Special Seminar: Maarit Käpylä "The Enigmatic Magnetic Fields of the Sun – and Why Should One Care About Them?"

The Enigmatic Magnetic Fields of the Sun – and Why Should One Care About Them?

Maarit Käpylä

Abstract:

The solar magnetic field exhibits remarkable properties - while observations show a very chaotic behavior instantaneously, the long-term behavior shows coherence over space and time. The sunspots, for example, arrange themselves in preferred latitude bands over the solar surface. This latitude band migrates towards the equator in an eleven-year cycle, after which the polarity of the sunspot pairs changes sign, the magnetic cycle hence being 22 years long. When the magnetic activity level of the Sun is high, the space weather is generally bad, meaning that eruptive events, such as flares and coronal mass ejections are ignited, disturbing communication systems and power grids at Earth and endangering space missions and forcing airplanes to re-route.

Explaining the existence of such coherence in a chaotic medium, and how the eruptive phenomena arise during this process, has turned out to be extremely challenging, and debate about how this so called dynamo mechanism actually operates in the Sun continues. One of the challenges, preventing analytical treatment of the problem, is the vigorous turbulence that prevails in the solar convection zone. Much – if not all - relies on numerical modelling. In this talk I will discuss the challenges related to the numerical modelling of the solar dynamo, recent progress that we have been able to make, and my concrete ideas how to go forward. Most importantly, I will present ideas on how to build societally relevant applications from my research.

Bio:

Maarit Käpylä is a computational astrophysicist, who has worked on a wide variety of real-world applications, developing and using a versatile toolbox of high-performance data analysis and numerical modelling applications. Her work, at the intersection of applied mathematics, astrophysics, and computer science, aims at explaining magnetism in astrophysical objects, ranging from the Sun to other stars, accretion disks around them, up to galaxies. During her awards-winning PhD work she developed the first self-consistent numerical model of the galactic dynamo, driven by supernova explosions. Recently, she has concentrated on the Sun and its dynamo mechanism, which has crucial relevance for the modern civilization: our society is becoming increasingly vulnerable to bad space weather, which, in turn, is directly driven by solar magnetism. Maarit’s research efforts have led to the development of one of the most sophisticated models of the solar interior. Such models contain huge potential to serve as a laboratory to understand and extract the key variables related to the formation of eruptive active regions. In the focus of her current research is to build data analysis tools to extract such information from the models, and use that knowledge to build automated tools that can predict the emergence of eruptive active regions based on observational signatures.