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Coronal electron temperature in the protracted solar minimum, the cycle 24 mini maximum, and over centuries
Author(s) -
Schwadron N. A.,
Goelzer M. L.,
Smith C. W.,
Kasper J. C.,
Korreck K.,
Leamon R. J.,
Lepri S. T.,
Maruca B. A.,
McComas D.,
Stevens M. L.
Publication year - 2014
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1002/2013ja019397
Subject(s) - solar minimum , coronal loop , solar wind , solar cycle 22 , corona (planetary geology) , coronal hole , solar maximum , coronal plane , coronal mass ejection , coronal cloud , physics , electron temperature , nanoflares , astrophysics , solar cycle , electron , plasma , astrobiology , nuclear physics , biology , venus , anatomy
Recent in situ observations of the solar wind show that charge states (e.g., the O 7+ /O 6+ and C 6+ /C 5+ abundance ratios) evolved through the extended, deep solar minimum between solar cycles 23 and 24 (i.e., from 2006 to 2009) reflecting cooler electron temperatures in the corona. We extend previous analyses to study the evolution of the coronal electron temperature through the protracted solar minimum and observe not only the reduction in coronal temperature in the cycles 23–24 solar minimum but also a small increase in coronal temperature associated with increasing activity during the “mini maximum” in cycle 24. We use a new model of the interplanetary magnetic flux since 1749 to estimate coronal electron temperatures over more than two centuries. The reduction in coronal electron temperature in the cycles 23–24 protracted solar minimum is similar to reductions observed at the beginning of the Dalton Minimum (∼1805–1840). If these trends continue to reflect the evolution of the Dalton Minimum, we will observe further reductions in coronal temperature in the cycles 24–25 solar minimum. Preliminary indications in 2013 do suggest a further post cycle 23 decline in solar activity. Thus, we extend our understanding of coronal electron temperature using the solar wind scaling law and compare recent reductions in coronal electron temperature in the protracted solar minimum to conditions that prevailed in the Dalton Minimum.