Main Objective: Observe long-lived polar crown coronal cavities at or near solar minimum to determine if they exhibit spinning motions like those reported by Wang & Stenborg (2010).
Scientific Justification: Spinning coronal cavities were observed during the last solar minimum when there were small active regions near the equator. Wang & Stenborg theorize that the direction of the spinning motion of the coronal cavity is determined by a steep poleward gradient in magnetic field strength and that the spinning motion represents a detached flux rope. Periodic observations of a long-lived polar crown prominence could help determine if spinning cavities are due to the emergence of a flux rope or creation of a flux rope due to magnetic reconnection of a sheared arcade. We will utilize data from Hinode, IRIS, CoMP, and AIA to provide a complete picture of the evolution of a coronal cavity to a spinning coronal cavity. Observations would include long-lived, E-W aligned polar crown filament channels that have a coronal cavity on the limb. Once a target has been identified, the requested observations consist of 1) portions of the on-disk filament channel and 2) coronal cavity at the limb several days later. These observations are needed periodically over several rotations to observe coronal cavity evolution.
Hinode provides temperature and coronal velocity information of the cavity and overlying arcade as well as magnetic field information of the on disk portion of the filament channel. We would like to run an observation program similar to HOP 264 for EIS and XRT with the addition of SOT vector magnetograms IQUV taken along the on-disk portion of the filament channel at central meridian several days prior to that portion of the filament channel reaching the limb.
The IRIS observations of the prominence material on the limb will determine how the coronal cavity spins relative to the cool prominence material. Wang & Stenborg theorize the prominence material lies below the pinched off portion of the flux rope. If and how the prominence interacts with a spinning coronal cavity would yield insights on how the magnetic field of a prominence-cavity system (i.e. filament channel) evolves. |
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