Role of the Ionospheric Conductance Profile in Sub‐Alfvénic Moon‐Magnetosphere Interactions: An Analytical Model

Simon, Sven; Liuzzo, Lucas; Addison, Peter

doi:10.1029/2021ja029191

Cited by 5 publications

(19 citation statements)

References 65 publications

(317 reference statements)

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“…Deflection of thermal ions around Europa's Alfvén wings reduces the ion surface flux by over an order of magnitude at nearly all locations on the upstream hemisphere (Addison et al, 2021). As shown by Simon et al (2021), the small number of ions which penetrate the wing tubes move almost completely in the corotation direction, since the ionospheric Hall Effect is too weak at Europa to drastically break the symmetry of the ion flow pattern between the sub-Jovian and anti-Jovian hemispheres. In analogy to the case of uniform fields, the influx pattern of these ions onto the upstream hemisphere is therefore determined by the cosine of the angle between the corotation direction and the local surface normal.…”

Section: Magnetospheric Ion Surface Fluxes and Sputtering Rates Of H 2 Omentioning

confidence: 98%

“…Hence, even when the field perturbations are taken into account, the spatial distribution of the thermal ion flux onto the upstream hemisphere retains something of the bullseye-like distribution seen in the case of uniform fields (Figure 5a). We note that the model of Simon et al (2021) applies a fluid approach to describe ion dynamics. Hence, their model does not capture individual ions from the "edges" of the Maxwellian upstream distribution that impinge onto Europa at large angles against the corotation direction.…”

Section: Magnetospheric Ion Surface Fluxes and Sputtering Rates Of H 2 Omentioning

confidence: 99%

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Effect of the Magnetospheric Plasma Interaction and Solar Illumination on Ion Sputtering of Europa’s Surface Ice

Addison¹,

Liuzzo

Simon³

2022

JGR Space Physics

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Section: Magnetospheric Ion Surface Fluxes and Sputtering Rates Of H 2 Omentioning

confidence: 98%

Section: Magnetospheric Ion Surface Fluxes and Sputtering Rates Of H 2 Omentioning

confidence: 99%

Effect of the Magnetospheric Plasma Interaction and Solar Illumination on Ion Sputtering of Europa’s Surface Ice

Addison¹,

Liuzzo

Simon³

2022

JGR Space Physics

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“…where m and n 0 denote the ion mass and number density of the undisturbed upstream plasma (see Equation 23in Simon et al, 2021). Since the flow in the Alfvénic far field is incompressible, the plasma density in that region has a constant value n 0 (Neubauer, 1980).…”

Section: Model Descriptionmentioning

confidence: 99%

“…In agreement with the estimations of Strobel et al (1990), the average Pedersen conductance in the model ionosphere is set to 〈Σ P 〉 ≈ 4.5 ⋅ 10 4 S. The radius of the obstacle to the flow is R = R T + 3H, with H = 70 km approximately representing the scale height of Triton's atmosphere (Broadfoot et al, 1989). The inclusion of a realistic shape for the ionospheric Pedersen conductance profile comes at the expense of having to set the Hall conductance to Σ H = 0 (Simon, 2015;Simon et al, 2021). However, this limitation does not affect our conclusions since the Hall effect would merely introduce a rotation of the flow pattern in planes perpendicular to the wing characteristics, that is, it would only break the symmetry between the y > 0 and y < 0 hemispheres (Saur et al, 1999;Simon, Saur, Kriegel, et al, 2011;Simon, Kriegel, et al, 2013).…”

Section: Wake Formation At Tritonmentioning

confidence: 99%

Formation of a Displaced Plasma Wake at Neptune's Moon Triton

2022

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Triton, the largest moon of Neptune (radius R T = 1,353 km), is located deep within the ice giant's magnetosphere at a distance of 14.4 Neptune radii (R N = 24,622 km), moving along a highly inclined and retrograde orbit around its parent planet. Similar to many large moons of Jupiter and Saturn, Triton is continuously exposed to a flow of sub-Alfvénic magnetospheric plasma that impinges at a relative velocity of about 40 km/s (Strobel et al., 1990). This magnetized flow sweeps particles out of Triton's ionosphere (Broadfoot et al., 1989;Majeed et al., 1990), generating ramside field pile-up and Alfvén wings in the process (Liuzzo et al., 2021;Strobel et al., 1990). Due to the combination of high ionospheric electron densities in excess of 10 4 cm −3 and a weak magnetospheric field along Triton's orbit (3-12 nT, see Connerney et al., 1991), the Pedersen conductance of the moon's ionosphere (Σ P ≈ 10 4 S) exceeds the Alfvén conductance of the ambient flow (Σ A ≈ 6 S) by four orders of magnitude (Strobel et al., 1990). Therefore, the interaction between Triton and Neptune's magnetospheric plasma is "saturated," that is, the streamlines of the impinging plasma are (almost) completely deflected around the Alfvén wing tubes

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“…Solving for the flow velocity 𝐴𝐴 𝐮𝐮 in the vicinity of the Alfvén wings (see also Simon, 2015;Simon et al, 2021) yields…”

Section: B 0 Oblique To Umentioning

confidence: 99%

Triton’s Variable Interaction With Neptune’s Magnetospheric Plasma

et al. 2021

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Neptune's largest moon Triton (radius 𝐴𝐴 𝐴𝐴𝑇𝑇 = 1, 353 km) is thought to be an erstwhile Kuiper belt object that was captured by the ice giant (Agnor & Hamilton, 2006). Orbiting at a radial distance of 𝐴𝐴 14.4𝑅𝑅𝑁𝑁 (radius of Neptune 𝐴𝐴 𝐴𝐴𝑁𝑁 = 24, 622 km), Triton is always located within Neptune's magnetosphere (Curtis & Ness, 1986;Mejnertsen et al., 2016;Ness et al., 1989;Richardson, 1993). The moon's highly inclined orbit-tilted nearly 𝐴𝐴 157 • with respect to its parent planet's rotational equator-results in a retrograde orbital motion around Neptune. Triton possesses the second-most dense moon atmosphere in the solar system after Titan (Broadfoot et al., 1989;Strobel et al., 1990;Strobel & Zhu, 2017). Mainly comprised of neutral 𝐴𝐴 N2 , its maximum surface number density is on the order of 𝐴𝐴 10 15 cm −3 , with a scale height between 10 and 70 km (Broadfoot et al., 1989). Additionally, trace gases including methane are present, with surface densities below 𝐴𝐴 10 11 cm −3 (e.g., Summers & Strobel, 1991;Trafton, 1984;Krasnopolsky et al., 1992). This neutral envelope is predominantly ionized by a combination of magnetospheric electron impacts and photoionization, resulting in an ionospheric Pedersen conductance that may exceed 𝐴𝐴 10 4 S (Strobel et al., 1990). In addition to this global atmosphere, observations during the Voyager 2 encounter of Neptune in 1989 indicated localized, geyser-like vapor plumes emanating from the surface to an altitude of ∼10 km (Smith et al., 1989). Since the moon's interior is likely differentiated in a hydrosphere and rocky mantle, it is possible that these plumes originate from a global, deep ocean sustained via radiogenic heating and/or tidal forcing (Nimmo & Spencer, 2015).

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Role of the Ionospheric Conductance Profile in Sub‐Alfvénic Moon‐Magnetosphere Interactions: An Analytical Model

Cited by 5 publications

References 65 publications

Effect of the Magnetospheric Plasma Interaction and Solar Illumination on Ion Sputtering of Europa’s Surface Ice

Effect of the Magnetospheric Plasma Interaction and Solar Illumination on Ion Sputtering of Europa’s Surface Ice

Formation of a Displaced Plasma Wake at Neptune's Moon Triton

Triton’s Variable Interaction With Neptune’s Magnetospheric Plasma

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