Computer Science
Scientific paper
Jan 1994
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994phdt........10z&link_type=abstract
Thesis (PH.D.)--UNIVERSITY OF CALIFORNIA, SAN DIEGO, 1994.Source: Dissertation Abstracts International, Volume: 56-02, Section:
Computer Science
1
Solar Flare
Scientific paper
The daughter protons of the energetic neutrons (10-200MeV) produced in the June 3 1982 solar flare are noted as excellent particles for testing cosmic ray interplanetary transport theory. The long-standing discrepancy of about an order of magnitude between theory and observation concerning the cosmic ray transport mean free path in the interplanetary space is also reviewed to show the need of understanding in this area. We have modeled the interplanetary transport of the neutron-decay protons as streaming, focusing and pitch angle scattering in a spiral magnetic flux tube connecting the Sun and the Earth. Using the flux of neutron emission constrained from gamma-ray observation of the June 3 82 flare and the in situ data of magnetic field fluctuations at 1AU, time-dependent proton fluxes can be calculated and compared with observation. Calculations made with quasi-linear pitch angle scattering coefficient agree with observation for the initial two hours. In order to fit the observation for 6-8 hours one needs to reduce the amount of pitch angle scattering by about a factor of 2 (compared to the former discrepancy of ~10). In reconciling this remaining discrepancy, we show how the neutron-decay proton flux is dependent on global properties of the heliospheric magnetic fields. These properties are: (1) the heliocentric radial variation of magnetic power spectra; (2) asymmetry of the helicity of the magnetic turbulence; (3) the effect of the heliospheric current sheet on cosmic ray transport. The last of the above appears most important if one believes the anomalous transport at the current sheet to be a particle loss mechanism. This assumption is tested by solving a three dimensional cosmic ray diffusion equation tailored to the case of a pulse flare neutron emission at the sun. When the equatorial plane in the heliosphere is taken to be a particle absorbing boundary and the cosmic ray across field transport determined by the observed coefficient of random walk of magnetic field lines, the calculated decay proton flux near the equatorial plane (+/- 30^circ in latitude) has a faster decrease and the behaviour of an exponential, which is in accord with observation.
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