National Aeronautics and Space Administration

Living With A Star

Targeted Research and Technology

Changes in Geomagnetic Cutoff Rigidities over a 400-Year Interval

ROSES ID: NRA-00-OSS-01      Selection Year: 2001      

Program Element: Independent Investigation: LWS

Principal Investigator: Don F. Smart

Affiliation(s): University of Alabama, Huntsville


We propose to determine the change in geomagnetic cutoff on a world wide basis over a 400-year interval from 1600 to the present. The geomagnetic field is recognized to be changing (i.e. decreasing) over the present epoch of human history. These changes are non-uniform over the surface of the earth. While a crude representation may be accomplished by considering only the dipole changes, we propose a better representation by utilizing higher order simulations of the geomagnetic field to calculate the geomagnetic cutoff rigidities from 1600 to the present. Our present work shows that over the 400-year time interval the change in cutoff rigidity is sufficiently large so that the change in the cosmic radiation flux impacting the earth is approximately equal to the relative change in flux over a solar cycle. Presuming the work of Svensmark and Friis-Christensen is correct, that the change in the cosmic ray intensity over a solar cycle affects the cloud cover, then an equivalent change over a 400-year period should have similar importance on the long-term climate effects.


Performance YearReferenceInvestigation TypeActions
1Shea, M. A.; Smart, D. F.; (2004), Preliminary study of...
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Performance YearReferenceActions
1Shea, M.; Smart, D.; (2002), Cosmic rays, geomagnetic f...
1Smart, D. F.; Shea, M. A.; (2002), Vertical Cutoff Rig...
1Smart, Don Frederick; Shea, M. A.; (2003), Geomagnetic...
1Shea, Margaret Ann; Smart, D. F.; (2003), Preliminary S...

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