Space physics

Chemical effects of electron precipitation

The highly energetic electrons that enter our atmosphere from above cause many chemical changes in the atmospheric gases. The energy the electrons carry will be transferred to the molecules, atoms and ions in the atmosphere. This may cause heating, initiation of chemical reactions, which again can give more radiation loss. Also the chemical composition might be altered, and there could be dynamical effects such as waves, winds and turbulence.

Main content

By using the x-ray measurements from PIXIE, we can find on a global scale where and how much energy that has been transferred from the precipitating electrons.

A chemical effect of electron precipitation is the increase of nitric oxide (NO) in the lower thermosphere. Energy from the incoming electrons is transferred to nitrogen molecules, splitting them into nitrogen atoms which can react with oxygen molecules to form nitric oxide.
Thermospheric NO has a lifetime of approximately one day. The Student Nitric Oxide Explorer (SNOE) measured the NO-density by observing emissions of NO in the dayglow (the image on the right). We here in Bergen have compared the time-integrated x-ray intensity accumulated for the entire night, with the NO density observed on the dayside. The results showed a quite good correlation.

C. Sætre, J. Stadsnes, H. Nesse, A. Aksnes, S. M. Petrinec, C. A. Barth, D. N. Baker, R. R. Vondrak, and N. Østgaard (2004), Energetic electron precipitation and the NO abundance in the upper atmosphere: A direct comparison during a geomagnetic storm, J. Geophys. Res., 109, A09302, doi:10.1029/2004JA010485.

C. Sætre, C. A. Barth, J. Stadsnes, N.Østgaard, S. M. Bailey, D. N. Baker and J. W. Gjerloev. Comparisons of electron deposition derived from observations of lower thermospheric nitric oxide and from X-ray bremsstrahlung measurements. J. Geophys. Res., Vol. 111, A04302, doi:10.1029/2005JA011391, 2006.