Middle atmosphere, solar variability, and climate interactions

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, volcanoes, wildfires). Solar signals transferred through the middle atmosphere are part of the natural forcing of the climate system; the middle atmosphere in turn can influence tropospheric weather systems and radiation. We apply our knowledge from terrestrial solar forcing to study the atmospheres of Earth-like (rocky) exoplanets in orbits around very active stars.

Photo of a Pyrocumulonimbus cloud NWS Albuquerque
Middle-lower atmosphere interactions
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:

More information

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Recent news and publications

Fluxes of precipitating electrons and the corresponding atmospheric ionizationCC BY
Ring current electron precipitation

Electrons from the ring currents and radiation belts accelerated to hundreds of keV precipitate into the atmosphere during geomagnetic storms. This precipitating flux and the ensuing atmospheric ionization are modelled here with a magnetospheric model, considering different acceleration mechanism within the ring currents.

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A CME of December 2003 seen by different instruments on SOHOSOHO (ESA & NASA)
Towards improved solar forcing for chemistry-climate model experiments

Solar variability is part of the natural forcing of the climate system. For climate model experiments, forcing data of the spectral irradiance and particle fluxes of high precission are necessary over many decades. The forcing data provided for the Coupled Model Intercomparison Project CMIP6 were extensively used for scientific studies and tested in intercomparison experiments; here, a roadmap is discussed for an improved forcing data-set for the upcoming CMIP7. 

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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 eventLarge 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 eventWhat 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.

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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. 

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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.

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