Latitude of Ephemeral Regions as Indicator of Strength of Solar Cycles

TL;DR

This study demonstrates that the average latitude of ephemeral regions can predict the strength of upcoming solar cycles, providing both short-term and long-term forecasting capabilities based on historical data.

Contribution

It introduces a novel method using ephemeral region latitudes as indicators for solar cycle amplitudes, improving prediction accuracy for solar activity.

Findings

Latitude of ERs correlates with cycle strength.

Short-term predictions are based on current cycle ER latitudes.

Long-term predictions use ER latitudes during declining phases.

Abstract

Digitized images of full disk CaK spectroheliograms from two solar observatories were used to study cycle variation of ephemeral regions (ERs) over ten solar cycles 14-23. We calculate monthly averaged unsigned latitude of ERs and compare it with annual sunspot number. We find that average latitude of ERs can be used as a predictor for strength of solar cycle. For a short-term prediction (dT about 1-2 years), maximum latitude of ephemeral regions (in current cycle) defines the amplitude of that cycle (higher is the latitude of ERs, larger are the amplitudes of sunspot cycle). For a long-term prediction (dT about 1.5 solar cycles), latitude of ERs at declining phase of n-th cycle determines the amplitude of (n+2)-th sunspot cycle (lower is the latitude of ERs, stronger is the cycle). Using this latter dependency, we forecast the amplitude of sunspot cycle 24 at W=92 +/- 13 (in units of annual sunspot number).