NON-STANDARD ENERGY SPECTRA OF SHOCK-ACCELERATED SOLAR PARTICLES

Journal Article · Sun Jul 01 04:00:00 EDT 2012 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/753/1/87· OSTI ID:22036904

Kocharov, Leon; Vainio, Rami; Pomoell, Jens ^[1]; Valtonen, Eino ^[2]; Klassen, Andreas ^[3]; Young, C Alex ^[4]

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1. Department of Physics, P.O. Box 64, University of Helsinki, FI-00014 (Finland)
2. Space Research Laboratory, Department of Physics and Astronomy, University of Turku, FI-20014 (Finland)
3. Institut fuer Experimentelle und Angewandte Physik, Christian-Albrechts-Universitaet Kiel, D-24118 (Germany)
4. ADNET Systems Inc., NASA Goddard Space Flight Center, Greenbelt, MD 20850 (United States)

We consider a numerical model for the shock acceleration of energetic ions in the magnetic environment of the solar corona. The model is motivated by observations of the deka-to-hecto-MeV proton energy spectra, ion and electron timing, and abundances in the beginning of major solar energetic particle (SEP) events, prior to the event's main phase associated with coronal mass ejection (CME) driven shock in the solar wind. Inasmuch as the obliquity of the CME-liftoff-associated shocks in solar corona and hence the seed-particle supply for the shock acceleration are essentially time dependent, a steady state energy spectrum of accelerated protons near the shock could not be attained. Energy spectrum of the SEP emission depends on the spatial and energy distribution of seed particles for the coronal shock acceleration, on the shock wave history, and on the location and scenario of the energetic particle escape into the interplanetary medium. We use a numerical model of the shock acceleration on a semicircular magnetic field line to learn a significance of different effects. If the shock geometry in a particular magnetic tube changes from nearly parallel to perpendicular, the resulting SEP spectrum in most distant sections of the tube, e.g., at the top of a transequatorial loop, resembles a wide beam, which is very different from the standard power-law spectrum that would be expected in a steady state. Possible escape of the shock-accelerated particles from more than one coronal location, stochastic re-acceleration, and the magnetic tube expansion can make the SEP spectra even more complicated.

• OSTI ID: 22036904
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 753; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ACCELERATION
ASTRONOMY
ASTROPHYSICS
COSMIC PROTONS
ELECTRON EMISSION
ELECTRONS
ENERGY SPECTRA
MAGNETIC FIELDS
MEV RANGE
SHOCK WAVES
SOLAR CORONA
SOLAR PARTICLES
SOLAR WIND
STEADY-STATE CONDITIONS
STOCHASTIC PROCESSES
SUN
TAIL IONS
TIME DEPENDENCE