New research suggests that understanding factors common to celestial light shows over Earth, Saturn and Jupiter could help predict risky space weather.
The stunning Northern Lights and Southern Lights are examples of auroras above Earth that are well known to sky watchers. Earlier in May, Earth experienced its most powerful aurora event in 21 years, reminding us of the stunning beauty of these phenomena.
Auroras are generated above our planet’s poles when charged particles that make up the Sun’s solar wind strike Earth’s protective magnetic field known as the magnetosphere. These particles travel along magnetic field lines, interacting with atoms in our atmosphere and causing them to emit light. However, the bombardment of charged particles from the sun does not only create beautiful light shows above the Earth. It can also result in “space weather,” such as geomagnetic storms that sometimes threaten satellites, communications systems and even Earth’s energy infrastructure.
Our planet isn’t the only world in the solar system to experience auroras at the poles. These incredible light shows also take place over the gas giants Jupiter and Saturn, as well as over the icy ice giant Uranus. In fact, auroras should be possible around any planet with an atmosphere and a magnetic field – and, as astronomers discovered in 2018, auroras can also be observed over planets outside the solar system, or ‘exoplanets’.
Related: Colossal X-class solar flare suggests return of sunspot group that fueled May’s epic aurora (video)
The magnetic fields of Earth, Saturn and Jupiter are similar in that they all have a funnel-shaped geometry. This causes energetic particles such as electrons in the solar wind to settle in the polar regions, localizing all but the strongest auroras at the poles of these planets.
However, there are many ways in which auroras are generated over each of these planets, making them unique from each other. Differences in the strength of magnetic fields, the speed at which these planets rotate, the conditions of the solar wind when they impact the planets, and even the activity of moons around these worlds can all result in different auroral structures.
But despite these differences, a team of scientists from the University of Hong Kong’s (HKU) Department of Earth Sciences think that a unified understanding of how the solar wind powers aurora shows across different planets could lead to important practical applications. This unit can help us monitor, predict and explore the magnetic environments of our solar system, including around Earth.
“Our study has revealed the complex interplay between solar wind and planetary rotation, providing a deeper understanding of the auroras on different planets,” Binzheng Zhang, team leader and HKU scientist, said in a statement. “These findings will not only advance our knowledge of the auroras in our Solar System, but may also extend to the study of auroras in exoplanetary systems.”
To study the dynamics of planetary magnetic fields, the team looked at how electromagnetic fields such as those of Earth’s magnetosphere interact with electrically conductive fluids that play the role of charged particles in solar winds. Modeling this in three dimensions allowed them to better understand how auroras over different planets take different shapes or ‘morphologies’. This can then be used to understand how these different auroral morphologies influence different planetary conditions.
It turns out that the combination of solar wind conditions and planetary rotation leads to a new parameter that controls the main structure of auroras. This may explain exactly why different auroral structures are observed on Earth, Saturn and Jupiter. The fact that the different auroras of Earth and Jupiter can be explained using a unified framework came as a big surprise, the team said.
The interaction of stellar winds with planetary magnetic fields is a fundamental process in the cosmos.
So these findings can not only help us better understand the magnetic environment of Earth and the broader solar system, but they can also help us better understand the conditions of distant planetary systems.
The team’s research was published in the journal Nature Astronomy.