Astronomy and Astrophysics – Astronomy
Scientific paper
Nov 1993
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1993jgr....9818895h&link_type=abstract
Journal of Geophysical Research (ISSN 0148-0227), vol. 98, no. A11, p. 18,895-18,906
Astronomy and Astrophysics
Astronomy
154
Irradiance, Solar Activity, Solar Convection (Astronomy), Solar Cycles, Solar Radiation, Solar Rotation, Sun, Sunspots, Umbras, Variations, Climate, Satellite Observation, Solar Magnetic Field, Solar Terrestrial Interactions, Statistical Analysis, Stellar Luminosity, Stellar Structure
Scientific paper
From satellite observations the solar total irradiance is known to vary. Sunspot blocking, facular emission, and network emission are three identified causes for the variations. In this paper we examine several different solar indices measured over the past century that are potential proxy measures for the Sun's irradiance. These indices are (1) the equatorial solar rotation rate, (2) the sunspot structure, the decay rate of individual sunspots, and the number of sunspots without umbrae, and (3) the length and decay rate of the sunspot cycle. Each index can be used to develop a model for the Sun's total irradiance as seen at the Earth. Three solar indices allow the irradiance to be modeled back to the mid-1700s. The indices are (1) the length of the solar cycle, (2) the normalized decay rate of the solar cycle, and (3) the mean level of solar activity. All the indices are well correlated, and one possible explanation for their nearly simultaneous variations is changes in the Sun's convective energy transport. Although changes in the Sun's convective energy transport are outside the realm of normal stellar structure theory (e.g., mixing length theory), one can imagine variations arising from even the simplest view of sunspots as vertical tubes of magnetic flux, which would serve as rigid pillars affecting the energy flow patterns by ensuring larger-scale eddies. A composite solar irradiance model, based upon these proxies, is compared to the northern hemisphere temperature departures for 1700-1992. Approximately 71% of the decadal variance in the last century can be modeled with these solar indices, although this analysis does not include anthropogenic or other variations which would affect the results. Over the entire three centuries, approx. 50% of the variance is modeled. Both this analysis and previous similar analyses have correlations of model solar irradiances and measured Earth surface temperatures that are significant at better than the 95% confidence level. To understand our present climate variations, we must place the anthropogenic variations in the context of natural variability from solar, volcanic, oceanic, and other sources.
Hoyt Douglas V.
Schatten Kenneth H.
No associations
LandOfFree
A discussion of plausible solar irradiance variations, 1700-1992 does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with A discussion of plausible solar irradiance variations, 1700-1992, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and A discussion of plausible solar irradiance variations, 1700-1992 will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-810815