Electrical and thermal transport properties of liquid Fe under high pressure have important implications for the dynamics and thermal evolution of planetary cores and the geodynamo. However, electrical resistivity (ρ) and thermal conductivity (k) of liquid Fe at high pressure still remain contentious properties. To date, only two experimental investigations of ρ of liquid Fe in the pressure region below 7 GPa are reported in literature. Here we report the results of measurements of ρ for solid and liquid Fe (inversely proportional to k through the Wiedemann-Franz law) at pressures from 3 to 12 GPa, using a large multi-anvil press. We show that ρ of liquid Fe decreases as a function of pressure up to the δ-γ-liquid triple point at ~5.2 GPa, and subsequently remains invariant from 6 to 12 GPa, which is consistent with an earlier study on liquid Ni. Our results demonstrate an important effect of solid phase on the structure and properties of liquid Fe. Our values of ρ for solid and liquid Fe are used to calculate k in Mercury’s solid inner core and along the adiabat in the liquid outer cores of Moon, Ganymede, Mercury and Mars. Our robust values of thermal conductivity place the focus on uncertainties in thermal expansion as the cause of variation in values of core conducted heat. Except for Mercury, our adiabatic heat flux values in these terrestrial cores validate the use of similar values used in several previous studies. Our high values of core adiabatic heat flux in Mercury would provide a stabilizing effect on, and lead to an increase in thickness of, the thermally stratified layer at the top of the core.

The electrical resistivity and thermal conductivity of liquid Fe alloys are the least constrained parameters in Earth's outer core (OC). These parameters are important as they modulate energy budget available for the geodynamo and affect the spatiotemporal evolution of the core. We report results of electrical resistivity measurements on solid and liquid Fe‐4.5 wt%Si from 3–9 GPa using a large volume multianvil press. The internally modified 18/11 octahedron cell was used to maintain the geometry of the liquid sample and to delay the onset of contamination. Electrical resistivity of solid Fe‐4.5Si decreases steadily with pressure and is very sensitive to increasing temperature‐driven onset of phase transitions. Along the melting boundary and within error, electrical resistivity remains constant and assumes the same value of 120 μΩcm as observed in pure liquid Fe. The results are interpreted in the context of icosahedral short‐range order (ISRO) structures that exhibit higher concentration with increasing pressure. Along the melting line, the increasing concentration of ISROs reduces charge carrier mean free path and prevents decrease of electrical resistivity with increasing pressure as seen in liquid metals, Cu, Ag, and Au, which do not have ISROs. In light of recent developments in understanding of the structure and dynamics of liquid transition metals and alloys, we postulate that our findings are applicable to other Fe alloys in the OC with small light element (C, S, and O) content. We calculated an adiabatic heat flow of 9.4–12 TW at the OC‐CMB interface, which admits thermal convection.

Studies of meteor trails have until now been limited to relatively simple models, with the trail often being treated as a conducting cylinder, and the head (if considered at all) treated as a ball of ionized gas. In this article, we bring the experience gleaned in other fields to the domain of meteor studies, and adapt this prior knowledge to give a much clearer view of the microscale physics and chemistry involved in meteor-trail formation, with particular emphasis on the first 100 or so milliseconds of the trail formation. We discuss and examine the combined physico-chemical effects of meteor-generated and ablationally amplified cylindrical shock waves which appear in the ambient atmosphere immediately surrounding the meteor train, as well as the associated hyperthermal chemistry on the boundaries of the high temperature postadiabatically expanding meteor train. We demonstrate that the cylindrical shock waves produced by overdense meteors are sufficiently strong to dissociate molecules in the ambient atmosphere when it is heated to temperatures in the vicinity of 6,000 K, which substantially alters the considerations of the chemical processes in and around the meteor train. We demonstrate that some ambient O₂, along with O₂ that comes from the shock dissociation of O₃, survives the passage of the cylindrical shock wave, and these constituents react thermally with meteor metal ions, thereby subsequently removing electrons from the overdense meteor train boundary through fast, temperature independent, dissociative recombination governed by the second Damköhler number. Possible implications for trail diffusion and lifetimes are discussed.

How effective are methods for estimating bolide energies from infrasound signal period-yield relationships? A single global period–energy relation can obscure significant variability introduced by parameters such as the atmospheric Doppler wind profile and the bolide’s energy deposition profile as a function of altitude. Bolide speed, entry angle, burst altitude, and multiepisode fragmentation may all play a role in defining the detected period of the shockwave. By leveraging bolide light-curve data from the Center for Near Earth Object Studies, we re-examined the period–energy relation as a function of these parameters. Through a bootstrap approach, we show that various event subsets can deviate from widely cited period–energy models and we identify which specific conditions most strongly reshape the period–energy scaling. The results define both the fidelity and reliability of period–energy relations when no additional data beyond the infrasound record is available and improve the outcome when supporting data from bolide trajectories and light curves are included. Ultimately, these findings expand the scope of earlier models, providing a nuanced and robust framework for infrasound-only yield estimation under a range of bolide scenarios.