Scatter-Free Propagation of Energetic Solar Electrons and Galactic Cosmic Rays in the Inner Heliosphere

Details Scatter-Free Propagation of Energetic Solar Electrons and Galactic Cosmic Rays in the Inner Heliosphere Scatter-Free Propagation of Energetic Solar Electrons and Galactic Cosmic Rays in the Inner Heliosphere

Aug 2008

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008aipc.1039..174r&link_type=abstract

PARTICLE ACCELERATION AND TRANSPORT IN THE HELIOSPHERE AND BEYOND: 7th Annual International Astrophysics Conference. AIP Confer

Astronomy and Astrophysics

Astrophysics

1

Astronomical Observations, Planetary Bow Shocks, Interplanetary Shocks, Flares, Particle Emission, Solar Wind, Particle Acceleration, Origin, Formation, And Abundances Of The Elements

Scientific paper

Spacecraft observations (ACE, Wind, Ulysses, Voyager1/2) of energetic particles during the just-completed Solar Cycle 23 (1996-2007) have provided multiple case studies in different regions throughout the heliosphere where weak scattering seems to have dominated the local transport process for energetic ions and electrons over a wide range of energies. This paper analyzes in detail two diverse phenomena observed near Earth: (1) approximately ``scatter-free'' (r<1 AU) with ``back-scatter'' (r>1 AU) propagation of near-relativistic electrons (rigidities R~0.5 MV) in impulsive solar energetic particle (SEP) events along magnetic field lines connecting the coronal injection region to spacecraft at 1 AU; and (2) the anisotropy of galactic cosmic rays (rigidities R~1-10 GV) as measured by the diurnal variation detected by ground-based neutron monitors. In the scatter-free limit, weak scattering can be mathematically described by a functional equation, rather than by a linear partial differential equation (as in focused diffusion). This is illustrated by (1) extracting the injection time history of near-relativistic electrons directly from the ACE/EPAM intensity measurements and (2) demonstrating that the ordinary diurnal variation in neutron monitors can be quantitatively explained solely by the E×B drift in the interplanetary field and the energy loss caused by that drift. Both results are obtained purely by assuming guiding center propagation inside the Earth's orbit (r<1 AU) consisting of mirroring in an essentially smooth Parker magnetic field.

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