Active Cavity Radiometer Irradiance Monitor         Hit Counter

SMM/ACRIM1

Principal discoveries:

The radiative deficit effect of sunspots and excess effects of faculae and ‘magnetic network’.

The direct relationship between solar magnetic activity and TSI on solar cycle timescales.

The ACRIM1 'Big Dipper' discovery

The radiative deficit effect of sunspots and radiative excess effects of faculae and the ‘magnetic network’ was discovered in the early days of the SMM/ACRIM1 experiment. The graphic shows the passage of two large active regions across the solar disk between April 3 - 10, 1980 and the TSI observations of the ACRIM1 experiment. The dip is caused by the sunspots. The peaks on either side are caused by the peripheral faculae surrounding these sunspot groups. This discovery provided a new paradigm for investigating solar active regions.

ACRIM1 solar cycle TSI dependence

 

The direct relationship between solar magnetic activity and TSI on solar cycle timescales was first discovered by the SMM/ACRIM1 experiment. The peak-to-peak TSI change was ~ 0.1 % between the activity maximum of 1980 and the minimum in 1986. This discovery provided a new paradigm for the connection between climate change and TSI variability. Correlations between TSI and climate have been made extending back in time using various solar activity proxies. The relationship between TSI and known climate changes, such as the  little ice age ~(1400 - 1900), the medeival climate optimum ~(800 - 1300) and other longer term climate events are now understandable in  terms of solar forcing.
 

 

 

 

 

 

 

Descriptive publication:

Willson et.al.,Observations of Solar Irradiance Variability, Science 13 February 1981, Vol. 211 no. 4483 pp. 700-702

DOI: 10.1126/science.211.4483.700


 

Click on graphic for link to descriptive publication (Willson et. al., Science, 1981)