Separating and quantifying ionospheric responses to proton and electron precipitation over Svalbard

Abstract

[1] On 16 December 2001, a variable and structured aurora associated with a period of high solar wind velocity and low solar wind density was recorded through optical, radar, and particle measurements from the ground and space. A comprehensive analysis of this data set is carried out using a coupled auroral electron deposition and ion chemistry model. The observations include H b, N 2 + 1N (0, 2), and O + 4 P-4 D optical and electron density radar measurements from the ground, particle data from NOAA 16 and DMSP F14 satellites, and Doppler-shifted H Lyman a images from the IMAGE satellite. Modulations in the energy flux of both protons and electrons are seen in the NOAA 16 data as well as in the optical signatures measured on ground and from above. At the time of closest approach of NOAA 16, the observed emissions and electron density at the peak of an enhancement are well reproduced when precipitating protons and electrons with total fluxes of 0.23 and 3.0 mW m −2 , respectively, and mean energies of 2.50 and 0.25 keV, respectively, are used as input for the model. These values are consistent with those measured by the NOAA satellite. The resulting modeled emissions agree well with the ground measurements of enhanced emissions. The correlation between the emissions from N 2 + and O + suggests that they are primarily due to electron precipitation. This result is confirmed by the agreement between the measured and modeled emissions and by the values of extinction obtained for all three emissions. The modulations to the E region ionization can be explained by proton precipitation alone, while soft electrons are responsible for the changes to the ionization at higher altitudes.

Proton impact ionization and a fast calculation method

“…While the Maxwellian spectral approximation sometimes proves convenient [e.g., Sharber, 1981], it might also introduce significant errors in describing precipitation conditions and thus the concomitant geoeffectiveness. For instance, the high-energy tail in particle distributions [e.g., Lyons and Evans, 1984] cannot be represented by the Maxwellian approximation, and significant errors may arise [Fang et al, 2010;Lanchester et al, 2011].…”

Short Wave Infrared Imaging for Auroral Physics and Aeronomy Studies

“…An ability to distinguish between the electron and proton components of auroral precipitation is essential to achieving a correct interpretation of auroral brightness in terms of ionospheric parameters such as ionization rate and conductivity (Galand et al 2002;Galand & Lummerzheim 2004;Lanchester et al 2011). Observations have shown that energetic electrons and protons do not interact with the upper atmosphere in the same way.…”

“…7 illustrates an example of evening and morning latitudinal regions identified with proton precipitation relative to the nighttime electron auroral oval. In addition, as protons retain the large-scale structure more efficiently than electrons, imaging the proton aurora is an excellent probe for investigating magnetospheric sub-storms and magnetosphere-ionosphere coupling processes (e.g., Deehr & Lummerzheim 2001;Immel et al 2002;Mende et al 2003;Zhang et al 2005;Lanchester et al 2011). Moreover, protons can be the dominant energy source in the cusp and at the equatorward boundary of the dusk-side auroral oval (Creutzberg et al 1988;Hardy et al 1989;Galand et al 2001).…”