Jovian Auroral Ion Precipitation: Field‐Aligned Currents and Ultraviolet Emissions

Houston, Stephen; Ozak, N.; Young, Jackson; Cravens, T. E.; Schultz, David

doi:10.1002/2017ja024872

Cited by 20 publications

(25 citation statements)

References 84 publications

(145 reference statements)

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“…These charge states are sufficiently reached for both species at an energy between 200 and 300 keV/u, where they become the most probable charge state for the given energy (a total energy of

\sim

3.2 and

\sim

6.4 MeV for oxygen and sulfur, respectively). These newly developed equilibrium fractions supersede previous models presented by Ozak et al () and Houston et al (), which showed an O

^{6 +}

peak at nearly 1 MeV/u and an S

^{6 +}

peak at 600 keV/u.…”

Section: Physical Processes and Model Descriptionsupporting

confidence: 83%

“…Hence, X‐ray observation can be used to estimate heavy ion fluxes with energies in excess of

\sim

200 keV/u (i.e., 3 MeV and higher) and to determine the morphology of this precipitation made over the polar caps. Such precipitation has been shown to be associated with downward field‐aligned currents, both due to the primary ion precipitation and the resultant secondary electron escape from the atmosphere (Cravens et al, ; Houston et al, ; Ozak et al, ; Ozak et al, ). The ion precipitation is also responsible as a source of ionization in the thermosphere, which was explored further in the earlier model presented by Houston et al ().…”

Section: Discussionmentioning

confidence: 99%

“…Houston et al () modeled oxygen precipitation using the nine relevant NSIM processes as the ion traversed the upper atmosphere using the atomic data describing the rates of these processes and the energy loss for each process as a function of ion energy given by Schultz et al (), summarized here:

O^{q +} + H_{2} \to ({, \begin{matrix} left left \\ array O^{q +} + H_{2}^{+} + e & array Single Ionization \\ array O^{q +} + 2 H^{+} + 2 e & array Double Ionization \end{matrix})

O^{q +} + H_{2} \to ({, \begin{matrix} left \\ array O^{(q - 1) +} + \{\begin{array}{ll} H_{2}^{+} & Single Capture \\ H^{+} + H^{+} + e & Transfer Ionization \end{array} \\ array O^{(q - 2) +} + \{\begin{array}{ll} 2 H^{+} \to O^{false(q - 1 false) +} + e & Double Capture - Autoionization \\ H^{+} + H^{+} & Double Capture \end{array} \end{matrix})

O^{q +} + H_{2} \to ({, \begin{matrix} center center \\ array O^{(q + 1)} + H_{2}^{+} + 2 e; H + H^{+} + 2 e & array Single Stripping \\ array O \end{matrix})

…”

Section: Physical Processes and Model Descriptionmentioning

confidence: 99%

“…The high charge state peaks have dramatically shifted to lower energies than previous models produced. Houston et al () and Ozak et al () had the peak of O

^{6 +}

\sim

900 keV/u; however, due to the use of newly developed SIM cross sections, the peak has now shifted down to an energy of

\sim

350 keV/u.…”

Section: Physical Processes and Model Descriptionmentioning

confidence: 99%

“…We expand on the ion precipitation models that have come before (Cravens et al, ; Houston et al, ; Ozak et al, , ), modeling oxygen from 10 keV/u to 25 MeV/u and sulfur between 10 keV/u and 2 MeV/u, in an attempt to explain the X‐ray emission from the Jovian polar caps. We consider all charge states of oxygen, including the negative charge state (O

^{q +}

, q =

-

1, 0, …, 8) and all sulfur positive charge states (S

^{q +}

, q = 0, …, 16).…”

Section: Introductionmentioning

confidence: 99%

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Jovian Auroral Ion Precipitation: X‐Ray Production From Oxygen and Sulfur Precipitation

et al. 2020

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Many attempts have been made to model X‐ray emission from both bremsstrahlung and ion precipitation into Jupiter's polar caps. Electron bremsstrahlung modeling has fallen short of producing the total overall power output observed by Earth‐orbit‐based X‐ray observatories. Heavy ion precipitation was able to reproduce strong X‐ray fluxes, but the proposed incident ion energies were very high ( >1 MeV per nucleon). Now with the Juno spacecraft at Jupiter, there have been many measurements of heavy ion populations above the polar cap with energies up to 300–400 keV per nucleon (keV/u), well below the ion energies required by earlier models. Recent work has provided a new outlook on how ion‐neutral collisions in the Jovian atmosphere are occurring, providing us with an entirely new set of impact cross sections. The model presented here simulates oxygen and sulfur precipitation, taking into account the new cross sections, every collision process, the measured ion fluxes above Jupiter's polar aurora, and synthetic X‐ray spectra. We predict X‐ray fluxes, efficiencies, and spectra for various initial ion energies considering opacity effects from two different atmospheres. We demonstrate that an in situ measured heavy ion flux above Jupiter's polar cap is capable of producing over 1 GW of X‐ray emission when some assumptions are made. Comparison of our approximated synthetic X‐ray spectrum produced from in situ particle data with a simultaneous X‐ray spectrum observed by XMM‐Newton shows good agreement for the oxygen part of the spectrum but not for the sulfur part.

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“…These charge states are sufficiently reached for both species at an energy between 200 and 300 keV/u, where they become the most probable charge state for the given energy (a total energy of

\sim

3.2 and

\sim

6.4 MeV for oxygen and sulfur, respectively). These newly developed equilibrium fractions supersede previous models presented by Ozak et al () and Houston et al (), which showed an O

^{6 +}

peak at nearly 1 MeV/u and an S

^{6 +}

peak at 600 keV/u.…”

Section: Physical Processes and Model Descriptionsupporting

confidence: 83%

“…Hence, X‐ray observation can be used to estimate heavy ion fluxes with energies in excess of

\sim

Section: Discussionmentioning

confidence: 99%

O^{q +} + H_{2} \to ({, \begin{matrix} left left \\ array O^{q +} + H_{2}^{+} + e & array Single Ionization \\ array O^{q +} + 2 H^{+} + 2 e & array Double Ionization \end{matrix})

O^{q +} + H_{2} \to ({, \begin{matrix} left \\ array O^{(q - 1) +} + \{\begin{array}{ll} H_{2}^{+} & Single Capture \\ H^{+} + H^{+} + e & Transfer Ionization \end{array} \\ array O^{(q - 2) +} + \{\begin{array}{ll} 2 H^{+} \to O^{false(q - 1 false) +} + e & Double Capture - Autoionization \\ H^{+} + H^{+} & Double Capture \end{array} \end{matrix})

O^{q +} + H_{2} \to ({, \begin{matrix} center center \\ array O^{(q + 1)} + H_{2}^{+} + 2 e; H + H^{+} + 2 e & array Single Stripping \\ array O \end{matrix})

…”

Section: Physical Processes and Model Descriptionmentioning

confidence: 99%

“…The high charge state peaks have dramatically shifted to lower energies than previous models produced. Houston et al () and Ozak et al () had the peak of O