Indications for diffusive coronal shock acceleration of protons in selected solar cosmic ray events

Journal Article · Sun Apr 01 04:00:00 EDT 1990 · Journal of Geophysical Research; (United States)

DOI:https://doi.org/10.1029/JA095iA04p04187· OSTI ID:5258321

Lockwood, J A ^[1]; Debrunner, H; Flueckiger, E O ^[2]

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1. Univ. of New Hampshire, Durham (United States)
2. Univ. of Bern (Switzerland)

Four solar cosmic ray events which occurred on November 22, 1977, May 7, 1978, June 3, 1982, and February 16, 1984, have been analyzed using data from near-Earth spacecraft and ground-based neutron monitors to study the acceleration of solar protons. For May 7, 1978, and February 16, 1984, the scattering mean free path of the protons in the interplanetary medium between the Sun and the Earth was greater than or equal to 2 AU. Therefore, direct information was obtained about the acceleration of the flare particles at the Sun and their release into the interplanetary magnetic field. The authors found that the intensity-time profiles observed at Earth for more than an hour after onsets for the May 7, 1978, and February 16, 1984, solar cosmic ray events represent the solar injection profiles even to energies as low as 20-MeV. The energy dependence of the onset time for the May 1978, June 1982, and February 1984 events indicates that the first low energy protons ({approximately}50-MeV) were accelerated at least 5 min earlier than the first relativistic protons. The duration of the injection of the solar protons into the interplanetary medium (or acceleration) depended upon energy for the November 1977, May 1978, and February 1984 events, ranging from about 40 min at 2-MeV to about 500 min at 10-MeV and was proportional to {radical}1/E. The deduced solar proton energy spectra at the Earth for these latter three events are similar. They conclude that for the solar cosmic ray events on November 22, 1977, May 7, 1978, June 3, 1982, and February 16, 1984, there are strong indications for shock acceleration of the solar protons. The presence of large scale coronal shocks was directly observed in the May 1978 and February 1984 solar cosmic ray events. However, by the present analysis they cannot determine whether or not stochastic acceleration of the protons in the downstream region of the shock took place in addition to the diffusive coronal shock acceleration.

• OSTI ID: 5258321
• Journal Information: Journal of Geophysical Research; (United States), Journal Name: Journal of Geophysical Research; (United States) Vol. 95:A4; ISSN 0148-0227; ISSN JGREA
• Country of Publication: United States
• Language: English

Related Subjects

640104* -- Astrophysics & Cosmology-- Solar Phenomena
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ACCELERATION
ATMOSPHERES
BARYONS
DATA ANALYSIS
ELEMENTARY PARTICLES
ENERGY SPECTRA
FERMIONS
HADRONS
INTERPLANETARY SPACE
MEAN FREE PATH
MEASURING INSTRUMENTS
MONITORS
NEUTRON MONITORS
NUCLEONS
PROTONS
RADIATION MONITORS
RADIATIONS
SHOCK WAVES
SOLAR ACTIVITY
SOLAR ATMOSPHERE
SOLAR CORONA
SOLAR FLARES
SOLAR PARTICLES
SOLAR PROTONS
SOLAR RADIATION
SPACE
SPECTRA
STELLAR ATMOSPHERES
STELLAR CORONAE
STELLAR RADIATION
STOCHASTIC PROCESSES