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| Titel |
Modulation of galactic cosmic ray protons and electrons during an unusual solar minimum |
| VerfasserIn |
B. Heber, J. Gieseler, A. Kopp, R. Müller-Mellin, H. Fichtner, K. Scherer, M. S. Potgieter, S. E. S. Ferreira |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250020188
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| Zusammenfassung |
| During the latest Ulysses out-of-ecliptic orbit the solar wind density, its pressure and the
magnetic field strength have been lowest ever observed in the history of space exploration.
Since cosmic ray particles respond to the heliospheric magnetic field in the expanding solar
wind and its turbulence, the weak heliospheric magnetic field and low plasma density and
pressure is expected to cause the smallest modulation since the 1970’s. In contrast to this
expectation the galactic cosmic ray proton flux measured in 2008 at Ulysses and
Earth does not exceed the one observed in the 1980’s and 1960’s significantly. In
contrast to protons the flux of galactic cosmic ray electrons exceeds the one measured
during the 1990’s by 10% after correcting the data for Ulysses’ latitude and radial
distance. Although solar activity, as indicated by the Sunspot number, has been low
the tilt angle of the magnetic field remained at intermediate values. Since current
sheet and gradient drifts prevent the galactic cosmic ray flux to rise to real solar
minimum values the observed galactic cosmic ray intensities at 2.5 GV should
increase by a factor of 1.25 |
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