Vol 15, No 9

Case studies of EUV cyclones and their associated magnetic fields

Xin-Ting Yu, Jun Zhang, Ting Li, Shu-Hong Yang


Abstract EUV cyclones are rotating structures in the solar corona, and they are usually rooted in the underlying rotating network magnetic fields in the photosphere. However, their connection with the surrounding magnetic fields remains unknown. Here we report an observational study of four typical cyclones which are rooted in different kinds of magnetic fields. We use Solar Dynamics Observatory/Atmospheric Imaging Assembly data to investigate the rotation of EUV features in cyclones and Helioseismic and Magnetic Imager data to study the associated magnetic fields. The results show that, (1) an EUV cyclone rooted in a sunspot rotates with the photospheric magnetic field; (2) two EUV cyclones in two faculae of an active region are connected to the same sunspot of the active region but rotate oppositely; (3) an EUV cyclone is rooted in a coronal hole with weak open magnetic fields; (4) a pair of conjugated cyclones is rooted in magnetic fields that have opposite polarity with opposite directions of rotation. The differences in the spatial extent of a cyclone, characteristics of its rotation and underlying fields indicate that cyclones are ubiquitous over the solar atmosphere and that the magnetic structures relevant to the cyclones are more complicated than expected.


Keywords Sun: activity — Sun: corona — Sun: magnetic fields — Sun: photosphere

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