Recent high-fidelity observations from ESA’s Solar Orbiter initiative have revealed that solar flares are instigated by a sequence of cascading magnetic reconnection phenomena, leading to the discharge of immense energy and the descent of plasma aggregates throughout the Sun’s atmospheric envelope.
Overview of the impulsive phase of an M-class solar flare, observed by ESA’s Solar Orbiter. Image credit: ESA / Solar Orbiter / Chitta et al., doi: 10.1051/0004-6361/202557253.
Solar flares are characterized as potent energetic outbursts emanating from the Sun.
These events are precipitated by the sudden release of energy sequestered within intricate magnetic field configurations, a process scientifically termed ‘reconnection.’
Within a brief temporal span, magnetic field lines that intersect and possess opposing orientations undergo fracture and subsequent rejoining.
The newly reformed magnetic field lines possess the capacity to rapidly escalate in temperature and propel plasma heated to millions of degrees, along with high-energy particles, away from the point of reconnection, thereby potentially generating a solar flare.
The most significant flares may initiate a cascade of reactions culminating in geomagnetic disturbances impacting Earth, possibly inducing radio communication disruptions, underscoring the paramount importance of their ongoing observation and comprehension.
However, the intricate mechanisms governing the remarkably swift liberation of such colossal energy reserves have heretofore remained inadequately elucidated.
An unparalleled collection of novel Solar Orbiter observations, derived from the synergistic operation of four mission instruments providing the most comprehensive depiction of a solar flare ever obtained, has now furnished a compelling explanation.
High-resolution imaging captured by Solar Orbiter’s Extreme Ultraviolet Imager (EUI) provided magnified views of structures measuring mere hundreds of kilometers across within the Sun’s outermost atmospheric layer (its corona), documenting transformations occurring every two seconds.
An additional trio of instruments—SPICE, STIX, and PHI—undertook analyses across a spectrum of depths and thermal regimes, extending from the corona down to the Sun’s visible surface, known as the photosphere.
“We were exceptionally fortunate to witness the preceding phenomena of this substantial flare with such remarkable clarity,” remarked Dr. Pradeep Chitta, an astronomer affiliated with the Max Planck Institute for Solar System Research.
“Acquiring such detailed, high-frequency observations of a flare is not consistently feasible due to temporal observational constraints and the substantial memory requirements for data of this nature on the spacecraft’s onboard computer.”
“Indeed, we were positioned optimally in both space and time to capture the granular specifics of this particular flare.”
The data acquired by Solar Orbiter elucidated a comprehensive panorama of the pre-flare and impulsive phases of a solar flare’s central mechanism, manifesting as a magnetic avalanche.
“We observed ribbon-like formations exhibiting extremely rapid downward movement through the Sun’s atmosphere, preceding the primary eruptive phase of the flare,” stated Dr. Chitta.
“These streams of descending plasma aggregates serve as indicators of energy deposition, which augment in intensity as the flare progresses.”
“Even after the flare activity has subsided, this plasma descent persists for a duration.”
“This represents the inaugural instance of observing such phenomena at this degree of spatial and temporal resolution within the solar corona.”
“We had not anticipated that the avalanche process could be instrumental in generating such high-energy particles.”
“Considerable research remains necessary to fully comprehend this process, and this will necessitate even more refined X-ray imaging capabilities from forthcoming missions for complete disentanglement.”
“This constitutes one of the most significant findings from Solar Orbiter to date,” commented Dr. Miho Janvie, co-project scientist for ESA’s Solar Orbiter.
“The observational data from Solar Orbiter illuminate the core mechanism driving a flare and underscore the critical role played by an avalanche-like magnetic energy release process in action.”
“An intriguing question to pursue is whether this mechanism is ubiquitous across all flares and whether it operates on other stellar bodies that exhibit flaring activity.”
The findings have been published in the esteemed journal Astronomy & Astrophysics.
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L.P. Chitta et al. 2026. A magnetic avalanche as the central engine powering a solar flare. A&A 705, A113; doi: 10.1051/0004-6361/202557253
