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Stellar Butterfly Diagrams

Stellar Butterfly Diagrams. Svetlana V. Berdyugina Institut f ür Astronomie, ETH Z ürich. Key ideas. Butterfly diagrams. Dynamo theory. Doppler imaging Differential rotation Migration of magnetic fields. Solar butterfly diagram. Migration of magnetic fields on the Sun.

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Stellar Butterfly Diagrams

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

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

  3. Solar butterfly diagram CS13, Hamburg, July 2004

  4. 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 CS13, Hamburg, July 2004 Berdyugina & Usoskin (2003)

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

  6. Migration of magnetic fields on cool stars Activity minimum Activity maximum • AB Dor, K1 V,  70 Myr surface differential rotation = -0.04 (Donati & Collier Cameron 1997) • activity minimum • minimum latitude (!) • change of migration rate (?) • maximum latitude • near max activity CS13, Hamburg, July 2004

  7. Migration of magnetic fields on cool stars LQ Hya K1 V,  70 Myr surface differential rotation = -0.002 (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

  8. Conclusions 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 CS13, Hamburg, July 2004

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