Conservation of open solar magnetic flux and the floor in the heliospheric magnetic field
Owens, M. J., Crooker, N. U., Schwadron, N. A., Horbury, T. S., Yashiro, S., Xie, H., St. Cyr, O. C. and Gopalswamy, N. (2008) Conservation of open solar magnetic flux and the floor in the heliospheric magnetic field. Geophysical Research Letters, 35 (20). L20108. ISSN 0094-8276
To link to this article DOI: 10.1029/2008GL035813
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.
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