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Full-Text Articles in Physical Sciences and Mathematics
Perpendicular Transport Of Charged Particles In Composite Model Turbulence: Recovery Of Diffusion, Gang Qin, William H. Matthaeus, John William Bieber
Perpendicular Transport Of Charged Particles In Composite Model Turbulence: Recovery Of Diffusion, Gang Qin, William H. Matthaeus, John William Bieber
Aerospace, Physics, and Space Science Faculty Publications
The computation of charged particle orbits in model turbulent magnetic fields is used to investigate the properties of particle transport in the directions perpendicular to the large-scale magnetic field. Recent results by Qin, Matthaeus, & Bieber demonstrate that parallel scattering suppresses perpendicular diffusion to a subdiffusive level when the turbulence lacks transverse structure. Here numerical computations are used to show that in turbulence in which there is substantial transverse structure, a second regime of diffusive transport can be established. In both the subdiffusion regime and this "second diffusion" regime, perpendicular transport is intrinsically nonlinear. The regime of second diffusion persists …
Spectral Properties Of He And Heavy Ions In ³He-Rich Solar Flares, Glenn M. Mason, Joseph R. Dwyer
Spectral Properties Of He And Heavy Ions In ³He-Rich Solar Flares, Glenn M. Mason, Joseph R. Dwyer
Aerospace, Physics, and Space Science Faculty Publications
Using advanced instrumentation on the ACE spacecraft, we have conducted a survey of solar energetic particle spectra in ³He-rich events over a broad energy range ∼80 keV nucleon-1 to 15 MeV nucleonˉ¹ during the period 1997 September-2001 March. The spectra of ⁴He and heavy ions (C, N, O, Ne, Mg, Si, S, Ca, Fe) were generally similar over this range but often hardened below ∼1 MeV nucleonˉ¹. In most of the events there was even stronger hardening of the ³He spectrum below ∼1 MeV nucleonˉ¹, leading to an energy-dependent ³He: ⁴He ratio. These observations point to unique and distinct properties …
A New Heavy Ion Abundance Enrichment Pattern In ³He-Rich Solar Particle Events, Glenn M. Mason, Joseph E. Mazur, Joseph R. Dwyer
A New Heavy Ion Abundance Enrichment Pattern In ³He-Rich Solar Particle Events, Glenn M. Mason, Joseph E. Mazur, Joseph R. Dwyer
Aerospace, Physics, and Space Science Faculty Publications
We report the first examples of ³He-rich solar energetic particle (SEP) events with heavy ion enrichments that are not ordered generally by mass. A second new feature is the large enrichment of ¹⁴N, the first time large enrichments have been seen for heavy ions lighter than O or Ne. These SEP events were too small and at too low an energy (<500 keV nucleon-1) to have been observed previously. The best observed event, 2001 July 16, had abundance ratios C : N : O : Ne : Mg : Si : S : Ca : Fe of ∼0.8 : 1.0 : ≡ 1 : 0.5 : 0.5 : 2.0 : 2.4 : 0.2 : 0.9, corresponding, respectively, to enhancements over the slow solar wind of ∼1.2 :15 : ≡ 1 : 5. : 3.4 : 12 :49 : 19 : 7. This pattern is incompatible with a gravitational settling enrichment mechanism. The simultaneous large enhancements of ¹⁴N and ²⁸Si, which have identical charge-to-mass ratios for certain ionization states, suggest that selective plasma wave heating plays a key role, as has long been suspected. Enhancement of ¹⁴N implies relatively low temperatures (<1.5 × 10 6 K) since fully stripped ¹⁴N cannot be preferentially heated. Also, the presence of enhanced species such as ¹⁴N and ²⁸Si, along with others with small or no enhancements ( 16)O, ²⁰Ne), may indicate that the plasma waves must operate over a relatively narrow range of frequencies and that the material must be heated while the waves are present.