Formation of the Large-Scale Magnetic Field and Forecasting Activity Cycles

The precursor method is used to forecast solar activity. One of these is the polar field precursor. On the other hand, there is evidence that the amplitude of the following solar cycle is associated with the low-latitude activity. Within the framework of the surface magnetic flux transport model, we build supersynoptic maps in latitude-time coordinates. It is shown that for the chosen transport parameters, including the diffusion coefficient D = 500 km²s^-1, the meridional circulation velocity u₀ = 10 m s^-1, and the tilt angle of the magnetic bipoles τ = 10°, there is a latitude θ₁ at which the magnetic field penetrates from the regions of the leading polarity into the opposite hemisphere and the dipole magnetic field of the Sun is formed. At θ > θ₁, the magnetic field does not penetrate into the opposite hemisphere, and the large-scale magnetic field at the poles remains insignificant. The value of θ₁ lies within the range of 10 – 20°. The active regions most important for the following cycle are those with latitude θ < θ₁. We propose prognostic indices for predicting the amplitude of activity cycles based on sunspot data in the current activity cycle with a correlation coefficient r > 0.8.

Sun, large-scale magnetic field, flux transport model, solar cycle prediction