The Fraction of the Sun's Lifetime in a Grand Minimum State Estimated from Studies of Solar-Type Stars
Abstract
The Maunder Minimum is a key event in climate change research, (1) from the vantage point as a natural control experiment in which greenhouse gas (GHG) abundances were at a pre-industrial constant while solar forcing changed by a magnitude comparable to recent GHG increases, and (2) given recent interest and speculation that a similar grand minimum might occur later this century. To date, periodicity in solar grand minima has been difficult to detect in geophysical proxy data, and an alternative approach involves estimating the frequency of the Sun's lifetime spent in a grand minimum state by searching for evidence of grand minima in solar-type stars. Most often this is done by measuring Ca H and K flux as an indicator of chromospheric activity, or by photometric observations of solar cycles on decadal timescales. Early estimates of grand minimum frequency in solar type stars ranged from 10-30%. However, these early studies inadvertently included many stars that have evolved off the main sequence. This paper discusses how measurements of stellar Lithium abundance, and spectroscopically constrained metallicity, are used as additional constraints on age and main sequence membership, to refine detections of grand minima in solar-type stars. Based on the most recent studies, an estimate emerges of 5-6% for the fraction of the Sun's lifetime spent in a low-activity and reduced luminosity state analogous to the Maunder Minimum.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2011
- Bibcode:
- 2011AGUFMGC23A0904L
- Keywords:
-
- 1650 GLOBAL CHANGE / Solar variability;
- 7537 SOLAR PHYSICS;
- ASTROPHYSICS;
- AND ASTRONOMY / Solar and stellar variability