Josh Pettit, University of Helsinki

Energetic Particle Precipitation in Earth’s Atmosphere: Thirty Years of MEPED Measurements and What Comes Next

Space weather research has expanded considerably over the past two decades, driven by its significant impacts on Earth’s middle and upper atmosphere. Among the many processes that influence the atmosphere, energetic particle precipitation (EPP) is well known for its substantial effects on both the chemistry and dynamics of these regions. EPP comes in two flavors: electron precipitation and proton precipitation. Proton precipitation is most influential during solar proton events (SPEs), when large fluxes of energetic protons are launched from the Sun, which typically following coronal mass ejections, bombard the middle atmosphere, creating odd nitrogen and destroying ozone directly in the stratosphere. Despite their significance, such events are somewhat rare, occurring mostly in the declining phase of solar maximum. Electron precipitation, on the other hand, is a nearly continuous stream of particles ranging from low, auroral energies of just a few eV to relativistic electrons of several MeV. Despite the lower energies relative to SPEs, their much higher frequency results in larger cumulative chemical impacts in the middle and upper atmosphere. Additionally, odd nitrogen created by ionization from electron precipitation can be transported dynamically throughout the mesosphere, enabling strong coupling between the upper and middle atmosphere. For nearly 30 years, researchers have benefited from the Medium Energy Proton and Electron Detector (MEPED) instruments aboard the Polar Orbiting Environmental Satellites (POES), which provided near-global coverage of electron and proton fluxes. Last year, however, NOAA ended data collection from its fleet of POES satellites, leaving only ESA’s two MEPED instruments aboard the MetOp satellites. Unfortunately, ESA has no plans to fly MEPED on future MetOp missions. This leaves a significant gap in researchers’ ability to monitor electron and proton fluxes for years to come. This seminar will discuss the history of the POES MEPED instruments, the datasets built from them, the research they have enabled, and the outlook for EPP monitoring without these vital measurements.

Passcode: irfseminar