Abstract
Abstract. We investigate Arctic polar atmospheric ozone responses to solar proton events (SPEs) using MLS (Microwave Limb Sounder) satellite measurements (2004–now) and WACCM-D (Whole Atmosphere Community Climate Model) simulations (1989–2012). Special focus is on lower-stratospheric (10–30 km) ozone depletion that has been proposed earlier based on superposed epoch analysis (SEA) of ozonesonde anomalies (up to 10 % ozone decrease at ∼ 20 km). SEA of the satellite dataset provides no solid evidence of any average SPE impact on the lower-stratospheric ozone, although at the mesospheric altitudes a statistically significant ozone depletion is present. In the individual case studies, we find only one potential case (January 2005) in which the lower-stratospheric ozone level was significantly decreased after the SPE onset (in both model simulation and MLS observation data). However, similar decreases could not be identified in other SPEs of similar or larger magnitude. Due to the input proton energy threshold of > 300 MeV, the WACCM-D model can only detect direct proton effects above 25 km, and simulation results before the Aura MLS era indicate no significant effect on the lower-stratospheric ozone. However, we find a very good overall consistency between WACCM-D simulations and MLS observations of SPE-driven ozone anomalies both on average and for the individual cases including January 2005.
Highlights
In the near-Earth space, solar wind charged particles are guided by the Earth’s magnetic field and are able to precipitate into the middle and upper atmosphere in the polar regions
Arctic polar ozone destruction in the mesosphere and upper stratosphere can be directly observed from satellite measurement anomaly, when following solar proton events (SPEs) in September– April with proton fluxes > 400 pfu and > 1000 pfu, respectively
The depletion appears before the epoch time, i.e., SPE onset
Summary
In the near-Earth space, solar wind charged particles are guided by the Earth’s magnetic field and are able to precipitate into the middle and upper atmosphere in the polar regions. Superposed epoch analysis of ozone anomalies at polar stations (Sodankylä, Ny-Ålesund and Lerwick) indicated that SPEs occurring during winter are causing ozone decrease by 5 %– 10 %, on average, at 20 km altitude This effect is not produced in the current models because SPE-induced ionization rates are insignificant at this altitude even during the largest events with high proton energies from 300 to 20 000 MeV (Jackman et al, 2011). Denton et al (2018a, b) included a large number of very small SPEs in their analysis Such ozone decreases have not been observed in the case studies of very extreme (particles with energies > 10 MeV are greater than 10 000 pfu, particle flux units) SPEs, e.g., the 2003 “Halloween” event, from either simulation or satellite observation (Funke et al, 2011, and references therein).
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call