HR: 0830h
AN: SP41B-10 [Abstracts]
TI: A "Toy" Simulation of Total Solar Irradiance Variations
AU: * Walton, S R
EM: stephen.walton@csun.edu
AF: San Fernando Observatory, CSUN, 18111 Nordhoff St., Northridge, CA 91330-8268 United States
AU: Preminger, D G
EM: dora.preminger@csun.edu
AF: San Fernando Observatory, CSUN, 18111 Nordhoff St., Northridge, CA 91330-8268 United States
AB:
Recently, we have developed a method for deducing the total solar irradiance S from sunspot area AS using a finite
impulse response FIR which, when convolved with AS, produces S (Preminger & Walton 2005, JGR, submitted). In an effort to gain physical insight into the meaning of the FIR, we have produced a simple model of the solar cycle with the following
characteristics: (1) nd sunspots per day are generated, each with a fixed area AS = 500 millionths of the solar
hemisphere; (2) sunspots decay exponentially with time constant τS = 10 days; (3) decayed sunspot area becomes
faculae, which in turn decay with a time constant τF = 45 days. These parameters were deduced from various
characteristics of the actual solar cycle. Each sunspot is generated at a random solar longitude, and the faculae remain at
the same longitude as the sunspots. Latitude variation is not modeled; that is, they are always zero. We allow nd to
vary as a simple cosine bell from 0 up to nd,max. Simple models of sunspot and facular contrast are used to compute a
pseudo-TSI.
When nd,max=1, the resulting model reproduces a few of the observed characteristics of the solar activity cycle; e.g., the projected sunspot and facular area peak at about 1500 and 45,000 parts per million of the solar disk. If we use
this simple model to compute a FIR, it has a very similar shape to the one found empirically from the actual measured S
and AS. The model FIR is also independent of nd,max over the range 0.1 to 10. It is missing some qualitatively
important characteristics, however, in particular the fact that S actually begins to rise some time before AS; we are
investigating refinements to our model which might reproduce this property of the empirical FIR.
DE: 7536 Solar activity cycle (2162)
DE: 7538 Solar irradiance
SC: Solar Physics Division - AAS [SP]
MN: 2005 Joint Assembly