Main Objective: To detect any mixed-polarity field, unresolved by HMI, at the base of solar plume and non-plume regions observed by IRIS and AIA
Scientific Justification: On-disk solar coronal plumes, best seen in EUV -- AIA 171 A -- form/decay as a result of flux convergence/divergence at their base (Wang et al. 2016; Avallone et al. 2018). It is proposed that flux cancellation, leading to small-scale jets at plume base, is the primary mechanism for plume formation (Raouafi and Stenborg 2014). Avallone et al. (2018) found that plumes are dominantly unipolar in HMI magnetograms, and have similar lifetimes, peak luminosities, base magnetic fluxes in quiet regions and coronal holes. They also found locations of flux convergence forming no plumes in AIA 171, thus suggesting that a critical magnetic field is necessary but not sufficient to form a plume. Moreover, this summer we found hardly any differences between bases of plume and non-plume regions using IRIS MgII and Si IV SJ and spectral data. We propose to repeatedly scan a large FOV of a coronal hole or quiet region by IRIS and SOT/SP, for more than a couple of days, to catch a few plumes, and similarly behaving non-plume areas, and investigate any differences between plume and non-plume regions -- this includes finding out if there is mixed-polarity flux present at plume/non-plume base in SP data. |
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