Aarhus University Seal / Aarhus Universitets segl

A greater understanding of solar activity through carbon-14 analysis of tree rings

PhD defence, Friday 18 September 2020. Alexandra Fogtmann-Schulz.

2020.09.18 | Sunitha Satkunam

Alexandra Fogtmann-Schulz

During her PhD studies, Alexandra Fogtmann-Schulz has analyzed carbon-14 in annual tree rings from Danish oak. Carbon-14 is produced in the atmosphere and the production rate varies with changes in the magnetic field of the Sun. The amount of carbon-14 stored in tree rings can therefore tell us about the solar magnetic field in the past. Alexandra Fogtmann-Schulz has studied time intervals with unusual solar activity to try to understand how the solar magnetic cycles changed during these intervals. Furthermore, she has studied past solar outbursts, which caused an unusually high increase in carbon-14 during very few years. A similar solar outburst today would likely have damaging consequences on modern technology, and it is therefore important to study these outbursts to be better prepared.

Alexandra Fogtmann-Schulz’ annual carbon-14 measurements are now part of a new international carbon-14 calibration curve, which is used to date geological or archeological samples.

The PhD study was completed at Department of Geoscience, Faculty of Natural Sciences, Aarhus University.

This summary was prepared by the PhD student.

Time: Friday, 18 September 2020 at 12.00
Place: Building 1671, room 137, the Lecture Theatre, Department of Geoscience, Aarhus University, Høegh-Guldbergs Gade 2, 8000 Aarhus – please note that due to corona restrictions there is only a limited number of seats.
The PhD defence will also be held online. To receive a link to the event, please send an e-mail to Mads Faurschou Knudsen, e-mail: mfk@geo.au.dk, at the latest on the day before the defence
Title of PhD thesis: Studies of Cosmic-Ray Events and Grand Solar Minima using radiocarbon in tree rings
Contact information: Alexandra Fogtmann-Schulz, e-mail: alfosc@geo.au.dk, tel.: +45 2896 5100
Members of the assessment committee:
Professor Ilya Usoskin, Space climate research unit, University of Oulu, Finland
Assistant Professor Michael Dee, Centre for Isotope Research, University of Groningen, the Netherlands
Associate Professor Stéphane Bodin (chair), Department of Geoscience, Aarhus University, Denmark
Main supervisor:
Associate Professor Mads Faurschou Knudsen, Department of Geoscience, Aarhus University, Denmark
Associate Professor Jesper Olsen, Department of Physics and Astronomy, Aarhus University, Denmark
Associate Professor Christoffer Karoff, Department of Geoscience and Department of Physics and Astronomy, Aarhus University, Denmark
Language: The PhD dissertation will be defended in English

The defence is public.

Due to the coronavirus situation, the PhD thesis will not be available for reading at the offices of the PhD administration. Instead, interested parties may send an e-mail to gradschool.nat@au.dk to receive a digital copy of the PhD thesis. Please note, it may in certain cases be necessary to make an individual arrangement to read the PhD thesis.

PhD defence
16882 / i43