dynamic, and another equation describes the evolution of EMIC …

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Observations Of The Pulsating White Dwarf G 185-32, Bárbara Garcia Castanheira, Matt A. Wood Jan 2004

Observations Of The Pulsating White Dwarf G 185-32, Bárbara Garcia Castanheira, Matt A. Wood

Aerospace, Physics, and Space Science Faculty Publications

We observed the pulsating hydrogen atmosphere white dwarf G 185-32 with the Whole Earth Telescope in 1992. We report on a weighted Fourier transform of the data detecting 18 periodicities in its light curve. Using the Hubble Space Telescope Faint Object Spectrograph time resolved spectroscopy, and the wavelength dependence of the relative amplitudes, we identify the spherical harmonic degree (ℓ) for 14 pulsation signals. We also compare the determinations of effective temperature and surface gravity using the excited modes and atmospheric methods, obtaining Teff = 11960 ± 80 K, log g = 8.02 ± 0.04 and M = 0.617 ± …

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Implications Of X-Ray Emission From Lightning, Joseph R. Dwyer Jan 2004

Implications Of X-Ray Emission From Lightning, Joseph R. Dwyer

Aerospace, Physics, and Space Science Faculty Publications

Dwyer et al. [2003, 2004a] recently reported measurements of bursts of x-rays, with energies up to ∼250 keV, originating from dart leaders and possibly the return strokes of rocket-triggered lightning. In this paper, these x-ray observations are compared with the relativistic runaway electron avalanche (RREA) model. It is found that for dart leaders the standard RREA model is inconsistent with the observed spectrum and flux of the x-ray emission. This result implies that the cold runaway electron model may be applicable to dart leaders. In this model, runaway electrons are directly accelerated out of the bulk electron population, produced by …

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Nonlinear Guiding Center Theory Of Perpendicular Diffusion: General Properties And Comparison With Observation, John W. Bieber, William H. Matthaeus, Andreas Shalchi, Gang Qin Jan 2004

Nonlinear Guiding Center Theory Of Perpendicular Diffusion: General Properties And Comparison With Observation, John W. Bieber, William H. Matthaeus, Andreas Shalchi, Gang Qin

Aerospace, Physics, and Space Science Faculty Publications

A nonlinear guiding center (NLGC) theory for diffusion of charged particles perpendicular to the mean magnetic field was recently proposed. Here, we draw attention to a number of attractive features of this theory: (1) The theory provides a natural mechanism to connect the perpendicular mean free path with the parallel mean free path. In fact, the parallel mean free path is the only particle property required to determine uniquely the perpendicular mean free path. (2) Under a broad range of conditions, the theory predicts that the perpendicular mean free path will be of order one percent or a few percent …

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