Radio Emissions Of Jupiter Research Articles

Particle-in-cell simulations of electron–positron cyclotron maser forming pulsar radio zebras

Context. The microwave radio dynamic spectra of the Crab pulsar interpulse contain fine structures represented via narrowband quasiharmonic stripes. The pattern significantly constrains any potential emission mechanism. Similar to the zebra patterns observed, for example, in type IV solar radio bursts or decameter and kilometer Jupiter radio emission, the double plasma resonance (DPR) effect of the cyclotron maser instability may allow for interpretion of observations of pulsar radio zebras. Aims. We provide insight at kinetic microscales of the zebra structures in pulsar radio emissions originating close to or beyond the light cylinder. Methods. We present electromagnetic relativistic particle-in-cell (PIC) simulations of the electron–positron cyclotron maser for cyclotron frequency smaller than the plasma frequency. In four distinct simulation cycles, we focused on the effects of varying the plasma parameters on the instability growth rate and saturation energy. The physical parameters were the ratio between the plasma and cyclotron frequency, the density ratio of the “hot” loss-cone to the “cold” background plasma, the loss-cone characteristic velocity, and comparison with electron–proton plasma. Results. In contrast to the results obtained from electron–proton plasma simulations (for example, in solar system plasmas), we find that the pulsar electron–positron maser instability does not generate distinguishable X and Z modes. On the contrary, a singular electromagnetic XZ mode was generated in all studied configurations close to or above the plasma frequency. The highest instability growth rates were obtained for the simulations with integer plasma-to-cyclotron frequency ratios. The instability is most efficient for plasma with characteristic loss-cone velocity in the range vth = 0.2 − 0.3c. For low density ratios, the highest peak of the XZ mode is at double the frequency of the highest peak of the Bernstein modes, indicating that the radio emission is produced by a coalescence of two Bernstein modes with the same frequency and opposite wave numbers. Our estimate of the radiative flux generated from the simulation is up to ∼30 mJy from an area of 100 km2 for an observer at 1 kpc distance without the inclusion of relativistic beaming effects, which may account for multiple orders of magnitude.

Jupiter's Auroral Radio Emissions Observed by Cassini: Rotational Versus Solar Wind Control, and Components Identification

AbstractReanalyzing Cassini radio observations performed during Jupiter's flyby of 2000–2001, we study the internal (rotational) versus external (solar wind) control of Jupiter's radio emissions, from kilometer to decameter wavelengths, and the relations between the different auroral radio components. For that purpose, we build a database of the occurrence of Jovian auroral radio components bKOM, HOM, and DAM observed by Cassini, and then frequency‐longitude stacked plots of the polarized intensity of these radio components. Comparing the results obtained inbound and outbound, as a function of the Observer's or Sun's longitude, we find that HOM & DAM are dominantly rotation‐modulated (i.e., emitted from searchlight‐like sources fixed in Jovian longitude), whereas bKOM is modulated more strongly by the solar wind than by the rotation (i.e., emitted from sources more active within a given Local Time sector). We propose a simple analytical description of these internal and external modulations and evaluate its main parameters (the amplitude of each control) for HOM + DAM and bKOM. Comparing Cassini and Nançay Decameter Array data, we find that HOM is primarily connected to the decameter emissions originating from the dusk sector of the Jovian magnetosphere. HOM and DAM components form a complex but stable pattern in the frequency‐longitude plane. HOM also seems to be related to the “lesser arcs” identified by Voyager. bKOM consists of a main part above 40 kHz in antiphase with HOM occurrence, and detached patches below 80 kHz in phase with HOM. The frequency‐longitude patterns formed by DAM, HOM and bKOM remain to be modeled.

Latitudinal Beaming of Jupiter's Radio Emissions From Juno/Waves Flux Density Measurements

AbstractThe observations from the Juno spacecraft in polar orbit of Jupiter provide for the first time a complete view of Jupiter's radio emissions from all latitudes. Characterizing the latitudinal distribution of radio emissions' occurrence and intensity is a useful step for elucidating their origin. Here, we analyze for that purpose the first 3 years of observations from the Waves experiment on the Juno spacecraft (mid‐2016 to mid‐2019). Two prerequisites for the construction of the latitudinal distribution of intensities for each Jovian radio component are (a) to work with absolute flux densities and (b) to be able to associate each radio measurement with a specific radio component. Accordingly, we develop a method to convert the Juno/Waves data in flux densities and then we build a catalog of all Jovian radio components over the first 3 years of Juno's orbital mission. From these, we derive occurrence and intensity distributions versus observer's latitude and frequency for each component; these will be the basis for future detailed studies and interpretations of each component's characteristics and origin.

Growth Rates of the Electrostatic Waves in Radio Zebra Models

Abstract Zebras were observed not only in the solar radio emission but also in radio emissions of Jupiter and the Crab Nebula pulsar. In their models, growth rates of the electrostatic waves play an important role. Considering the plasma composed from the thermal background plasma and hot and rare component with the Dory–Guest–Harris distribution, we compute the growth rates γ and dispersion branches of the electrostatic waves in the ω − k ⊥ domain. We show complexity of the electrostatic wave branches in the upper-hybrid band. In order to compare the results, which we obtained using the kinetic theory and particle-in-cell (PIC) simulations, we define and compute the integrated growth rate Γ, where the “characteristic width” of dispersion branches was considered. We found a very good agreement between the integrated growth rates and those from PIC simulations. For maximal and minimal Γ we showed locations of dispersion branches in the ω − k ⊥ domain. We found that Γ has a maximum when the dispersion branches not only cross the region with high growth rates γ, but when the dispersion branches in this region are sufficiently long and wide. We also mentioned the effects of changes in the background plasma and hot component temperatures.

Jupiter radio emission induced by Ganymede and consequences for the radio detection of exoplanets

By analysing a database of 26 yr of observations of Jupiter with the Nançay Decameter Array, we unambiguously identify the radio emissions caused by the Ganymede–Jupiter interaction. We study the energetics of these emissions via the distributions of their intensities, duration, and power, and compare them to the energetics of the Io–Jupiter radio emissions. This allows us to demonstrate that the average emitted radio power is proportional to the Poynting flux from the rotating Jupiter’s magnetosphere intercepted by the obstacle. We then generalize this result to the radio-magnetic scaling law that appears to apply to all plasma interactions between a magnetized flow and an obstacle, magnetized or not. Extrapolating this scaling law to the parameter range corresponding to hot Jupiters, we predict large radio powers emitted by these objects, that should result in detectable radio flux with new-generation radiotelescopes. Comparing the distributions of the durations of Ganymede–Jupiter and Io–Jupiter emission events also suggests that while the latter results from quasi-permanent Alfvén wave excitation by Io, the former likely results from sporadic reconnection between magnetic fields Ganymede and Jupiter, controlled by Jupiter’s magnetic field geometry and modulated by its rotation.

A twofold mission to the moon: Objectives and payloads

Ukraine has scientific and technical potential to construct a spacecraft and payloads for exploration of the Moon in collaboration with other interested countries. In this paper we propose a double mission that consists of two parts: (1) orbiter exploration from an elongated orbit with a pericenter over the north pole (100 km above the surface) and the apocenter over the south pole (altitude about 3000 km), and (2) exploration with a lander located on the lunar farside near the south pole in the surroundings of the crater Braude. The lander carries five antennas for radio astronomy observations from hundreds of KHz to 40 MHz. The farside landing is necessary to provide effective shielding electromagnetic noises from the Earth, including aurora and lighting radiation. The lander communicates with the relay satellite in a high portion of the orbit; the orbiter is equipped with scientific payloads for investigation of the lunar surface. In the mode of a radio spectrometer, the radio antennas may study solar flares of various types, coronal mass ejections, Jupiter radio emission (L and S bursts), and Saturn (lightning and kilometer radio emission). Overlapping frequencies in the range of 10–40 MHz will allow coordination with terrestrial radio telescopes of IRA NAS, Ukraine (UTR-2, GURT), whose operation is limited by the Earth ionosphere. The absence of terrestrial noise allows us to approach the solution of the problem of searching for cosmological effects associated with the line of neutral hydrogen at Z = 50 … 100. The lander panoramic camera equipped with color and polarization filters provides important observations of horizon glow caused by the effect of electrostatic levitation of the lunar dust. For the orbital module we suggest remote-sensing instruments, which had not previously been used in space exploration of the Moon. The expected spatial resolution of the data will be about 100 m for the northern hemisphere. The equipment should include instruments, prototypes of which are already available in science organizations of Ukraine. These include an infrared spectrometer to map the abundance of OH/H2O compounds in the lunar soil. A HiRes camera operating in two spectral bands is suggested for mapping structural and mineralogical characteristics of young surface formations. The 3-mm radar, working in a squint mode, will not only map the radio brightness of the surface, which characterizes its roughness, but also improve the lunar topographic model with a spatial resolution of 100 m.

Io's volcanism controls Jupiter's radio emissions

AbstractJupiter's sodium nebula showed an enhancement in late May through the beginning of June 2007. This means Io's volcanic activity and the magnetosphere's plasma content increased during this period. On the other hand, Jupiter's radio emission called HOM became quiet after the sodium nebula enhancement. The HOM emission is considered to be related to the activity of aurorae on Jupiter. These observation results therefore suggest that the increase in plasma supply from Io into Jupiter's magnetosphere weakens its field‐aligned current, which generates the radio emissions and aurorae on Jupiter. By comparing our observation results to recent model and observation results, we add supporting evidence to the possibility that Io's volcanism controls Jupiter's magnetospheric activity.

Explanation of dominant oblique radio emission at Jupiter and comparison to the terrestrial case

The Io–Jupiter S-bursts are series of quasi-periodic impulsive decameter radio emissions from the magnetic flux tube connecting Jupiter to its closest galilean satellite Io. This paper discusses the possibility, suggested by previous works by Hess et al., that the S-bursts are triggered by upgoing electrons accelerated (downward) by trapped Alfvén waves, that have mirrored above the Jupiter ionosphere. According to this theory, the S-bursts would correspond to wave modes that propagate at oblique angles with respect to the magnetic field. Oblique propagation is also inferred for the more slowly varying components of Io–Jupiter radio emissions. Previous works, mainly based on observations of the terrestrial AKR, whose generation process is closely related to those of S-bursts, showed that these waves are emitted on perpendicular wave modes. This discrepancy between the Jovian and Terrestrial cases has led to a controversy about the credibility of the S-bursts model by Hess et al. In the present paper, we show that indeed, the most unstable wave modes for Earth AKR, and Io–Jupiter S-bursts, as they are seen from ground based radio-telescopes, are not the same. Several causes are evaluated: observational bias, the different degree of plasma magnetization above Earth and Jupiter, the role of a cold plasma component and of plasma auroral cavities. Furthermore, we make predictions about what kind of radiation modes a probe crossing the low altitude Io–Jupiter flux tube will see.

Effect of electric potential structures on Jovian S‐burst morphology

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 Alfvén 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.

Generation of the jovian radio decametric arcs from the Io Flux Tube

Jupiter's radio emissions are dominated in intensity by decametric radio emissions due to the Io‐Jupiter interaction. Previous analyses suggest that these emissions are cyclotron‐maser emissions in the flux tubes connecting Io or Io's wake to Jupiter. The electrons that trigger the emission are thought to be accelerated toward Jupiter. We present simulations of this hot electron population under the assumption of impulsive acceleration, consistent with the accelerated electron populations seen in the Io's wake by Galileo during its flyby in 1995. After the impulsive acceleration phase, the electrons are supposed to have an adiabatic motion along the magnetic field lines. Near Jupiter, a loss cone and a shell appear in the magnetically mirrored electron population. Such features are able to amplify extraordinary (X) mode radio waves. We compute the X‐mode growth rate, which allows us to build theoretical dynamic spectra of the resulting Jovian radio emissions. The study of the growth rates obtained by simulation and their comparison with ground‐based radio observations provide strong constraints on the acceleration process and energy sources at the origin of the Io‐controlled decameter emissions.

Jovian S burst generation by Alfvén waves

Jupiter's radio emissions are dominated in intensity by decametric radio emissions due to the Io‐Jupiter interaction. Previous analyses suggest that these emissions are cyclotron‐maser emissions in the flux tubes connecting Io or Io's wake to Jupiter. Electrons responsible for the emission are thought to be accelerated from Io to Jupiter. We present simulations of this hot electron population under the assumption of acceleration by Alfvén waves in the Io flux tube. Outside of limited acceleration regions where a parallel electric field associated with Alfvén waves exists, the electrons are supposed to have an adiabatic motion along the magnetic field lines. Near Jupiter a loss cone appears in the magnetically mirrored electron population, which is able to 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, whose characteristics match those observed for Jovian S bursts.

LOFAR and Jupiter's radio (synchrotron) emissions

Jupiter's radio emissions at frequencies below 300 MHz have never been imaged at high spatial resolution. In this paper we discuss the role of LOFAR to image Jupiter's synchrotron radiation at low frequencies to study the low-energy, barely relativistic, electron population in the planet's radiation belts. Radio spectra of Jupiter's synchrotron radiation have revealed significant modifications over time at frequencies between ∼ 100 and 1000 MHz, suggestive of processes such as pitch angle scattering by plasma waves, Coulomb scattering and perhaps energy degradation by dust. With LOFAR we may begin investigating the cause of such variability through its imaging capabilities at frequencies ≲ 200 MHz at high angular resolution. In particular, quasi-simultaneous observations with LOFAR and higher frequency arrays, such as the Very Large Array (VLA), may provide the necessary data to identify the cause of such variability, which is tightly coupled to the origin and mode of transport (including source/loss terms) of the high-energy electrons in Jupiter's inner radiation belts.

Control of Jupiter's radio emission and aurorae by the solar wind

Control of Jupiter's radio emission and aurorae by the solar wind

Control of Jupiter's radio emission and aurorae by the solar wind.

Radio emissions from Jupiter provided the first evidence that this giant planet has a strong magnetic field and a large magnetosphere. Jupiter also has polar aurorae, which are similar in many respects to Earth's aurorae. The radio emissions are believed to be generated along the high-latitude magnetic field lines by the same electrons that produce the aurorae, and both the radio emission in the hectometric frequency range and the aurorae vary considerably. The origin of the variability, however, has been poorly understood. Here we report simultaneous observations using the Cassini and Galileo spacecraft of hectometric radio emissions and extreme ultraviolet auroral emissions from Jupiter. Our results show that both of these emissions are triggered by interplanetary shocks propagating outward from the Sun. When such a shock arrives at Jupiter, it seems to cause a major compression and reconfiguration of the magnetosphere, which produces strong electric fields and therefore electron acceleration along the auroral field lines, similar to the processes that occur during geomagnetic storms at the Earth.

Jupiter Quest

The authors describe a scientific endeavor that excites students and changes their thought processes as they embark on a journey of discovery. ALL SCIENCE teachers want to convey to students the true meaning of the scientific endeavor. We want them not just to understand science, but also to feel some part of the exhilaration that comes with scientific discovery. But there remains a significant difference between even advanced science classrooms and professional science. For students to get a taste of the world of professional science, they must have access to the scientific community and be given the chance to be real scientists. The Goldstone Apple Valley Radio Telescope (GAVRT) Project began as a proposal from two educators at the Lewis Center for Educational Research (then called the Apple Valley Science & Technology Center) in Apple Valley, California, to allow students in middle and high schools to experience science using a 34-meter radio antenna located at the Goldstone (California) facility of NASA's Deep Space Network. The dish had already been scheduled to be decommissioned. This idea has given rise to a partnership involving NASA (National Aeronautics and Space Administration), the Jet Propulsion Laboratory, and the Lewis Center for Educational Research. Today, the project has one complete curriculum package, called Jupiter Quest, and a number of others are under development. The new curriculum packages will focus on the sun/Earth relationship, the birth of new stars in our galaxy, and the mapping of radio sources on the galactic plane. The goal of all these curriculum packages is to allow students to step briefly into the world of professional research scientists and to experience the process of discovery. The Jupiter Quest curriculum concerns a hypothetical space mission to the Jovian system. Students work in teams to study Jupiter and its four largest moons. They perform experiments to understand science concepts that may be new to them, they observe Jupiter with the radio antenna, and they scrutinize data collected during observations. Then the students select Jupiter itself or one of its larger moons for further study and as a destination for a hypothetical manned or unmanned mission. They must consider environment, planetary geology, gravity, time, nutrition, and health concerns. In the process, they learn the importance of asking such questions as What further information is needed? and How do scientific teams plan missions to collect specific types of information? Depending on the focus of each class, students may investigate one or a few areas in depth while just touching on others. Skills in scientific reasoning, in the presentation of evidence, and in effective communication are stressed, while students learn the value of peer review and how research scientists discover, verify, and share information and ideas. Jupiter Quest, which partners middle schools and high schools nationwide with the Jet Propulsion Laboratory and the Lewis Center for Educational Research, engages students in the process of scientific discovery while helping teachers provide a standards-based course of study. At the close of the 1999-2000 school year, 58 teachers in 36 schools in nine states had been trained to use Jupiter Quest. This project gives students a chance to become part of a team whose members truly depend on one another. It gives them a chance to collect and process real-world scientific data, using state-of-the-art equipment and software, and to contribute that information to the scientific community. Because Jupiter Quest is a real investigation, not a simulation in which nothing ever goes wrong, students must learn to anticipate likely problems and to handle those that cannot be anticipated as they arise. After the data from the antenna have been collected and analyzed, they are posted on a special Internet site along with other Jupiter data collected by other radio antennas or arrays of antennas, and a long- term picture of Jupiter's radio emissions emerges. …

Developments in Jovian Radio Emissions Tomography and Observations Techniques

Jupiter radio emission is known to be the most powerful nonthermal planetary radiation. In recent years specifically space-based observations allow us to permanently cover a large frequency band (from 100 kHz up to 40 MHz combined with ground-based telescopes) of the Jovian spectrum. The Plasma and Wave Science experiment onboard Galileo enables the observation of Jovian kilo-metric and hectometric emissions; Wind/WAVES and ground-based telescopes (mainly Decametric Array in Nancay, France, and UTR-2 in Kharkov, Ukraine) cover also hectometric and mainly decametric emissions. Specific geometrical configurations between Cassini approaching Jupiter and Wind spacecraft orbiting Earth, with Galileo orbiting Jupiter and Wind, in combination with ground-based observations provide a new approach to perform Jovian radio tomography. The tomography technique is used to analyze ray paths of Jovian radio emission observed in different directions (e.g. solar and anti-solar direction) and for different declination of Earth. The developments of Jovian radio emission tomography in recent years treated refraction effects and its connection to the local magnetic field in the radio source as well as the radio wave propagation through the Io torus and the terrestrial ionosphere. Most recently ground-based multi-site and simultaneous Jupiter decametric radio observations by means of digital spectropolarimeter and waveform receiver provide the basis of a new data analysis treatment. The above addressed topics are without exemption deeply connected to the plasma structures the radio waves are generated in and propagating through.

An intercomparison of three‐dimensional reconstruction techniques using data and models of Jupiter's synchrotron radiation

We present and compare results from two different tomographic reconstruction techniques: a backprojection technique [from de Pater et al., 1997b] and a three‐dimensional (3‐D) Fourier technique [from Sault et al., 1997]. We applied both techniques to very large array (VLA) data of Jupiter's synchrotron radiation and to models which simulate 2‐D images of Jupiter's radio emission [from de Pater et al., 1997a]. The 3‐D images thus constructed represent the apparent radio emissivity. Results from the two techniques are quite compatible. A comparison between the tomographic reconstructions of the data and model yields information on models of the electron flux,j(L, αe, E), and the magnetic field configuration. At first glance, results from the data and model agree quite well. Longitudinal differences between the data and model suggest the need for modifications to the magnetic field model, while differences in the radial profile are caused by imperfections in the radial profile of the electron flux. We suggest that the magnetic equatorial surface should be less warped than in the O6 model. We further find that the change in the modeled pitch angle distribution at Amalthea's orbit [from de Pater et al., 1997a] should be modified by, for example, the inclusion of diffusion both in pitch angle and L, while there also appear to be more emitters at high latitudes outside of Amalthea's orbit than assumed in the model.

Evidence for periodic modulation of Jupiter's decametric radio emission

A plausible explanation for the strong correlation between the occurrence of Jupiter's sporadic decametric radio emission and the orbital position of Io is that the emission is either generated in discrete radio sources located along the instantaneous magnetic flux tube connecting Io with Jupiter or in multiple discrete radio sources associated with other flux tubes excited by ionospheric Alfvén wave reflections downstream from Io. On the assumption that a periodic increase in the probability of receiving radio emission should be observable as the directional emission beams from these multiple discrete radio sources are swept past the observer by Io's orbital motion, a search has been made for periodic modulation of the Jupiter radio emission using a statistical analysis of the data from a total of 34 Io‐B radio noise storms recorded at a wave frequency of 20 MHz during the 1984 and 1996 apparitions of Jupiter. This analysis shows that a weak periodic modulation of the radio emission with a repetition interval near 15 min is present in this source. Assuming that this modulation results from the action of multiple sweeping radio beams, calculations using the O4 model of Jupiter's magnetic field and recently measured emission cone half‐angles give an angular separation between successive Alfvén wave reflections in the Io plasma torus of 7.8±1° (or possibly half this value, depending on assumptions). This estimate is in approximate agreement with theoretical predictions.

Multi-Frequency Radio Observations of Jupiter at Effelsberg during the SL9 Impact

Jupiter's radio emission was monitored before, during, and after the impacts of the multi-nucleus comet Shoemaker–Levy 9 in July 1994 at the Effelsberg 100-m radio telescope of the Max-Planck-Institut für Radioastronomie. Full polarization measurements (four Stokes parameters) were recorded in near-simultaneous mode at the three wavelengths 2.8, 6, and 11 cm. A steady increase in the flux density levels at 6 and 11 cm became apparent after the first few impacts. The absolute (relative) increase in nonthermal flux density over the 7 days of cometary bombardment, referred to the standard distance of 4.04 AU, was 1.2 ± 0.1 Jy (28%) at λ = 11 cm and 1.4 ± 0.1 Jy (43%) at λ = 6 cm. The additional radio emission is partially linearly polarized (⇒ synchrotron radiation), implying a source from energetic electrons in Jupiter's radiation belts. The total flux density at λ = 2.8 cm also increased by 2.1 ± 1.0 Jy. This is attributed to synchrotron emission, albeit at a wavelength still dominated by the thermal contribution. The brightness increase is attributed to a change in the resident electron electron population by (a) an energization of the electrons due to enhanced radial diffusion or shock acceleration, and (b) a broadening of the undisturbed electron velocity distribution due to pitch-angle scattering.

Radial diffusion models of energetic electrons and Jupiter's synchrotron radiation: 2. Time variability

We used a radial diffusion code for energetic electrons in Jupiter's magnetosphere to investigate variations in Jupiter's radio emission due to changes in the electron phase space density at L shells between 6 and 50, and due to changes in the radial diffusion parameters. We suggest that the observed variations in Jupiter's radio emission are likely caused by changes in the electron phase space density at some boundary L1 > 6, if the primary mode of transport of energetic electrons is radial diffusion driven by fluctuating electric and/or magnetic fields induced by upper atmospheric turbulence. We noticed an excellent empirical correlation, both in phase and relative amplitude, between changes in the solar wind ram pressure and Jupiter's synchrotron radiation if the electron phase space density at the boundary L1 (L1 ≃ 20‐50) varies linearly with the square root of the solar wind ram pressure, fnof; ∼ (Ns υs2)1/2. The calculations were carried out with a diffusion coefficient DLL = DnLn with n = 3. The diffusion coefficient which best fit the observed variations in Jupiter’s synchrotron radiation D3 = 1.3 ± 0.2 × 10−9 s−1 ≃ 0.041 yr−1, which corresponds to a lagtime of approximately 2 years. A comparison with previous estimates on diffusion coefficients in Jupiter's inner magnetosphere (L ≲ 10‐20) suggests that all estimates can be described by n = 2.5 and D2.5 = 4.5 × 10−9 s−1 ≃ 0.142 year−1. We further show that the observed short term (days‐weeks) variations in Jupiter’s radio emission cannot be explained adequately when radial diffusion is taken into account.