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correlation between GCR and TSI, 6 and Russell et al. (1984) presented a discussion of the link between
the modulated energetic particle flux and nitrogen oxide production in the stratosphere showing a link to
ozone. 7 The destruction of ozone changes the energy balance in the atmosphere because ozone absorbs
solar radiation. Baker discussed how Randall et al. (2010) quantified this in terms of the trend in ozone
using the WACCM general circulation model that includes the upper-atmosphere dynamics and
chemistry. 8 The high-latitude case shows a depletion of stratospheric ozone due to increases in nitrogen
oxides from energetic particles that then is reflected in a lower-atmosphere increase in ozone due to
destruction of chlorine oxide through reactions with nitrogen oxides. Baker concluded, however, that all
of these processes appear to have a minimal effect on surface temperatures.
Behavior of Quiet Sun Contributions to Solar Irradiance
Peter Foukal, Heliophysics, Inc.
The main aim of Peter Foukal's presentation was to consider whether the Sun dimmed enough
during the 17th century Maunder Minimum of solar activity to influence climate. He argued that the
simplest way to achieve sufficient dimming is through a decline in the area coverage of small flux tubes
in the quiet magnetic network and internetwork (Figure 2.2).
The fractional decline required may be less than the complete disappearance required by earlier
irradiance models, judging by recent findings from solar photometry. These findings 9 indicate that the
excess radiative flux/unit area of faculae increases with their decreasing cross section. This relationship
suggests that climatically significant variations in TSI might be achieved without the need for the
complete disappearance of photospheric magnetism. Foukal noted that this relationship is important
because 10 Be proxy record studies indicate persistence of a residual 11-year solar cycle through the
Maunder Minimum.
Foukal then pointed out that present estimates of the quiet network's contribution to total
irradiance (Figure 2.3) are uncertain because of limitations on angular resolution, angular coverage, or
wavelength coverage. He described how, ideally, the measurement should be carried out with the Solar
Bolometric Imager, which has been flown by the Johns Hopkins University Applied Physics Laboratory
on NASA balloons, 10 but modified for larger image scale and higher angular resolution.
If the contribution of the quiet network to TSI is significant, it is still necessary to know whether
the network's area decayed. This decay is controversial, 11 but the most reproducible indices of network
area (such as MgII) did indicate a decline by 5-10 percent below the average of previous minimum
values, during the most recent 2008-2009 activity minimum. 12 This amount of decline during a minimum
that was only about 1 year longer than normal suggests an even greater decline during a Maunder
6 M. Lockwood, What do cosmogenic isotopes tell us about past solar forcing of climate? Space Science Review
125:95-109, 2005.
7 J.M. Russell, S. Solomon, L.L. Gordley, E.E. Remsberg, and L.B. Callis, The variability of stratospheric and
mesospheric NO 2 in the polar winter night observed by LIMS, Journal of Geophysical Research 89:7267-7275,
8 C. Randall, E.D. Peck, L.A. Holt, V. Harvey, D.R. Marsh, X. Fang, C.H. Jackman, M.J. Mills, and S.M.
Bailey, Atmospheric coupling via energetic particle precipitation, paper presented at the American Geophysical
Union Fall Meeting, December 13-17, 2010, San Francisco, Calif., 2010.
9 P. Foukal, A. Ortiz, and R. Schnerr, Dimming of the 17th Century Sun, The Astrophysical Journal Letters
733:L38, 2011.
10 P. Bernasconi, H.A.C. Eaton, P. Foukal, and D.M. Rust, The solar bolometric imager, Advances in Space
Research 33:1746-1754, 2004.
11 C.J. Schrijver, W.C. Livingston, T.N. Woods, and R.A. Mewaldt, The minimal solar activity in 2008-2009
and its implications for long-term climate modeling, Geophysical Research Letters 38: L06701, 2011.
12 C. Frölich, Evidence of a long-term trend in total solar irradiance, Astronomy and Astrophysics 501: L27-L30,
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