Jupiter experiences a widespread atmospheric heating event following a collision with solar wind, prompting a new perspective on giant planet dynamics. (CREDIT: NASA, ESA, and J. Nichols (University of Leicester))
Jupiter’s atmosphere is known to illuminate with dazzling lights surpassing those seen on Earth. Its polar auroras shine brightly as charged particles collide with the upper atmosphere, generating bursts of energy and heat. While these occurrences are distant from Earth, they offer valuable insights into how the Sun influences not only giant gas planets but also impacts our own planet’s infrastructure, such as power grids, satellites, and GPS systems.
A recent study has unveiled an unexpected correlation between solar activity and Jupiter’s expansive upper atmosphere. Researchers discovered that surges of solar wind – streams of charged particles emanating from the Sun – can collide with Jupiter, compress its magnetic field, and trigger planet-wide waves of heat. While previous assumptions placed these effects solely at the poles, new evidence indicates that the Sun’s influence extends much further.
An Enveloping Aura of Gas and Energy
Extending hundreds of kilometers into space above Jupiter’s swirling clouds, its upper atmosphere comprises a thermosphere of neutral hydrogen gas and an ionosphere teeming with charged particles like electrons and ions. Both components react to energy from Jupiter’s magnetosphere and solar radiation.
A notable source of this energy is Io, a volcanic moon ejecting gas into space. As this gas disperses and becomes ionized by sunlight, it permeates Jupiter’s magnetosphere with plasma. With the planet’s rapid rotation every 9 hours and 56 minutes, its magnetosphere whips around, generating electric currents between the magnetosphere and ionosphere that contribute to the formation of Jupiter’s iconic auroras.
At the poles, these auroras elevate the upper atmosphere’s temperature to over 900 K (approximately 627°C), whereas temperatures elsewhere hover around 700 K (427°C). Solar heating alone would yield temperatures as low as 200 K, presenting a significant 500 K disparity that has puzzled scientists for decades.
Theories of Thermal Transport: Waves and Circulation
To address this thermal anomaly, researchers proposed two primary theories. One posited that waves originating deep within Jupiter – gravity and acoustic waves – could propagate upward and transport heat, while the other suggested that heat from the polar regions could distribute across the planet.
Gravity waves were found to elevate temperatures by a few dozen degrees, while acoustic waves could produce temperature increases of several hundred degrees. In 2016, a hot region above Jupiter’s Great Red Spot surpassed 1,600 K, believed to be due to acoustic heating. However, subsequent investigations did not identify similar hotspots, casting doubt on this explanation.
The focus then shifted back to global circulation as a means of heat distribution. One model demonstrated how heat from the poles could migrate towards the equator. Observations indicated that auroral temperatures declined more rapidly than radiation alone could
Poles, causing limited movement on a large scale. Then, a new discovery emerged: a significant surge of heat. In 2017, scientists utilized the Keck telescope to create detailed maps of Jupiter’s upper atmosphere. What they found was unexpected—an extensive warm zone located far from the poles. This warm region spanned 160 degrees of longitude, nearly half the planet, with temperatures reaching 950 K, which was 200 K higher than the surrounding areas.
The warmth observed was linked to H3+ temperatures and the sub-auroral hot feature, captured at local noon on the planet. Researchers speculated that this unusual feature may have originated from the poles and slowly drifted towards the equator. Doppler measurements revealed that winds in the auroral regions moved swiftly at hundreds of meters per second, while the warm region seemed to be moving away from the auroral oval at a speed of 620 meters per second. However, the initial estimates only considered changes in latitude, lacking a comprehensive understanding of the situation.
The likely cause of this heat surge was believed to be a strong solar wind blast. Concurrently, data from NASA’s Juno spacecraft indicated a remarkable finding—Jupiter’s magnetic field, which typically extends far into space, had been significantly compressed. This compression was attributed to a surge in solar wind, characterized by an influx of dense and fast-moving particles from the Sun.
Dr. James O’Donoghue, the lead author of the study published in Geophysical Research Letters, highlighted the unprecedented nature of Jupiter’s response to solar wind. The solar wind compressed Jupiter’s magnetic field, leading to increased energy at the poles, resulting in the heating and expansion of the upper atmosphere. This phenomenon generated powerful winds that propelled hot gases towards the equator, creating a vast region of elevated temperatures exceeding 500°C.
The study advanced further by combining Juno data, Keck telescope maps, and solar wind models to track the movement of heat across Jupiter’s atmosphere. By estimating the arrival of the solar wind and observing how rapidly the atmosphere reacted, researchers gained valuable insights into the dynamics of such events. For the first time, velocity measurements were taken across all longitudes, providing crucial information about how the heat feature migrated and aiding in determining its launch time. These findings suggested that solar wind impacts on Jupiter could occur frequently, potentially two to three times a month.
A researcher from the University of Reading stated, “Our solar wind model accurately predicted the disruption of Jupiter’s atmosphere, enhancing our understanding of the reliability of our forecasting systems crucial for safeguarding Earth from hazardous space weather.” These discoveries challenge existing beliefs about giant planets, as it was commonly thought that their size and rapid rotation made them less susceptible to solar influences. However, Jupiter’s reaction demonstrates that even distant planets can be significantly impacted by solar storms.
The Keck telescope, located at the W. M. Keck Observatory, plays a key role in studying these phenomena. Solar wind storms also pose a threat to Earth’s magnetic field, potentially causing damage to satellites, disruptions in GPS signals, and power outages. By observing Jupiter’s responses to such events, researchers can refine their predictions regarding the potential effects of solar storms on Earth.
Despite Jupiter’s vast distance of over 700 million kilometers, it serves as an invaluable laboratory for the study of space weather. Each encounter with solar wind offers insights into planetary reactions, atmospheric heat distribution, and the transformative effects of cosmic energy on celestial bodies within our solar system. With ongoing missions like Juno and advanced technologies such as the Keck telescope, scientists are making strides in monitoring these significant energy fluctuations. This study has revealed that Jupiter’s upper atmosphere is more dynamic and susceptible than previously assumed.
