scispace - formally typeset
Search or ask a question
Journal ArticleDOI

Io Jupiter interaction, millisecond bursts and field-aligned potentials

TL;DR: In this paper, the authors performed an automated analysis of 230 high-resolution dynamic spectra of S-bursts, providing 5 × 10 6 frequency drift measurements and confirmed over a large number of measurements that the frequency drift d f / d t (f ) is in average negative and decreases (in absolute value) at high frequencies, as predicted by the adiabatic theory.
About: This article is published in Planetary and Space Science.The article was published on 2007-01-01. It has received 61 citations till now. The article focuses on the topics: Jupiter & Jovian.
Citations
More filters
Journal ArticleDOI
TL;DR: In this paper, an introduction to the acceleration of the electrons that cause polar auroras is presented, focusing on acceleration processes involving Alfven waves and their role in the global auroral context.
Abstract: This paper is an introduction to the acceleration of the electrons that cause polar auroras. Emphasis is placed on acceleration processes involving Alfven waves and their role in the global auroral context.

3 citations

DOI
21 Mar 2022
TL;DR: In this article , an up-to-date magnetic field model and three methods to position the active Io Flux Tube (IFT) were used to accurately locate the radiosources and determine their emission angle from the local magnetic field vector.
Abstract: We investigate the beaming of 11 Io‐Jupiter decametric (Io‐DAM) emissions observed by Juno/Waves, the Nançay Decameter Array, and NenuFAR. Using an up‐to‐date magnetic field model and three methods to position the active Io Flux Tube (IFT), we accurately locate the radiosources and determine their emission angle θ from the local magnetic field vector. These methods use (a) updated models of the IFT equatorial lead angle, (b) ultraviolet (UV) images of Jupiter's aurorae, and (c) multi‐point radio measurements. The kinetic energy Ee− of source electrons is then inferred from θ in the framework of the Cyclotron Maser Instability. The precise position of the active IFT achieved from methods (b and c) can be used to test the effective plasma density of the Io torus. Simultaneous radio/UV observations reveal that multiple Io‐DAM arcs are associated with multiple UV spots and provide the first direct evidence of an Io‐DAM arc associated with a trans‐hemispheric beam UV spot. Multi‐point radio observations probe the Io‐DAM sources at various altitudes, times and hemispheres. Overall, θ varies a function of frequency (altitude), by decreasing from 75°−80° to 70°−75° over 10−40 MHz with slightly larger values in the northern hemisphere, and independently varies as a function of time (or longitude of Io). Its uncertainty of a few degrees is dominated by the error on the longitude of the active IFT. The inferred values of Ee− also vary as a function of altitude and time. For the 11 investigated cases, they range from 3 to 16 keV, with a 6.6 ± 2.7 keV average.

2 citations

01 Sep 2010
TL;DR: In this paper, the power generated at the satellite is compared to the power of the observed auroral emissions, which implies an efficient power transfer between the satellite and the planet where the emission occurs.
Abstract: Several cases of interactions between planetary magnetospheres and satellite atmospheres have been observed in the giant planet magnetospheres. Io, Europa, Ganymede and Enceladus generate observable auroral emissions on their parent planet. This implies an efficient power transfer between the satellite – where the interaction occurs – and the planet – where the emission occurs. In this chapter, we discuss the power generation at the satellite, the transport of energy and momentum along the magnetic field lines via Alfven waves and the transfer of wave power to electrons. We relate the power generated at the satellite to the power of the observed auroral emissions.

2 citations

01 Dec 2010
TL;DR: In this article, a waveform receiver (WFR) and wave modulations (WMs) were used to detect the ionospheric Alfven resonator (IAR) expected in the system of Jupiter.
Abstract: [1] On 4 June 2008 UT, the position of the satellite Io with respect to Jupiter was the so-called Io-A, we observed Jovian decametric (DAM) radio emissions using a waveform receiver (WFR) and detected wave modulations (WMs) in the DAM emissions. WMs appeared four times at intervals of approximately 7 min for durations of 3–10 s each. We found that the WMs had fundamental frequencies of 2.5–5 Hz, and the 1st and 2nd harmonics of these frequencies were odd resonances at the fundamental frequencies. Simulations confirmed that strong Alfven waves arrive at the polar regions of Jupiter at 5–7 min intervals when Io is located at the center of the Io plasma torus, and Io was located at that location when WMs were detected. The 7 min intervals of WMs are consistent with the characteristic periods of Alfven waves, suggesting the existence of the ionospheric Alfven resonator (IAR) expected in the system of Jupiter. Thus far, few observations have suggested the existence of IAR in Jupiter. In this research, we suggest the existence of IAR in Jupiter by using a WFR and the millisecond modulations of Jovian L-burst emissions.

1 citations

Posted Content
TL;DR: In this paper, the effects of the frequency-related delay of radiation in broadband Jovian radio storms consisting of periodic S-bursts (S-burst trains) at 16 to 30 MHz were investigated.
Abstract: The dominant viewpoint on Jovian decametric S-burst emission neglects the time delay of the radiation, although its base theory of electron cyclotron maser instability allows a significant decreasing of X-mode group velocity near the cutoff frequency at the bottom of source region. We searched for effects of the frequency-related delay of radiation in broadband Jovian radio storms consisting of periodic S-bursts (S-burst trains) at 16 to 30 MHz. It was found that up to 1% of bursts in a train are of distorted meandering shape in dynamic spectrum, where the emission from one radio source was observed at several frequencies simultaneously. It is difficult to explain such spectra in terms of radio waves beaming or causality without significant frequency-related delay of radio emission. We found experimentally that the frequency drift rate of middle lines of such events coincides with the drift rate of disturbances in common S-bursts. This indicates a general distortion of the dynamic spectrum of S-bursts. As a result, the correlation method for the measurement of the spectral distortion is proposed. Using this method, we found the approximation coefficients for the distortion in 32 spectra of 8 Io-B storms. The corrected spectra formally show that S-burst trains do not move mainly outward from Jupiter, as it is usually assumed, but fly in the opposite direction. Our simulation confirms that the dispersion is capable in principle to reproduce the found spectral distortion. Hence, the dispersion-like phenomena in Jovian S-bursts deserve discussion because they have no satisfactory explanations in terms of traditional approach.

1 citations

References
More filters
Journal ArticleDOI
TL;DR: In this paper, it was found that reflected electrons can result in the amplification of electromagnetic waves via a relativistic normal cyclotron resonance, which may explain the recently discovered terrestrial kilometric radiation.
Abstract: During magnetospheric substorms, electrons with energies of about 1 keV are injected from the plasma-sheet region into the auroral region. A fraction of these energetic electrons can precipitate into the upper atmosphere, and the rest are reflected because of the mirror effect of the convergent geomagnetic field. It is found that these reflected electrons can result in the amplification of electromagnetic waves via a relativistic normal cyclotron resonance. This process may explain the recently discovered terrestrial kilometric radiation.

951 citations


"Io Jupiter interaction, millisecond..." refers background in this paper

  • ...The magnetic mirror at the foot of the Io flux tube (IFT) reflects a part of the electrons, whose distribution is then unstable relative to the cyclotron-maser instability and produces emission at the local cyclotron frequency (Wu and Lee, 1979; Louarn, 1992)....

    [...]

Journal ArticleDOI
TL;DR: In this article, a polar orbiting satellite was used to measure spatially confined regions of extremely large electric fields in the auroral zone at altitudes below 8000 km, which are identified as paired electrostatic shocks which are associated with electrostatic ion cyclotron wave turbulence.
Abstract: dc and ac plasma-density and vector-electric-field detectors on a polar orbiting satellite have measured spatially confined regions of extremely large (\ensuremath{\sim}\textonehalf{} V/m) electric fields in the auroral zone at altitudes below 8000 km. Such regions frequently have double structures of opposing electric fields containing characteristic and different wave spectra internal and external to themselves. These structures are identified as paired electrostatic shocks which are associated with electrostatic ion cyclotron wave turbulence.

671 citations


"Io Jupiter interaction, millisecond..." refers background in this paper

  • ...Potential drops like those evidenced in Section 5 are observed in situ in the terrestrial auroral zones (Mozer et al., 1977)....

    [...]

Journal ArticleDOI
TL;DR: In this article, a nonlinear analytical model of the Alfven current tubes continuing the currents through Io (or rather its ionosphere) generated by the unipolar inductor effect due to Io's motion relative to the magnetospheric plasma was presented.
Abstract: We present a nonlinear analytical model of the Alfven current tubes continuing the currents through Io (or rather its ionosphere) generated by the unipolar inductor effect due to Io's motion relative to the magnetospheric plasma. We thereby extend the linear work by Drell et al. (1965) to the fully nonlinear, sub-Alfvenic situation also including flow which is not perpendicular to the background magnetic field. The following principal results have been obtained: (1) The portion of the currents feeding Io is aligned with the Alfven characteristics at an angle θA = tan−1 MA to the magnetic field for the special case of perpendicular flow where MA is the Alfven Mach number. (2) The Alfven tubes act like an external conductance ΣA = 1/(µ0VA(1 + MA² + 2MA sin θ)1/2) where VA is the Alfven speed and θ the angular deviation from perpendicular flow towards the direction of Alfven wave propagation. Hence the Jovian ionospheric conductivity is not necessary for current closure. (3) In addition, the Alfven tubes may be reflected from either the torus boundary or the Jovian ionosphere. The efficiency of the resulting interaction with these boundaries varies with Io position. The interaction is particularly strong at extreme magnetic latitudes, thereby suggesting a mechanism for the Io control of decametric emissions. (4) The reflected Alfven waves may heat both the torus plasma and the Jovian ionosphere as well as produce increased diffusion of high-energy particles in the torus. (5) From the point of view of the electrodynamic interaction, Io is unique among the Jovian satellites for several reasons: these include its ionosphere arising from ionized volcanic gases, a high external Alfvenic conductance ΣA, and a high corotational voltage in addition to the interaction phenomenon with a boundary. (6) We find that Amalthea is probably strongly coupled to Jupiter's ionosphere while the outer Galilean satellites may occasionally experience super-Alfvenic conditions.

538 citations


"Io Jupiter interaction, millisecond..." refers background in this paper

  • ...This electric field induces currents and/or Alfvén waves (Goldreich and Lynden-Bell, 1969; Neubauer, 1980; Saur, 2004) which accelerate electrons from the Io torus toward Jupiter along the magnetic field...

    [...]

  • ...As the Io–Jupiter plasma has the structure of an Alfvén wing (Neubauer, 1980; Saur, 2004), we can expect that Alfvén waves play an important role in the acceleration of the electrons....

    [...]

Journal ArticleDOI

492 citations


"Io Jupiter interaction, millisecond..." refers background in this paper

  • ...This electric field induces currents and/or Alfvén waves (Goldreich and Lynden-Bell, 1969; Neubauer, 1980; Saur, 2004) which accelerate electrons from the Io torus toward Jupiter along the magnetic field...

    [...]

Journal ArticleDOI
TL;DR: In this paper, a spherical harmonic model of the magnetic field of Jupiter was derived from in situ magnetic field measurements and remote observations of the position of the foot of the Io flux tube in Jupiter's ionosphere.
Abstract: Spherical harmonic models of the planetary magnetic field of Jupiter are obtained from in situ magnetic field measurements and remote observations of the position of the foot of the Io flux tube in Jupiter's ionosphere. The Io flux tube (IFT) footprint locates the ionospheric footprint of field lines traced from Io's orbital radial distance in the equator plane (5.9 Jovian radii). The IFT footprint is a valuable constraint on magnetic field models, providing “ground truth” information in a region close to the planet and thus far not sampled by spacecraft. The magnetic field is represented using a spherical harmonic expansion of degree and order 4 for the planetary (“internal”) field and an explicit model of the magnetodisc for the field (“external”) due to distributed currents. Models fitting Voyager 1 and Pioneer 11 magnetometer observations and the IFT footprint are obtained by partial solution of the underdetermined inverse problem using generalized inverse techniques. Dipole, quadrupole, octupole, and a subset of higher-degree and higher-order spherical harmonic coefficients are determined and compared with earlier models.

426 citations


"Io Jupiter interaction, millisecond..." refers methods in this paper

  • ...A more accurate magnetic field model is VIP4 (Connerney et al., 1998) based on Voyager and Pioneer magnetometer measurements together with IR observation of the IFT footprint at the surface of Jupiter....

    [...]

  • ...Thus, we analyze each individual dynamic spectrum, using the more accurate VIP4 magnetic field model (Connerney et al., 1998)....

    [...]