Speaker
Description
Understanding the magnetic field structure of spicules is essential for developing formation models of spicules, which are important for understanding mass transport to the corona and the coronal heating.
We report the spatial distribution of spicule magnetic fields along the line-of-sight ($B_{\rm{LOS}}$) from spectropolarimetric observations of the solar limb with SUNRISE-III/SCIP under seeing-free conditions, applying the Weak Field Approximation to the Stokes $\textit{I}$ and $\textit{V}$ profiles of the Ca II 8542 $\mathrm{\mathring{A}}$ line.
We find that $B_{\rm{LOS}}$ ranges up to 20 $\rm{G}$, nearly independent of height, in the region up to 2 $\rm{Mm}$ from the limb, whereas the distribution broadens to 40 $\rm{G}$ at 2-4 $\rm{Mm}$ from the limb.
The Stokes $\textit{I}$ profiles averaged over the same distance from the limb changed from a double-peaked shape to a single-peaked one at around 2 $\rm{Mm}$ from the limb.
This suggests that the observed $B_{\rm{LOS}}$ depends on the optical thickness of the Ca II lines.
In the optically thick region with double-peaked profiles, the estimated $B_{\rm{LOS}}$ represents a superposition of few foreground spicules, whereas in the optically thin region with single-peaked profiles, the estimated $B_{\rm{LOS}}$ reflects contribution from a prominent tall inclined spicule, leading to more dispersed $B_{\rm{LOS}}$ values.
We further report the spatial structure of spicule magnetic fields by incorporating the $B_{\rm{LOS}}$ spatial distribution obtained from the Ca II 8498 $\mathrm{\mathring{A}}$ line, which has a different optical thickness from the Ca II 8542 $\mathrm{\mathring{A}}$ line, and examine how the difference in optical thickness affects the inferred magnetic field structure of spicules.