Erupting Magnetic Flux Rope Affects Running Penumbral Waves

TL;DR

This study investigates how erupting magnetic flux ropes influence running penumbral waves, revealing that magnetic reconnection in the corona impacts low-atmosphere wave behavior and offers a new diagnostic tool for flare reconnections.

Contribution

It provides new observational evidence linking coronal magnetic reconnection to changes in sunspot wave dynamics during eruptions.

Findings

Rope buildup causes penumbral field conversion and increased currents.

Rope erosion leads to mixed field inclination effects and heating at flare loop footpoints.

Post-eruption RPWs show enhanced contrast and lower frequency bandwidth.

Abstract

It is well known that solar flares have broad impacts on the low atmosphere, but it is largely unknown how they affect sunspot waves and oscillations. It is also under debate as to whether the flare-induced photospheric changes are due to the momentum conservation with coronal mass ejections or due to magnetic reconnection. To shed light on the so-called "back reaction" of solar eruptions, we investigated how running penumbral waves (RPWs) at one foot of an erupting magnetic flux rope (MFR) responds to the rope buildup and subsequent erosion. During the rope-buildup stage, the western foot of the rope, which is completely enclosed by a hooked ribbon, expands rapidly and consequently overlaps a sunspot penumbra. This converts the original penumbral field into the rope field, which is associated with a transient increase in electric currents flowing through the ribbon-swept penumbral region. During the rope-erosion stage, the rope foot shrinks as the eastern section of the hooked ribbon slowly sweeps the same penumbral region, where the rope field is converted into flare loops. This conversion induces mixed effects on the photospheric field inclination but heats up the low atmosphere at the footpoints of these flare loops to transition-region temperatures, therefore resulting in the post-eruption RPWs with an enhanced contrast in the 1600A passband and an extended bandwidth to low frequencies at 3-5 mHz, compared with the pre-eruption RPWs that peak at 6 mHz. This observation clearly demonstrates that it is the magnetic reconnection in the corona that impacts the low atmosphere and leads to the changing behaviors of RPWs, which, in turn, offer a new window to diagnose flare reconnections.