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
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TL;DR: In this article, emission signatures of binary compact star gravitational wave sources consisting of strongly magnetized neutron stars and/or white dwarfs (WDs) in their late-time inspiral phase were investigated.
Abstract: We investigate emission signatures of binary compact star gravitational wave sources consisting of strongly magnetized neutron stars (NSs) and/or white dwarfs (WDs) in their late-time inspiral phase. Because of electromagnetic interactions between the magnetospheres of the two compact stars, a substantial amount of energy will be extracted, and the resultant power is expected to be $\sim 10^{38} - 10^{44}$ erg/s in the last few seconds before the two stars merge, when the binary system contains a NS with a surface magnetic field $10^{12}$ G. The induced electric field in the process can accelerate charged particles up to the EeV energy range. Synchrotron radiation is emitted from energetic electrons, with radiative energies reaching the GeV energy for binary NSs and the MeV energy for NS - WD or double WD binaries. In addition, a blackbody component is also presented and it peaks at several to hundreds keV for binary NSs and at several keV for NS - WD or double WD binaries. The strong angular dependence of the synchrotron radiation and the isotropic nature of the blackbody radiation lead to distinguishable modulation patterns between the two emission components. If coherent curvature radiation is presented, fast radio bursts could be produced. These components provide unique simultaneous electromagnetic signatures as precursors of gravitational wave events associated with magnetized compact star mergers and short gamma ray bursts (e.g., GRB 100717).
35 citations
Cites methods from "Io Jupiter interaction, millisecond..."
...…was analogous to the UI model originally proposed for the the Jupiter-Io system (Piddington & Drake 1968; Goldreich & Lynden-Bell 1969, see also Hess et al. (2007)), which was also generalized for white dwarf (WD) binaries (Wu et al. 2002; Willes & Wu 2004; Dall’Osso et al. 2006, 2007; Wu et…...
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TL;DR: In this paper, emission signatures of binary compact star gravitational wave (GW) sources consisting of strongly magnetized neutron stars (NSs) and/or white dwarfs (WDs) in their late-time inspiral phase were investigated.
Abstract: We investigate emission signatures of binary compact star gravitational wave (GW) sources consisting of strongly magnetized neutron stars (NSs) and/or white dwarfs (WDs) in their late-time inspiral phase. Because of electromagnetic interactions between the magnetospheres of the two compact stars, a substantial amount of energy will be extracted, and the resultant power is expected to be ∼1038-1044 erg s-1 in the last few seconds before the two stars merge, when the binary system contains a NS with a surface magnetic field 1012 G. The induced electric field in the process can accelerate charged particles up to the EeV energy range. Synchrotron radiation is emitted from energetic electrons, with radiative energies reaching the GeV energy for binary NSs and the MeV energy for NS-WD or double WD binaries. In addition, a blackbody component is also presented, and it peaks at several to hundreds keV for binary NSs and at several keV for NS-WD or double WD binaries. The strong angular dependence of the synchrotron radiation and the isotropic nature of the blackbody radiation lead to distinguishable modulation patterns between the two emission components. If coherent curvature radiation is presented, fast radio bursts could be produced. These components provide unique simultaneous electromagnetic signatures as precursors of GW events associated with magnetized compact star mergers and short gamma-ray bursts (e.g., GRB 100717).
32 citations
TL;DR: In this article, the authors present simulations of these electrons under the assumption of acceleration by Alfven waves in the Io flux tube and provide evidence of bipolar electrostatic structures in the Jovian auroral region.
Abstract: [1] Jupiter's radio emissions are dominated in intensity by decametric radio emissions due to the Io-Jupiter interaction. A significant part of these emissions consists of short radio bursts (so-called S-bursts) drifting in time and frequency. Previous analyses suggest that these emissions are cyclotron-maser emissions in the flux tube connecting Io or Io's wake to Jupiter. We present simulations of these electrons under the assumption of acceleration by Alfven waves in the Io flux tube. Near Jupiter, a loss cone and a ring distribution appear in the magnetically mirrored electron population, which can then amplify extraordinary (X) mode radio waves. The X-mode growth rate is computed, which allows us to build theoretical dynamic spectra of the resulting Jovian radio emissions. Additional potential structures are assumed in the Jovian auroral region. We reconstruct their impact on the morphology of the emission. They match some of the time-frequency patterns observed with Jovian S-bursts. This provides the first evidence of bipolar electrostatic structures in the Jovian auroral region.
31 citations
Cites background or methods or result from "Io Jupiter interaction, millisecond..."
... Hess et al. [2007a] observed that the emission region can host many regions in which the electron motion is adiabatic separated by potential jump....
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...[8] Hess et al. [2007a, 2009] , have shown from experimental data the presence of potential jumps of few 100’s eV, located at altitudes around 0.1 RJ, which move at the local sound velocity along the magnetic field lines....
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...Their sources propagate like electrons in quasi-adiabatic motion moving along the magnetic field lines away from Jupiter [Ellis, 1965; Hess et al., 2007a, and references therein]....
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...Their sources propagate like electrons in quasi-adiabatic motion moving along the magnetic field lines away from Jupiter [Ellis, 1965; Hess et al., 2007a, and references therein]....
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...We simulate three kinds of potential structures: the potential jumps discovered by Hess et al. [2007a] , which are localized (less than few hundredsofkilometerswide),withanamplitudeupto1.5kV; and the bipolar electrostatic structures (with both polarizations),whicharecommonlyobservedintheterrestrialauroral region....
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TL;DR: In this article, the conditions for electron-cyclotron maser (ECM) emission in the solar corona were investigated by considering the ratio of the electron plasma frequency ω p to the electron cyclotron frequency Ωe.
Abstract: Context. The Sun is an active source of radio emission ranging from long duration radio bursts associated with solar flares and coronal mass ejections to more complex, short duration radio bursts such as solar S bursts, radio spikes and fibre bursts. While plasma emission is thought to be the dominant emission mechanism for most radio bursts, the electron-cyclotron maser (ECM) mechanism may be responsible for more complex, short-duration bursts as well as fine structures associated with long-duration bursts.Aims. We investigate the conditions for ECM in the solar corona by considering the ratio of the electron plasma frequency ω p to the electron-cyclotron frequency Ωe . The ECM is theoretically possible when ω p / Ωe Two-dimensional electron density, magnetic field, plasma frequency, and electron cyclotron frequency maps of the off-limb corona were created using observations from SDO/AIA and SOHO/LASCO, together with potential field extrapolations of the magnetic field. These maps were then used to calculate ω p /Ωe and Alfven velocity maps of the off-limb corona.Results. We found that the condition for ECM emission (ω p / Ωe ⊙ in an active region near the limb; that is, where magnetic field strengths are >40 G and electron densities are >3 × 108 cm-3 . In addition, we found comparatively high Alfven velocities (>0.02c or >6000 km s-1 ) at heights ⊙ within the active region.Conclusions. This demonstrates that the condition for ECM emission is satisfied within areas of the corona containing large magnetic fields, such as the core of a large active region. Therefore, ECM could be a possible emission mechanism for high-frequency radio and microwave bursts.
30 citations
TL;DR: A numerical tool is presented, called ExPRES (Exoplanetary and Planetary Radio Emission Simulator), which is able to reproduce the occurrence in time-frequency plane of CMI-generated radio emissions from planetary magnetospheres, exoplanets or star-planet interacting systems.
Abstract: Context . Earth and outer planets are known to produce intense non-thermal radio emissions through a mechanism known as cyclotron maser instability (CMI), requiring the presence of accelerated electrons generally arising from magnetospheric current systems. In return, radio emissions are a good probe of these current systems and acceleration processes. The CMI generates highly anisotropic emissions and leads to important visibility effects, which have to be taken into account when interpreting the data. Several studies have shown that modelling the radio source anisotropic beaming pattern can reveal a wealth of physical information about the planetary or exoplanetary magnetospheres that produce these emissions.Aims . We present a numerical tool, called ExPRES (Exoplanetary and Planetary Radio Emission Simulator), which is able to reproduce the occurrence in a time-frequency plane of R −X CMI-generated radio emissions from planetary magnetospheres, exoplanets, or star–planet interacting systems. Special attention is given to the computation of the radio emission beaming at and near its source.Methods . We explain what physical information about the system can be drawn from such radio observations, and how it is obtained. This information may include the location and dynamics of the radio sources, the type of current system leading to electron acceleration and their energy, and, for exoplanetary systems, the orbital period of the emitting body and the strength, rotation period, tilt, and the offset of the planetary magnetic field. Most of these parameters can only be remotely measured via radio observations.Results . The ExPRES code provides the proper framework of analysis and interpretation for past, current, and future observations of planetary radio emissions, as well as for future detection of radio emissions from exoplanetary systems (or magnetic, white dwarf–planet or white dwarf–brown dwarf systems). Our methodology can be easily adapted to simulate specific observations once effective detection is achieved.
27 citations
References
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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)....
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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)....
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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...
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...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....
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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...
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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....
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...Thus, we analyze each individual dynamic spectrum, using the more accurate VIP4 magnetic field model (Connerney et al., 1998)....
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