Magnetic helicity is a measure of the twist and linkage of a magnetic field. Magnetic helicity’s dynamics can tell us important information about CMEs (coronal mass ejections), which can be used for space weather forecasting and prediction, and, therefore, for preventing technological and social hazards for humanity. This helicity significantly influences the strength of CMEs on Earth’s magnetosphere, and currently there are no routine measurements of the CMEs’ magnetic fields.

The CMEs erupt from the sun’s active regions, and, if it’s possible to calculate these active regions’ helicity, following the magnetic helicity’s conservation law, it is possible to calculate the magnetic helicity carried by the CMEs, by calculating the active region’s helicity budget before and after eruptions. With this information it is possible to estimate the geometrical parameters of the CME, such as length and radius, and with the geometrical parameters of the CME and the helicity budget, it is possible to estimate the CME’s magnetic field at near-Sun environment. Considering near-Earth CME’s magnetic field measurements, it becomes possible to understand how these magnetic fields evolve from near-Sun to near-Earth.

You can imagine what was described above by thinking of a football player kicking a ball and trying to score a goal. The player is like the Sun, the ball flying away from the player’s foot is the CME, and the spin the player gives to the ball when kicking it represents the helicity. If the goalkeeper can “measure” the ball’s spin, he can better predict the ball’s trajectory and most likely save it. By calculating the magnetic helicity carried by the CMEs, just like the goalkeeper, we can prevent major damages on many systems we, as a society, rely on, by forecasting these extreme events.

Although the CMEs experience significant drag and magnetic erosion during their path to Earth, understanding their near-Sun magnetic field strength is key to improve storm prediction and reduce the risk of damage, for example, in spacecraft or satellite operations.

If you want to understand in more detail the importance of magnetic helicity on CMEs’ magnetic fields’ evolution from near-Sun to near-Earth environments, watch Shifana Koya’s webinar via: Space Webinar: Investigating the Magnetic Field of Earth-Directed Coronal Mass Ejections – YouTube