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Time Dependence of Solar Modulation throughout Solar Cycle 23 as Inferred from ACE Measurements of Cosmic-Ray Energy Spectra

Wiedenbeck, M. E. and Davis, A. J. and Cohen, C. M. S. and Cummings, A. C. and Labrador, A. W. and Leske, R. A. and Mewaldt, R. A. and Stone, E. C. and Binns, W. R. and Israel, M. H. and Lave, K. A. and Christian, E. R. and de Nolfo, G. A. and von Rosenvinge, T. T. (2009) Time Dependence of Solar Modulation throughout Solar Cycle 23 as Inferred from ACE Measurements of Cosmic-Ray Energy Spectra. In: Proceedings of the 31st International Cosmic Ray Conference. , Lodz, Poland.

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Since the launch of the Advanced Composition Explorer (ACE) in August 1997, the Cosmic Ray Isotope Spectrometer (CRIS) has been providing measurements of cosmic-ray energy spectra between ∼50 and ∼500 MeV/nuc for a wide range of elements. The shape of these low-energy spectra, which are measured with good statistical precision on time scales as short as a solar rotation, are strongly influenced by modulation in the heliosphere. By combining calculated local interstellar spectra from a leaky-box propagation model with a sphericallysymmetric, steady-state model of solar modulation, we have derived the time dependence of the modulation strength throughout solar cycle 23. In addition, we have investigated hysteresis effects in the modulation by comparing time dependences at different energies in two ways. First, we have compared values of the modulation parameter, φ, calculated based on CRIS spectral measurements with published values derived from neutron monitor data. Second, we have studied effects over relatively small energy ranges by comparing CRIS intensity measurements at different energies. We report the ACE/CRIS observations, discuss the trends in the data, and compare with previous results on the variations of the solar modulation level over the solar cycle.

Item Type:Book Section
Related URLs:
URLURL TypeDescription
Wiedenbeck, M. E.0000-0002-2825-3128
Cohen, C. M. S.0000-0002-0978-8127
Cummings, A. C.0000-0002-3840-7696
Labrador, A. W.0000-0001-9178-5349
Leske, R. A.0000-0002-0156-2414
Mewaldt, R. A.0000-0003-2178-9111
Stone, E. C.0000-0002-2010-5462
Binns, W. R.0000-0001-6110-3407
Israel, M. H.0000-0002-8104-208X
Christian, E. R.0000-0003-2134-3937
de Nolfo, G. A.0000-0002-3677-074X
Additional Information:Copyright University of Łódź. Department of High Energy Astrophysics, 2010. We thank Dr. I. Usoskin for providing an extension of the neutron monitor analysis to cover the time period subsequent to that reported in [8]. This work was supported by NASA at Caltech (under grant NNX8AI11G), JPL, Washington U., and GSFC.
Group:Space Radiation Laboratory
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Space Radiation Laboratory2009-23
Record Number:CaltechAUTHORS:20150528-144033949
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:57882
Deposited By: Deborah Miles
Deposited On:01 Jun 2015 23:37
Last Modified:09 Mar 2020 13:19

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