NJIT Student Unveils Shock Sunquake Discoveries at SC22 NASA Exhibit

NJIT Ph.D. physics student John Stefan has new findings about earthquake-like events on the Sun that have recently shaken up the world of space science during one of the biggest international conferences for high-performance computing of the year — the SC22 Supercomputing Conference.

At SC22 in Dallas, TX, Stefan and NJIT physics professor Alexander Kosovichev showcased research at NASA's conference exhibit, which has offered surprising new details about how solar flares generate powerful sunquakes that ripple along the Sun’s surface, similar in effect to earthquakes.

Stefan’s findings have since been featured on the front page of NASA’s Supercomputing Division website.

“It was a lot of fun to present my research to such a diverse crowd at SC22 and get them excited about our nearest star,” said Stefan, a North Brunswick native who was awarded a NASA fellowship to conduct his Ph.D. research. “Not all solar flares generate sunquakes, so it's an active area of research to figure out why this is.”

Sunquakes can take place after solar flares ignite. Solar flares are intense eruptions on the Sun powerful enough to accelerate particles to near-light speed, and when some of these charged particles penetrate the Sun’s surface, they can transfer their energy in the form of pressure waves.

By studying this seismic activity and measuring how long these acoustic waves take to return to the surface, as well as their magnitude, researchers like Stefan can better gauge the location and quantity of energy released from the Sun during a solar flare event.

“Most current solar flare research focuses on how electrons behave after being accelerated and their effects on the local plasma, and since electrons are so much lighter than protons, they tend to be accelerated to much greater speeds and are thought to be responsible for most of the activity we see related to solar flares,” explained Stefan.

“The big question we addressed was whether accelerated protons could be responsible for sunquakes, rather than electrons, and if we could observe a difference in the sunquakes that are generated.”

At NJIT’s Center for Computational Heliophysics, Stefan sought answers to his question by analyzing solar flare models to study heating rates in the Sun’s atmosphere, giving him insight into the particle energies involved.

In the process, he uncovered surprising factors driving the greatest sunquakes.

“We initially expected higher-energy protons would produce stronger sunquakes when they penetrate the solar atmosphere, but we actually found the opposite,” explained Stefan. “It turns out that lower-energy protons are more efficient at transferring momentum through collisions with the plasma in the Sun’s atmosphere and there can be many more of them produced during a solar flare compared to high-energy protons. … The strength of sunquakes is driven by this combination of factors.”

Video: Cross-section of the Sun during and after flare heating. The waves that initially travel upward pass through the thinner layers of the Sun’s atmosphere where the sound speed is much greater, so the wavefront moves more quickly than the downward wavefront. Red corresponds to upward motion of the plasma, blue to downward motion, and intensity to how quickly the plasma is moving. John Stefan, NJIT; Nina McCurdy, NASA/Ames

The findings suggest that a “sweet spot” of particle energies from solar flares may exist that helps explain why some flares generate sunquakes while others do not.

Stefan plans to continue his research into sunquakes with support from an NSF grant awarded to NJIT and University of Colorado-Boulder.

For now, however, Stefan hopes the new findings have not only shed fresh insight into these seismic events, but inspire new investigations into fundamental energy processes behind the most powerful explosions in the solar system.

“We hope our research will broaden interest in studying the energetics of protons in solar flares by showing that protons can be just as important as electrons to the transfer of energy into the solar atmosphere,” said Stefan.