A 20 year decline in solar photospheric magnetic fields: Inner‐heliospheric signatures and possible implications

Autor: Munetoshi Tokumaru, Ken'ichi Fujiki, P. Janardhan, Susanta Kumar Bisoi, R. Sridharan, Lijo Jose, S. Ananthakrishnan
Rok vydání: 2015
Předmět:
Zdroj: Journal of Geophysical Research: Space Physics. 120:5306-5317
ISSN: 2169-9402
2169-9380
DOI: 10.1002/2015ja021123
Popis: We report observations of a steady 20 year decline of solar photospheric fields at latitudes ≥45° starting from ∼1995. This prolonged and continuing decline, combined with the fact that cycle 24 is already past its peak, implies that magnetic fields are likely to continue to decline until ∼2020, the expected minimum of the ongoing solar cycle 24. In addition, interplanetary scintillation observations of the inner heliosphere for the period 1983–2013 and in the distance range 0.2–0.8 AU have also shown a similar and steady decline in solar wind microturbulence levels, in sync with the declining photospheric fields. Using the correlation between the polar field and heliospheric magnetic field (HMF) at solar minimum, we have estimated the value of the HMF in 2020 to be 3.9 (±0.6) nT and a floor value of the HMF of ∼3.2 (±0.4) nT. Given this floor value for the HMF, our analysis suggests that the estimated peak sunspot number for solar cycle 25 is likely to be 62 (±12).
Databáze: OpenAIRE
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