Investigating the impact of energetic particle precipitation on middle atmosphere climate chemistry using high altitude measurements of NO in conjunction with AMPERE.

The influence of solar activity on the coupled magnetosphere-ionosphere-neutral atmosphere system has significant impact on middle atmosphere climate chemistry. It is now considered a driver for influencing the concentration of chemical species such as Nitric Oxide (NO) which can act catalytically to deplete ozone. This is important as its removal in the stratosphere alters the temperature distribution of the atmosphere, leading to major consequences for the environment, such as hindering plant growth and disrupting ecosystems. We present a multi-instrumental study which combines satellite measurements linking the energy transfer from energetic particle precipitation (EPP) into the upper atmosphere to the formation of nitric oxide in the mesosphere via the “direct effect” and stratosphere via the “indirect effect”. The former is characterised by an enhanced and localised stream of NO in the path of the particles traveling through the atmosphere. The “indirect effect” is a secondary enhancement due to the transport of the NO generated by the direct effect into the stratosphere via atmospheric processes such as the residual circulation, zonal winds and the polar vortex.

The study utilises the Solar Occultation For Ice Experiment (SOFIE) dataset, extending the work by Smith-Johnson et al. (2017), to determine the relative change in NO density over the solar cycle from 2008 to 2019. We have also been able to determine the average response of NO within the mesosphere and stratosphere as a result of geomagnetic storms between 2008 and 2014, through application of a Superposed Epoch Analysis. This demonstrates a strong direct feature at the onset of the storms in both hemispheres. However, the indirect response varies, extending lower into the stratosphere in the southern hemisphere than the northern hemisphere. This analysis is complemented by field aligned currents derived by the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) to analyse the variability in the NO density following periods of intense geomagnetic activity and associated EPP. This will provide a greater understanding of the energy transfer and coupling mechanisms between the magnetosphere, Mesosphere and Lower thermosphere regions (MLT) and the middle atmosphere and offer insights on the impacts of space weather on Earth’s climate.