Energetic ion populations and periodicities near Jupiter

Anagnostopoulos, Georgios C.; Marhavilas, P. K.; Sarris, E. T.; Karanikola, I.; Balogh, A.

doi:10.1029/98je01218

Cited by 25 publications

(12 citation statements)

References 39 publications

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“…It is evident that several ion events, extending in energy up to ~300 keV (channels P1-P4) were observed by Ulysses near the bow shock. These ion events, marked as #A, #B, #C, #D in Figure 1 have been analyzed extensively in the scientific literature ( [20], its Figure 10) and were found consistent with the predictions of the shock-drift acceleration process. For instance, Anagnostopoulos et al [20] presented anisotropic pitch-angle distributions upstream from the bow shock (their Figure 10), suggesting the existence of field-aligned beams of energetic protons reflected at the bow shock.…”

Section: Observations and Discussionsupporting

confidence: 66%

“…These ion events, marked as #A, #B, #C, #D in Figure 1 have been analyzed extensively in the scientific literature ( [20], its Figure 10) and were found consistent with the predictions of the shock-drift acceleration process. For instance, Anagnostopoulos et al [20] presented anisotropic pitch-angle distributions upstream from the bow shock (their Figure 10), suggesting the existence of field-aligned beams of energetic protons reflected at the bow shock. In Figure 1 we show Ulysses' 1 min averaged time profiles of the energy density of HI-SCALE energetic ions (assumed protons) and of the VHM/FGM magnetic field (panels c and d).…”

Section: Observations and Discussionsupporting

confidence: 66%

“…More explicitly we present in Figure of the ion events observed upstream from a quasiparallel bow shock is not consistent with either SDA or a diffusive type acceleration process, but is consistent with a magnetospheric origin [20,25,26], (b) the quasi-periodic variation of the ion intensity and anisotropy at a period of ~20 / 40 min (characteristic Jovian periodicities) confirm that the Jovian magnetosphere controlled the ion observations.…”

Section: Near Jupiter's Bow Shock High-beta Events Due To Leakage Frosupporting

confidence: 68%

“…In panel e, we show the ratio β ep of energetic ion and the magnetic field for the same period 00:00-06:00, 045/1992, during the spacecraft outbound approach of Jupiter, including the times of two bow shock crossings. The major peak with a value as high as β ep(max) = 27.01, at 04:28, 045/1992, was produced by the enhancement of the energetic proton intensities, due to the Jupiter's bow shock acceleration [20,21].…”

Section: Observations and Discussionmentioning

confidence: 98%

“…The Jovian magnetosphere is known to be an interesting plasma laboratory and an important source of emissions in our solar system. Ulysses' flyby past Jupiter in February 1992, provided the scientists with observations that have improved the understanding of the structure and the dynamic processes taking place within the planet's magnetosphere and allowed a new insight into the problem of the energetic particles' origin in the near interplanetary environment [20,21,22,23].…”

Section: Near Jupiter's Bow Shock High-beta Events Due To Leakage Fromentioning

confidence: 99%

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Occurrence of high-beta superthermal plasma events in the close environment of Jupiter’s bow shock as observed by Ulysses

Marhavilas¹,

Sarris²,

Anagnostopoulos³

2011

AIP Conference Proceedings

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The ratio of the plasma pressure to the magnetic field pressure (or of their energy densities) which is known as the plasma parameter "beta" (β) has important implications to the propagation of energetic particles and the interaction of the solar wind with planetary magnetospheres. Although in the scientific literature the contribution of the superthermal particles to the plasma pressure is generally assumed negligible, we deduced, by analyzing energetic particles and magnetic field measurements recorded by the Ulysses spacecraft, that in a series of events, the energy density contained in the superthermal tail of the particle distribution is comparable to or even higher than the energy density of the magnetic field, creating conditions of high-beta plasma. More explicitly, in this paper we analyze Ulysses/HI-SCALE measurements of the energy density ratio (parameter β ep ) of the energetic ions' (20 keV to ~5 MeV) to the magnetic field's in order to find occurrences of high-beta (β ep >1) superthermal plasma conditions in the environment of the Jovian magnetosphere, which is an interesting plasma laboratory and an important source of emissions in our solar system. In particular, we examine high-beta ion events close to Jupiter's bow shock, which are produced by two processes: (a) bow shock ion acceleration and (b) ion leakage from the magnetosphere.

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Section: Observations and Discussionsupporting

confidence: 66%

Section: Observations and Discussionsupporting

confidence: 66%

Section: Near Jupiter's Bow Shock High-beta Events Due To Leakage Frosupporting

confidence: 68%

Section: Observations and Discussionmentioning

confidence: 98%

Section: Near Jupiter's Bow Shock High-beta Events Due To Leakage Fromentioning

confidence: 99%

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Occurrence of high-beta superthermal plasma events in the close environment of Jupiter’s bow shock as observed by Ulysses

Marhavilas¹,

Sarris²,

Anagnostopoulos³

2011

AIP Conference Proceedings

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Periodicities in Saturn's magnetosphere

Carbary

Mitchell

2013

Reviews of Geophysics

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Although the exact rotation period of Saturn is unknown, Saturn's magnetosphere displays an abundance of periodicities near ~10.7 h. Such modulations appear in charged particles, magnetic fields, energetic neutral atoms, radio emissions, motions of the plasma sheet and magnetopause, and even in Saturn's rings themselves. Known to an accuracy of four significant figures, these periodicities do not remain constant but vary by ~1% over time scales of a year or longer. Magnetospheric periodicities also display slightly different periods in the northern and southern hemispheres: ~10.6 h and ~10.8 h, respectively. The magnetic and spin axes of Saturn are aligned to within ~1°, so that Saturn's magnetospheric periodicities cannot be explained as “wobble” caused by a geometric tilt, unlike those of the Earth and Jupiter. Furthermore, the variations in periodicity argue against a cause related to changes interior to an object as large as Saturn. Several models have been proposed for the periodicities, including rotating planetary vortices, periodic plasma releases, and a flapping magnetodisk, but none can satisfactorily explain all of Saturn's periodicities. This review discusses the observations of these periodicities from their initial discovery during the Pioneer flyby to their long‐term surveillance by Cassini and examines the various struggles to explain and model them. Understanding Saturn's periodicity may elucidate periodic phenomena in other magnetospheric environments.

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Jovian periodicities (∼10 h, ∼40 min) on Ulysses’ Distant Jupiter Encounter observations around the Halloween CIR events

Anagnostopoulos¹,

Louri²,

Marhavilas³

et al. 2009

Advances in Space Research

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Energetic ion populations and periodicities near Jupiter

Abstract: Abstract. The HISCALE experiment, during Ulysses' approach to Jupiter, observed a -10 hour periodic softening in ion spectrum outside the plasma sheet that (1) is not related to the approach of the plasma sheet, (2) is in phase with the <> relativistic electron modulation, and (3)

Cited by 25 publications

References 39 publications

Occurrence of high-beta superthermal plasma events in the close environment of Jupiter’s bow shock as observed by Ulysses

Occurrence of high-beta superthermal plasma events in the close environment of Jupiter’s bow shock as observed by Ulysses

Periodicities in Saturn's magnetosphere

Jovian periodicities (∼10 h, ∼40 min) on Ulysses’ Distant Jupiter Encounter observations around the Halloween CIR events

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