Observed expansion of a solar magnetic cloud
A physics team headed by the University of Iowa has quantified the increase in size of a magnetic cloud that originated from a large solar gas explosion as it traveled toward Earth. The observations were made by two spacecraft that happened to be positioned at different points along the cloud's path.
The cloud traveled roughly 21 million kilometres before encountering Earth, expanding its diameter by about one‑fifth during that journey. Researchers refer to this phenomenon as “super expansion,” noting that the growth coincided with a heating of the plasma trapped inside the magnetic structure.
Data indicate that the plasma temperature rose significantly, pushing magnetic field lines farther apart. Such a coupling of thermal energy and magnetic field dynamics has rarely been documented for solar events of this magnitude.
- Measurements obtained from two independent spacecraft.
- The cloud grew by 20 % over a 21 million‑kilometre distance.
- Plasma heating accompanied the expansion.
The findings improve understanding of space‑weather processes and their possible impacts on satellite operations and terrestrial power grids.