SMM observations of Si IV and O IV bursts in solar active regions

Journal Article · Thu Jan 01 04:00:00 EST 1987 · Astrophys. J.; (United States)

DOI:https://doi.org/10.1086/164939· OSTI ID:6446978

Hayes, M; Shine, R A

Observations of Si IV and O IV lines in solar active regions taken by the ultraviolet spectrometer and polarimeter on board the SMM are analyzed. The average frequency of UV bursts of all types is one every four minutes in a 28 arcsec by 28 arcsec field of view. About 80 percent of the bursts show an increased Si IV/O IV ratio, suggesting a density increase. The indicated electron densities are generally in the 10 to the 11th-12th range, with 16 percent indicating higher densities. Some of the more energetic bursts exhibit flarelike characteristics, and some of these show a secondary brightening which may be an analog of the soft X-ray gradual phase of flares. The high frequency of these UV bursts and their possible association with hard X-ray microflares and chromospheric evaporation may make them extremely important in the energetics of active regions and in the maintenance of their enhanced coronal emission. 23 references.

• Research Organization: Eidgenoessische Technische Hochschule, Zurich, Switzerland; Lockheed Research Labs., Palo Alto, CA
• OSTI ID: 6446978
• Journal Information: Astrophys. J.; (United States), Journal Name: Astrophys. J.; (United States) Vol. 312; ISSN ASJOA
• Country of Publication: United States
• Language: English

Related Subjects

640104* -- Astrophysics & Cosmology-- Solar Phenomena
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ATMOSPHERES
CHARGED PARTICLES
CHROMOSPHERE
ELECTROMAGNETIC RADIATION
ELECTRON DENSITY
ELEMENTS
ENERGY SPECTRA
IONIZING RADIATIONS
IONS
OXYGEN IONS
RADIATIONS
SEMIMETALS
SILICON
SOFT X RADIATION
SOLAR ACTIVITY
SOLAR ATMOSPHERE
SOLAR FLARES
SPECTRA
ULTRAVIOLET SPECTRA
X RADIATION