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Conservation of open solar magnetic flux and the floor in the heliospheric magnetic field
Author(s) -
Owens M. J.,
Crooker N. U.,
Schwadron N. A.,
Horbury T. S.,
Yashiro S.,
Xie H.,
St. Cyr O. C.,
Gopalswamy N.
Publication year - 2008
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2008gl035813
Subject(s) - physics , heliospheric current sheet , solar minimum , flux (metallurgy) , solar irradiance , coronal mass ejection , solar cycle 23 , maxima and minima , magnetic flux , heliosphere , current sheet , magnetic field , drop (telecommunication) , solar cycle , geophysics , atmospheric sciences , solar wind , magnetohydrodynamics , mathematics , materials science , quantum mechanics , metallurgy , mathematical analysis , telecommunications , computer science
The near‐Earth heliospheric magnetic field intensity, | B |, exhibits a strong solar cycle variation, but returns to the same “floor” value each solar minimum. The current minimum, however, has seen | B | drop below previous minima, bringing in to question the existence of a floor, or at the very least requiring a re‐assessment of its value. In this study we assume heliospheric flux consists of a constant open flux component and a time‐varying contribution from CMEs. In this scenario, the true floor is | B | with zero CME contribution. Using observed CME rates over the solar cycle, we estimate the “no‐CME” | B | floor at ∼4.0 ± 0.3 nT, lower than previous floor estimates and below | B | observed this solar minimum. We speculate that the drop in | B | observed this minimum may be due to a persistently lower CME rate than the previous minimum, though there are large uncertainties in the supporting observational data.