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Auroral precipitation is the second major energy source after solar irradiation that ionizes the Earth’s upper atmosphere. Diffuse electron aurora caused by wave-particle interaction in the inner magnetosphere (L < 8) takes over 60% of total auroral energy flux, strongly contributing to the ionospheric conductance and thus to the ionosphere-thermosphere dynamics. This paper quantifies the impact of chorus waves on the diffuse aurora and the ionospheric conductance during quiet, medium, and strong geomagnetic activities, parameterized by AE <100, 100 < AE < 300, and AE > 300, respectively. Using chorus wave statistics and inner-magnetosphere plasma conditions from Timed History Events and Macroscale Interactions during Substorms (THEMIS) observations, we directly derive the energy spectrum of diffuse electron precipitation under quasi-linear theory. We then calculate the height-integrated conductance from the wave-driven aurora spectrum using the electron impact ionization model of Fang et al. (Geophys. Res. Lett., 2010, 37) and the MSIS atmosphere model. By utilizing Fang’s ionization model, the US Naval Research Laboratory Mass Spectrometer and Incoherent Scattar Radar (NRLMSISE-00) model from 2000s for the neutral atmosphere components, and the University of California, Los Angeles (UCLA) Full Diffusion Code, we improve upon the standard generalization of Maxwellian diffuse electron precipitation patterns and their resulting ionosphere conductance. Our study of global auroral precipitation and ionospheric conductance from chorus wave statistics is the first statistical model of its kind. We show that the total electron flux and conductance pattern from our results agree with those of Ovation Prime model over the pre-midnight to post-dawn sector as geomagnetic activity increases. Our study examines the relative contributions of upper band chorus (UBC) and lower band chorus wave (LBC) driven conductance in the ionosphere. We found LBC waves drove diffuse electron precipitation significantly more than UBC waves, however it is possible that THEMIS data may have underestimated the upper chorus band wave observations for magnetic latitudes below 65 .
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The Significance of Magnetospheric Precipitation for the Coupling of Magnetosphere-Ionosphere-Thermosphere Systems: Sources and Properties
Magnetospheric precipitation plays an important role for the coupling of Magnetosphere, Ionosphere, and Thermosphere (M-I-T) systems. Particles from different origins could be energized through various physical mechanisms and in turn disturb the Ionosphere, the ionized region of the Earth’s atmosphere that is important for telecommunication and spacecraft operations. Known to cause aurora, bright displays of light across the night sky, magnetospheric particle precipitation, modifies ionospheric conductance further affecting the plasma convection, field-aligned (FAC) and ionospheric currents, and ionospheric/thermospheric temperature and densities. Therefore, understanding the properties of different sources of magnetospheric precipitation and their relative roles on electrodynamic coupling of M-I across a broad range of spatiotemporal scales is crucial. In this paper, we detail some of the important open questions regarding the origins of magnetospheric particle precipitation and how precipitation affects ionospheric conductance. In a companion paper titled “The Significance of Magnetospheric Precipitation for the Coupling of Magnetosphere-Ionosphere-Thermosphere Systems: Effects on Ionospheric Conductance”, we describe how particle precipitation affects the vertical structure of the ionospheric conductivity and provide recommendations to improve its modelling.
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- Award ID(s):
- 2225405
- PAR ID:
- 10516085
- Publisher / Repository:
- Bulletin of the American Astronomical Society
- Date Published:
- Journal Name:
- Bulletin of the AAS
- ISSN:
- 0002-7537
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.3847/25c2cfeb.be32d93d
