Middle atmosphere, solar variability, and climate interactions

We investigate the solar-terrestrial coupling due to solar wind, solar coronal mass ejections, and solar UV/EUV forcing via the middle atmosphere. The middle atmosphere comprises the altitude region between 10 km and 120 km and is a transition region between the lower atmosphere and space. As such, it is strongly influenced by external (solar) forcings as well as by forcings from below (tropospheric weather systems), and solar signals transferred through the middle atmosphere are part of the natural forcing of the climate system. We apply our knowledge from terrestrial solar forcing to study the atmospheres of Earth-like (rocky) exoplanets in orbits around very active stars.

Aurora seen from the ISS, @ESA, CC BY-SA 3.0 IGO ESA, Space_Aurora.jpg, CC BY-SA 3.0 IGO
Solar variability and the atmosphere
Pale blue dot NASA/JPL - Caltech / Space Science Team
Stellar activity and exoplanetary atmospheres:


The group

Our field of research in a nutshell; People; Projects; Publications.

Theoretical transit spectra of Trappist-1e considering different types of Earth-likes atmospheres, with and without stellar particle events. From Herbst et al, 2023: https://arxiv.org/pdf/2311.04684.pdf
What impact does stellar activity have on observable spectral features of Earth-like exoplanets?

M-stars like Trappist can be much more active than the sun. But how does that affect possible atmospheres of planets in orbit around such starts? And, will that have an impact on the detectability of biosignatures like ozone?

This is explored in a recent publications exemplarily for the exoplanet Trappist 1e.

Draft of the paper on arxiv:
Ozone loss due to the "Halloween" solar storm of October 2003 compared to the AD774/775 extreme eventCC by 4, Copernicus
Large solar particle events and the impact of chlorine ion chemistry

How does a once-per-millenia solar storm compare to the well-known "Halloween" solar storm of October 2003, and does the anthropogenic chlorine loading of the early 20th century increase the impact on stratospheric ozone?

For a short summary, see the EGU blog here

To the publication:
Modelled change of UV index after a once-per-millenia solar extreme eventCC By 4.0 DEED, Copernicus
What would an extreme solar event do to the atmosphere?

Even the largest solar proton events of the last 70 years had a relatively small impact on the atmosphere below 30 km altitude. But what would happen if a much larger solar event as occurred, e.g., in paleonucleid records in AD774/775? We investigated the impact on atmospheric composition and the change in UV radiation at the surface.

Learn more:
Space_AuroraOnline-seminar on energetic electron precipitation

Want to learn more about the impact of electron precipitation from the radiation belts? Watch recent online-seminar from Miriam Sinnhuber:

To seminar talk
Daily mean NOx from MIPAS at 68 km, 14/12/2009Exceptional electron precipitation observed by balloon

Exceptionally electron precipitation was observed by a research balloon on December 14, 2009, in magnetic mid-latitudes. Trace gas observations confirm that precipitation in midlatitudes probably took place, despite low geomagnetic activity. 

To the publication
Mesospheric NO observation compared to model resultsNew results of Heppa III intercomparison experiment published

The High Energetic Particle Precipitation into the  Atmosphere (HEPPA) intercomparison experiment is an international initiative to constrain and improve the representation of (solar) particle precipitation in state-of-the art chemistry-climate models. It is ongoing since 2008. Newest results of round III published recently focus on NO formation during a geomagnetic storm in April 2010.

To the publication