Coronal mass ejections are colossal eruptions of magnetized plasma that the Sun hurls into interplanetary space, sometimes with enough force to trigger geomagnetic storms when they strike Earth’s magnetic shield. Streamer blowout CMEs are a particularly intriguing subset. They erupt from within the streamer belt, the band of dense, helmet-shaped magnetic structures that encircles the Sun’s equator, and their passage leaves the streamer visibly inflated, disrupted, and ultimately blown apart. Because these events often lack the dramatic low-coronal signatures of more impulsive eruptions, they can be difficult to detect and classify, and their origins remain debated among solar physicists.

The research team, led by Leonardo Di Lorenzo of the INFAP institute at the Universidad Nacional de San Luis and CONICET in Argentina, together with colleagues from Argentina, the United States, Belgium, Romania, and Germany, focused on three candidate streamer blowout events from 2013. To follow these eruptions from their earliest moments, the team paired extreme ultraviolet images from the SWAP instrument aboard the PROBA2 satellite and the EUVI telescopes on NASA’s twin STEREO spacecraft with white-light coronagraph data from LASCO on the SOHO observatory and the SECCHI suite on STEREO. This combination allowed the scientists to track the eruptions continuously from below two solar radii, where most coronagraphs lose sight of the action, out to heliocentric distances approaching twenty solar radii.

The multi-viewpoint approach proved essential. Using tie-point triangulation, a geometric technique that combines simultaneous observations from separated spacecraft to pin down true three-dimensional positions, and the Graduated Cylindrical Shell forward-modeling method, which fits a hollow flux-rope shape to coronagraph images, the researchers derived continuous kinematic profiles for both the erupting prominences and the leading edges of the CMEs. Because streamer blowout events unfold over significantly longer timescales than typical CMEs, the team could sample the leading edge in far greater detail than is usually possible, and this denser sampling paid off with an unexpected discovery.

All three events displayed a characteristic slow-to-fast kinematic evolution: an initial slow-rise phase followed by a faster, roughly linear ascent. What surprised the researchers was where the transition between these two phases occurred. For conventional CMEs, the change in slope of the height-time profile typically appears at relatively low altitudes, but in these streamer blowout events the transition took place at heliocentric distances of approximately 3.5 to 4.5 solar radii, considerably higher in the corona. The sharpness of the transition also varied from event to event. The third event in the sample stood out in particular, showing a notably shorter streamer swelling phase and a smoother, more gradual shift from slow to fast motion than its two companions.

These findings carry real weight for space weather forecasting. The height at which a CME transitions from slow rise to rapid acceleration influences how much warning time forecasters have before the eruption reaches Earth, and understanding the kinematic signatures of different CME classes helps refine models of eruption initiation. The results suggest that streamer blowout CMEs occupy a distinct niche in the CME population, characterized by their extended timescales and the unusually high altitudes at which their acceleration phase begins, signatures that could help identify such events even when their low-coronal precursors are faint or absent.

To understand the magnetic environment from which these eruptions emerged, the team turned to potential field source surface, or PFSS, modeling, a widely used technique that extrapolates the Sun’s measured surface magnetic field into the corona under simplifying assumptions. Combined with the observed positions of white-light streamers, the PFSS analysis placed all three events within the large-scale streamer belt environment, consistent with the streamer blowout classification. However, the study also exposed a sobering limitation of this approach. When the researchers used different input magnetograms and different source-surface heights, the resulting magnetic extrapolations disagreed with one another, sometimes substantially, making it impossible to uniquely determine the underlying magnetic topology of the events from PFSS modeling and coronagraph observations alone.

This ambiguity matters because distinguishing between a helmet-streamer configuration and a pseudostreamer configuration fundamentally changes how scientists interpret an eruption’s origin and evolution. The team’s extensive validation effort, which included quantitative comparisons between modeled open-field regions and observed coronal holes using overlap metrics such as the Jaccard index and boundary-distance measures across multiple magnetogram types and source-surface heights, showed that no single configuration was definitively superior for every event. The authors conclude that identifying streamer blowout events reliably will require magnetic field models that go beyond the simplifying assumptions of PFSS and provide a more realistic representation of the coronal magnetic configuration, such as magnetohydrodynamic simulations.

The study also underscores how much the era of multi-vantage solar observation has transformed the field. Only by viewing the Sun from separated spacecraft simultaneously could the researchers accurately reconstruct the three-dimensional evolution of the eruptions, constrain their initiation heights, and characterize their early development in relation to the surrounding magnetic structures. As the Sun progresses through its activity cycle, events like these offer a window into the quiet, drawn-out side of solar explosiveness, a reminder that not every storm announces itself with fireworks, and that some of the most important eruptions build slowly in the tangled magnetic architecture of the streamer belt before finally breaking free.

Subject of Research: Multi-viewpoint and multi-wavelength analysis of the morphology and kinematics of streamer blowout coronal mass ejections

Article Title: A Closer Look at Streamer Blowout Coronal Mass Ejections: Multi-Wavelength and Multi-Viewpoint Analysis of Morphology and Kinematics

Article References: Di Lorenzo, L., Cremades, H., López, F. M., Balmaceda, L. A., Talpeanu, D.-C., D’Huys, E., Mierla, M., Lloveras, D., & Aznar Cuadrado, R. (2026). A Closer Look at Streamer Blowout Coronal Mass Ejections: Multi-Wavelength and Multi-Viewpoint Analysis of Morphology and Kinematics. Solar Physics, 301(9), Article 135. https://doi.org/10.1007/s11207-026-02724-z

Image Credits: AI Generated

DOI: 10.1007/s11207-026-02724-z

Keywords: coronal mass ejections, streamer blowout, solar physics, space weather, STEREO, SOHO LASCO, PROBA2 SWAP, tie-point triangulation, Graduated Cylindrical Shell model, PFSS modeling, streamer belt, solar corona