Energy spectrum of 20 keV--20 MeV electrons accelerated in large solar flares

Journal Article · Mon Feb 15 04:00:00 EST 1982 · Astrophys. J.; (United States)

DOI:https://doi.org/10.1086/159693· OSTI ID:5023274

Lin, R P; Mewaldt, R A; Van Hollebeke, M A.I.

We present IMP 6, 7, and 8 measurements of the energy spectrum of 20 keV to 20 MeV electrons observed from large solar flares. To minimize propagation effects, only events from flare located at W30/sup 0/ to W90/sup 0/ solar longitude were chosen for study. The energy spectra were constructed using the maximum flux observed at each energy. These spectra are shown to be representative of the spectra of the electrons escaping from the Sun over this range of energies. We find that every event shows the same spectral shape: a double power law with a smooth transition around 100--200 keV and power law exponents of 0.6--2.0 below and 2.4--4.3 above. The more intense the event, the harder the spectrum observed. In some cases the spectra are observed to steepen above 3 MeV. The spectra are generally similar to those inferred from hard x-ray and microwave measurements, and the peak >20 keV electron flux is well correlated with the peak microwave emission at 10 cm. These findings indicate that the observed electron spectra are representative of the accelerated electron spectra at the Sun. Thus, a double power law appears to be the characteristic spectral shape produced in flare second phase acceleration. Comparisons with proton spectra from the same events suggest that the acceleration is velocity dependent. The shock waves observed in these large flare events are likely to be the accelerating agent.

• Research Organization: Space Sciences Laboratory, University of California-Berkeley
• OSTI ID: 5023274
• Journal Information: Astrophys. J.; (United States), Journal Name: Astrophys. J.; (United States) Vol. 253:2; ISSN ASJOA
• Country of Publication: United States
• Language: English

Related Subjects

640104* -- Astrophysics & Cosmology-- Solar Phenomena
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ACCELERATION
DATA
ELECTRON SPECTRA
ELECTRONS
ELEMENTARY PARTICLES
ENERGY SPECTRA
EXPERIMENTAL DATA
FERMIONS
INFORMATION
LEPTONS
MEASURING INSTRUMENTS
NUMERICAL DATA
PLASMA ACCELERATION
RADIATION DETECTORS
RADIATIONS
SHOCK WAVES
SOLAR ACTIVITY
SOLAR ELECTRONS
SOLAR FLARES
SOLAR PARTICLES
SOLAR RADIATION
SPECTRA
STELLAR RADIATION