Multiple Component Outflows in an Active Region Observed with the EUV Imaging Spectrometer on Hinode

TL;DR

This study uses Hinode's EUV Imaging Spectrometer to observe persistent, multi-component outflows in an active region, revealing velocities up to 200 km/s and suggesting complex, unresolved flow structures.

Contribution

It demonstrates that multiple outflow components exist in active regions and models these with double-Gaussian fits, improving understanding of solar outflows.

Findings

Outflows persist for at least 6 days.

Double-Gaussian fits better represent emission line profiles.

Outflow velocities reach up to 200 km/s.

Abstract

We have used the Extreme Ultraviolet Imaging Spectrometer (EIS) on the Hinode spacecraft to observe large areas of outflow near an active region. These outflows are seen to persist for at least 6 days. The emission line profiles suggest that the outflow region is composed of multiple outflowing components, Doppler-shifted with respect to each other. We have modeled this scenario by imposing a double-Gaussian fit to the line profiles. These fits represent the profile markedly better than a single Gaussian fit for Fe XII and XIII emission lines. For the fastest outflowing components, we find velocities as high as 200 km/s. However, there remains a correlation between the fitted line velocities and widths, suggesting that the outflows are not fully resolved by the double-Gaussian fit and that the outflow may be comprised of further components.