Observations of Fan-Spine Topology by Solar Orbiter/EUI: Rotational Motions and Indications of Alfvén Waves

Abstract

Torsional Alfvén waves do not produce any intensity variation and are, therefore, challenging to observe with imaging instruments. Previously, Alfvén wave observations were reported throughout all the layers of the solar atmosphere using spectral imaging. We present an observation of a torsional Alfvén wave detected in an inverted y-shape structure observed with the HRIEUV telescope of the EUI instrument onboard Solar Orbiter in its 174 Å channel. The feature consists of two footpoints connected through short loops and a spine with a length of 30 Mm originating from one of the footpoints. In the current work, we also make use of the simultaneous observations from two other instruments onboard Solar Orbiter. The first one is PHI that is used to derive the magnetic configuration of the observed feature. The second one is SPICE that provided observations of intensity maps in different lines including Ne VIII and C III lines. We also address the issues of the SPICE point spread function and its influence on the Doppler maps via performed forward modeling analysis. The difference movie shows clear signatures of propagating rotational motions in the spine. Doppler maps obtained with SPICE show strong signal in the spine region. Under the assumption that the recovered point spread function is mostly correct, synthesized raster images confirm that this signal is predominantly physical. We conclude that the presented observations are compatible with an interpretation of either propagating torsional Alfvén waves in a low coronal structure or untwisting of a flux rope. This is the first time we see signatures of propagating torsional motion in corona as observed by the three instruments onboard Solar Orbiter.

14 pages, 16 figures accepted by A&A

References in corpus (13)

• Alfven Waves in the Lower Solar Atmosphere
• Chromospheric Anemone Jets as Evidence of Ubiquitous Reconnection
• Why Is Non-thermal Line Broadening of Spectral Lines in The Lower Transition Region of the Sun Independent of Spatial Resolution?
• Solar coronal heating from small-scale magnetic braids
• First direct observation of a torsional Alfvén oscillation at coronal heights
• Ultra-high-resolution Observations of Persistent Null-point Reconnection in the Solar Corona
• Decayless oscillations in solar coronal bright points
• First observations from the SPICE EUV spectrometer on Solar Orbiter
• Imaging and spectral study on the null point of a fan-spine structure during a solar flare
• A Statistical Investigation of Decayless Oscillations in Small-scale Coronal Loops Observed by Solar Orbiter/EUI
• A multiple spacecraft detection of the 2 April 2022 M-class flare and filament eruption during the first close Solar Orbiter perihelion
• Non-thermal line broadening due to braiding-induced turbulence in solar coronal loops
• The dynamics and observability of circularly polarized kink waves

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• Uniturbulence and Alfven wave solar model
• Resolving Interchange Reconnection Dynamics in a Fan-Spine-like Topology Observed by Solar Orbiter
• Active region upflows in various coronal structures and their coupling to the lower atmosphere
• Fine Structures of Tiny Quiet Sun Jets Observed by Solar Orbiter and Big Bear Solar Observatory