Temporal Variability of Active Region Outflows

TL;DR

This study investigates the temperature-specific dynamics of active region outflows, confirming their association with 1 MK plasma and revealing transient blue wing enhancements, while contrasting behaviors at 0.6 MK.

Contribution

It provides detailed temperature-dependent analysis of active region outflows using EIS, clarifying their transient nature and differing behaviors at various temperatures.

Findings

Confirmed 1 MK outflows are associated with blue-shifted profiles.

Detected transient blue wing enhancements at 5-minute cadence.

Observed no outward propagating disturbances at 0.6 MK in fan loops.

Abstract

Recent observations from the Extreme-ultraviolet Imaging Spectrometer (EIS) on board Hinode have shown that low density areas on the periphery of active regions are characterized by strong blue-shifts at 1 MK. These Doppler shifts have been associated with outward propagating disturbances observed with Extreme-ultraviolet and soft X-ray imagers. Since these instruments can have broad temperature responses we investigate these intensity fluctuations using the monochromatic imaging capabilities of EIS and confirm their 1 MK nature. We also find that the Fe XII 195.119 A blue shifted spectral profiles at their footpoints exhibit transient blue wing enhancements on timescales as short as the 5 minute cadence. We have also looked at the fan peripheral loops observed at 0.6 MK in Si VII 275.368 A in those regions and find no sign of the recurrent outward propagating disturbances with velocities of 40 - 130 km/s seen in Fe XII. We do observe downward trends (15 - 20 km/s) consistent with the characteristic red-shifts measured at their footpoints. We, therefore, find no evidence that the structures at these two temperatures and the intensity fluctuations they exhibit are related to one another.