Vortical Amplification of the Magnetic Field at an Inward Shock of Supernova Remnant Cassiopeia A.

We present an interpretation of the time variability of the x-ray flux recently reported from a multiepoch campaign of 15 years of observations of the supernova remnant Cassiopeia A by Chandra. We show for the first time quantitatively that the [4.2-6] keV nonthermal flux increase up to 50% traces the growth of the magnetic field due to a vortical amplification mechanism at a reflection inward shock colliding with inner overdensities.

Global anisotropies in TeV cosmic rays related to the Sun's local galactic environment from IBEX.

Observations with the Interstellar Boundary Explorer (IBEX) have shown enhanced energetic neutral atom (ENA) emission from a narrow, circular ribbon likely centered on the direction of the local interstellar medium (LISM) magnetic field. Here, we show that recent determinations of the local interstellar velocity, based on interstellar atom measurements with IBEX, are consistent with the interstellar modulation of high-energy (tera-electron volts, TeV) cosmic rays and diffusive propagation from supernova sources revealed in global anisotropy maps of ground-based high-energy cosmic-ray observatories (Milagro, Asγ, and IceCube). Establishing a consistent local interstellar magnetic field direction using IBEX ENAs at hundreds to thousands of eV and galactic cosmic rays at tens of TeV has wide-ranging implications for the structure of our heliosphere and its interactions with the LISM, which is particularly important at the time when the Voyager spacecraft are leaving our heliosphere.

Interplanetary Magnetic Field Line Mixing Deduced from Impulsive Solar Flare Particles.

We have studied fine-scale temporal variations in the arrival profiles of approximately 20 keV nucleon-1 to approximately 2 MeV nucleon-1 ions from impulsive solar flares using instrumentation on board the Advanced Composition Explorer spacecraft at 1 AU between 1997 November and 1999 July. The particle events often had short-timescale ( approximately 3 hr) variations in their intensity that occurred simultaneously across all energies and were generally not in coincidence with any local magnetic field or plasma signature. These features appear to be caused by the convection of magnetic flux tubes past the observer that are alternately filled and devoid of flare ions even though they had a common flare source at the Sun.

Small-scale Gradients and Large-scale Diffusion of Charged Particles in the Heliospheric Magnetic Field.

We have carried out numerical simulations of the propagation of energetic charged particles in a turbulent magnetic field similar to that observed in the solar wind. If the particles are released impulsively near the Sun, in a region small compared with the field coherence scale (a solar flare, for example), they exhibit characteristic fluctuations in intensity at 1 AU (dropouts) associated with very steep localized gradients. These numerical simulations are quantitatively very similar to recent observations by the Advanced Composition Explorer spacecraft and are the result of the convection of alternatively filled and empty flux tubes past the spacecraft.

Corotating variations of cosmic rays near the South heliospheric pole.

Three-dimensional simulations of the heliospheric modulation of galactic cosmic ray protons show that corotating variations in the intensity can persist to quite high heliographic latitudes. Variations are seen at latitudes considerably higher than the maximum latitude extension of the heliographic current sheet, in regions where the solar wind velocity and magnetic field show no significant variation. Similar conclusions may apply also to lower energy particles, which may be accelerated at lower latitudes.