Space Weather & Heliophysics

The Role of High Energy Photoelectrons on the Dissociation of Molecular Nitrogen in Earth’s Ionosphere

By Keith Cowing
Press Release
September 22, 2022
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The Role of High Energy Photoelectrons on the Dissociation of Molecular Nitrogen in Earth’s Ionosphere
Input Solar Spectra. Dashed line is the high resolution NRLFLARE Spectrum for X9 flare of September 6,2017. Bold line is the Quiet Spectrum derived by reducing irradiance in the different bins of the NRFLARE model. The first nine bins, from 0.05-0.8 nm of the Quiet Spectrum are derived from GOES data and bins longer than 0.8 nm were derived from EUVAC model

Soft x-ray radiation from the sun is responsible for the production of high energy photoelectrons in the D and E regions of the ionosphere, where they deposit most of their ionization energy.

The photoelectrons created by this process are the main drivers for dissociation of Nitrogen molecule (N2) below 200 km. Furthermore, the dissociation of N2 is one of main mechanisms of the production of Nitric Oxide (NO) at these altitudes. In order to estimate the dissociation rate of N2 we need its dissociation cross-sections.

The dissociation cross-sections for N2 by photoelectrons are primarily estimated from the cross-sections of its excitation states using predissociation factors and dissociative ionization channels. Unfortunately, the lack of cross-sections data, particularly at high electron energies and of higher excited states of N2 and N+2, introduces a lot of uncertainty in the dissociation rate calculation, which subsequently leads to uncertainties in the NO production rate from this source.

Srimoyee Samaddar, Karthik Venkataramani, Justin Yonker, Scott. M. Bailey

Subjects: Chemical Physics (physics.chem-ph); Earth and Planetary Astrophysics (astro-ph.EP); Atmospheric and Oceanic Physics (
Cite as: arXiv:2209.11185 [physics.chem-ph] (or arXiv:2209.11185v1 [physics.chem-ph] for this version)
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Submission history
From: Srimoyee Samaddar
[v1] Tue, 20 Sep 2022 22:21:17 UTC (1,223 KB)

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