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Astrophysics and Astronomy

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2003

Florida Institute of Technology

Articles 1 - 11 of 11

Full-Text Articles in Physical Sciences and Mathematics

Perpendicular Transport Of Solar Energetic Particles In Heliospheric Magnetic Fields, Ming Zhang, Jack Randy Jokipii, Robert Bruce Mckibben Sep 2003

Perpendicular Transport Of Solar Energetic Particles In Heliospheric Magnetic Fields, Ming Zhang, Jack Randy Jokipii, Robert Bruce Mckibben

Aerospace, Physics, and Space Science Faculty Publications

This paper presents direct observational evidence for large perpendicular diffusive flows of solar energetic particles in heliospheric magnetic fields. Using anisotropy measurements of 40-92 MeV protons obtained by the High-Energy Telescope of the COSPIN consortium on Ulysses at high heliographic latitudes, we find that during several gradual solar particle events, for periods of many hours, the observed particle flow is directed at significant angles to the measured local magnetic field direction, which can only be explained by cross-field diffusion. The variation of the particle flow direction with the magnetic field direction seen in the 2000 July 14 solar energetic particle …

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Constraining The Evolution Of Zz Ceti, Anjum S. Mukadam, Matt A. Wood, Nicole M. Silvestri Sep 2003

Constraining The Evolution Of Zz Ceti, Anjum S. Mukadam, Matt A. Wood, Nicole M. Silvestri

Aerospace, Physics, and Space Science Faculty Publications

We report our analysis of the stability of pulsation periods in the DAV star (pulsating hydrogen atmosphere white dwarf) ZZ Ceti, also called R548. On the basis of observations that span 31 years, we conclude that the period 213. 13 s observed in ZZ Ceti drifts at a rate dP/dt ≤ (5.5 ± 1.9) × 10ˉ¹⁵ s sˉ¹, after correcting for proper motion. Our results are consistent with previous Ṗ values for this mode and an improvement over them because of the larger time base. The characteristic stability timescale implied for the pulsation period is | Ṗ / |≥ 1.2 …

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Elemental Fractionation In Small Solar Energetic Particle Events, Penny L. Slocum, Joseph R. Dwyer Sep 2003

Elemental Fractionation In Small Solar Energetic Particle Events, Penny L. Slocum, Joseph R. Dwyer

Aerospace, Physics, and Space Science Faculty Publications

Using the Solar Isotope Spectrometer on the Advanced Composition Explorer (ACE), we have measured the 11.0-21.8 MeV nucleon-1 heavy (Z ≥ 6) element abundances of 39 small solar energetic particle (SEP) events that occurred between 1998 April 3 and 2002 February 26. Using He isotope data from the UltraLow-Energy Isotope Spectrometer on ACE, we have classified the events according to their 0.5-2.0 MeV nucleonˉ¹ ³He/⁴He ratios. We find that their average heavy-element composition is similar to that of either large gradual events or ³He-rich events, depending on their ³He/⁴He ratio. As seen in recent studies of small SEP events, we …

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Pks 0736+017: A Striking Optical Flare And Intriguing Microvariability, Sandra D. Clements, A Jenks, Y Torres Jul 2003

Pks 0736+017: A Striking Optical Flare And Intriguing Microvariability, Sandra D. Clements, A Jenks, Y Torres

Aerospace, Physics, and Space Science Faculty Publications

The compact, flat-spectrum radio quasar PKS 0736+017 was monitored for microvariability on 10 nights in early 2002 using the 0.9 m SARA telescope on Kitt Peak in Arizona. On January 14, PKS 0736+017 flared dramatically, brightening by 1.3 R mag in 2 hours. Prior to the flare, PKS 0736+017 exhibited quasi-periodic variations. During and after the flare, more complex oscillations occurred. Impressive variability was displayed on two additional nights in January, while observations during the following 3 months found PKS 0736+017 to be fairly quiescent. PKS 0736+017 was somewhat redder while brighter and fading than when dimmer but flaring. During …

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Nonlinear Collisionless Perpendicular Diffusion Of Charged Particles, William H. Matthaeus, Gang Qin, John William Bieber, Gary Paul Zank Jun 2003

Nonlinear Collisionless Perpendicular Diffusion Of Charged Particles, William H. Matthaeus, Gang Qin, John William Bieber, Gary Paul Zank

Aerospace, Physics, and Space Science Faculty Publications

A nonlinear theory of the perpendicular diffusion of charged particles is presented, including the influence of parallel scattering and dynamical turbulence. The theory shows encouraging agreement with numerical simulations.

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Evidence For A Suprathermal Seed Population Of Heavy Ions Accelerated By Interplanetary Shocks Near 1 Au, Mihir I. Desai, Glenn M. Mason, Joseph R. Dwyer, Joseph E. Mazur, Robert E. Gold, Stamatios M. Krimigis, Charles W. Smith, Ruth M. Skoug May 2003

Evidence For A Suprathermal Seed Population Of Heavy Ions Accelerated By Interplanetary Shocks Near 1 Au, Mihir I. Desai, Glenn M. Mason, Joseph R. Dwyer, Joseph E. Mazur, Robert E. Gold, Stamatios M. Krimigis, Charles W. Smith, Ruth M. Skoug

Aerospace, Physics, and Space Science Faculty Publications

We have surveyed the 0.1-10 MeV nucleonˉ¹ elemental abundances at 72 interplanetary (IP) shocks observed by the Ultra-Low-Energy Isotope Spectrometer on board the Advanced Composition Explorer from 1997 October through 2002 September. We find the following: (1) The C/O ratios in IP shocks were substantially depleted (by more than ∼40%) relative to solar wind values. (2) The IP shock abundances were poorly correlated with those measured in the slow and fast solar wind. (3) Energetic ions above ∼0.1 MeV nucleonˉ¹ from impulsive and gradual solar energetic particle events (SEPs) were present upstream of all the IP shocks in our survey. …

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Delay In Solar Energetic Particle Onsets At High Heliographic Latitudes, Silvia C. Dalla, Ming Zhang Jan 2003

Delay In Solar Energetic Particle Onsets At High Heliographic Latitudes, Silvia C. Dalla, Ming Zhang

Aerospace, Physics, and Space Science Faculty Publications

Ulysses observations have shown that solar energetic particles (SEPs) can easily reach high heliographic latitudes. To obtain information on the release and propagation of SEPs prior to their arrival at Ulysses, we analyse the onsets of nine large high-latitude particle events. We measure the onset times in several energy channels, and plot them versus inverse particle speed. This allows us to derive an experimental path length and time of release from the solar atmosphere. We repeat the procedure for near-Earth observations by Wind and SOHO. We find that the derived path lengths at Ulysses are 1.06 to 2.45 times the …

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2mass J0516288+260738: Discovery Of The First Eclipsing Late K + Brown Dwarf Binary System?, Sonja L. Schüh, Matt A. Wood Jan 2003

2mass J0516288+260738: Discovery Of The First Eclipsing Late K + Brown Dwarf Binary System?, Sonja L. Schüh, Matt A. Wood

Aerospace, Physics, and Space Science Faculty Publications

We report the discovery of a new eclipsing system less than one arcminute south of the pulsating DB white dwarf KUV 05134+2605 . The object could be identified with the point source 2MASS J0516288+260738 published by the Two Micron All Sky Survey. We present and discuss the first light curves as well as some additional colour and spectral information. The eclipse period of the system is 1.29 d, and, assuming this to be identical to the orbital period, the best light curve solution yields a mass ratio of m₂/m₁=0.11, a radius ratio of r₂/r₁ ≈ 1 and an inclination of …

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Multisite Observations Of The Pms Δ Scuti Star V351 Ori, Vincenzo Ripepi, T D. Oswalt, Mark J. Rudkin, Kyle B. Johnston Jan 2003

Multisite Observations Of The Pms Δ Scuti Star V351 Ori, Vincenzo Ripepi, T D. Oswalt, Mark J. Rudkin, Kyle B. Johnston

Aerospace, Physics, and Space Science Faculty Publications

We present the results of multisite observations spanning two years on the pre-main-sequence (PMS) star V351 Ori. A total of around 180 hours of observations over 29 nights have been collected, allowing us to measure five different periodicities, most likely related to the δ Scuti variability of V351 Ori. Comparison with the predictions of linear nonadiabatic radial pulsation models put stringent constraints on the stellar parameters and indicate that the distance to V351 Ori is intermediate between the lower limit measured by Hipparcos (210 pc) and that of the Orion Nebula (450 pc). However, radial pulsation models are unable to …

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The Everchanging Pulsating White Dwarf Gd358, Souza Oliveira Kepler, Matt A. Wood, Nicole M. Silvestri, Thomas J. Ahrens Jan 2003

The Everchanging Pulsating White Dwarf Gd358, Souza Oliveira Kepler, Matt A. Wood, Nicole M. Silvestri, Thomas J. Ahrens

Aerospace, Physics, and Space Science Faculty Publications

We report 323 hours of nearly uninterrupted time series photometric observations of the DBV star GD 358 acquired with the Whole Earth Telescope (WET) during May 23rd to June 8th, 2000. We acquired more than 232 000 independent measurements. We also report on 48 hours of time-series photometric observations in Aug 1996. We detected the non-radial g-modes consistent with degree ℓ = 1 and radial order 8 to 20 and their linear combinations up to 6th order. We also detect, for the first time, a high amplitude ℓ = 2 mode, with a period of 796 s. In the 2000 …

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Ulysses Cospin Observations Of Cosmic Rays And Solar Energetic Particles From The South Pole To The North Pole Of The Sun During Solar Maximum, Robert Bruce Mckibben, Ming Zhang Jan 2003

Ulysses Cospin Observations Of Cosmic Rays And Solar Energetic Particles From The South Pole To The North Pole Of The Sun During Solar Maximum, Robert Bruce Mckibben, Ming Zhang

Aerospace, Physics, and Space Science Faculty Publications

In 2000–2001 Ulysses passed from the south to the north polar regions of the Sun in the inner heliosphere, providing a snapshot of the latitudinal structure of cosmic ray modulation and solar energetic particle populations during a period near solar maximum. Observations from the COSPIN suite of energetic charged particle telescopes show that latitude variations in the cosmic ray intensity in the inner heliosphere are nearly non-existent near solar maximum, whereas small but clear latitude gradients were observed during the similar phase of Ulysses’ orbit near the 1994–95 solar minimum. At proton energies above ∼10 MeV and extending up to …

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