SLAM Research Group

SLAM Research Group

The "Solar Lower Atmosphere and Magnetism" Group (SLAM) is a research group of about 20 people within the Sun and Heliosphere Department of the Max Planck Institute for Solar System Research. Its research activities focuses on the solar lower atmosphere, concerning how the solar magnetic field structures the dynamics of the photosphere and chromosphere layers. 

Magnetic activity of the Sun plays a dominant role in virtually all processes in the solar atmosphere. It is responsible for the energy balance of the outer atmosphere, it causes the activity cycle and the concomitant variability of the solar luminosity and it produces most of the sometimes spectacular visible phenomena, like sunspots, prominences, flares and coronal mass ejections.

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The solar photosphere

“The solar photosphere is the layer in which the magnetic field has been most reliably and most often measured. Zeeman- and Hanle-effect based probes have revealed many details of a rich variety of structures and dynamic processes, but the number of open and debated questions has remained large. The magnetic field in the quiet Sun has maintained a particularly large number of secrets and has been a topic of a particularly lively debate as new observations and analysis techniques have revealed new and often unexpected aspects of its organization, physical structure and origin.”

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The solar chromosphere

“The chromosphere is an intriguing part of the Sun that has stubbornly resisted all attempts at a comprehensive description. Thus, observations carried out in different wavelength bands reveal very different, seemingly incompatible properties. Not surprisingly, a debate is raging between supporters of the classical picture of the chromosphere as a nearly plane parallel layer exhibiting a gentle temperature rise from the photosphere to the transition region and proponents of a highly dynamical atmosphere that includes extremely cool gas...”

Solanki, S. K. 2004, Proceedings of IAU, No. 223, p. 195

The Zeeman effect causes a splitting of spectral lines in sunspots.

Zeeman polarimetry

The empirical study of solar magnetic fields is intimately linked to the measurement and the interpretation of spectra in polarized light. In the presence of a magnetic field light becomes polarized through the Zeeman effect. When the electric vector of the electromagnetic radiation vibrates in a fixed plane, the radiation is called linearly polarised. When the electric vector describes an helix about the direction of propagation, the radiation is said to be circularly polarised. A combination of both usually yields elliptical polarisation. Polarimetry aims at measuring the degree to which a radiation from a light source is polarised, as well the polarisation state of the corresponding light. Polarimetry embraces the most complete and detailed measurement and analysis of light, as well as its interaction with matter.

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