Emission Of Jupiter Research Articles

Lessons from Hubble and Spitzer: 1D Self-consistent Model Grids for 19 Hot Jupiter Emission Spectra

We present a population-level analysis of the dayside thermal emission spectra of 19 planets observed with Hubble WFC3 and Spitzer IRAC 3.6 and 4.5 μm, spanning equilibrium temperatures 1200–2700 K and 0.7–10.5 Jupiter masses. We use grids of planet-specific 1D, cloud-free, radiative–convective–thermochemical equilibrium models (1D-RCTE) combined with a Bayesian inference framework to estimate atmospheric metallicity, the carbon-to-oxygen ratio, and day-to-night heat redistribution. In general, we find that the secondary eclipse data cannot reject the physics encapsulated within the 1D-RCTE assumption parameterized with these three variables. We find a large degree of scatter in atmospheric metallicities, with no apparent trend, and carbon-to-oxygen ratios that are mainly consistent with solar or subsolar values but do not exhibit population agreement. Together, these indicate either (1) formation pathways vary over the hot and ultra-hot Jupiter population and/or (2) more accurate composition measurements are needed to identify trends. We also find a broad scatter in derived dayside temperatures that do not demonstrate a trend with equilibrium temperature. Like with composition estimates, this suggests either significant variability in climate drivers over the population and/or more precise dayside temperature measurements are needed to identify a trend. We anticipate that 1D-RCTE models will continue to provide valuable insights into the nature of exoplanet atmospheres in the era of JWST.

СПОРАДИЧНЕ РАДІОВИПРОМІНЮВАННЯ КОСМІЧНИХ ОБ’ЄКТІВ НА НИЗЬКИХ ЧАСТОТАХ

Purpose: The results of studies of sporadic radio emission of several types of space radio sources, including neutron stars and planets of the Solar System, are presented. The aim of this work is to review the latest achievements in the study of low-frequency radio emission of the Solar System planets and transient signals similar to pulsar pulses using the UTR-2 radio telescope. The importance of the development of the verification methods of the spaceborne radio emission in the study of sporadic signals from various sources is shown. Design/methodology/approach: The studies of sporadic signals of different nature are based on the common set of procedures for cleaning records from the terrestrial radio frequency interference (RFI) in the frequency-time pattern using the information on the nature of the particular type of sporadic radio emission, possible types of interference and signal distortion. Characteristic features of sporadic radio emission of different sources are given, and for each of them the optimal method of signal extraction is developed. The efficiency of the developed procedures for cleaning from noise using adjustable parameters is shown. This is done on the basis of observations of diverse types of space radio sources, such as lightnings in the atmospheres of planets, single pulses of neutron stars and sporadic radio emission of Jupiter. Findings: The developed methods of signal extraction detection in the presence of radio-interference have allowed obtaining the unique results such as: the distribution of the total intensity of single pulses of neutron stars depending on the galactic latitude; the automatic search of lightnings in the Saturn’s atmosphere in data due to the carefully elaborated RFI mitigation procedures, which made it possible to obtain the Saturn electrostatic discharge (SED) emission parameters based on the most complete set of events. Increased efficiency of the selection of Jupiter’s S-radiation signals despite the data corruption by the presence of radio-interference, which was reached due to the carefully chosen parameters of data cleaning procedures, have allowed us to detect short and intensive bursts, being the most informative for determining the physical parameters of radio emission in the area of their generation. Conclusions: The large effective area and high sensitivity of the UTR-2 radio telescope allow making the sporadic radio emission study with high temporal and frequency resolutions. Due to these factors we can apply a wide range of methods of space signals’ detection in the presence of terrestrial radio-frequency interference of natural and artificial origin. The data cleaning parameters allow accounting for the characteristic features of space signals and to obtain important and even unique scientific results. Key words: decameter wavelength range; UTR-2; sporadic radio emission; transients; lightning in the atmospheres of planets; Jupiter S-bursts

Suzaku observations of Jovian diffuse hard X-ray emission

Abstract We report on results of systematic analyses of the entire three X-ray data sets of Jupiter taken by Suzaku in 2006, 2012, and 2014. Jovian diffuse hard X-ray emission was discovered by Suzaku in 2006 when the solar activity went toward its minimum. The diffuse emission was spatially consistent with the Jovian inner magnetosphere and was spectrally fitted with a flat power-law function suggesting non-thermal emission. Thus, a scenario in which ultra-relativistic (tens of MeV) electrons in the Jovian inner magnetosphere inverse-Comptonize solar visible photons into X-ray bands has been hypothetically proposed. We focused on the dependence of the Jovian diffuse hard X-ray emission on the solar activity to verify this scenario. The solar activity in 2012 and 2014 was around the maximum of the 24th solar cycle. By combining the imaging and spectral analyses for the three data sets, we successfully separated the contribution of the diffuse emission from the emission of Jupiter’s body (i.e., the aurora and disk emission). The 1–5 keV luminosity of the diffuse emission has been stable and did not vary significantly, and did not simply depend on the solar activity, which is also known to affect the high-energy electron distribution in the Jovian inner magnetosphere scarcely. The luminosity of the body emission both in 0.2–1 and 1–5 keV, in contrast, probably depended on the solar activity and varied by a factor of 2–5. These results strongly supported the inverse-Compton scattering scenario by the ultra-relativistic electrons. In this paper, we estimate spatial and spectral distributions of the inverse-Compton scattering X-rays by Jovian magnetospheric high-energy electrons with reference to the Divine–Garrett model and found a possible agreement in an inner region (≲10 RJ) for the X-ray observations.

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.

Zebra pattern in decametric radio emission of Jupiter

We report the systematic analysis of zebra-like fine spectral structures in decametric frequency range of Jovian radio emission. Observations were performed by the large ground-based radio telescope URAN-2 during three observation campaigns between, Sep., 2012, and May, 2015. In total, 51 zebra pattern (ZP) events were detected. These rare fine radio features are observed in frequency range from 12.5 to 29.7 MHz as quasi-harmonically related bands of enhanced brightness. ZPs are strongly polarized radio emission with a duration from 20 s to 290 s and flux densities ~105−106 Jy (normalized to 1 AU), that is, 1–2 orders lower than for Io-decametric radio emission (DAM). Occurrence of the events does not depend on the position of Io satellite but is strongly controlled by the Jovian central meridian longitude (CML). ZPs are mainly detected in two active sectors of Jovian CMLs: 100∘ to 160∘ for Northern sources (right-handed polarized) and 300∘ and 60∘ (via 360∘) for the Southern sources (left-handed). The frequency interval between neighboring stripes is from 0.26 to 1.5 MHz and in most cases this interval increases with frequency. We discussed the double plasma resonance with electrons or ions as a possible source of the ZPs. The performed analysis of the observations allows us to conclude that the observed ZPs are a new type of narrow band spectral structures in the Jovian DAM.

Hubble observations of Jupiter’s north–south conjugate ultraviolet aurora

Comparisons of the northern and southern far ultraviolet (UV) auroral emissions of Jupiter from the Hubble Space Telescope (HST) or any other ultraviolet imager have mostly been made so far on a statistical basis or were not obtained with high sensitivity and resolution. Such observations are important to discriminate between different mechanisms responsible for the electron acceleration of the different components of the aurora such as the satellite footprints, the «main oval» or the polar emissions. The field of view of the ACS and STIS cameras on board HST is not wide enough to provide images of the full jovian disk. We thus compare the morphology of the north and south aurora observed 55min apart and we point out similarities and differences. On one occasion HST pointed successively the two polar regions and auroral images were seen separated by only 3min. This makes it possible to compare the emission structure and the emitted FUV power of corresponding regions. We find that most morphological features identified in one hemisphere have a conjugate counterpart in the other hemisphere. However, the power associated with conjugate regions of the main oval, diffuse or discrete equatoward emission observed quasi-simultaneously may be different in the two hemispheres. It is not directly nor inversely proportional to the strength of the B-field as one might expect for diffuse precipitation or field-aligned acceleration with equal ionospheric electron density in both hemispheres. Finally, the lack of symmetry of some polar emissions suggests that some of them could be located on open magnetic field lines.

Natural radio emission of Jupiter as interferences for radar investigations of the icy satellites of Jupiter

Radar instruments are part of the core payload of the two Europa Jupiter System Mission (EJSM) spacecraft: NASA-led Jupiter Europa Orbiter (JEO) and ESA-led Jupiter Ganymede Orbiter (JGO). At this point of the project, several frequency bands are under study for radar, which ranges between 5 and 50MHz. Part of this frequency range overlaps with that of the natural jovian radio emissions, which are very intense in the decametric range, below 40MHz. Radio observations above 40MHz are free of interferences, whereas below this threshold, careful observation strategies have to be investigated. We present a review of spectral intensity, variability and sources of these radio emissions. As the radio emissions are strongly beamed, it is possible to model the visibility of the radio emissions, as seen from the vicinity of Europa or Ganymede. We have investigated Io-related radio emissions as well as radio emissions related to the auroral oval. We also review the radiation belts synchrotron emission characteristics. We present radio sources visibility products (dynamic spectra and radio source location maps, on still frames or movies), which can be used for operation planning. This study clearly shows that a deep understanding of the natural radio emissions at Jupiter is necessary to prepare the future EJSM radar instrumentation. We show that this radio noise has to be taken into account very early in the observation planning and strategies for both JGO and JEO. We also point out possible synergies with RPW (Radio and Plasma Waves) instrumentations.

A CORRELATION BETWEEN STELLAR ACTIVITY AND HOT JUPITER EMISSION SPECTRA

We present evidence for a correlation between the observed properties of hot Jupiter emission spectra and the activity levels of the host stars measured using Ca II H & K emission lines. We find that planets with dayside emission spectra that are well-described by standard 1D atmosphere models with water in absorption (HD 189733, TrES-1, TrES-3, WASP-4) orbit chromospherically active stars, while planets with emission spectra that are consistent with the presence of a strong high-altitude temperature inversion and water in emission orbit quieter stars. We estimate that active G and K stars have Lyman alpha fluxes that are typically a factor of 4-7 times higher than quiet stars with analogous spectral types, and propose that the increased UV flux received by planets orbiting active stars destroys the compounds responsible for the formation of the observed temperature inversions. In this paper we also derive a model-independent method for differentiating between these two atmosphere types using the secondary eclipse depths measured in the 3.6 and 4.5 micron bands on the Spitzer Space Telescope, and argue that the observed correlation is independent of the inverted/non-inverted paradigm for classifying hot Jupiter atmospheres.

Characteristic infrared radiation of the first-order phase transitions and its connection with atmospheric optics

It is shown that the nature of some IR sources in the Earth’s atmosphere is based on the characteristic IR radiation (IRCR) of the first-order phase transitions (water condensation and crystallization). Experimental and theoretical evidence of the existence of IRCR are discussed. The theory of the phenomenon is based on the statement that a particle (atom, molecule, or cluster) emits one or a few photons while transiting from a higher metastable energetic level (vapor or liquid) to a lower one (liquid or crystal); the energy of these photons is connected in some way with the latent energy of the phase transition. The effect under study plays a very important role in atmospheric phenomena: it is one of the sources of the cooling of the Earth; the formation of clouds, especially storm ones, is accompanied by intensive IRCR, which could be detected for process characterization and storm warnings. The effect can be used for energy accumulation in the atmosphere. The IRCR might explain the red color and infrared emission of Jupiter.

Spectral morphology of the X‐ray emission from Jupiter's aurorae

Simultaneous Chandra X‐ray and Hubble Space Telescope FUV observations of Jupiter's aurorae carried out in February 2003 have been re‐examined to investigate the spatial morphology of the X‐ray events in different energy bands. The data clearly show that in the Northern auroral region (in the main auroral oval and the polar cap) events with energy > 2 keV are located at the periphery of those with energy < 2 keV and coincide with FUV bright features. In addition, X‐ray spectra extracted from the areas where the two event distributions are concentrated possess different shapes. We associate the > 2 keV events (∼45 MW emitted power) with the electron bremsstrahlung component recently revealed by XMM‐Newton in the spectra of Jupiter's aurorae, and the < 2 keV emission (∼230 MW) with the product of ion charge exchange, now established as the likely mechanism responsible for the soft X‐ray Jovian aurora. We suggest that the same population of energetic electrons may be responsible for both, the X‐ray bremsstrahlung and the FUV emission of Jupiter's aurorae. Comparison of the > 2 keV X‐ray and FUV (340 GW) powers measured during the observations shows that they are broadly consistent with the predicted emissions from a population of energetic electrons precipitating in the planet's atmosphere, thus supporting our interpretation.

Dependence of the Io-related decametric radio emission of Jupiter on the central meridian longitude and Io's “active” longitudes

Context.The statistical analysis of the Io-related decametric radio emission of Jupiter shows that this emission depends precisely on the central meridian longitude. This dependence is the result of the existence of Io's “active” longitudes, i.e. particular regions of Io's orbit, which are fixed with respect to the Jovian magnetic field and at which Io-related emission occurs more often.

Solar control on Jupiter's equatorial X‐ray emissions: 26–29 November 2003 XMM‐Newton observation

During Nov. 26–29, 2003 XMM‐Newton observed soft (0.2–2 keV) X‐ray emission from Jupiter for 69 hours. The low‐latitude X‐ray disk emission of Jupiter is observed to be almost uniform in intensity with brightness that is consistent with a solar‐photon driven process. The simultaneous light curves of Jovian equatorial X rays and solar X rays (measured by the TIMED/SEE and GOES satellites) show similar day‐to‐day variability. A large solar X‐ray flare occurring on the Jupiter‐facing side of the Sun is found to have a corresponding feature in the Jovian X rays. These results support the hypothesis that X‐ray emission from Jovian low‐latitudes are solar X rays scattered from the planet's upper atmosphere, and suggest that the Sun directly controls the non‐auroral X rays from Jupiter's disk. Our study also suggests that Jovian equatorial X rays can be used to monitor the solar X‐ray flare activity on the hemisphere of the Sun that is invisible to space weather satellites.

Electron acceleration at the Io’s ionosphere and origin of active longitudes in the Jovian decametric radio emission

A mechanism for the acceleration of electrons in the ionosphere of Io due to the motion of the satellite in the magnetic field of Jupiter and the presence of an Io ionosphere, is considered. The electron acceleration is caused by an electric field due to charge separation in Io’s ionosphere and is a result from the anisotropic conductivity of its ionosphere. This field has a component parallel to the magnetic field and its value is comparable with that of the induced field. The electron “runaway” along the magnetic field is also considered in the work. Besides, the occurrence of “active longitudes” and preferable locations of the sources of the decametric radio emission of Jupiter in the northern hemisphere are interpreted. Typical energies and fluxes of the accelerated electrons injected into the Io flux tube (IFT) are estimated. It is shown that the energy stored in the electron fluxes is sufficient to support electromagnetic emissions observed from the IFT.

INTERBALL-1 Observations of the Kilometric “Continuum” of the Earth's Magnetosphere

The electromagnetic radio-frequency emission of the inner region of the Earth's plasmasphere discovered recently by the GEOTAIL satellite [4] and referred to as the “kilometric continuum” was observed by the INTERBALL-1 satellite (1995–2000) in the 100–500 kHz band in the AKR-X experiment. During a period of low solar activity (1995–1997), this “continuum” was found leaving the inner plasmasphere at geocentric distances of 2–4RE as isolated pencil-like (1°–6°) beams located in the magnetic equator plane. During a time of high solar activity (1999–2000), the occurrence of the emission was extremely rare (it was observed only at a considerable fall of this activity). If detected, at the same geocentric distances (2–4RE) the “continuum” demonstrated a strongly variable and perturbed character, as well as a considerably larger extension of the beam over the geomagnetic latitude (10°–20° and more). In addition, quasi-periodic (QP) signals, similar to the observed QP emissions of Jupiter, were sometimes detected in this period. The probable nature of the observed features of the “kilometric continuum” is briefly discussed.

Contribution à l'étude des émissions radioélectriques aurorales de Jupiter

We study the radioelectric emissions of Jupiter in the frequency range 1–40 MHz with the decametric observatory of Nançay and the Wind spacecraft. A wake in front of Io explains the Φ Io/CML chart. An appropriate coordinate system shows that the Ioontrolled emissions occur mainly when Io is located in the northern magnetic hemisphere of Jupiter.

Synthesis of magnetospheric radio emissions during and after the Jupiter/SL-9 collision

A worldwide network of ground-based and spaced-based radiotelescopes monitored the continuum emission of Jupiter from millimetric to kilometric wavelengths throughout the SL-9 impacts in July 1994. Within 2 days of the first impact, an increase of flux density was detected and confirmed by many observatories at wavelengths from 3 to 90 cm. The increase involved only the synchrotron emission from the energetic electrons trapped in the Jovian radiation belts. At decameter and kilometer wavelengths, normally from radio sources located in the polar regions, no abnormal emission can be associated with certainty with the impacts. At short centimeter and millimeter wavelengths a search was made for impact-associated changes in Jupiter's deep atmosphere, but no detections have been reported and confirmed. The present knowledge of the synchrotron radio emission from the Jovian radiation belts is reviewed and the changes which occurred during and after the collision are commented on. During the week of cometary impacts, the synchrotron flux density increased, depending on the wavelength, by 10–40% and the radio spectrum hardened. Following the week of impacts, the flux density decreased at all wavelengths, more rapidly at 36–90 cm than at 6–22 cm. The observed decline was not a simple exponential decay, and the timescale was more than 100 days at 6–20 cm and less than 30 days at 36–90 cm. The beaming curve was flattened and distorted during and after the impacts, with long-lasting enhancements localized in longitude. Two-dimensional images show that the belts became brighter than before the impacts, and they remained bright at least one week after the first impact. The increase of brightness at the magnetic equator was concentrated in a limited range of longitude, from ≈80 to ≈300°. The radial distance of the peak intensity decreased over that week. Images in 3-D, constructed from observations with the Australia Telescope Compact Array, reveal distinct brightenings confined in longitude that can be attributed to the longitudes of individual impacts or group of impacts.

A Baseline Spectroscopic Study of the Infrared Auroras of Jupiter

We present the results of a spectroscopic study of the H+3infrared emissions of Jupiter, obtained using the United Kingdom Infrared Telescope (UKIRT) on Mauna Kea, Hawaii, during May 3–5, 1993. Although we have obtained data from the whole of the planet, in this paper we concentrate on the auroral regions. Derived H+3temperatures for these vary between 700 and 1000 K, and column densities are of the order of 1012cm−2. There is a strong (anti-)correlation between these parameters, however, that requires the introduction of new variables to characterize the jovian auroras fully. The total H+3auroral emission is presented as a function of central meridian longitude. A simple geometric model of this emission does not describe the data adequately. The integrated infrared auroral emission in each hemisphere is of the order of a few × 1012W, making it comparable to auroral output in the ultraviolet.

Peculiar oscillations in the microwave emission of Jupiter during the impact of K fragment of comet Shoemaker-Levy 9

In this article we report the peculiar oscillations in the intensity of microwave (4.15 GHz) emission seen during the impact of K fragment of comet Shoemaker-Levy 9 on July 19, 1994. The oscillations begin at 10h 13m 25s UT suddenly with a frequency of ~0.3 Hz and gradually the frequency of these oscillations increases to ~ 1 Hz. The oscillations are not due to local atmosphere or the radio interference from signals of geostationary satellite. They are intrinsic to the microwave emission from Jupiter during the impact of K fragment. Peak-to-peak amplitude of the oscillations is about 34% of the total microwave emission from Jupiter. If we assume that only 50% of the microwave emission is non-thermal and only the non-thermal emission suffered oscillations, then the oscillations are about 68% of the non-thermal emission from Jupiter. The observations also indicate that there are three continuum enhancements during this event and periodic oscillations almost all through. The third enhancement was the largest and during this enhancement there were some additional aperiodic variations. The aperiodic variations were of the order of few minutes and were possibly generated by the gravity waves. The periodic oscillations could be synchrotron emission modulated by the plasma oscillation in the outer magnetosphere. kg]Key words

The cyclotron maser instability - Application to low-density magnetoplasmas

The cylcotron maser instability is applied to low-density magnetoplasmas to derive simple expressions relating the wave-emergent angle of the amplified wave (theta) and the ratio f/f(c) at the source to the normalized (to the light velocity c) parallel bulk velocity (PBV) of the instability (characteristic for an auroral electron distribution function). It is shown that, for PBV corresponding to 1-10 keV, theta is nearly perpendicular with respect to the magnetic field and is decreasing as PBV increases. The results are highly relevant to the lower-frequency auroral emission of Jupiter and Saturn. 21 refs.