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Spatial evolution of 26-day recurrent galactic cosmic ray decreases: Correlated Ulysses COSPIN/KET and SOHO COSTEP observationsA Lomb (spectral) analysis was performed on the galactic comsic ray flux from February 1996 to June 1996. The most probable frequency is approximately 28 days and not 26 or 27 days, corresponding to one solar rotation. The amplitude of the recurrent cosmic ray decreases (RCRDs) is approximately 2.3 percent on both spacecraft. The variation in the solar wind speed shows the same periodicites and is anticorrelated to the variation in the cosmic ray flux. In contrast to the RCRDs, the amplitude found in the solar wind speed is four times larger at WIND (120 km/s) than at Ulysses (32 km/s). The solar wind proton density and magnetic field strength yielded no significant periodicities, neither at Ulysses nor at WIND. Comparing the RCRDs with coronal hole structures observed in the FE XIV line, it was found that a single coronal hole close to the heliographic equator can account for the RCRDs observed 'simultaneously' at Ulysses and SOHO. The coronal hole boundaries changed towards lower Carrington longitudes and vanished slowly. The changes of the boundaries during the investigated period could explain a 28-day periodicity.
Document ID
19990056505
Acquisition Source
Goddard Space Flight Center
Document Type
Conference Paper
Authors
Heber, B.
(Kiel Univ. Germany)
Bothmer, V.
(Kiel Univ. Germany)
Droege, W.
(Kiel Univ. Germany)
Kunow, H.
(Kiel Univ. Germany)
Mueller-Mellin, R.
(Kiel Univ. Germany)
Posner, A.
(Kiel Univ. Germany)
Ferrando, P.
(Commissariat a l'Energie Atomique Saclay France)
Raviart, A.
(Commissariat a l'Energie Atomique Saclay France)
Paizis, C.
(Milan Univ. Italy)
McComas, D.
(Los Alamos National Lab. NM United States)
Forsyth, R. J.
(Imperial Coll. of Science and Technology London, United Kingdom)
Szabo, A.
(NASA Goddard Space Flight Center Greenbelt, MD United States)
Lazarus, A. J.
(Massachusetts Inst. of Tech. Cambridge, MA United States)
Date Acquired
August 19, 2013
Publication Date
December 1, 1997
Publication Information
Publication: Proceedings of the 31st ESALB Symposium on Correlated Phenomena at the Sun, in the Heliosphere and in Geospace
Subject Category
Solar Physics
Funding Number(s)
CONTRACT_GRANT: DARA-50-ON-9106
Distribution Limits
Public
Copyright
Other
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