Publication:
Dynamo Wave Patterns Inside the Sun Revealed by Torsional
Oscillations Authors: Alexander G. Kosovichev, Valery V. Pipin,
Astrophysical Journal Letters, Volume 871, Issue 2, article id. L20 (2019)https://arxiv.org/abs/1809.10776
Summary. Torsional oscillations are exhibited by
bands of fast and slow zonal flows beneath the visible surface of
the Sun, similar to stream jets in the Earth's atmosphere.Analysis of
helioseismology data obtained by two NASA missions in 1996-2018
for nearlytwo solar
cycles reveals zones of deceleration of torsional oscillations
inside the Sun due to a back reaction of magnetic fields generated
by the solar dynamo.Deceleration
of the flow originates about 120,000 miles beneath the solar
surface at high latitude regions of the solar tachocline.This zonal deceleration
migrates through the convection zone revealing patterns of
magnetic dynamo waves, analysis of which explains the phenomenon
of the extended solar cycle observed in the evolving shape of
the solar corona, and why the polar magnetic field strength
predicts the solar maxima. The results indicate a further decline
of sunspot activity in the next solar cycle.
Image
caption. Image of the zonal acceleration
pattern beneath the solar surface shows zone of flow
acceleration (red) and deceleration (blue). The flow
deceleration is caused by the magnetic field. The inner
sphere shows the bottom of the convection zone (the solar
tachocline). The tachocline region marked with “A” is the
primary seat of the solar dynamo, where the magnetic is
initially generated.“B”
and “C” indicate the polar and equatorial branches of the
dynamo wave. When the polar branch reaches the surface it
causes polar field reversals, while the equatorial branch,
amplified by magnetic field stretching due to differential
rotation, leads to formation of sunspots. The insert shows
the evolution of the sunspot number during 22 years of
helioseismic observations. The image shows a snapshot of the
zonal deceleration in 2003 near the maximum of the sunspot
number of Solar Cycle 23 (point B), when the generation of
magnetic field of the next solar cycle already started in
the tachocline (point A). (Visualization by Tim Sandstrom,
NASA Ames Research Center). (high-resolution
image)
Movies and Images Evolution of the solar magnetic structure during the last
two solar cycles
