Jupiter's Enigmatic Ionosphere: Electron Density Profiles From the Pioneer, Voyager, and Galileo Radio Occultation Experiments

Mendillo, M.; Narvaez, C.; Moore, Luke; Withers, Paul

doi:10.1029/2021je007169

Cited by 3 publications

(5 citation statements)

References 65 publications

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“…At the Jovian planets, however, the vertical structure of the dayside ionospheres appears highly variable in radio occultation observations, as reported by Mendillo et al. (2022) for Jupiter and Nagy et al. (2006), Kliore et al.…”

Section: Saturn's Ionospherementioning

confidence: 71%

“…At the Jovian planets, however, the vertical structure of the dayside ionospheres appears highly variable in radio occultation observations, as reported by Mendillo et al (2022) for Jupiter and Nagy et al (2006), Kliore et al (2009), and Kliore et al (2014) for Saturn. Yet other observations, which are admittedly relatively few in number, may present a more stable picture.…”

Section: Saturn's Ionospherementioning

confidence: 78%

“…Typically, TEC is proportional to the product of the peak density and width of the dominant ionospheric layer (e.g., Fox et al., 1991; Huang et al., 2016; Mendillo et al., 2015; Rishbeth & Garriott, 1969; Titheridge, 1973). It has proven particularly useful in studies of the ionospheres of the Jovian planets that, as illustrated in Figures 4–11, do not display stable, predictable layered structures (Mendillo et al., 2022; L. Moore et al., 2010, 2019).…”

Section: Discussionmentioning

confidence: 99%

“…It is unclear whether this issue also affects the altitude scales of other electron density profiles from the giant planets, such as the Pioneer 11 observations of Saturn reported by and or the Galileo observations of Jupiter reported by Mendillo et al (2022).…”

Section: Cassini Radio Occultation Observationsmentioning

confidence: 99%

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Cassini Radio Occultation Observations of Saturn's Ionosphere: Electron Density Profiles From 2005 to 2013

et al. 2023

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A set of electron density profiles of Saturn's ionosphere acquired by Cassini radio occultations is archived at the NASA Planetary Data System. However, the reference surface that defines zero altitude in these profiles is unknown and appears to vary by 1,500 km at fixed latitude. These profiles are immensely valuable for addressing questions pertaining to the vertical structure, meridional structure, diurnal variations, or solar cycle dependence of Saturn's ionosphere, but their value is severely limited by their questionable altitude scales. Here we have resolved this problem by independently generating the set of 60 electron density profiles. These profiles confirm that, as noted by previous authors, the structure of Saturn's ionosphere is highly variable. Nevertheless, the profiles suggest an underlying morphology of a broad layer at relatively high altitude (often at approximately 2,000–3,000 km altitude) and a series of narrower layers at lower altitude (often at approximately 1,000 km altitude). The vertical structure of Saturn's ionosphere depends on latitude and local time. At low latitudes, densities are greater at dusk than at dawn. Conversely, at mid latitudes, densities are greater at dawn than at dusk. The plasma scale height of the topside ionosphere is relatively small at low latitudes. The high, broad ionospheric layer is apparent at mid and high latitudes at both dawn and dusk, but is not present at low latitudes at either dawn or dusk. Total electron content also shows a strong dependence on latitude, with high latitudes having greater values than low and mid latitudes.

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Section: Saturn's Ionospherementioning

confidence: 71%

Section: Saturn's Ionospherementioning

confidence: 78%

Section: Discussionmentioning

confidence: 99%

Section: Cassini Radio Occultation Observationsmentioning

confidence: 99%

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Cassini Radio Occultation Observations of Saturn's Ionosphere: Electron Density Profiles From 2005 to 2013

et al. 2023

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“…As for the meteoroid influx, it is difficult to know accurately the meteoroid influx into the Jovian atmosphere due to the lack of observation of meteoroid flux at Jupiter's orbit. Radio occultation measurements made by Voyager 1 and 2 spacecraft, Pioneer 10, and Galileo spacecraft have revealed that there were some peaks in the ionospheric electron density profiles (Fjeldbo et al, 1975;Hinson et al, 1997Hinson et al, , 1998Mendillo et al, 2022). The uppermost peak at around 1,000 km altitude is considered to be related to H + , while the origin of the other peaks at lower altitudes remains unknown.…”

Section: Discussionmentioning

confidence: 99%

Simulation of Dawn‐To‐Dusk Electric Field in the Jovian Inner Magnetosphere via Region 2‐Like Field‐Aligned Current

et al. 2023

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The presence of the dawn‐to‐dusk electric field of about 4 mV/m in the Jovian inner magnetosphere and its response to the enhancement of the solar wind dynamic pressure are still a mystery of the rotation‐dominated Jovian magnetosphere. Previous studies have suggested that magnetosphere‐ionosphere (M‐I) coupling via Region 2‐like (R2‐like) field‐aligned current (FAC) could be the origin of the Jovian dawn‐to‐dusk electric field. This study investigates whether the dawn‐to‐dusk electric field is formed from this scenario by using a Jovian ionosphere model and a two‐dimensional ionospheric potential solver. Our results show that the dawn‐dusk asymmetry in the ionospheric potential form even at middle latitudes and that the dawn‐to‐dusk electric field is induced in the inner magnetosphere if the electric potential is mapped to the magnetospheric equatorial plane. Around the Io orbit, the calculated electric field strength for the ionosphere without meteoroid influx is too large, 200 mV/m at dawn and 88 mV/m at dusk. One of the solutions is to consider long‐lived meteoric ions in the Jovian ionosphere, which reduce the electric field strength to 15 mV/m at dawn and 12 mV/m at dusk. The model also shows that the electric field strength increases with the intensity of R2‐like FAC, consistent with its response to the solar wind dynamic pressure observed by the Hisaki satellite.

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Field Line Resonances and Cavity Modes at Earth and Jupiter

Lysak

2022

Front. Astron. Space Sci.

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Ultra-Low-Frequency (ULF) waves provide a means for the rapid propagation of energy and field-aligned current in planetary magnetospheres. At Earth, the ULF frequency range is usually defined as including waves with periods of 0.2–600 s; however, at Jupiter these waves can extend to periods of tens of minutes. In both magnetospheres, shear mode Alfvén waves can form field line resonances that exist between the ionospheres, with periods of a few minutes at Earth and a few tens of minutes at Jupiter. A major distinction between these two magnetospheres is in the density distribution. Earth has a dense ionosphere full of heavy ions, an extended, cold plasmasphere and a relatively low-density plasma sheet. In contrast, at Jupiter, the ionosphere is largely hydrogen (both in atomic form and in the H3+ molecular ion), there is no appreciable plasmasphere and the plasma disk is dense and populated with heavy ions (largely sulfur and oxygen) originating at the moon Io and to some extent from other moons. As at Earth, the sharp Alfvén speed gradient above the ionosphere forms an ionospheric Alfvén resonator at Jupiter with periods of seconds. Furthermore, the high-latitude lobes at Jupiter have very low density and a resonant structure can be formed by waves bouncing between the ionosphere and the dense plasma disk. This structure leads to periods of tens of seconds. Finally, the dense Io plasma torus and plasma sheet provide conditions for compressional cavity modes to form in this region. Thus, the structure of the field line resonance modes is quite different at the two planets. Implications of these resonances on auroral particle acceleration will be discussed.

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Jupiter's Enigmatic Ionosphere: Electron Density Profiles From the Pioneer, Voyager, and Galileo Radio Occultation Experiments

Cited by 3 publications

References 65 publications

Cassini Radio Occultation Observations of Saturn's Ionosphere: Electron Density Profiles From 2005 to 2013

Cassini Radio Occultation Observations of Saturn's Ionosphere: Electron Density Profiles From 2005 to 2013

Simulation of Dawn‐To‐Dusk Electric Field in the Jovian Inner Magnetosphere via Region 2‐Like Field‐Aligned Current

Field Line Resonances and Cavity Modes at Earth and Jupiter

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