During a solar proton event atomic nitrogen is produced by the primary protons in dissociative ionisation of N2 and by the secondary electrons in dissociation of N2. Furthermore, because of the ionisation caused by the primary protons, the ion chemistry can produce atomic nitrogen as well as nitric oxide and be an important additional source of odd nitrogen.
We have studied how ion chemistry contributes to the odd nitrogen production during solar proton events. We found that a significant amount of odd nitrogen can be produced through ion chemistry, which is often neglected in particle event studies. In our study we used the Sodankylä ion and neutral chemistry model, which combines a detailed ion chemistry scheme with a simple neutral chemistry scheme. We have also studied the production of secondary electrons under solar proton forcing using a Monte Carlo model of proton aurora.