The effect of increasing solar activity on the Sun's total and open magnetic flux during multiple cycles: Implications for solar forcing of climate

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Read Full Article (file size: 210165 bytes) Cited by GEOPHYSICAL RESEARCH LETTERS, VOL. 29, NO. 24, 2224, doi:10.1029/2002GL015880, 2002 The effect of increasing solar activity on the Sun's total and open magnetic flux during multiple cycles: Implications for solar forcing of climate J. L. Lean E. O. Hulburt Center for Space Research, Naval Research Laboratory, Washington DC, USA Y.-M. Wang E. O. Hulburt Center for Space Research, Naval Research Laboratory, Washington DC, USA N. R. Sheeley Jr. E. O. Hulburt Center for Space Research, Naval Research Laboratory, Washington DC, USA Abstract We investigate the relationship between solar irradiance and cosmogenic isotope variations by simulating with a flux transport model the effect of solar activity on the Sun's total and open magnetic flux. As the total amount of magnetic flux deposited in successive cycles increases, the polar fields build up, producing a secular increase in the open flux that controls the interplanetary magnetic field which modulates the cosmic ray flux that produces cosmogenic isotopes. Non-axisymmetric fields at lower latitudes decay on time scales of less than a year; as a result the total magnetic flux at the solar surface, which controls the Sun's irradiance, lacks an upward trend during cycle minima. This suggests that secular increases in cosmogenic and geomagnetic proxies of solar activity may not necessarily imply equivalent secular trends in solar irradiance. Questions therefore arise about the interpretation of Sun-climate relationships, which typically assume that the proxies imply radiative forcing. Published 28 December 2002. Index Terms: 7537 Solar Physics, Astrophysics, and Astronomy: Solar and stellar variability; 7524 Solar Physics, Astrophysics, and Astronomy: Magnetic fields; 7536 Solar Physics, Astrophysics, and Astronomy: Solar activity cycle (2162); 7538 Solar Physics, Astrophysics, and Astronomy: Solar irradiance; 1650 Global Change: Solar variability. Read Full Article (file size: 210165 bytes) Cited by Citation: Lean, J. L., Y.-M. Wang, and N. R. Sheeley Jr. (2002), The effect of increasing solar activity on the Sun's total and open magnetic flux during multiple cycles: Implications for solar forcing of climate, Geophys. Res. Lett., 29(24), 2224, doi:10.1029/2002GL015880. This paper is not subject to U.S. copyright. Published in 2002 by the American Geophysical Union.

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