Uncovering the Sun's Swirling Jets

Overview

The Sun is the closest star to Earth, and it impacts us in a variety of ways, many of which are not well understood. Radiation from the Sun plays a role in influencing our planet’s climate, and its violent plasma storms directly impact Earth’s space environment, which can lead to significant disruptions of technologies we depend on, such as GPS reception and power grid stability. To better understand how the Sun’s atmosphere is shaped and heated, and how it impacts Earth, our team is simulating a small piece of the Sun in a computational box that could hold the Earth six times over, and comparing the results with high-resolution solar observations from NASA’s Interface Region Imaging Spectrograph (IRIS) Mission. Harnessing the power of NASA’s Pleiades supercomputer, we show for the first time how such jets naturally occur in simulations of the solar atmosphere.

Project Details

This project uses advanced, multi-dimensional radiative magnetohydrodynamic (MHD) simulations to take into account the complex physical processes that power the Sun’s atmosphere. We compare the properties of simulated features, such as jets, with real features in the solar atmosphere observed with NASA’s IRIS observatory. This combination of numerical modeling and observations is focused on revealing how the outer solar atmosphere is heated to much greater temperatures than those at the Sun’s surface through the dissipation of magnetic field energy—in particular, how ion-neutral interactions affect the formation, evolution, and recurrence of violent ejections of plasma.

Results and Impact

By comparing the results of our simulations with images and spectra taken by the IRIS observatory, we have been able to explain some of the mission’s puzzling findings. For example, the simulations helped reveal how small-scale magnetic fields can release energy and mass that impact the lower solar atmosphere, or chromosphere. Understanding the properties of the chromosphere is important, since this layer of the Sun is the source of most of the ultraviolet radiation that impacts Earth’s upper atmosphere.

Our simulations bring critical insight into the physical mechanisms that drive some of the violent events observed by IRIS. They have also provided much needed advances in how to interpret the complex radiation data recorded by the solar observatory. The combination of simulations and observations is crucial to solve a fundamental puzzle in solar physics: how magnetic fields energize the atmosphere.

Why HPC Matters

Numerical modeling of the complex radiative transfer and physical processes of the Sun, combined with the enormous contrasts of density, temperature, and magnetic field within the solar atmosphere, demands powerful supercomputing resources. We use the massively parallel capabilities of the Pleiades supercomputer at the NASA Advanced Supercomputing facility at NASA’s Ames Research Center for both the MHD simulations and for performing detailed calculations of the radiation emerging from the simulations. Approximately 0.8 million processor hours were required to compute one hour of solar time.

What’s Next

As we learn more from the discrepancies between the observations and simulations, we are producing new solar simulations with much higher spatial resolution. These will better resolve some of the dominant spatial scales in the solar atmosphere. We will also simulate larger computational volumes to capture the large-scale behavior of the Sun’s magnetic field, expanding to 3D domains and different magnetic environments. This is expected to lead to better agreement with IRIS observations, which will provide a better understanding of mass and energy release mechanisms at work in our closest star.

More Information

• Scientists Uncover Origins of the Sun’s Swirling Spicules
• On the Generation of Solar Spicules and Alfvénic Waves
• See additional images/videos related to this demo in our media gallery.
• See the poster for this demonstration (PDF, 3.7MB), as shown in the NASA booth at SC17.