First-order fermi acceleration in solar flares as a mechanism for the second-step acceleration of prompt protons and relativistic electrons

Journal Article · Fri Apr 01 04:00:00 EST 1983 · Astrophys. J.; (United States)

DOI:https://doi.org/10.1086/160881· OSTI ID:5915344

Bai, T; Hudson, H S; Pelling, R M; Lin, R P; Schwartz, R A; von Rosenvinge, T T

We find that for two of the hard X-ray bursts of an energetic flare on 1980 June 27, the time profile of the hard X-rays above 235 keV is delayed by 3 s with respect to the time profiles of the lower energy X-rays and that the high energy spectrum becomes flatter with time during each of these bursts. From these findings we argue that during this flare a second-step mechanism accelerated further some of the high-energy tail population of the first-step electrons. By noticing that all of the flares with second-step delays produced interplanetary energetic protons, and that gamma-ray lines were detected from all of these flares except one that was not observed by any gamma-ray detector, we conclude that the second-step mechanism accelerates not only (mildly) relativistic electrons but also protons and heavy nuclei. Small delays of the nuclear gamma-ray time profiles with respect to the hard X-ray time profiles observed by SMM from the 1980 June 7 and 21 flares are consistent with this conclusion. After estimating the acceleration rate, we conclude that first-order Fermi acceleration operating in a closed flare loop is a very likely mechanism for the second-step acceleration.

• Research Organization: Center for Astrophysics and Space Sciences, University of California, San Diego
• OSTI ID: 5915344
• Journal Information: Astrophys. J.; (United States), Journal Name: Astrophys. J.; (United States) Vol. 267:1; ISSN ASJOA
• Country of Publication: United States
• Language: English

Related Subjects

640104* -- Astrophysics & Cosmology-- Solar Phenomena
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ACCELERATION
BARYONS
ELECTROMAGNETIC RADIATION
ELECTRONS
ELEMENTARY PARTICLES
FERMIONS
GAMMA RADIATION
HADRONS
IONIZING RADIATIONS
LEPTONS
NUCLEONS
PLASMA ACCELERATION
PROTONS
RADIATIONS
SOLAR ACTIVITY
SOLAR ELECTRONS
SOLAR FLARES
SOLAR PARTICLES
SOLAR PROTONS
SOLAR RADIATION
SOLAR X-RAY BURSTS
SPECTRA
STELLAR RADIATION
X-RAY SPECTRA