What Can we Learn Studying Long-Term Magnetic Evolution of Solar Active Regions? van Driel-Gesztelyi, L. ; Kovari, Zs. ; Lopez-Fuentes, M. ; Mandrini, C. H. ; Demoulin, P. Abstract Publication: The Solar Cycle and Terrestrial Climate, Solar and Space weather Pub Date: 2000 Bibcode: 2000ESASP.463..451V