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At least 127 records · Page 7
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NASA NTRS2024

TOI-3568 b: A Super-Neptune in the Sub-Jovian Desert

The sub-Jovian desert is a region in the mass–period and radius–period parameter space that typically encompasses short-period ranges between super-Earths and hot Jupiters, and exhibits an intrinsic dearth of planets. This scarcity is likely shaped by photo evaporation caused by the stellar irradiation received by giant planets that have migrated inward. We report the detection and characterization ofTOI-3568 b, a transiting super-Neptune with a mass of26.4±1.0M⊕, a radius of5.30±0.27R⊕, a bulk density of0.98±0.15g cm−3, and an orbital period of 4.417965 (5) d situated in the vicinity of the sub-Jovian desert. This planet orbiting a K dwarf star with solar metallicity was identified photometrically by the Transiting Exoplanet Survey Satellite (TESS). It was characterized as a planet by our high-precision radial-velocity (RV) monitoring program using MAROON-X at Gemini North, supplemented with additional observations from the SPICE large program with SPIRou at CFHT. We performed a Bayesian MCMC joint analysis of the TESSand ground-based photometry, and MAROON-X and SPIRou RVs, to measure the orbit, radius, and mass of the planet, as well as a detailed analysis of the high-resolution flux and polarimetric spectra to determine the physical parameters and elemental abundances of the host star. Our results reveal TOI-3568 b to be a hot super-Neptune rich in hydrogen and helium, with a core of heavier elements of between 10 and 25 M⊕in mass. We analyzed the photo evaporation status of TOI-3568 b and find that it experiences one of the highest extreme-ultraviolet (EUV) luminosities among planets with a mass of Mp<2MNep, yet it has an evaporation lifetime exceeding 5 Gyr. Positioned in the transition between two significant populations of exoplanets on the mass–period and energy diagrams, this planet presents an opportunity to test theories concerning the origin of the sub-Jovian desert.

stars: individual: TOI-3568↗
NASA NTRS2013

Jovian Plasmas Torus Interaction with Europa. Plasma Wake Structure and Effect of Inductive Magnetic Field: 3D Hybrid Kinetic Simulation

The hybrid kinetic model supports comprehensive simulation of the interaction between different spatial and energetic elements of the Europa moon-magnetosphere system with respect to a variable upstream magnetic field and flux or density distributions of plasma and energetic ions, electrons, and neutral atoms. This capability is critical for improving the interpretation of the existing Europa flyby measurements from the Galileo Orbiter mission, and for planning flyby and orbital measurements (including the surface and atmospheric compositions) for future missions. The simulations are based on recent models of the atmosphere of Europa (Cassidy et al., 2007; Shematovich et al., 2005). In contrast to previous approaches with MHD simulations, the hybrid model allows us to fully take into account the finite gyroradius effect and electron pressure, and to correctly estimate the ion velocity distribution and the fluxes along the magnetic field (assuming an initial Maxwellian velocity distribution for upstream background ions). Photoionization, electron-impact ionization, charge exchange and collisions between the ions and neutrals are also included in our model. We consider the models with Oþ þ and Sþ þ background plasma, and various betas for background ions and electrons, and pickup electrons. The majority of O2 atmosphere is thermal with an extended non-thermal population (Cassidy et al., 2007). In this paper, we discuss two tasks: (1) the plasma wake structure dependence on the parameters of the upstream plasma and Europa's atmosphere (model I, cases (a) and (b) with a homogeneous Jovian magnetosphere field, an inductive magnetic dipole and high oceanic shell conductivity); and (2) estimation of the possible effect of an induced magnetic field arising from oceanic shell conductivity. This effect was estimated based on the difference between the observed and modeled magnetic fields (model II, case (c) with an inhomogeneous Jovian magnetosphere field, an inductive magnetic dipole and low oceanic shell conductivity).

Jovian magnetosphere↗
NASA NTRS2015

Observations and Numerical Modeling of the Jovian Ribbon

Multiple wavelength observations made by the Hubble Space Telescope in early 2007 show the presence of a wavy, high-contrast feature in Jupiter's atmosphere near 30 degrees North. The "Jovian Ribbon," best seen at 410 nanometers, irregularly undulates in latitude and is time-variable in appearance. A meridional intensity gradient algorithm was applied to the observations to track the Ribbon's contour. Spectral analysis of the contour revealed that the Ribbon's structure is a combination of several wavenumbers ranging from k equals 8-40. The Ribbon is a dynamic structure that has been observed to have spectral power for dominant wavenumbers which vary over a time period of one month. The presence of the Ribbon correlates with periods when the velocity of the westward jet at the same location is highest. We conducted numerical simulations to investigate the stability of westward jets of varying speed, vertical shear, and background static stability to different perturbations. A Ribbon-like morphology was best reproduced with a 35 per millisecond westward jet that decreases in amplitude for pressures greater than 700 hectopascals and a background static stability of N equals 0.005 per second perturbed by heat pulses constrained to latitudes south of 30 degrees North. Additionally, the simulated feature had wavenumbers that qualitatively matched observations and evolved throughout the simulation reproducing the Jovian Ribbon's dynamic structure.

Saturnian Ribbon↗
NASA NTRS2015

Jovian plasma modeling for mission design

The purpose of this report is to address uncertainties in the plasma models at Jupiter responsible for surface charging and to update the jovian plasma models using the most recent data available. The updated plasma environment models were then used to evaluate two proposed Europa mission designs for spacecraft charging effects using the Nascap-2k code. The original Divine/Garrett jovian plasma model (or "DG1", T. N. Divine and H. B. Garrett, "Charged particle distributions in Jupiter's magnetosphere," J. Geophys. Res., vol. 88, pp. 6889-6903,1983) has not been updated in 30 years, and there are known errors in the model. As an example, the cold ion plasma temperatures between approx.5 and 10 Jupiter radii (Rj) were found by the experimenters who originally published the data to have been underestimated by approx.2 shortly after publication of the original DG1 model. As knowledge of the plasma environment is critical to any evaluation of the surface charging at Jupiter, the original DG1 model needed to be updated to correct for this and other changes in our interpretation of the data so that charging levels could beproperly estimated using the Nascap-2k charging code. As an additional task, the Nascap-2k spacecraft charging tool has been adapted to incorporate the so-called Kappa plasma distribution function--an important component of the plasma model necessary to compute the particle fluxes between approx.5 keV and 100 keV (at the outset of this study,Nascap-2k did not directly incorporate this common representation of the plasma thus limiting the accuracy of our charging estimates). The updating of the DG1 model and its integration into the Nascap-2k design tool means that charging concerns can now be more efficiently evaluated and mitigated. (We note that, given the subsequent decision by the Europa project to utilize solar arrays for its baseline design, surface charging effects have becomeeven more of an issue for its mission design). The modifications and results of those modifications to the DG1 model to produce the new DG2 model presented here and the steps taken to integrate the DG2 predictions into Nascap-2k are described in this report.

Voyager 2↗
DOE OSTI2023

Wave and Particle Analysis of Z-Mode and O-Mode Emission in the Jovian Inner Magnetosphere

We report some of the most intense Z-mode and O-mode observations obtained by the Juno spacecraft while in orbit about Jupiter in a low to mid-latitude region near the inner edge of the Io torus. We have been able to estimate the density of the plasma in this region based on the lower frequency cutoff of the observed Z-mode emission. The results are compatible with the electron density measurements of the Jovian Auroral Distributions Experiment (JADE), on board the Juno spacecraft, if we account for unmeasured cold plasma. Direction-finding measurements indicate that the Z- and O-mode emission have distinct source regions. We have also used the measured phase space density of the JADE and the Jupiter energetic particle detector instruments to calculate estimated local growth rates of the observed O-mode and Z-mode emission assuming a loss cone instability and quasilinear analysis. The results suggest the emissions were observed near, but not within, a source region, and the free energy source is consistent with a loss cone. We have thus carried out the quasilinear wave analysis of the assumed remote Z- and O-mode wave growths. It is shown that the remotely generated waves, propagated through an inhomogeneous medium to the satellite location, may account for the observed wave characteristics. The importance of Z-mode in accelerating electrons in the inner Jovian magnetosphere makes these new wave mode confirmations at Jupiter of particular interest.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2020

KMT-2016-BLG-1836Lb: A Super-Jovian Planet from a High-cadence Microlensing Field

We report the discovery of a super-Jovian planet in the microlensing event KMT-2016-BLG-1836, which was found by the Korea Microlensing Telescope Network (KMTNet) high-cadence observations (Γ~4 hr -1 ). The planet–host mass ratio q ~ 0.004. A Bayesian analysis indicates that the planetary system is composed of a super-Jovian M{ planet =2.2 -1.1 +1.9 M J planet orbiting an M or K dwarf, M{ host =0.49 -0.25 0.38 M ⊙ , at a distance of D L =7.1 -2.4} +0.8 kpc. The projected planet–host separation is 3.5 -0.9 +1.1 au, implying that the planet is located beyond the snow line of the host star. Future high-resolution images can potentially strongly constrain the lens brightness and thus the mass and distance of the planetary system. Without considering detailed detection efficiency, selection, or publication biases, we find a potential mass-ratio desert at -3.7 ≲ log q ≲ -3.0 for the 31 published KMTNet planets.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1962

The jovian environment

Jovian atmosphere and environment - composition, structure, and photometric properties of atmosphere, period of rotation, magnetic field, and Jovian radiofrequency spectrum

PLANETARY MAGNETIC FIELD↗
NASA NTRS1972

Photoelectron emission from Io as the cause of enhancements of the Jovian decametric radiation.

A theoretical explanation for the dependence of the Jovian decametric radiation on the position of its satellite Io is advanced in terms of electrostatic instabilities created by injection into the hot natural plasma of cold photoelectrons from Io. This may be tested with appropriately positioned and presently planned deep-space probes that search for variations of the Jovian decametric radiation at times following local sunset and sunrise at Io.

Mozer, F. S.↗
NASA NTRS1972

The plasma physics of the Jovian decameter radiation.

We have assumed that the decameter radiation from Jupiter is produced near the local electron gyrofrequency and is amplified as it propagates out of the Jovian magnetosphere. We have derived the growth rate for radiation that propagates almost perpendicular to the direction of the magnetic field. When the electrons are described by a loss-cone distribution function, the growth rate is large enough to lead to a large amplification factor over a source of 100-4000 km, depending on the choice of parameters. Because we expect low-energy electrons to be trapped in the Jovian dipole field regardless of the position of the satellite Io, we maintain that this model provides a plausible mechanism for the decametric radiation not associated with Io.

Goldstein, M. L.↗
NASA NTRS1974

Organic synthesis in a simulated Jovian atmosphere. III - Synthesis of aminonitriles

The products from spark and semicorona discharges through mixtures simulating the Jovian atmosphere were analyzed by gas chromatography combined with mass spectrometry. When the reaction was performed at -80 C, 3-ethylaminopropionitrile and a number of higher homologs were formed. On the other hand, at +20 C, higher molecular-weight material appeared which yielded aminonitrile-derived fragments on mass spectrometry. Although the spectra were not identical, there were notable similarities between these and the mass spectra of some compounds present in the Murray and Orgeuil meteorites. Aminonitriles may occur as minor constituents of the Jovian atmosphere and perhaps by cyclization may produce pyrimidines.

Molton, P. M.↗
NASA NTRS1974

The occultation of beta Scorpii by Jupiter. II - The hydrogen-helium abundance in the Jovian atmosphere

The helium abundance in the Jovian atmosphere has been determined by a new method from our observations of the occultation of beta Scorpii by Jupiter. The occultation light curves, consisting of simultaneous records at three wavelengths with a time resolution of 0.01 sec, are dominated by sharp, well-defined intensity peaks or spikes. Because of the wavelength-dependence of the refractivity of the Jovian atmosphere, the arrival time of a given spike at the Earth is also wavelength dependent. A new method for determining the composition of a hydrogen-helium atmosphere from such data is presented, and the principal sources of error are discussed and evaluated.

Elliot, J. L.↗
NASA NTRS1975

Jovian protons and electrons: Pioneer 11

A preliminary account of the Pioneer 11 passage through the Jovian magnetosphere as viewed by particle detector systems is presented. Emphasis is placed on the region well within the Jovian magnetosphere using data from the LET-II telescope, which measured the proton flux from 0.2 to 21.2 MeV in seven energy intervals and electrons from 0.1 to 2 MeV in four energy intervals. The relative trajectories of Pioneer 10 and 11 are discussed and indicate that Pioneer 11 was exposed to a much lower total radiation dose than Pioneer 10, largely as a result of the retrograde trajectory which approached and exited the inner region of the magnetosphere at high latitudes. Angular distributions, calculations from Pioneer 11 magnetic field data, and the low-energy nucleon component are included in the discussion.

Trainor, J. H.↗
NASA NTRS1974

Periodic escape of relativistic electrons from the Jovian magnetosphere

We adopt a model in which the Jovian magnetospheric tail is forced open by plasma that is accelerated out of the ionosphere by the centrifugal force of corotation. Any longitudinal asymmetry that exists in the ionospheric plasma source and/or the planetary magnetic field will cause a diurnal variation in the radial extent of the trapping region for energetic electrons. This diurnal variation in the extent of the particle trapping region can result in a time-dependent loss of relativistic electrons from the Jovian magnetosphere, modulated at the planetary rotation period. The diurnal trapping process may be relevant to the observation of electron pulses in interplanetary space during the Pioneer 10 approach to Jupiter.

Hill, T. W.↗
NASA NTRS1975

Jovian protons and electrons - Pioneer 11

The report presented takes into account data from the low energy telescope which were obtained during the passage of Pioneer 11 through the Jovian magnetosphere. The detector system used measures the proton flux in the range from 0.2 to 21.2 MeV in seven energy intervals and the electron flux in the range from 0.1 to 2 MeV in four intervals. The significance of the effects measured in the inner core region of the magnetosphere is discussed and attention is given to the effects of Jovian moons on the particle flux in the planetary environment.

Trainor, J. H.↗
NASA NTRS1975

Denouement of Jovian radiation belt theory

Predictions of theoretical models of Jupiter's radiation belts are compared with Pioneer 10 measurements. A brief quasi-historical review is given of the evolution of the basic theoretical ideas with emphasis on the three physical processes that were believed to be dominant in the Jovian electron fluxes: radial-diffusion transport, limitation of particle fluxes by plasma wave turbulence, and particle losses from collisional sweep-up by the Galilean satellites. Pioneer 10 data on the inner zone are discussed which yield the clearest evidence for radial diffusion being the dominant transport process, the synchrotron flux density is estimated using Pioneer 10 measurements, and the observed outer-zone electron fluxes are favorably compared with the qualitative and quantitative predictions of the whistler-mode stable-trapping model. The outer-zone electron-precipitation flux is estimated, and it is suggested that precipitation could affect the structure of the Jovian ionosphere. Satellite sweep-up is shown to be less severe than had been anticipated.

Coroniti, F. V.↗
NASA NTRS1975

Models of Jovian decametric radiation

A critical review is presented of theoretical models of Jovian decametric radiation, with particular emphasis on the Io-modulated emission. The problem is divided into three broad aspects: (1) the mechanism coupling Io's orbital motion to the inner exosphere, (2) the consequent instability mechanism by which electromagnetic waves are amplified, and (3) the subsequent propagation of the waves in the source region and the Jovian plasmasphere. At present there exists no comprehensive theory that treats all of these aspects quantitatively within a single framework. Acceleration of particles by plasma sheaths near Io is proposed as an explanation for the coupling mechanism, while most of the properties of the emission may be explained in the context of cyclotron instability of a highly anisotropic distribution of streaming particles.

Smith, R. A.↗
NASA NTRS1975

High Ph, Ammonia Toxicity, and the Search for Life on the Jovian Planets

The effects of pH and ammonia concentration were studied separately, where possible, on a variety of organisms, including some isolated from natural environments of high pH and/or ammonia concentration. Escherichia coli and Bacillus subtilis are both extremely sensitive to ammonia. An aerobic organism (growth up to pH 11.4) from an alkaline spring is more resistant, but exhibits a toxic response to ammonia at a pH much lower than its maximum for growth. The greatest ammonia resistance has been found in an unidentified organism growing at near neutral pH. Even in this case, however, urvival at ammonia concentrations reasonably expected on the Jovian planets is measured in hours. This is two to three orders of magnitude longer than for E. coli. Results support the tentative conclusion that contamination of the Jovian planets with terrestrial organisms that can grow is unlikely. However, the range of toxic response noted, coupled with the observation that terrestrial life has not been exposed to high ammonia concentrations for millions of years, suggests that adaptation to greater ammonia tolerance may be possible.

Deal, P. H.↗