Data for secondary-electron production from ion precipitation at Jupiter III: Target and projectile processes in H+, H, and H− + H

Abstract

To improve the physical completeness of the data previously calculated (Schultz et al., 2017) to enable modeling of the effects of secondary electrons produced by energetic ion precipitation at Jupiter, we extend the treatment to include inelastic processes that occur simultaneously on the projectile (O q+ , q = 0-8)) and target (H 2). Here, processes considered in the previous work (single and double ionization, transfer ionization, double capture with subsequent autoionization, single and double stripping, single and double charge transfer, and target excitation) reflecting non-simultaneous projectile and target electron transitions, are replaced with processes that include both non-simultaneous and simultaneous electronic transitions on the target and projectile. These include, for example, single ionization, single ionization with simultaneous single projectile excitation, single ionization with double projectile excitation, single ionization with single projectile stripping, and single ionization with double projectile stripping. Using this expanded set of processes, we show, via Monte Carlo ion-transport simulation, that improved representation of the energy deposition, measured by the stopping power, is obtained as compared to accepted recommended values for intermediate energies (100-2000 keV/u) where the stopping power is largest, while maintaining the existing good agreement with these recommended values for low (∼10-100 keV/u) and high (≥2000 keV/u) energies. In addition, the ion-fraction distribution is altered by use of the improved data set. Both of these effects have implications for the energy deposition by oxygen ion precipitation in an H 2 atmosphere. Therefore, use of this expanded data set can provide a more physically realistic secondary-electron distribution, and consequently improved atmospheric reaction network, improved description of ion contribution to atmospheric currents, and therefore improved understanding of Jovian ionosphere-atmosphere coupling.

Data for secondary-electron production from ion precipitation at Jupiter II: Simultaneous and non-simultaneous target and projectile processes in collisions of Oq+ + H<

“…As summarized in our previous work [1] the need for data describing secondary-electron production in 1-2000 keV/u O q+ + H 2 (q = 0-8) collisions is motivated by requirements for modeling dissociation of atmospheric molecules and contribution to currents arising from precipitation of these and other ions into the upper atmosphere of Jupiter [2,3]. Such data and their incorporation into ion-precipitation models was particularly timely in light of the arrival of the NASA Juno probe at Jupiter in July 2016 with the unique orbital characteristics to enable observations of the precipitating ion populations and their interactions with the upper atmosphere.…”

“…As described in the previous work [1], treating the full range of non-simultaneous (NSIM) target or projectile processes (SI, TI, DI, DCAI, SS, DS, SC, DC, and TEX) for all charges states (q = 0-8) of oxygen colliding with H 2 over the energy range of 1-2000 keV/u is presently only achievable with the classical trajectory Monte Carlo (CTMC) method [14,15], and in particular with the CTMC models developed for H 2 [16,17] (target processes) or for multi-electron atoms and ions (nCTMC) [18] (here used for projectile processes). Critical comparisons of the secondary-electron production using the CTMC method with measurements and other theoretical methods, noted in Ref.…”

“…Therefore, a comprehensive data set of integral cross sections, which provides the probability of the various secondaryelectron-producing collisions or other energy-or charge-changing reactions, and the differential cross sections for secondaryelectron-production processes, which describe the energy and angle of ejection of the secondary electrons, was produced [1] using the best theoretical methods available in the general lack of measurements for the huge range of data required. Specifically, these processes included the following secondary-electron-producing reactions: where q runs from 0 to 8, depending on the number of electrons possibly involved (e.g., for O + DCAI is not considered, or for O 7+ DS is not possible) and where X stands for any product (i.e., H 2 , H + H, H * 2 ).…”

“…[2][3][4][5]) for the initial energy at the top of the atmosphere, to 1 keV/u, at which point the secondary-electron production drops off rapidly. As noted [1], very little data from measurements exists for comparison with this very large, computationally generated data set. Previous work considered comparisons with the limited experimental data available and also drew on assessment of the accuracy of results in the context of numerous similar comparisons for other collision systems for which more experimental data is available.…”

“…While an expanded set of integral cross sections is required to treat both non-simultaneous and simultaneous projectile and target processes, the same set of differential cross sections for the electron ejection angle and energy calculated in the previous work [1] may be used without modification. Specifically, to simulate the secondary-electron production in a collision event, instead of selecting an electron angle and energy for a single process such as SI, one uses combinations of samplings for the simultaneous processes such as SI with simultaneous SS for example.…”