Louis Siebenaler

The most intense radio feature in the Solar System are the solar Type‐III radio bursts, which are associated with electron beams that propagate along open magnetic field lines. Although solar radio bursts have been studied since the 1940s, observations remain mainly restricted within 1 AU. In this study, we explore 16.5 years of data (2005–2021) from the Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) onboard Mars Express. While not the central aim of the instrument, MARSIS has been recording solar radio bursts since its deployment in mid‐2005. Given the potential of this new radio burst data set for heliophysics studies, we have created a catalog of Type‐III solar radio burst events between 1.38 and 1.66 AU (Mars' orbit) within the frequency range of 0.1 and 5.5 MHz and with an instrument measuring cadence of 7.5 s. We demonstrate that these emissions seen at Mars come from the Sun, follow the solar cycle pattern, and are not influenced by the planet's own properties such as crustal magnetic fields. We also compare the propagation of a few illustrative events from the Sun to Mars to demonstrate the utility of this new data set for heliophysics studies. Mars catalogs provide a fundamentally new perspective on the spatial extent, directivity, and evolution of solar radio emission in the inner heliosphere. It serves as an essential benchmark for multi‐point heliospheric studies and for constraining radio emissions mechanisms beyond Earth orbit, and demonstrating the usefulness of planetary missions in contributing to heliophysics science in diverse ways.

Context . Alkali lines, in particular the sodium Na D (5891 Å, 5897 Å) and potassium K D (7667 Å, 7701 Å) resonance doublets, are dominant opacity sources in giant planets over a wide range of temperatures (≳1000 K). Their strong pressure-broadened wings significantly influence the thermal structure of giant planets, especially at high pressures. Most detailed line-profile calculations have so far been limited to perturber densities up to 10 ²¹ cm ⁻³ . However, conditions in the deep atmospheres and interiors of giant planets can reach significantly higher densities, making the temperature gradients increasingly uncertain. Aims . We determined how physically consistent collisional broadening of the Na D and K D lines at extreme densities affects opacity calculations and consequently the inferred interior structure of giant planets. Methods . We computed detailed Na D and K D line profiles using unified line theory, extending to molecular hydrogen perturber densities of n H ₂ = 5×10 ²² cm ⁻³ , which translates to pressures up to ∼20 kbar. The revised cross sections were incorporated into Rosseland mean opacity tables, which were then used to evaluate their effect on planetary thermal structures. Results . At densities n H ₂ > 10 ²¹ cm ⁻³ , the line profiles predicted by unified line theory exhibit significantly stronger and more extended wings than commonly used Voigt profiles, as well as density-dependent line shifts. The revised line profiles increase Rosseland mean opacities by a factor of 2 at 10 ³ bar and by an order of magnitude at 10 ⁴ bar. Consequently, the radiative-convective boundary of warm and hot giant planets can shift to lower pressures, producing warmer interior adiabats and increasing inferred core masses by up to 9 M _earth . We further find that Jupiter is highly unlikely to host a stable radiative layer at the present time or throughout most of its evolution, as the required Na and K abundances for this are well below observational constraints. Our new opacity tables span metal mass fractions Z ∈ [0.0044, 0.696] and are publicly available.

Alkali lines, in particular the sodium (Na D) and potassium (K D) resonance doublets, are dominant opacity sources in giant planets over a wide range of temperatures (~ 1000 – 3000 K). Their strong pressure-broadened wings, produced by collisions with hydrogen, can significantly influence the thermal structure of giant planets, especially at high pressures. Most detailed line-profile calculations have so far been limited to moderate perturber densities up to 1021 cm-3. However, conditions in the deep atmospheres and interiors of giant planets can reach significantly higher densities, causing temperature gradients to become increasingly uncertain. This is particularly relevant in the context of stable radiative layers that can exist in Solar System giants and warm giant exoplanets, as well as for hot giant planets that may remain radiative well beyond 100 bar.In this work, we compute detailed Na D and K D line profiles using the unified line theory, extending to hydrogen perturber densities relevant for the deep atmospheres and interiors of giant planets. At high pressures, the revised line profiles exhibit significantly stronger and more extended wings than those predicted by the commonly used impact approximation, as well as density-dependent line shifts. We further show that Rosseland mean opacities can increase by up to an order of magnitude when using the revised line profiles. Consequently, the radiative-convective boundaries of warm and hot giant planets can shift to lower pressures, producing warmer adiabats and increasing inferred planetary bulk metallicities. While this work addresses the dominant absorption lines relevant for high-pressure opacity calculations in giant planets, it also highlights the broader need for accurate opacity modeling at extreme densities.

In recent years, significant advances have been made in exoplanet and brown dwarf observations. By using state-of-the-art models, astronomers can determine properties of their atmospheres, such as temperatures, the presence of clouds, or the chemical abundances of molecules and atoms. Accurate and up-to-date opacities are crucial to avoid inconclusive or biased results, but it can be challenging to compute opacity cross-sections from the line lists provided by various online databases. We introduce pyROX, an easy-to-use Python package to calculate molecular and atomic cross-sections. Since pyROX works on CPUs, it can compute a small line list on a regular workstation, but it is also easily parallelised on a cluster for larger line lists. In addition to line opacities, pyROX also supports calculations of collision-induced absorption. Tutorials are provided in the online documentation which explain the configuration parameters and different functionalities of pyROX.

Mean opacities are essential tools for modeling the atmospheres, interiors, and thermal evolution of exoplanets. Although significant progress has been made in recent years in developing molecular line lists, many widely used mean opacity tables still rely on outdated data and are therefore subject to considerable uncertainties.In this work, we present new Rosseland and Planck mean opacity tables relevant to the atmospheres of giant planets. These tables are based on state-of-the-art molecular line lists and include updated pressure broadening treatments. They extend to higher pressures than commonly used tables, making them particularly relevant for modeling planetary interiors and deep atmospheres. We compare our results to existing opacity tables and investigate their impact on key properties of planets. In addition, we assess the influence of solid grains on the opacities by performing calculations for various grain sizes.

Interior models of giant planets in the Solar System traditionally assume convection as the dominant heat transport mechanism in the molecular hydrogen envelope. However, several observations of Jupiter are challenging to explain under this assumption, including the measured abundances of CO and water in the atmosphere, as well as the depth of the zonal winds. A stable layer located around the kilobar level has been proposed to reconcile these observations, an idea that has gained more support with recent Juno measurements of alkali metals, which suggest a depletion in the deep atmosphere. While the presence of a stable layer around the kilobar level appears promising, the degree of alkali depletion required to sustain it remains unclear.In this work, we compute new opacity tables to determine the specific atmospheric compositions that can give rise to stable stratification in the outer envelopes of Jupiter and Saturn. Using evolution models, we investigate the long-term conditions that allow stable layers to persist, and how their depth changes over time. In addition, we investigate how stable layers influence key observables, such as the effective temperature and the atmospheric helium abundance.

Recent measurements from the Juno spacecraft have revived interest in the possible existence of a radiative zone within Jupiter's atmosphere. If such a layer exists, it would create a stably stratified region, estimated to extend up to 2000 km, challenging the traditional view of a predominantly convective envelope associated with the planet’s zonal jet streams, which penetrate approximately 3000 km. In this study, we explore the potential effects of this radiative zone on Jupiter’s jet stream properties and gravity field. Combining gravity measurement constraints with numerical simulations of a shallow atmospheric model representative of Jupiter, we investigate the dynamical implications of a radiative layer. Our analysis evaluates how the presence of this zone could alter atmospheric dynamics, offering new insights into the planet’s internal structure and questioning the hypothesis of a fully convective dynamical layer. Additionally, through gravity data analysis, we assess whether the existence of such a radiative zone is feasible within Jovian conditions. These findings highlight the importance of considering layered atmospheric models in planetary data interpretation. Moreover, the presence of a radiative zone could be a common feature in other planetary systems and exoplanets, underscoring the need for further research into planetary atmospheres and interiors and their broader implications for planetary science.

Traditionally, interior models of gas giants assume convection as the dominant heat transport mechanism in the hydrogen-dominated envelope. However, recent observations from the Juno mission suggest a possible depletion of alkali metals in Jupiter’s molecular hydrogen envelope, indicating that a stable radiative layer might exist at the kilobar level. Deep stable layers have been proposed to reconcile key observations of Jupiter, including its atmospheric water and CO abundances and the depth of its zonal winds. In this study, we present the most comprehensive opacity tables to date, enabling us to determine the alkali depletion required to develop a radiative zone in Jupiter, both at present and throughout its evolution. Using evolutionary models, we explore how deep radiative zones influence key observational constraints, such as Jupiter's effective temperature and its current atmopsheric helium abundance.

Context. Interior models of gas giants in the Solar System traditionally assume a fully convective molecular hydrogen envelope. However, recent observations from the Juno mission suggest a possible depletion of alkali metals in Jupiter’s molecular hydrogen envelope, indicating that a stable radiative layer could exist at the kilobar level. Recent studies propose that deep stable layers help reconcile various Jupiter observations, including its atmospheric water and CO abundances and the depth of its zonal winds. However, opacity tables used to infer stable layers are often outdated and incomplete, leaving the precise molecular hydrogen envelope composition required for a deep radiative zone uncertain. Aims. In this paper, we determine atmospheric compositions that can lead to the formation of a radiative zone at the kilobar level in Jupiter and Saturn today. Methods. We computed radiative opacity tables covering pressures up to 10⁵ bar, including the most abundant molecules present in the gas giants of the Solar System, as well as contributions from free electrons, metal hydrides, oxides, and atomic species, using the most up-to-date line lists published in the literature. These tables were used to calculate Rosseland-mean opacities for the molecular hydrogen envelopes of Jupiter and Saturn, which were then compared to the critical mean opacity required to maintain convection. Results. We find that the presence of a radiative zone is controlled by the existence of K, Na, and NaH in the atmosphere of Jupiter and Saturn. For Jupiter, the elemental abundance of K and Na must be less than ∼10⁻³ times solar to form a radiative zone. In contrast, for Saturn, the required abundance for K and Na is below ∼10⁻⁴ times solar.