Survey of thermal ions in the Io plasma torus with the Galileo spacecraft

Frank, L. A.; Paterson, W. R.

doi:10.1029/2000ja000159

Cited by 38 publications

(58 citation statements)

References 52 publications

(37 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Similar caution must be exercised when attempting to apply in situ measurements obtained in one azimuthal region to the torus as a whole. This may help to explain some of the wide range in electron densities measured by the Galileo PLS (Frank and Paterson 2001).…”

Section: Discussionmentioning

confidence: 99%

“…URAP found the plasma flow speeds to be generally close to corotation but with significant deviations having an rms value of 5.3 km/s. Finally, on five passes through the Io torus, the Galileo PLS observed that the bulk plasma flow lagged the corotation velocity by 2-10 km/s, with an average deviation of ∼2-3 km/s (Frank and Paterson 2001).…”

Section: In Situ Plasma Measurementsmentioning

confidence: 99%

See 1 more Smart Citation

Cassini UVIS observations of the Io plasma torusIII. Observations of temporal and azimuthal variability

Steffl

Delamere

Bagenal

2006

Icarus

221

View full text Add to dashboard Cite

In this third paper in a series presenting observations by the Cassini Ultraviolet Imaging Spectrometer (UVIS) of the Io plasma torus, we show remarkable, though subtle, spatio-temporal variations in torus properties. The Io torus is found to exhibit significant, near-sinusoidal variations in ion composition as a function of azimuthal position. The azimuthal variation in composition is such that the mixing ratio of S II is strongly correlated with the mixing ratio of S III and the equatorial electron density and strongly anti-correlated with the mixing ratios of both S IV and O II and the equatorial electron temperature. Surprisingly, the azimuthal variation in ion composition is observed to have a period of 10.07 hours-1.5% longer than the System III rotation period of Jupiter, yet 1.3% shorter than the System IV period defined by Brown (1995). Although the amplitude of the azimuthal variation of S III and O II remained in the range of 2-5%, the amplitude of the S II and S IV compositional variation ranged between 5-25% during the UVIS observations. Furthermore, the amplitude of the azimuthal variations of S II and S IV appears to be modulated by its location in System III longitude, such that when the region of maximum S II mixing ratio (minimum S IV mixing ratio) is aligned with a System III longitude of ∼200±15 • , the amplitude is a factor of ∼4 greater than when the variation is anti-aligned. This behavior can explain numerous, often apparently contradictory, observations of variations in the properties of the Io plasma torus with the System III and System IV coordinate systems.

show abstract

Section: Discussionmentioning

confidence: 99%

Section: In Situ Plasma Measurementsmentioning

confidence: 99%

Cassini UVIS observations of the Io plasma torusIII. Observations of temporal and azimuthal variability

Steffl

Delamere

Bagenal

2006

Icarus

221

View full text Add to dashboard Cite

show abstract

“…This is also an appropriate place in the text to discuss the errors in the computation of temperatures due to errors in the distribution of ions with different M / Q values. It has been established from the analyses of Voyager 1 and Galileo plasma data that the most abundant heavy ions are characterized with M / Q values of 8, 10.7, 16, and 32 [ Bagenal , 1994; Crary et al , 1998; Frank and Paterson , 2000, 2001b]. The maximum error in temperature occurs when the densities of the two major M / Q species are about equal.…”

Section: Observationsmentioning

confidence: 99%

“… Russell et al [1998] report the existence of patches of strongly northward and southward magnetic fields at distances >50 R J in the magnetotail, which may be the signatures of magnetic reconnection which are convecting tailward. Frank and Paterson [2001b] report in situ measurements of thermal plasmas in the torus that show that there is an “active sector” with greater latitudinal extent that is corotating with Jupiter. These investigations represent only the initial, as yet seemingly disconnected ingredients for a comprehensive understanding of Jupiter's remarkable magnetosphere.…”

Section: Introductionmentioning

confidence: 99%

Observations of thermal plasmas in Jupiter's magnetotail

2002

Self Cite

View full text Add to dashboard Cite

[1] A survey of thermal plasmas and magnetic fields is presented for the orbit of the Galileo spacecraft around Jupiter that occurred during the period May 4 through June 22, 1997. This orbit traversed the magnetotail out to Jovian radial distances of 100.2 R J in the magnetotail. Perijove was positioned at 9.3 R J . Three primary ion populations were detected with the plasma analyzer: cool hydrogen ions with temperatures of 10 eV, hot hydrogen ions with temperatures of $10 keV, and a third population of heavy ions such as O ++ , O + , S ++ , and S +++ with temperatures in the range of 500 eV. Plasma flows near perijove were in the corotational direction but with speeds $60% of those for rigid corotation with the planet out to radial distances of $18 R J . In the radial range of 18 -26 R J there were significant radial components for the bulk flows, and the flow components in the corotational direction reached values expected for rigid corotation when the current sheet was crossed. The transient character of the plasma parameters suggests that strong ion plasma acceleration is occurring in this region. The temperatures of the heavy ions increased from 5 Â 10 6 K at 9.3 R J to $10 8 K at 26 R J . At distances <20 R J there is a strong dependence of ion temperatures on System III longitude. The scalar magnetic field outside of the current sheet in the radial distance range 9.3-20 R J varied as R À2.78 and similar to that for a dipole field, and at distances >50 R J it varied as R À1.19 . The thermal plasma pressure in the current sheet is a factor of $10 less than the magnetic pressure at 9.3 R J at positions above or below the sheet but becomes equal to this magnetic pressure at radial distances >30 R J . The corresponding values of the ratio of the plasma to magnetic pressure, b, are in the range of 10-100 in the current sheet. The number densities and temperatures of these plasmas are 0.05-0.1 /cm 3 and 0.5 -1 Â 10 8 K, respectively. In the magnetotail the bulk flows of the thermal plasmas exhibit substantial components in the corotational and radially outward directions, but the bulk speeds of 50 -200 km s À1 are significantly less than those for rigid corotation. For this single orbit the average bulk flows were $50 km s À1 in the premidnight sector and 200 km s À1 in the early morning sector at radial distances >$50 R J . At apojove of 100 R J an antisunward flow of $200 km s À1 is found that is supportive of the magnetospheric ''wind'' reported for Voyager measurements of energetic charged particles. The 10-hour periodicity of the pairs of current sheet crossings at the position of the Galileo spacecraft includes a variety of dynamical signatures, which are suggested to be due to the changes in direction and pressures in the solar wind and due to the transient acceleration of plasmas in the current sheet.

show abstract

“…Frank and Paterson (2001) If volcanic activities increase, the neutral-torus density initially increases. 558…”

Section: Long-term Variations 547mentioning

confidence: 99%

Low-energy energetic neutral atom imaging of Io plasma and neutral tori

Futaana

Barabash

Wang

et al. 2015

Planetary and Space Science

View full text Add to dashboard Cite

21Io's plasma and neutral tori play significant roles in the Jovian 22 magnetosphere. We present feasibility studies of measuring low-energy 23 energetic neutral atoms (LENAs) generated from the Io tori. We calculate the 24 LENA flux between 10 eV and 3 keV. The energy range includes the 25 corotational plasma flow energy. The expected differential flux at Ganymede 26 distance is typically 10 3 -10 5 cm -2 s -1 sr -1 eV -1 near the energy of the corotation. It 27 is above the detection level of the planned LENA sensor that is to be flown to 28 the Jupiter system with integration times of 0.01-1 seconds. The flux has strong 29 asymmetry with respective to the Io phase. The observations will exhibit 30 periodicities, which can be attributed to the Jovian magnetosphere rotation and 31 the rotation of Io around Jupiter. The energy spectra will exhibit dispersion 32 signatures, because of the non-negligible flight time of the LENAs from Io to the 33 satellite. In 2030, the Jupiter exploration mission JUICE will conduct a LENA 34 2 measurement with a LENA instrument, the Jovian Neutrals Analyzer (JNA). From 35 the LENA observations collected by JNA, we will be able to derive characteristic 36 quantities, such as the density, velocity, velocity distribution function, and 37 composition of plasma-torus particles. We also discuss the possible physics to 38 be explored by JNA in addition to the constraints for operating the sensor and 39 analyzing the obtained dataset. 40 41

show abstract

Survey of thermal ions in the Io plasma torus with the Galileo spacecraft

Cited by 38 publications

References 52 publications

Cassini UVIS observations of the Io plasma torusIII. Observations of temporal and azimuthal variability

Cassini UVIS observations of the Io plasma torusIII. Observations of temporal and azimuthal variability

Observations of thermal plasmas in Jupiter's magnetotail

Low-energy energetic neutral atom imaging of Io plasma and neutral tori

Contact Info

Product

Resources

About