Jupiter’s Aurora: Data analysis of Juno/JEDI data and modeling of auroral electron acceleration

• Applicant: Professor Dr. Joachim Saur
• Subject Area: Astrophysics and Astronomy
• Term: since 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 437450396

The understanding of Jupiter’s aurora currently experiences a paradigm change due to the new observations by the NASA Juno spacecraft, which is in a polar orbit around Jupiter since July 2016. One of the key discoveries of Juno was that auroral electrons mostly display broad-band energy distributions and are directed towards and away from Jupiter. These types of electron beams are different compared to the pre-Juno expectation of uni-directional mono-energetic beams based on a steady-state electric current system connecting Jupiter’s ionosphere with its magnetosphere. The broadband bi-directional electrons are generally considered to be caused by stochastic acceleration, however our understanding of this stochastic acceleration is currently only at its infancy. Therefore, we propose a combination of data analysis and theoretical modeling for a better understanding of Jupiter’s acceleration processes: (i) We intend to analyze measurements of energetic electrons obtained by the JEDI instrument onboard of Juno to characterize the spatial/temporal structuring of the electron beams and relate them with the theoretically expected structures based on turbulent/stochastic acceleration. (ii) We plan in parallel to theoretically investigate how turbulent Alfvén waves down to kinetic wavelength scales evolve while propagating towards Jupiter’s ionosphere along the strongly increasing magnetic field strength and decreasing plasma density of Jupiter’s magnetosphere. (iii) In these wave fields we then investigate using Monte-Carlo models how electrons are being accelerated and analyse the resulting electron energy distribution functions. We are specifically interested in understanding the effects of a) the strongly evolving waves due to the inhomogeneous magnetospheric properties while propagating towards Jupiter and b) the effects of the turbulent nature of the waves on the resulting electron energy spectra of the beams. (iv) Because electron energies above 300 keV as repeatedly observed by Juno require consideration of the relativistic electron momentum, we also investigate the effects of a fully-relativistic dispersion relationship for Alfvén waves in their kinetic limits.

• DFG Programme: Research Grants
• International Connection: United Kingdom, USA
• Cooperation Partners: George Clark, Ph.D.; Dr. Daniel Verscharen