Relevance of Tidal Heating on Large TNOs

We examine the relevance of tidal heating for large Trans-Neptunian Objects, with a focus on its potential to melt and maintain layers of subsurface liquid water. Depending on their past orbital evolution, tidal heating may be an important part of the heat budget for a number of discovered and hypothetical TNO systems and may enable formation of, and increased access to, subsurface liquid water. Tidal heating induced by the process of despinning is found to be particularly able to compete with heating due to radionuclide decay in a number of different scenarios. In cases where radiogenic heating alone may establish subsurface conditions for liquid water, we focus on the extent by which tidal activity lifts the depth of such conditions closer to the surface. While it is common for strong tidal heating and long lived tides to be mutually exclusive, we find this is not always the case, and highlight when these two traits occur together.Comment: Submitted to Icaru

Exposure Assessment Using the Dual-Grid Finite-Difference Time-Domain Method

A new way to carry out numerical cellular telephone simulation in the presence of the head is presented. Here, two finite-difference time-domain (FDTD) simulations with different spatial and time resolutions are sequentially combined to perform a dual-grid FDTD (DG-FDTD) simulation. The DG-FDTD approach has the significant advantages to remain stable along the computation and to be easy to implement in a typical FDTD code. When compared with classical FDTD analysis, the DG-FDTD approach exhibits a reduction in computation time and memory requirements by a factor of 2.3 and 3.2, respectively, while providing accurate results both in near-field and far-field radiation

Near-field data compression for the far-field computation in FDTD

This paper presents a technique to compress the near-field data required to compute the radiated fields using FDTD. This technique is applied to the study of a UWB planar diamond antenna. The results show a 99.8% gain in memory storage, while maintaining good accuracy: less than 1% error on the far-field radiation patterns

Extending the capabilities of the dual-grid finite-difference time-domain method

In this paper, improvements of the dual-grid finite-difference time-domain (DG-FDTD) method are proposed. This multiresolution approach is particularly suitable for the simulation of surrounded antenna problems. By successively combining two finite-difference time-domain (FDTD) simulations with different resolutions, it allows the evaluation of the environment effects on the radiated fields, and it also gives information on the antenna input impedance. In this paper, we propose two different techniques to extend the DG-FDTD capabilities. The first one consists of a correction procedure. Its application to a lens antenna analysis exhibits accurate results while providing a computation speedup of 16.7. The second technique consists of its hybridization with the multiple-region FDTD to make the simulation of transmission problems possible. A study involving two ultra-wide band antennas shows the relevance of the hybrid method that allows a fast and accurate characterization of scattering parameters

Irreversible transformation of ferromagnetic ordered stripe domains in single-shot IR pump - resonant X-ray scattering probe experiments

The evolution of a magnetic domain structure upon excitation by an intense, femtosecond Infra-Red (IR) laser pulse has been investigated using single-shot based time-resolved resonant X-ray scattering at the X-ray Free Electron laser LCLS. A well-ordered stripe domain pattern as present in a thin CoPd alloy film has been used as prototype magnetic domain structure for this study. The fluence of the IR laser pump pulse was sufficient to lead to an almost complete quenching of the magnetization within the ultrafast demagnetization process taking place within the first few hundreds of femtoseconds following the IR laser pump pulse excitation. On longer time scales this excitation gave rise to subsequent irreversible transformations of the magnetic domain structure. Under our specific experimental conditions, it took about 2 nanoseconds before the magnetization started to recover. After about 5 nanoseconds the previously ordered stripe domain structure had evolved into a disordered labyrinth domain structure. Surprisingly, we observe after about 7 nanoseconds the occurrence of a partially ordered stripe domain structure reoriented into a novel direction. It is this domain structure in which the sample's magnetization stabilizes as revealed by scattering patterns recorded long after the initial pump-probe cycle. Using micro-magnetic simulations we can explain this observation based on changes of the magnetic anisotropy going along with heat dissipation in the film.Comment: 16 pages, 6 figure

The Exoplanet Modeling and Analysis Center at NASA Goddard

The Exoplanet Modeling and Analysis Center (EMAC) at NASA Goddard Space Flight Center is a web-based catalog, repository, and integration platform for modeling and analysis resources focused on the study of exoplanet characteristics and environments. EMAC hosts user-submitted resources ranging in category from planetary interior models to data visualization tools. Other features of EMAC include integrated web tools developed by the EMAC team in collaboration with the tools' original author(s) and video demonstrations of a growing number of hosted tools. EMAC aims to be a comprehensive repository for researchers to access a variety of exoplanet resources that can assist them in their work, and currently hosts a growing number of code bases, models, and tools. EMAC is a key project of the NASA GSFC Sellers Exoplanet Environments Collaboration (SEEC) and can be accessed at https://emac.gsfc.nasa.gov.Comment: 3 pages and 1 figure. Published in RNAA

Exoplanet Diversity in the Era of Space-based Direct Imaging Missions

This whitepaper discusses the diversity of exoplanets that could be detected by future observations, so that comparative exoplanetology can be performed in the upcoming era of large space-based flagship missions. The primary focus will be on characterizing Earth-like worlds around Sun-like stars. However, we will also be able to characterize companion planets in the system simultaneously. This will not only provide a contextual picture with regards to our Solar system, but also presents a unique opportunity to observe size dependent planetary atmospheres at different orbital distances. We propose a preliminary scheme based on chemical behavior of gases and condensates in a planet's atmosphere that classifies them with respect to planetary radius and incident stellar flux.Comment: A white paper submitted to the National Academy of Sciences Exoplanet Science Strateg