Active region properties and irradiance variations

Abstract

Total solar irradiance (TSI) has been measured for more than three decades. These observations demonstrate that total irradiance changes on time scales ranging from minutes to years and decades. Considerable efforts have been made to understand the physical origin of irradiance variations and to model the observed changes using measures of sunspots and faculae. In this paper, we study the short-term variations in TSI during the declining portion and minimum of solar cycle 22 and the rising portion of cycle 23 (1993 -1998). This time interval of low solar activity allows us to study the effect of individual sunspot groups on TSI in detail. In this paper, we indicate that the effect of sunspot groups on total irradiance may depend on their type in the Zürich classification system and/or their evolution, and on their magnetic configuration. Some uncertainties in the data and other effects are also discussed.

Modeling Quiet Solar Luminosity Variability from TSI Satellite Measurements and Proxy Models during 1980–2018

“…Problems in properly reconstructing solar cycles 23 and 24 maxima were also observed. Such divergences have been typically observed and are likely due to solar effects not taken into account in the models [66]. After empirically adjusting the models for these biases, our best result appeared to be the one shown in Figure 11A where we found consistency between the adjusted proxy models and the TSI composite proposed by Dudok de Wit et al [28] constructed with the unmodified TSI database since about 1981.…”

Solar Variability, Galactic Cosmic Rays and Climate: A Review

“…The total solar irradiance (TSI) varies from minute to minute (Frohlich, 2009), reflecting activity-driven changes on the face of the Sun, from day to day in step with solar rotation and the evolution of solar active regions, with day to day amplitudes of up to about 0.3%; and more important in terms of climate, from year to year with a peak to peak amplitude of about 0.1%, in phase with Schwabe's 11-year sunspot cycle (Eddy, 2009, Frohlich, 2012. In years when the Sun is more active, and more spots are seen, more radiative energy is delivered to the Earth (Baranyi and Pap, 2012). Fig.…”

“…Independent space-based solar radiometers universally agree that solar irradiance is higher when the Sun is more active, as indicated by an elevated number of sunspots on its surface (Lean et al, 2005;Shapiro et al, 2011;Vieira et al, 2011;Baranyi and Pap, 2012). Total solar irradiance (TSI) is Earth's dominant energy input exceeding the next largest energy source by nearly 10 4 (Kopp and Lean, 2011;Frohlich, 2012).…”

“…Also detected with high reliability are shorter-term irradiance changes of as much as 0.3%, associated with the Sun's rotation on its axis (with a period of approximately 27 days). Longer-term irradiance trends that may underlie the activity cycle (and manifest during solar minima) have not yet been reliably detected because the radiometers deployed prior to 2003 lack the needed calibration stability (Frohlich, 2011;Baranyi and Pap, 2012). As a result, different composite records of solar irradiance constructed with diametric assertions of instrumental behavior in independent radiometers differ in their absolute scale and temporal variations, including relative strengths during solar minima (Frohlich and Lean, 2004).…”