Chromospheric Flashes in a Solar Pore: Insights from Multi-line Spectropolarimetric Diagnostics

TL;DR

This study investigates chromospheric flashes in a solar pore using multi-line spectropolarimetric diagnostics, revealing their magnetic, thermal, and dynamic properties and their association with wave phenomena in the lower solar atmosphere.

Contribution

It provides the first detailed multi-line spectropolarimetric analysis of pore flashes, linking their properties to wave activity and magnetic field configurations.

Findings

Flashes are cooler, magnetically stronger, and show persistent upflows.

They are associated with enhanced photospheric power and chromospheric upflows.

Flashes are confined to the lower and mid-chromosphere with wave activity.

Abstract

Solar pores are strongly magnetized regions lacking a photospheric penumbra and characterized by predominantly vertical magnetic fields. We present a multi-line study of flashes in a solar pore using high-resolution observations from the Swedish 1-m Solar Telescope in Fe~\textsc{i}~6302~\AA, Ca~\textsc{ii}~8542~\AA\ and K, and H-$\beta$, complemented by (E)UV data from \textit{IRIS} and \textit{SDO}/AIA. Bisector analysis and spectral inversions with \textsc{SIR} and \textsc{NICOLE} were used to infer stratifications of temperature, line-of-sight velocity, and magnetic field. Flashes, confined to one half of the pore, exhibit cooler photospheric temperatures ($\Delta T \approx 400$~K), stronger magnetic fields ($\Delta B \approx 250$~G), larger inclinations ($\sim25^{\circ}$ versus $\sim18^{\circ}$), and persistent upflows ($\sim0.5$~km~s$^{-1}$) compared to the quiescent pore. They are co-spatial with enhanced 3- and 5-minute power in the photosphere, while only 3-minute power persists in the chromosphere. Flashes are detected down to $\sim50\%$ line depth in Ca~\textsc{ii}~8542~\AA\ intensity and show central chromospheric upflows ($\sim1$~km~s$^{-1}$) flanked by strong downflows ($\sim8$~km~s$^{-1}$). Temperature enhancements reach $\sim500$~K at $\log\tau \approx -5$ and $\sim2500$~K at $\log\tau \approx -6$, with a bimodal velocity distribution. Flashes correspond one-to-one with radially outward running waves near the pore boundary (5--15~km~s$^{-1}$). Strong Ca~\textsc{ii} core emission, occasional Stokes~$V$ reversals, and H-$\beta$ enhancements indicate that pore flashes are confined to the lower and mid-chromosphere, with little influence on higher atmospheric layers.