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AOSC Seminar
February 14, 2019

Title: Terminators: The Death of the Solar Cycles and La NiƱa 2020

Robert Leamon
NASA-GSFC, Heliospheric Physics Lab

The Sun ultimately provides the all energy required to sustain life on Earth and
drive our planet's weather. However, establishing a solid physical connection
between solar variability and tropospheric variability has posed a considerable
challenge across the spectrum of Earth system science. Over the past few years a
new picture to describe solar variability has developed, based on observing
bands of magnetism that belong to the Sun's *22-year* magnetic activity cycle,
and migrate from high latitudes towards the equator. One of the most important
events in the progression of these bands is their abrupt death, or termination,
at the solar equator that signals a global increase in magnetic activity that
becomes the new solar cycle. Indeed, the triggering of growth in the new solar
cycle is almost immediate -- within about one solar rotation (27 days). Rather
than focussing on weather or climate correlations with the maxima and minima of
sunspot number, here we show solar cycle termination events and major oceanic
oscillations (the El Niño Southern Oscillation--ENSO and the North Atlantic
Oscillation--NAO) are correlated, going back many decades (five solar cycles).
Should current projections of the Sun's magnetic behavior hold, we predict the
current solar cycle termination to occur in spring 2020, and thus we expect to
see El Niño conditions in the Pacific up to that time, transitioning to La Niña
conditions within 2-3 months of the termination. Should this come to pass, our
challenge becomes: when does correlation become causation and how does the
process work?

Potential mechanisms involving modulation of the incoming galactic cosmic ray
flux and changes in stratospheric temperatures & chemistry and tropical-polar
teleconnections will be discussed.