Zusammenfassung
The average tilt angle of sunspot groups emerging throughout the solar cycle
determines the net magnetic flux crossing the equator, which is correlated with
the strength of the subsequent cycle. I suggest that a deep-seated, non-local
process can account for the observed cycle-dependent changes in the average
tilt angle. Motivated by helioseismic observations indicating cycle-scale
variations in the sound speed near the base of the convection zone, I
determined the effect of a thermally perturbed overshoot region on the
stability of flux tubes and on the tilt angles of emerging flux loops. I found
that 5-20 K of cooling is sufficient for emerging flux loops to reproduce the
reported amplitude of cycle-averaged tilt angle variations, suggesting that it
is a plausible effect responsible for the nonlinearity of the solar activity
cycle.
Nutzer