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Disputation: Henrik Eklund

Doctoral candidate Henrik Eklund at the Institute of Theoretical Astrophysics, Faculty of Mathematics and Natural Sciences, is defending the thesis “Investigating dynamic small-scale events in the Sun with the Atacama Large Millimeter/sub-millimeter Array” for the degree of Philosophiae Doctor.

portrait photo of a young man, smiling with a blue shirt
Doctoral fellow, Henrik Eklund. Photo: private.

The PhD defence will be fully digital and streamed directly using Zoom. The host of the session will moderate the technicalities while the chair of the defence will moderate the disputation.

Ex auditorio questions: the chair of the defence will invite the audience to ask ex auditorio questions either written or oral. This can be requested by clicking 'Participants -> Raise hand'.

  • Join the disputation

    The meeting opens for participation just before the disputation starts, and closes for new participants approximately 15 minutes after the defence has begun.

Trial lecture


"Life in Icy Worlds? Prospects of the JUICE mission"

The video recording of the trial lecture will be available here from the 20.09.21 – 22.09.21

Conferral summary

Studies of the Sun in the radio regime using highly temporally and spatially resolved interferometric observations of the Sun with the Atacama Large Millimeter/sub-millimeter Array have been performed.

With a combination of the novel solar observations and state-of-the-art numerical simulations, the small-scale dynamics in the solar atmosphere has been studied, which provides further understanding of the dynamic nature of the Sun.

Main research findings

The Sun is dynamic and influences the surrounding planetary system which becomes increasingly imperative to be able to predict as we increase the technology and space exploration. To this end, it is important to understand the transport of energy and the dynamical processes that take place in the solar atmosphere. Radiation at millimeter wavelengths which mainly forms in the mid-layers of the solar atmosphere, the Chromosphere, is a powerful indicator of the temperature of the plasma.

To achieve high sensitivity and resolution, interferometric observations are performed with the Atacama Large Millimeter/sub-millimeter Array (ALMA), which consist of about 66 radio antennas. Many challenges come with interferometric observations of the Sun and the data needs to be carefully handled to reconstruct reliable high frame-rate time-series of images. In the observations, several hundred small-scale dynamic brightening events are detected and their evolution is tracked through time. The origin and physical properties of the brightening events are determined by comparison of their characteristics to state-of-the-art three-dimensional numerical simulations. The accurate temperature measurements of the brightening events provides one step further to understanding the energy transport in the solar atmosphere.

plot showing a real observation of the sun at millimeter wavelengths
Image of solar observation at millimeter wavelengths with ALMA, showing a small part of the Sun. Credits: H. Eklund.


Published Sep. 8, 2021 10:23 AM - Last modified Sep. 14, 2021 10:04 AM