An upper limit to the anisotropy of solar hard X-ray emission

Journal Article · Tue Mar 01 04:00:00 EST 1977 · Astrophys. J.; (United States)

DOI:https://doi.org/10.1086/155075· OSTI ID:7309403

Datlowe, D W; O'Dell, S L; Peterson, L E; Elcan, M J

A statistical study of center-to-limb variations in the frequency of occurrence of solar hard X-ray bursts is used to look for directivity in the emission. The X-ray data consist of 148 bursts observed by the University of California, San Diego, solar X-ray instrument on the OSO-7 satellite. No center-to-limb variation in hard X-ray burst occurrence was found. The upper limit on any limb darkening or limb brightening of 20 keV X-ray emission is 40% at the 95% confidence level. This result rules out downward-streaming thick-target models for the motion of the X-ray emitting electrons. Furthermore, strong east-west streaming is also ruled out when the observed center-to-limb spectral variation is combined with the directivity result. Either the motions of the electrons which emit hard X-rays are predominantly random, or a variety of different emitting-region geometries commonly occur.

• Research Organization: University of California, San Diego
• OSTI ID: 7309403
• Journal Information: Astrophys. J.; (United States), Journal Name: Astrophys. J.; (United States) Vol. 212:2; ISSN ASJOA
• Country of Publication: United States
• Language: English

Related Subjects

640104* -- Astrophysics & Cosmology-- Solar Phenomena
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ANISOTROPY
ELECTROMAGNETIC RADIATION
HARD X RADIATION
IONIZING RADIATIONS
MAGNETIC FIELDS
MATHEMATICS
PLASMA
POLARIZATION
RADIATIONS
SOLAR ACTIVITY
SOLAR FLARES
SOLAR X-RAY BURSTS
SPECTRA
STATISTICS
X RADIATION
X-RAY SPECTRA