期刊
ASTROPHYSICAL JOURNAL
卷 765, 期 2, 页码 -出版社
IOP PUBLISHING LTD
DOI: 10.1088/0004-637X/765/2/146
关键词
magnetic fields; solar wind; Sun: corona
资金
- National Science Foundation (NSF) grant [ATM-0925177]
- NASA LWS [NNX08AU30G, NNH08CC02C]
- NASA grant [NNX08AL23G]
- National Science Foundation
- NASA [NNX08AL23G, 98565] Funding Source: Federal RePORTER
Among many other measurable quantities, the summer of 2009 saw a considerable low in the radiative output of the Sun that was temporally coincident with the largest cosmic-ray flux ever measured at 1 AU. Combining measurements and observations made by the Solar and Heliospheric Observatory (SOHO) and Solar Dynamics Observatory (SDO) spacecraft we begin to explore the complexities of the descending phase of solar cycle 23, through the 2009 minimum into the ascending phase of solar cycle 24. A hemispheric asymmetry in magnetic activity is clearly observed and its evolution monitored and the resulting (prolonged) magnetic imbalance must have had a considerable impact on the structure and energetics of the heliosphere. While we cannot uniquely tie the variance and scale of the surface magnetism to the dwindling radiative and particulate output of the star, or the increased cosmic-ray flux through the 2009 minimum, the timing of the decline and rapid recovery in early 2010 would appear to inextricably link them. These observations support a picture where the Sun's hemispheres are significantly out of phase with each other. Studying historical sunspot records with this picture in mind shows that the northern hemisphere has been leading since the middle of the last century and that the hemispheric dominance has changed twice in the past 130 years. The observations presented give clear cause for concern, especially with respect to our present understanding of the processes that produce the surface magnetism in the (hidden) solar interior-hemispheric asymmetry is the normal state-the strong symmetry shown in 1996 was abnormal. Further, these observations show that the mechanism(s) which create and transport the magnetic flux are slowly changing with time and, it appears, with only loose coupling across the equator such that those asymmetries can persist for a considerable time. As the current asymmetry persists and the basal energetics of the system continue to dwindle we anticipate new radiative and particulate lows coupled with increased cosmic-ray fluxes heading into the next solar minimum.
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