Investigating the wave-driven physics of sunspots using novel balloon observations
Lead Research Organisation:
QUEEN'S UNIVERSITY BELFAST
Abstract
The Sun provides a unique astrophysical laboratory that enables plasma dynamics, including energy flow, wave interactions, and heating processes to be observed, characterised and modelled. Understanding the dynamics of the solar atmosphere is crucial for unravelling the mechanisms governing solar activity and its impact on space weather.
Sunspots play a crucial role in energy transport across the Sun's lower layers (i.e., the photosphere and chromosphere extending around 2000km above the visible surface). Here, strong magnetic fields act as conduits for magnetohydrodynamic (MHD) waves. Observing how these waves propagate, interact, and dissipate is key to unravelling the long-standing mystery of how the Sun's atmosphere remains continuously heated.
A key question in our proposed research is whether sunspots with more irregular shapes display increasingly complex wave behaviour, particularly higher-order wave modes that are believed to dissipate their energies more readily. By decomposing a sunspot's wave field into constituent MHD modes, we will be able to determine how much energy these waves contribute to the atmosphere's overall energy budget, where and how they lose energy, and whether the dissipated energy produces measurable heating signatures in the surrounding plasma. Additionally, our proposed research will examine the wave-driven interactions between charged ions and neutral atoms (through processes such as ambipolar diffusion) to investigate the role partial ionisation effects play in wave dissipation processes throughout the solar atmosphere. This final question will only be made possible through the fusion of high resolution spectropolarimetric observations with modern MHD numerical simulations. Thankfully, our team comprises leading experts in solar physics, spectropolarimetry, wave analysis, and numerical modelling, ensuring that the project benefits from state-of-the-art methodologies.
Our project will utilise unique high-resolution observations from the Sunrise III balloon-borne solar observatory, which employed its 1m telescope (the largest solar telescope to ever leave the ground) to capture distortion-free spectropolarimetric data of a complex-shaped sunspot near the centre of the solar disk on 14 July 2024, making these observations incredibly timely. These novel, high time-resolution observations include more than 100 spectral lines from neutral and ionised atoms, and following the application of cutting-edge spectropolarimetric inversion routines (e.g., DeSIRe/SPINOR), will allow us to construct a stratified picture of velocity, temperature, density, and magnetic field fluctuations across different heights in the Sun's lower atmosphere. Sophisticated analysis methods, such as those detailed in the project team's WaLSAtools (https://WaLSA.tools) online repository, will then be used to identify distinct wave patterns, track their evolution, and determine the mechanisms underpinning their energy dissipation.
In parallel, we will employ advanced MHD simulations, such as the Mancha3D code, to model wave behaviour in a realistic environment that is based on the observed sunspot structure. These simulations will allow us to compare numerical signatures with those observed in the Sunrise III spectra to identify and benchmark the ion-neutral interactions (e.g., ambipolar diffusion) and establish their role in wave-driven plasma heating.
Our combined efforts of high-resolution observations and numerical modelling will provide a step-change in understanding how waves transport and dissipate energy within sunspots, and will also contribute to broader questions in solar physics, such as how magnetic energy is transformed into heat and how non-equilibrium processes affect plasma diagnostics. Ultimately, our proposed research helps to explain fundamental processes occurring in the Sun, with implications for understanding plasma behaviour throughout the universe.
Sunspots play a crucial role in energy transport across the Sun's lower layers (i.e., the photosphere and chromosphere extending around 2000km above the visible surface). Here, strong magnetic fields act as conduits for magnetohydrodynamic (MHD) waves. Observing how these waves propagate, interact, and dissipate is key to unravelling the long-standing mystery of how the Sun's atmosphere remains continuously heated.
A key question in our proposed research is whether sunspots with more irregular shapes display increasingly complex wave behaviour, particularly higher-order wave modes that are believed to dissipate their energies more readily. By decomposing a sunspot's wave field into constituent MHD modes, we will be able to determine how much energy these waves contribute to the atmosphere's overall energy budget, where and how they lose energy, and whether the dissipated energy produces measurable heating signatures in the surrounding plasma. Additionally, our proposed research will examine the wave-driven interactions between charged ions and neutral atoms (through processes such as ambipolar diffusion) to investigate the role partial ionisation effects play in wave dissipation processes throughout the solar atmosphere. This final question will only be made possible through the fusion of high resolution spectropolarimetric observations with modern MHD numerical simulations. Thankfully, our team comprises leading experts in solar physics, spectropolarimetry, wave analysis, and numerical modelling, ensuring that the project benefits from state-of-the-art methodologies.
Our project will utilise unique high-resolution observations from the Sunrise III balloon-borne solar observatory, which employed its 1m telescope (the largest solar telescope to ever leave the ground) to capture distortion-free spectropolarimetric data of a complex-shaped sunspot near the centre of the solar disk on 14 July 2024, making these observations incredibly timely. These novel, high time-resolution observations include more than 100 spectral lines from neutral and ionised atoms, and following the application of cutting-edge spectropolarimetric inversion routines (e.g., DeSIRe/SPINOR), will allow us to construct a stratified picture of velocity, temperature, density, and magnetic field fluctuations across different heights in the Sun's lower atmosphere. Sophisticated analysis methods, such as those detailed in the project team's WaLSAtools (https://WaLSA.tools) online repository, will then be used to identify distinct wave patterns, track their evolution, and determine the mechanisms underpinning their energy dissipation.
In parallel, we will employ advanced MHD simulations, such as the Mancha3D code, to model wave behaviour in a realistic environment that is based on the observed sunspot structure. These simulations will allow us to compare numerical signatures with those observed in the Sunrise III spectra to identify and benchmark the ion-neutral interactions (e.g., ambipolar diffusion) and establish their role in wave-driven plasma heating.
Our combined efforts of high-resolution observations and numerical modelling will provide a step-change in understanding how waves transport and dissipate energy within sunspots, and will also contribute to broader questions in solar physics, such as how magnetic energy is transformed into heat and how non-equilibrium processes affect plasma diagnostics. Ultimately, our proposed research helps to explain fundamental processes occurring in the Sun, with implications for understanding plasma behaviour throughout the universe.
People |
ORCID iD |
| David Jess (Principal Investigator) | |
| Shahin Jafarzadeh (Researcher) |