Active-region evolution and solar rotation variations in solar UV irradiance, total solar irradiance, and soft X ray

Journal Article · Wed Dec 01 04:00:00 EST 1982 · J. Geophys. Res.; (United States)

DOI:https://doi.org/10.1029/JA087iA12p10318· OSTI ID:6249332

Donnelly, R F; Heath, D F; Lean, J L

Variations in the solar UV spectral irradiance, the total solar irradiance, and solar soft X ray emission over days and weeks are analyzed by using concurrent measurements from the NUMBUS 7 and GOES satellites. The UV variations at wavelengths (160-400 nm) of interest to ozone photochemistry and the physics of the middle atmosphere are emphasized. The nonflare variations studied are caused by two types of processes: (1) the birth, growth, peak, and decay of solar active regions and (2) solar rotation, for example, when portions of active regions are occulted near the solar limb. The observations are interpreted by using simple empirical models that relate ground-based observations of the size and location of sunspots and plages to the full-disk temporal variations. The major dips observed in the total solar irradiance on August 20--23 and November 6--10, 1979, and April 8, May 25, and September 1, 1980, are accompanied by only average UV and X ray enhancements. The models show that the active regions associated with the sunspots responsible for the major dips in the total solar irradiance caused strong but not outstanding emission enhancements at UV and X ray wavelengths. The solar rotation variations are studied as a function of the central meridian distance for solar active regions where the central meridian distance width at half the maximium is narrowest for decreases in the total solar irradiance (approx.83/sup 0/), slightly wider and also a function of wavelength for UV enhancements (approx.95 at 198 nm), wider still for the 10.7 cm radio flux (approx.150/sup 0/), and extremely wide for soft X rays (> or =205/sup 0/).

• Research Organization: Air Resource Laboratories, NOAA/ERL, Boulder, Colorado 80303
• OSTI ID: 6249332
• Journal Information: J. Geophys. Res.; (United States), Journal Name: J. Geophys. Res.; (United States) Vol. 87:A12; ISSN JGREA
• Country of Publication: United States
• Language: English

Related Subjects

640104* -- Astrophysics & Cosmology-- Solar Phenomena
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
DIRECT SOLAR RADIATION
ELECTROMAGNETIC RADIATION
FAR ULTRAVIOLET RADIATION
GOES SATELLITES
IONIZING RADIATIONS
MAIN SEQUENCE STARS
MOTION
NEAR ULTRAVIOLET RADIATION
NIMBUS SATELLITES
RADIATIONS
ROTATION
SATELLITES
SOFT X RADIATION
SOLAR ACTIVITY
SOLAR FLUX
SOLAR PROMINENCES
SOLAR RADIATION
STARS
STELLAR RADIATION
SUN
ULTRAVIOLET RADIATION
VARIATIONS
X RADIATION