Large-Scale Magnetic Funnels in the Solar Corona
Abstract
The existence of open coronal magnetic fields with peculiar geometry - large-scale coronal magnetic funnels - can be attributed to two main factors: (i) the presence of two or more coronal holes of the same polarity forming coronal pseudostreamers, (ii) specific configurations of closed magnetic field in the low corona - filament channels. The important property of magnetic funnels is their strongly non-monotonic expansion factor below 2 solar radii. In the case study presented here we consider a double pseudostreamer near the equator, formed between a triplet of isolated coronal holes of the same polarity, and harboring two pairs of twin filaments in its base. Following the evolution of these coronal holes we find that the pseudostreamer and, therefore, magnetic funnel topology, changes when two coronal holes have merged together. Using a potential field source-surface (PFSS) extrapolation to compute the coronal field from photospheric maps (SDO/HMI), we show that the funnel - like geometry of the open magnetic field changes to a regular one with monotonic expansion factor after the merging of coronal holes. The presence of coronal magnetic funnels becomes directly visible when sufficient plasma accumulates inside them: when the plasma density grows to become observable, coronal cloud prominences appear in the corona, mostly in 304 A spectral line. We study the evolution of the funnel - like open magnetic fields during several solar rotations and find a direct relation between magnetic funnels and the presence of coronal clouds at great heights in the solar corona. 1D numerical analysis of pseudostreamers with funnel topology shows that the properties of the solar wind from coronal magnetic funnels depend on the presence/absence of filament channels, number of channels and chirality at the pseudostreamer base low in the solar corona.
- Publication:
-
42nd COSPAR Scientific Assembly
- Pub Date:
- July 2018
- Bibcode:
- 2018cosp...42E2566P