Observations of MeV electrons in Jupiter's innermost radiation belts and polar regions by the Juno radiation monitoring investigation: Perijoves 1 and 3
Heidi N. BeckerDaniel Santos‐CostaJohn Leif JørgensenTroelz DenverA. AdrianiA. MuraJ. E. P. ConnerneyS. J. BoltonS. LevinR. M. ThorneJames W. AlexanderVirgil AdumitroaieE. A. Manor-ChapmanI. J. DaubarClifford LeeMathias BennJulia SushkovaA. CicchettiR. Noschese
35
Citation
17
Reference
10
Related Paper
Citation Trend
Abstract:
Abstract Juno's “Perijove 1” (27 August 2016) and “Perijove 3” (11 December 2016) flybys through the innermost region of Jupiter's magnetosphere (radial distances <2 Jovian radii, 1.06 R J at closest approach) provided the first in situ look at this region's radiation environment. Juno's Radiation Monitoring Investigation collected particle counts and noise signatures from penetrating high‐energy particle impacts in images acquired by the Stellar Reference Unit and Advanced Stellar Compass star trackers, and the Jupiter Infrared Auroral Mapper infrared imager. This coordinated observation campaign sampled radiation at the inner edges of the high‐latitude lobes of the synchrotron emission region and more distant environments. Inferred omnidirectional >5 MeV and >10 MeV electron fluxes derived from these measurements provide valuable constraints for models of relativistic electron environments in the inner radiation belts. Several intense bursts of high‐energy particle counts were also observed by the Advanced Stellar Compass in polar regions outside the radiation belts.Keywords:
Jupiter (rocket family)
Particle radiation
We have systematized and recorded our study of the phase of the 10‐hour modulation of energetic electrons seen by Pioneers 10 and 11 in the Jovian magnetosphere. To start with, we focus on the peaks rather than the valleys of each cycle because the peaks are where physically interesting features occur, such as particle acceleration, current sheets, etc. To identify the peaks, we demand that the instantaneous intensity be higher than the 5‐hour running average and the 5‐hour running average be greater than the 10‐hour running average. These criteria select an interval rather than a point and we feel that this interval is an appropriate estimate of the experimental uncertainty. When the phases of the peaks are plotted together, they create patterns which we discuss in terms of disk‐like, clock‐like, and rotating anomaly models of the magnetosphere. Each model fits some of the data, but no model explains all of the data convincingly. We conclude that we still do not understand the configuration of the outer Jovian magnetosphere.
Modulation (music)
Cite
Citations (8)
Observations by the plasma wave receivers on Voyagers 1 and 2 show that a wide variety of electrostatic waves are present within the Jovian magnetosphere and that the Jovian electrostatic waves are for the most part very similar to those observed in the terrestrial magnetosphere. Bands of emission near the upper hybrid resonance frequency in the dayside outer magnetosphere are detected between higher harmonics of the electron gyrofrequency. Inside of about 23 R J , electron cyclotron harmonic emissions appear to be durable features of the inner Jovian magnetosphere and are extremely well confined to the Jovian magnetic equator. The cyclotron emissions extend from just above the local electron gyrofrequency to the upper hybrid resonance frequency.
Magnetosphere of Jupiter
Atmosphere of Jupiter
Jupiter (rocket family)
Cyclotron resonance
Cite
Citations (87)
Being based on the existence of the disc plasma flowing outward in the localized flow region with the super magnetosonic velocity called Jovian disc wind, a dynamical feature of the Jovian magnetosphere has been studied in the equatorial plane. Using a concept that the pressures inside and outside of the magnetopause are balanced by each other, a pressure balance equation has been obtained and calculated numerically to express the shape of the Jovian magnetosphere. The main pressure supporting the solar wind pressure is not the planetary magnetic pressure but the dynamic pressure of the Jovian disc wind. The nature of the Jovian disc wind with large azimuthal component in its bulk flow, therefore, has a great influence on the shape of the Jovian magnetosphere. The results of our numerical calculation of the pressure balance equation indicate a clear dawn-dusk asymmetry of the Jovian magnetosphere; i. e., Jupiter has a large scale magnetosphere in the dawn side and has a relatively small scale magnetosphere in the dusk side. Our calculation also indicates a sensitive response of the location of the Jovian magnetopause for the variation of the solar wind pressure. This feature coincides with the in-situ observations by Pioneer 10, 11, Voyager 1 and 2, and is called the "spongy nature" of the Jovian magnetosphere. In addition to the calculation for the super magnetosonic wind solution, we have obtained the shape of the magnetosphere for the case of sub-magnetosonic breeze. The results for the breeze case indicate that the stable magnetopause is able to exist only in the limited region in the day side.
Magnetosphere of Jupiter
Magnetosphere of Saturn
Magnetosheath
Jupiter (rocket family)
Atmosphere of Jupiter
Cite
Citations (2)
The plasma-analyzer experiments on Pioneers 10 and 11 have determined that the characteristics of the solar-wind interaction with the Jovian magnetosphere are basically similar to those observed for the solar-wind interaction of earth and differ mainly in terms of the scale size of the interaction. The Jovian magnetosheath flow field and the calculated normals to the Jovian magnetosphere indicate that the Jovian magnetosphere is extremely thick and blunt in shape. The size of the Jovian magnetosphere in the sunward (dayside) direction can change by as much as a factor of two in response to relatively minor changes in solar-wind dynamic pressure. The outer dayside Jovian magnetosphere is inflated with a high-beta thermal plasma.
Magnetosheath
Atmosphere of Jupiter
Magnetosphere of Jupiter
Cite
Citations (21)
We present a new model of the Jovian magnetospheric field which couples the internal field spherical harmonic coefficients from the Goddard Space Flight Center O 6 model with an Euler potential formulation of the external field. The effects of the hinging and the delay of the Jovian current sheet and the sweep‐back of the field lines resulting from the subcorotation of plasma in the magnetosphere are incorporated self‐consistently into the Euler potential equations. Because Jovian magnetosphere undergoes substantial temporal changes in its configuration, it was found necessary to obtain different fit parameters for each of the outbound passes of Pioneer 10, Voyager 1, and Voyager 2. A detailed comparison of the model with the observations obtained in the nightside Jovian magnetosphere reveals that the Euler potential approach can be used successfully to represent the field of external origin in the Jovian magnetosphere. The proposed models are applicable to the inner magnetosphere at all local times and to the middle and the outer magnetosphere on the nightside. The models should provide reliable magnetic field predicts along the trajectory of Galileo in all 11 of the initially planned orbits. We also discuss further extensions of the model which would extend their applicability to all local times and radial distances.
Jupiter (rocket family)
Plasma sheet
Cite
Citations (208)
Ring current
Cite
Citations (2)
Using observations of the Galileo PWS experiment, we show that energetic phenomena recurrently occur in the jovian magnetosphere. They are characterized by intensifications of the auroral radio emissions and the creation of new sources of radiations in the outer regions of the Io torus. Simultaneously, modifications of the structure of the plasmasheet are observed at large distance (more than 60 Rj) from Jupiter. These large‐scale processes, presenting a periodicity of 50 to 80 hours, could be linked to global instabilities of the jovian magnetosphere.
Jupiter (rocket family)
Galileo (satellite navigation)
Atmosphere of Jupiter
Cite
Citations (75)
The Jovian magnetosphere is modulated by the solar wind and centrifugal force. The configuration of the magnetic field in the previous model of the magnetosphere including the centrifugal force is consistent with the observations at low magnetic latitude (Λ < 50°), while there is a substantial difference between the results of the model and the observations at high magnetic latitude (Λ ≥ 50°), especially in the distant magnetotail. Based on the previous model, a new configuration of the Jovian magnetosphere in the night side is suggested by a three-step transformation in this study. The new magnetosphere obtained by the transformation method is flattened in the z-direction and stretched in the x-direction in distant magnetotail, which agree with general knowledge.
Magnetosphere of Jupiter
Magnetosphere of Saturn
Mercury's magnetic field
Low latitude
Cite
Citations (0)
The relevant parameters of the magnetospheres of Jupiter and earth are studied from the point of view of wave‐particle resonant interactions that are believed to be responsible for the generation of VLF chorus emissions observed on Voyager‐1. Using existing models of the cold and energetic plasma distributions in the Jovian magnetosphere, expressions for the wave‐particle interaction length ( L I ) and the nonlinearity parameter (ρ) are derived. Values of these parameters are compared with those computed for the earth's magnetosphere. It is found that the typical interaction lengths are at least 2–5 times larger in the Jovian than in the terrestrial magnetosphere. Also, the wave intensity necessary to reach the threshold of nonlinearity in the Jovian magnetosphere was found to be up to 5–100 times lower. The Voyager 1 measurements show, however, that the inferred wave magnetic field intensities of the Jovian chorus are in the range of reported intensities for terrestrial chorus. This is attributed to fact that the fluxes of few keV resonant particles found in the Jovian magnetosphere were typically two orders of magnitude higher. In this case, it is predicted that the temporal growth rates of Jovian chorus bursts should be higher than for the earth. Growth rate measurements on Voyager 1 broadband wave data are used to confirm this hypothesis.
Chorus
Jupiter (rocket family)
Atmosphere of Jupiter
Cite
Citations (30)
A review and analysis are presented of data derived from the Pioneer 10 and Pioneer 11 flybys of Jupiter on the Jovian plasma, magnetic field, and energetic particles in circumjovian space. The design of the space probes is described along with the principal experiments flown. Overall features of the Jovian magnetosphere are drawn and contrasted with the earth's magnetosphere. The trajectories of the two space probes are contrasted and their data on Jupiter's plasmasphere are correlated. Isointensity contours and count rates of energetic particles are plotted, flux tubes within the Jovian magnetosphere are mapped, the ring current (plasma torus) encircling the planet is described, and possible effects of solar wind and of the moons immersed in Jupiter's magnetosphere are considered.
Jupiter (rocket family)
Magnetosphere of Jupiter
Plasmasphere
Atmosphere of Jupiter
Ring current
Cite
Citations (0)