Modeling the magnetic cores of solar storms

The Sun produces solar storms, clouds of plasma containing strong magnetic fields which are episodically ejected from its outermost layer. In the space between the planets, they decelerate and expand, and given the right direction, they may sweep over the Earth to produce colorful aurorae in the night sky. Seldomly, their impacts can lead to problems with modern technology such as failures in power grids and global navigation systems. This project is devoted to a better physical understanding of the magnetic fields at their cores, which have a relatively ordered structure in contrast to the turbulent medium they are embedded in, the solar wind. If the solar storm core collides with the Earths magnetic field and only if the storms magnetic field points in the right direction, energy is transferred to the magnetic field of the Earth. Thus, the ordered structures at the storm cores must be better understood in order to predict their effects at the Earth and other planets. We will establish a new type of simulation that can model these cores based on the hypothesis that their shape can be represented by an extremely large bent tube with an embedded special type of magnetic field. Our method represents a new way of modeling solar storms which has several advantages, such as that is computationally very quick, so it can be applied many times with different parameters, and it is designed to be used one day for forecasting solar storm effects at Earth. Especially the wealth of just recently available data from spacecraft residing between the Sun and the Earth makes this project groundbreaking, as we now can test our new model with data of many storms that show a solar storm hitting two or more planets consecutively, for instance first Mercury, then Venus and later Earth. This allows to greatly reduce the free parameters of the simulation in order to find robust results on how solar storms move and evolve between the Sun and the Earth. As a bonus, the Parker Solar Probe is planned to be launched in 2018 and will be the first spacecraft to temporarily reside inside the orbit of Mercury, which could result in unprecedented observations of solar storms close to the Sun. Our new simulation is ideally suited to interpret these groundbreaking observations, which may allow to decipher how the Sun produces the ordered structures in the storm cores and how they propagate towards the Earth.

In this research project, physical models of the magnetic fields inside solar storms were developed, which could subsequently allow better prediction of the effects of solar storms on Earth. Predicting the solar wind that constantly flows around the Earth`s magnetic field is an important future technology to better prepare for potential destructive events such as power supply outages that can result from very strong solar storms. Northern lights could also be better predicted by this kind of weather forecasting for near-Earth space. Solar storms are clouds of plasma containing strong magnetic fields, often ejected from the Suns outermost layer. They often have an ordered structure that can be described as spiral-shaped. Equations that normally describe liquids can be used to model these storms, but one must also consider their magnetic field. This magnetic field is crucial to the effects on Earth, but its large-scale structure is not well understood. One therefore needs data from not just one, but several spacecraft cruising in the solar wind, directly measuring the magnetic field of the storm as the solar storm moves across the spacecraft, comparable to a weather station on Earth. We therefore hope for situations where interplanetary spacecraft such as Parker Solar Probe, Solar Orbiter, BepiColombo, STEREO-Ahead, or Wind are suitably spaced and impacted by the same solar storm, one after another. Combined with our rapid computational model, we were able to better constrain how these magnetic fields look like. During the project, the Solar Orbiter spacecraft was launched, and soon measured a solar storm along with BepiColombo. We were able to show that for the cross section of the storm, an ellipse with an aspect ratio of one to two is a surprisingly good approximation. It was also possible with our new method to fit the model to data from multiple spacecraft simultaneously, for the first time ever. This showed that the assumption of a rigid circular axis of the storm is not a good approximation. We therefore developed a mathematical model that allows an arbitrarily deformed shape of the solar storm. Furthermore, we could show with simulations that it should be possible that the spacecraft Parker Solar Probe, which flies very close to the Sun every few months, could observe a solar storm twice in the next few years and thus finally confirm or disprove the hypothesis of the spiral structure of the magnetic fields. Our models, which provide a basis for improved applied space weather forecasting, are the foundations for application to data from ESA`s "Vigil" mission, which will be launched toward the end of the 2020s and will provide a permanent human outpost for protection from solar storms.