Publication Date:
2023-01-13
Description:
Recent observations by the Juno spacecraft have shown that electrons contributing to Jupiter's main auroral emission appear to be frequently characterized by broadband electron distributions, but also less often mono‐energetic electron distributions are observed as well. In this work, we quantitatively derive the occurrence rates of the various electron distributions contributing to Jupiter's aurora. We perform a statistical analysis of electrons measured by the JEDI‐instrument within 30–1,200 keV from Juno's first 20 orbits. We determine the electron distributions, either pancake, field‐aligned, mono‐energetic, or broadband, through energy and pitch angles to associate various acceleration mechanisms. The statistical analysis shows that field‐aligned accelerated electrons at magnetic latitudes greater than 76° are observed in 87.6% ± 7.2% of the intervals time averaged over the dipole L‐shells according the main oval. Pancake distributions, indicating diffuse aurora, are prominent at smaller magnetic latitudes (〈76°) with an occurrence rate of 86.2% ± 9.6%. Within the field‐aligned electron distributions, we see broadband distributions 93.0% ± 3.8% of the time and a small fraction of isolated mono‐energetic distribution structures 7.0% ± 3.8% of the time. Furthermore, these occurrence statistics coincide with the findings from our energy flux statistics regarding the electron distributions. Occurrence rates thus also characterize the overall energetics of the different distribution types. This study indicates that stochastic acceleration is dominating the auroral processes in contrast to Earth where the discrete aurora is dominating.
Description:
Plain Language Summary:
With the Juno spacecraft arriving in the magnetosphere of Jupiter, first flyby particle measurements have changed the knowledge about the developing process of Jupiter's intense aurora. The observations of auroral particles show a stochastic behavior rather than a preference for specific energy. Our statistical analysis of the first 20 flybys at Jupiter compares the occurrence of different particle distributions and highlights the importance of different generation theories for Jupiter's aurora. A generation via stochastic rather than mono‐energetic behavior is deduced and supports previous observations.
Description:
Key Points:
We present a statistical study of Jupiter's auroral electrons within 30–1,200 keV based on Juno's first 20 perijoves.
Broadband electron distributions dominates Jupiter's main auroral zone as they are observed in 93% ± 3% of the intervals studied here.
Dominance of broadband distributions underlines the importance of a turbulent or stochastic acceleration process.
Description:
Deutsche Forschungsgemeinschaft
http://dx.doi.org/10.13039/501100001659
Description:
Universität zu Köln
http://dx.doi.org/10.13039/501100008001
Description:
https://lasp.colorado.edu/home/mop/files/2015/02/CoOrd_systems7.pdf
Description:
https://pds-ppi.igpp.ucla.edu/mission/JUNO/JNO/JEDI
Description:
https://lasp.colorado.edu/home/mop/files/2020/04/20190412_Imai_MagFootReader_UIowa_rev.pdf
Keywords:
ddc:523
;
auroral precipitation budget
;
particle distribution
;
Jupiter
;
Juno
Language:
English
Type:
doc-type:article
Permalink
