First Evidence for Multiple‐Harmonic Standing Alfvén Waves in Jupiter's Equatorial Plasma Sheet

Manners, Harry; Masters, A.

doi:10.1029/2019gl083899

Cited by 18 publications

(28 citation statements)

References 37 publications

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“…The results presented here represent the first model of ULF wave propagation in the Jovian magnetosphere based on realistic magnetic field and plasma parameters. Our conclusions support and extend the suggestions of Nichols et al (2017), Manners et al (2018), and Manners and Masters (2019) that resonant Alfvén waves can result in the quasiperiodic oscillations in the 10–40 min range. Our model, based on the magnetic field model of Connerney et al (1981) and the plasma model of Bagenal and Delamere (2011), shows a rich spectrum of wave modes in this range.…”

Section: Discussionsupporting

confidence: 92%

“…In situ observations at Jupiter have indicated that magnetic fluctuations in the 10–20 min range were present in Voyager 2 data (Khurana & Kivelson, 1989). Similar observations were made by Galileo (Manners & Masters, 2019; Manners et al, 2018; Wilson & Dougherty, 2000). In addition, Alfvén waves have long been associated with the coupling of the moon Io with the ionosphere of Jupiter (e.g., Acuña et al, 1981; Bagenal, 1983; Belcher et al, 1981; Chust et al, 2005; Crary, 1997; Goertz, 1980; Gurnett & Goertz, 1981; Hinton et al, 2019; Neubauer, 1980); however, the focus of this letter will be on the main auroral oval.…”

Section: Introductionsupporting

confidence: 81%

“…Next, we should consider the wave forms associated with these eigenmodes. Since there are multiple harmonics in the region of interest and a wide variety of field lines to consider, we will be guided by the observations of Manners and Masters (2019), who observed a number of resonant modes by the Galileo satellite. Their observations occurred near the equatorial plane at a radial distance of 23 R J , so the M = 23 field line is appropriate.…”

Section: Calculation Of the Field Line Resonance Frequenciesmentioning

confidence: 99%

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Field Line Resonances in Jupiter's Magnetosphere

Lysak

Song

2020

Geophysical Research Letters

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The arrival of the Juno satellite at Jupiter has led to an increased interest in the dynamics of the Jovian magnetosphere. Jupiter's auroral emissions often exhibit quasiperiodic oscillations with periods of tens of minutes. Magnetic observations indicate that ultralow-frequency (ULF) waves with similar periods are often seen in data from Galileo and other satellites traversing the Jovian magnetosphere. Such waves can be associated with field line resonances, which are standing shear Alfvén waves on the field lines. Using model magnetic fields and plasma distributions, the frequencies of field line resonances and their harmonics on field lines connecting to the main auroral oval have been determined. Time domain simulations of Alfvén wave propagation have illustrated the evolution of such resonances. These studies indicate that harmonics of the field line resonances are common in the 10-40 min band. Plain Language Summary The magnetic field lines of planets like Earth and Jupiter can act like the strings of a musical instrument and can support waves at specific frequencies in the same way that a guitar or violin string has a particular frequency. The rapid rotation of Jupiter causes its field line to be stretched out, and Jupiter's moon Io produces a dense cloud of ionized gas (plasma) that populates these stretched field lines. By making a numerical model of Jupiter's magnetic field and plasma, we have calculated the frequencies of these field lines, which have much lower frequencies than a musical instrument so that the periods are tens of minutes. This period corresponds to oscillations in the visible aurora (northern and southern lights) at Jupiter.

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Section: Discussionsupporting

confidence: 92%

Section: Introductionsupporting

confidence: 81%

Section: Calculation Of the Field Line Resonance Frequenciesmentioning

confidence: 99%

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Field Line Resonances in Jupiter's Magnetosphere

Lysak

Song

2020

Geophysical Research Letters

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“…However, if this periodicity originated in the solar wind, it is unclear how it would be preserved traveling across Jupiter's bow shock and magnetosheath. Another explanation could involve ultralow frequency (ULF) waves that have been measured to have periods of ∼10 min (Dunn et al, , ; Khurana & Kivelson, ; Manners et al, ; Manners & Masters, ). The frequencies of ULF waves depend on the length and the mass content of the perturbed field line.…”

Section: Discussionmentioning

confidence: 99%

Temporal and Spectral Studies by XMM‐Newton of Jupiter's X‐ray Auroras During a Compression Event

et al. 2020

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We report the temporal and spectral results of the first XMM-Newton observation of Jupiter's X-ray auroras during a clear magnetospheric compression event on June 2017 as confirmed by data from the Jovian Auroral Distributions Experiment (JADE) instrument onboard Juno. The northern and southern auroras were visible twice and thrice respectively as they rotated in and out of view during the ∼23-hr (almost 2.5 Jupiter rotations) long XMM-Newton Jovian-observing campaign. Previous auroral observations by Chandra and XMM-Newton have shown that the X-ray auroras sometimes pulse with a regular period. We applied wavelet and fast Fourier transforms (FFTs) on the auroral light curves to show that, following the compression event, the X-ray auroras exhibited a recurring 23-to 27-min periodicity that lasted over 12.5 hr (longer than a Jupiter rotation). This periodicity was observed from both the northern and southern auroras, suggesting that the emission from both poles was caused by a shared driver. The soft X-ray component of the auroras is due to charge exchange processes between precipitating ions and neutrals in Jupiter's atmosphere. We utilized the Atomic Charge Exchange (ACX) spectral package to produce solar wind and iogenic plasma models to fit the auroral spectra in order to identify the origins of these ions. For this observation, the iogenic model gave the best fit, which suggests that the precipitating ions are from iogenic plasma in Jupiter's magnetosphere. Plain Language SummaryThe solar wind is a continuous stream of charged particles released by the Sun that flows out toward the edge of the Solar System. It meets obstacles along the way, such as the magnetic fields of planets like the Earth to create a magnetic bubble around them called a magnetosphere. The magnetosphere prevents most of these charged particles from reaching the Earth's atmosphere. Those that make their way through interact with the gas molecules in the atmosphere above the polar regions and cause them to glow to produce the auroras or the northern and southern lights. Jupiter's auroras are much more powerful than the Earth's, and they emit different types of radiation, including X-rays. It is currently unclear as to what causes Jupiter's X-ray auroras. Its moon, Io, spews volcanic material into the magnetosphere that can be accelerated into the planet's atmosphere. We created models that consisted of the particles found in the solar wind and in the material from Io's volcanoes to see which one was responsible for Jupiter's X-ray auroras. In this case, it was Io's volcanoes. We also found that the auroras pulsate every ∼23-27 min in the north and ∼23-33 min in the south.

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“…The magnetosphere can therefore be treated as an infinite set of independent resonators, each with its own natural frequency and so its own set of harmonics (Wright & Mann, 2013). A case study by Manners and Masters (2019) presented a multiple-harmonic SAW confined to the plasma sheet in the Jovian magnetotail, with spectral properties consistent with frequently observed QPO periods. This demonstrates that at least a subset of QPOs is described by SAWs.…”

Section: Introductionmentioning

confidence: 88%

The Global Distribution of Ultralow‐Frequency Waves in Jupiter's Magnetosphere

Manners

Masters

2020

JGR Space Physics

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Jupiter's giant magnetosphere is a complex system seldom in a configuration approximating steady state, and a clear picture of its governing dynamics remains elusive. Crucial to understanding how the magnetosphere behaves on a large scale are disturbances to the system on length-scales comparable to the cavity, which are communicated by magnetohydrodynamic waves in the ultralow-frequency band (<1 mHz). In this study we used magnetometer data from multiple spacecraft to perform the first global heritage survey of these waves in the magnetosphere. To map the equatorial region, we relied on the large local-time coverage provided by the Galileo spacecraft. Flyby encounters performed by Voyager 1 and 2, Pioneer 10 and 11, and Ulysses provided local-time coverage of the dawn sector. We found several hundred events where significant wave power was present, with periods spanning ∼5-60 min. The majority of events consisted of multiple superposed discrete periods. Periods at ∼15, ∼30, and ∼40 min dominated the event-averaged spectrum, consistent with the spectra of quasi-periodic pulsations often reported in the literature. Most events were clustered in the outer magnetosphere close to the magnetopause at noon and dusk, suggesting that an external driving mechanism may dominate. The most energetic events occurred close to the planet, though more sporadically, indicating an accumulation of wave energy in the inner magnetosphere or infrequent impulsive drivers in the region. Our findings suggest that dynamics of the system at large scales is modulated by this diverse population of waves, which permeate the magnetosphere through several cavities and wave guides.

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First Evidence for Multiple‐Harmonic Standing Alfvén Waves in Jupiter's Equatorial Plasma Sheet

Cited by 18 publications

References 37 publications

Field Line Resonances in Jupiter's Magnetosphere

Field Line Resonances in Jupiter's Magnetosphere

Temporal and Spectral Studies by XMM‐Newton of Jupiter's X‐ray Auroras During a Compression Event

The Global Distribution of Ultralow‐Frequency Waves in Jupiter's Magnetosphere

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