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Self-consistent numerical simulations for the formation and dynamics of solar prominences

This paper presents comprehensive 3D numerical simulations demonstrating that solar prominences form self-consistently through a combination of random chromospheric plasma ejections and coronal condensation, highlighting the critical role of subsurface dynamics in their formation and potential eruptions.

Original authors: Lisa-Marie Zessner, Robert H. Cameron, Sami K. Solanki, Damien Przybylski

Published 2026-05-04

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CC BY 4.0

Original authors: Lisa-Marie Zessner, Robert H. Cameron, Sami K. Solanki, Damien Przybylski

Original paper licensed under CC BY 4.0 (http://creativecommons.org/licenses/by/4.0/). ✨ This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer

The Big Picture: Floating Clouds on the Sun

Imagine the Sun's surface as a giant, boiling pot of soup. Above this surface lies the "corona," a super-hot atmosphere that is millions of degrees. Floating in this scorching soup are solar prominences. These are massive, cool, and dense clouds of gas.

Think of a prominence like a cold iceberg floating in a hot ocean. It's strange because the ocean is boiling, yet the iceberg stays cool and doesn't melt away immediately. Scientists have known these exist for a long time, but they've never been 100% sure how they form or how they stay together without evaporating.

The Experiment: A Virtual Solar Kitchen

The researchers in this paper didn't just look at the Sun; they built a virtual, 3D computer model of it. They used a sophisticated simulation code called "MURaM" (think of it as a high-end video game engine for physics).

Unlike previous models that only looked at the top layer (the corona), this simulation is special because it cooks the entire meal at once. It simulates:

The photosphere (the Sun's visible surface).
The chromosphere (the layer just above the surface).
The corona (the super-hot outer atmosphere).

By including the surface and the layers below it, they could see how the "churning" motions of the Sun's interior affect the clouds floating above.

How the Prominence Was Born: The "Seed" and the "Rain"

The simulation showed that a prominence doesn't just appear out of nowhere. It forms in two distinct stages, like building a sandcastle:

1. The Seed (The Injection)
First, the simulation needed a starting point. The turbulent, churning gas at the Sun's surface randomly shoots a small, dense "blob" of cool gas up into the hot corona.

Analogy: Imagine a geyser suddenly shooting a splash of cold water high into a hot steam room. This splash is the "seed."
In the simulation, this seed gets caught in a magnetic "bowl" (a dip in the magnetic field lines) and stays there. Without this initial seed, the prominence never starts.

2. The Growth (Condensation and More Seeds)
Once the seed is stuck in the magnetic bowl, the prominence starts to grow in two ways:

The Rain (Condensation): Hot gas from the surrounding corona flows down the magnetic lines toward the cool seed. As it hits the cool seed, it loses energy and turns into more cool, dense gas, adding to the pile.
More Splashes (Turbulent Injection): The simulation showed that the Sun doesn't stop after the first splash. The churning surface keeps shooting more cool blobs up into the magnetic bowl.
The Result: The paper found that while the "rain" (condensation) helps, the splashes (injections) from the surface actually provide the majority of the mass (about 60–80%).

The Dance: Waving and Draining

The prominence isn't a static statue; it's alive and moving.

The Sway: The magnetic field holds the cloud up, but it's not a rigid cage. The cloud sways back and forth like a heavy curtain in a breeze.
The Drain: Sometimes, the cloud gets too heavy or tilts, and the cool gas "rains" back down to the Sun's surface. This is called "draining."
The Cycle: The simulation showed a constant cycle: the Sun shoots up new material, the cloud grows, it sways, some of it falls back down, and the cycle repeats. The cloud is stable for hours, but it is constantly changing its shape and mass.

What They Found

The researchers ran three different versions of this simulation with slightly different magnetic setups.

The Match: The clouds they created looked very much like the real prominences astronomers see through telescopes. They had the right temperature, density, and "fine structure" (the tiny threads and swirls seen in real photos).
The Key Insight: The most important discovery is that you cannot understand how these clouds form without looking at the Sun's surface. The random, turbulent motions below the surface are the engine that drives the whole process. If you ignore the surface, you miss the "seed" that starts the whole show.

Summary

In short, this paper used a super-computer to simulate the Sun from the inside out. They discovered that solar prominences are like floating clouds built by a chaotic construction crew:

The surface randomly shoots up a seed of cool gas.
The magnetic field catches it in a bowl.
Hot gas rains down to fill the bowl, while the surface keeps shooting up more seeds.
The whole thing sways and drains, creating a dynamic, living structure that matches what we see in the sky.

This proves that to understand these beautiful solar features, we have to look at the whole Sun, not just the top layer.

1. Problem Statement

Solar prominences are cool, dense plasma structures suspended in the hot solar corona. While they are ubiquitous and can persist for days to months, their formation mechanisms remain a subject of debate.

The Gap: Existing models often treat prominence formation using heuristic initial conditions or focus on isolated atmospheric layers (e.g., only the corona). They frequently lack a self-consistent treatment connecting the turbulent convection zone and photosphere to the chromosphere and corona.
The Question: How do the dynamics at and below the solar surface (photosphere/chromosphere) influence the initiation, mass supply, and evolution of solar prominences? Specifically, what is the relative role of direct plasma injection versus in-situ condensation?

2. Methodology

The authors performed comprehensive, fully three-dimensional (3D) radiative magnetohydrodynamic (MHD) simulations using the MURaM code.

Code Capabilities: MURaM is a "box-in-a-star" code that explicitly treats energy transport across all solar atmospheric layers:
- Photosphere: Includes turbulent convection and small-scale dynamo action.
- Chromosphere: Uses non-equilibrium (NLTE) treatment of hydrogen ionization and multi-group scattering radiation transfer.
- Corona: Includes optically thin radiative losses and field-aligned heat conduction.
Simulation Setup:
- Three distinct runs were conducted: Run I and Run II (based on non-sheared, potential magnetic field configurations with different field strengths and convection zone depths) and a Shear Run (Run I with an imposed shear to mimic active region conditions).
- Initial Conditions: A quadrupolar magnetic field structure was established with dipped magnetic field lines (magnetic dips) essential for supporting plasma against gravity.
- Boundary Conditions: The lower boundary pins magnetic footpoints to the convection zone, allowing turbulent motions to drive the system. Horizontal boundaries are periodic; the upper boundary is open with a potential field extrapolation.
Physics Included: The simulations solve the non-ideal MHD equations, including the Lorentz force, gravity, radiative cooling/heating, and Spitzer heat conduction. Both Local Thermodynamic Equilibrium (LTE) and Non-LTE (NLTE) versions were used, with LTE results forming the main analysis and NLTE used for synthetic H $\alpha$ emission.

3. Key Contributions

Self-Consistent Formation: This is the first simulation to demonstrate the spontaneous, self-consistent formation of a solar prominence starting from a realistic photospheric convection zone, without manually injecting plasma or imposing artificial heating profiles.
Dual Mass Supply Mechanism: The study identifies and quantifies a hybrid mechanism for mass accumulation:
1. Turbulent Injection: Random ejections of dense, cool chromospheric plasma blobs driven by subsurface convection.
2. Radiative Condensation: Siphon flows of hot coronal plasma that cool and condense onto the existing structure due to radiative instability.
Role of Subsurface Dynamics: The paper establishes that the turbulent driving from the convection zone is not merely a background noise but a critical driver for the initial "seed" injection and ongoing mass supply.

4. Key Results

Formation Process

Initiation: Prominence formation begins with the random ejection of a dense "seed" blob of cool plasma from the chromosphere into the magnetic dips.
- In Run I, seeds are injected along small magnetic loops on the side.
- In Run II, seeds are ejected from below the magnetic dips (polarity inversion line).
Growth: Once the seed settles, two processes sustain growth:
- Condensation: Hot coronal plasma flows along field lines toward the cool seed, loses energy via radiation, and condenses (siphon flow).
- Continued Injection: The turbulent convection continues to eject additional cool blobs, which merge with the structure.
Mass Budget: The simulations reveal that turbulent injection is the dominant mass supply mechanism, contributing 58–82% of the total mass, while condensation contributes 18–42%.

Dynamics and Stability

Oscillations and Draining: The formed prominences exhibit dynamic stability, swaying side-to-side. During these oscillations, cool plasma occasionally drains back down to the chromosphere along field lines.
Run I vs. Run II:
- Run I: The prominence remains stable for the entire 12-hour simulation, with mass increasing slightly over time.
- Run II: The prominence is unstable; it forms, drains completely in a massive event, and reforms multiple times.
Flow Patterns: The simulations reproduce observed counter-streaming flows (upflows and downflows side-by-side), a hallmark of prominence fine structure.

Comparison with Observations

Fine Structure: The simulated fine structures (turbulent, vertical, and horizontal filaments) qualitatively match observations from the Hinode Solar Optical Telescope (SOT).
- Non-sheared runs resemble intermediate and quiescent prominences.
- The Shear Run produces horizontal structures typical of active region prominences.
Physical Parameters: The simulated cores show temperatures of 6,000–8,000 K and densities of $10^{-13}$ – $10^{-12}$ g cm $^{-3}$ , consistent with observational data. Magnetic field strengths range from 15–80 G, fitting active and intermediate prominence regimes.
Synthetic Emission: The study successfully generated synthetic H $\alpha$ and AIA 171 images, showing absorption features and fine structures comparable to real solar data.

5. Significance

Paradigm Shift: The results challenge the view that prominences form solely via evaporation-condensation or levitation. Instead, they highlight a unified model where subsurface turbulence provides the initial seed and continuous mass supply, which is then augmented by coronal condensation.
Space Weather Implications: Since prominence mass can trigger or influence eruptions (Coronal Mass Ejections), understanding the subsurface dynamics driving mass accumulation is crucial for improving long-term space weather forecasts.
Model Validation: By successfully reproducing the formation, fine structure, and dynamic behavior of prominences in a self-consistent framework, the MURaM code is validated as a powerful tool for studying the coupled solar atmosphere.

In conclusion, this paper demonstrates that the formation of solar prominences is a complex, multi-layered process driven by the interplay between subsurface convection and coronal thermodynamics, with turbulent injection playing a more significant role in mass supply than previously assumed in purely coronal models.