Event Title

Magnetosphere-Ionosphere Coupling at Jupiter and Saturn: Evidence from X-Ray Emission

Location

Yosemite National Park

Start Date

2-13-2014 6:15 PM

End Date

2-13-2014 6:30 PM

Description

Auroral particle precipitation dominates the chemical and physical environment of the upper atmospheres and ionospheres of the outer planets. Precipitation of energetic electrons from the middle magnetosphere is responsible for the main auroral oval at Jupiter, but both energetic electron and ion precipitation take place in the polar caps. Most focus at both Earth and Jupiter has been on electron precipitation and the associated upward field-aligned current regions. However, x-ray emission that is observed from Jupiter’s polar regions appears to be due to the precipitation of energetic heavy ions coming from the outer magnetosphere and magnetopause. Bunce et al. have suggested that magnetic reconnection at the dayside magnetopause is responsible for the downward currents. The ions must be accelerated to MeV energies in order for the sulfur and oxygen ions to lose most of their electrons during collisions with atmospheric molecular hydrogen. Charge exchange collisions follow the electron removal collisions and the product ions emit the observed x-rays. We have used a Monte Carlo code to study the ion precipitation process, including the altitude-dependence of the energy deposition and the x-ray production from charge-exchange collisions. We have also calculated the spectrum of the secondary electrons produced during this process as well as the fieldaligned currents. Escaping secondary electrons should be accelerated upward to MeV energies due to the same field-aligned potentials responsible for the downward ion acceleration. Evidence exists for relativistic electrons in the outer magnetosphere. An x-ray aurora has not been observed at Saturn, which is perhaps not surprising given that major differences exist in the two planets magnetosphere-ionosphere (MI) coupling. Ion precipitation processes, particularly those leading to x-ray emission at Jupiter, will be discussed during this talk, as well as the implications for MI coupling at the outer planets.

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Feb 13th, 6:15 PM Feb 13th, 6:30 PM

Magnetosphere-Ionosphere Coupling at Jupiter and Saturn: Evidence from X-Ray Emission

Yosemite National Park

Auroral particle precipitation dominates the chemical and physical environment of the upper atmospheres and ionospheres of the outer planets. Precipitation of energetic electrons from the middle magnetosphere is responsible for the main auroral oval at Jupiter, but both energetic electron and ion precipitation take place in the polar caps. Most focus at both Earth and Jupiter has been on electron precipitation and the associated upward field-aligned current regions. However, x-ray emission that is observed from Jupiter’s polar regions appears to be due to the precipitation of energetic heavy ions coming from the outer magnetosphere and magnetopause. Bunce et al. have suggested that magnetic reconnection at the dayside magnetopause is responsible for the downward currents. The ions must be accelerated to MeV energies in order for the sulfur and oxygen ions to lose most of their electrons during collisions with atmospheric molecular hydrogen. Charge exchange collisions follow the electron removal collisions and the product ions emit the observed x-rays. We have used a Monte Carlo code to study the ion precipitation process, including the altitude-dependence of the energy deposition and the x-ray production from charge-exchange collisions. We have also calculated the spectrum of the secondary electrons produced during this process as well as the fieldaligned currents. Escaping secondary electrons should be accelerated upward to MeV energies due to the same field-aligned potentials responsible for the downward ion acceleration. Evidence exists for relativistic electrons in the outer magnetosphere. An x-ray aurora has not been observed at Saturn, which is perhaps not surprising given that major differences exist in the two planets magnetosphere-ionosphere (MI) coupling. Ion precipitation processes, particularly those leading to x-ray emission at Jupiter, will be discussed during this talk, as well as the implications for MI coupling at the outer planets.