CS13, Hamburg, July 2004 Stellar Butterfly Diagrams Svetlana V. Berdyugina Institut für Astronomie, ETH Zürich

CS13, Hamburg, July 2004 Key ideas  Doppler imaging  Differential rotation  Migration of magnetic fields Dynamo theory Butterfly diagrams

CS13, Hamburg, July 2004 Solar butterfly diagram

CS13, Hamburg, July 2004 Migration of magnetic fields on the Sun two active longitudes  in both North & South  separated by 180   persistent for 120 yrs non-linear migration  surface differential rotation  changes of mean spot latitude (butterfly diagram) activity minimum  lower mean latitude  change of migration rate maximum latitude  between min and max activity Berdyugina & Usoskin (2003)

CS13, Hamburg, July 2004 Migration of magnetic fields on cool stars RS CVn-type stars (Berdyugina & Tuominen 1998) II Peg EI Eri  Gem HR 7275

CS13, Hamburg, July 2004 Migration of magnetic fields on cool stars AB Dor, K1 V,  70 Myr surface differential rotation  = (Donati & Collier Cameron 1997) activity minimum  minimum latitude (!)  change of migration rate (?) maximum latitude  near max activity Activity minimum Activity maximum

CS13, Hamburg, July 2004 Migration of magnetic fields on cool stars LQ Hya K1 V,  70 Myr surface differential rotation  = (Berdyugina et al. 2002) activity minimum  minimum latitude (?)  change of migration rate (?) maximum latitude  near max activity Activity minimum Activity maximum

CS13, Hamburg, July 2004 Conclusions On stars with differential rotation changes of mean spot latitudes result in non-linear migration of active longitudes On the Sun, migration of active longitudes is a new tracer of the differential rotation On stars, migration of active longitudes can be used to recover butterfly diagrams The solar paradigm is appropriate for magnetic activity on cool stars Conclusions