Stellar Wakes from Dark Matter Subhalos

We propose a novel method utilizing stellar kinematic data to detect low-mass substructure in the Milky Way's dark matter halo. By probing characteristic wakes that a passing dark matter subhalo leaves in the phase space distribution of ambient halo stars, we estimate sensitivities down to subhalo masses $\sim 10^7\,M_\odot$ or below. The detection of such subhalos would have implications for dark-matter and cosmological models that predict modifications to the halo-mass function at low halo masses. We develop an analytic formalism for describing the perturbed stellar phase-space distributions, and we demonstrate through simulations the ability to detect subhalos using the phase-space model and a likelihood framework. Our method complements existing methods for low-mass subhalo searches, such as searches for gaps in stellar streams, in that we can localize the positions and velocities of the subhalos today.Comment: 6 + 3 pages, 1 + 2 figures, code available at: https://github.com/bsafdi/stellarWake

Evolving Tropical Cyclone Tracks in the North Atlantic in a Warming Climate

Tropical cyclone (TC) track characteristics in a changing climate remain uncertain. Here, we investigate the genesis, tracks, and termination of \u3e35,000 synthetic TCs traveling within 250 km of New York City (NYC) from the pre‐industrial era (850–1800 CE) to the modern era (1970–2005 CE) to the future (2080–2100 CE). Under a very high‐emissions scenario (RCP8.5), TCs are more likely to form closer to the United States (U.S.) southeast coast (\u3e15% increase), terminate in the northeastern Atlantic (\u3e6% increase), and move most slowly along the U.S. Atlantic coast (\u3e15% increase) from the pre‐industrial to future. Under our modeled scenarios, TCs are more likely to travel within 100 km of Boston, MA, USA (p = 0.01) and Norfolk, VA, USA (p = 0.05) than within 100 km of NYC in the future. We identify reductions in the time between genesis and the time when TCs come within 100 km of NYC, Boston, or Norfolk, as well as increased duration of TC impacts from individual storms at all three cities in the future

RUNOFF GENERATING PROCESSES IN A MOUNTAINOUS HEADWATER IN THE TRANSITION ZONE BETWEEN STEPPE AND TAIGA IN NORTHERN MONGOLIA

Northern Mongolia faces a variety of water-related problems that are related to both, the harsh natural conditions and the lack of structures to control the distribution and protection of water. The Kharaa River Basin (KRB), which is located north of Mongolia's capital Ulaanbaatar, was chosen as a model region for the development and implementation of an integrated water resources management (IWRM) project called MoMo (Model Region Mongolia). The aim of IWRM is to provide insight into both, societal structural and eco-systematic conditions as a whole. Besides an improvement of the structures, especially in the urban sector, all relevant water related processes are captured. This includes the identification of “water towers” and the underlying runoff generating processes. The KRB stretches from the steppe towards the western Khentii Mountains. Thus, it covers a wide range of environmental conditions and can be considered to be representative for many regions within Mongolia. The Sugnugr Basin situated within the western Khentii Mountain ranges is one of the most important tributaries of the Kharaa. The climate is highly continental and semi-arid; average annual precipitation in the mid-reaches remains below 400 mm. With a fraction of 90 %, precipitation is predominantly falling during the summer half year (May to October). Air temperature in 2011 and 2012 was -2°C and -3°C, with monthly air temperatures ranging between 28°C in January and 16°C in July. The Sugnugr Basin is situated in the transition zone between steppe and taiga, and is part of the discontinuous permafrost zone. Thus, it is characterized by a heterogeneous mosaic of herbaceous steppe vegetated south-exposed slopes and taiga vegetated north-exposed slopes that exhibit permafrost. Above the tree line of approximately 2300 m a.s.l. alpine scree prevails. In 2004 and 2007 widespread forest fires destroyed considerable amounts of the taiga, especially in the headwaters. Forest regrowth under the prevailing natural conditions can last 200 years and more. The following presented runoff generating processes are based on comprehensive and detailed field studies in an anthropogenic unaffected headwater of the Sugnugr. The results indicate hydrological processes in the study area to be controlled by the dominant vegetation cover. It has been shown that steppe vegetated south-exposed hillslopes only sporadically contribute to river runoff during intense precipitation events. Infiltration rates into the soil matrix are small and evenly distributed and no signs of preferential flow were found. In general, these sites were characterized by dry conditions and soil moisture content occasionally reached the permanent wilting point during the summer months. A majority of river runoff must hence be generated by taiga vegetated north-exposed hillslopes. Especially the thick organic surface layer and the depth of the active layer have been shown to control runoff response. On the catchment scale, hydrograph recession analysis revealed a quick transfer of event water on top of a thin active layer towards the rivers in early summer. In the course of summer, active layer depth and thus storage capacity is increasing, resulting in enhanced recession periods and increased low-flow runoff. Simultaneously, it could be shown that hillslope runoff only occurs after a threshold of 5 % increase of the relative volumetric water content of the upper soil zone, including the organic surface, is reached. Wildfires alter this system sustainably. As the insulating organic surface cover is removed, soil temperatures have been shown to increase, while permafrost subsided to deeper depth. This resulted in a network of preferential flow paths on top of the frost table, which effectively transfers event water towards the adjacent river without substantial retention. Land-cover change scenarios were simulated with the conceptual hydrological model HBV-D. As a consequence of a wildfire, with all taiga stands being burned, monthly runoff was simulated to decrease during the winter half year, while it increased during the summer half year. However, results of the field studies suggest that the simulated increase in summer runoff following wildfire does not lead to greater water availability, as stormflow runoff increased while low flow runoff decreased. The results support the conservation of the alpine headwaters, especially from deforestation and wildfire in order to safeguard the current amount of surface water quantity. This gains further importance regarding the flourishing Mongolian economy and the related increasing water demands

Magnetic tests for magnetosome chains in Martian meteorite ALH84001

Transmission electron microscopy studies have been used to argue that magnetite crystals in carbonate from Martian meteorite ALH84001 have a composition and morphology indistinguishable from that of magnetotactic bacteria. It has even been claimed from scanning electron microscopy imaging that some ALH84001 magnetite crystals are aligned in chains. Alignment of magnetosomes in chains is perhaps the most distinctive of the six crystallographic properties thought to be collectively unique to magnetofossils. Here we use three rock magnetic techniques, low-temperature cycling, the Moskowitz test, and ferromagnetic resonance, to sense the bulk composition and crystallography of millions of ALH84001 magnetite crystals. The magnetic data demonstrate that although the magnetite is unusually pure and fine-grained in a manner similar to terrestrial magnetofossils, most or all of the crystals are not arranged in chains

Computer-aided Optical Plasma Postprocessing Applied on Model Spark Gaps

Spark gaps are used as surge protective devices (SPD class 1) for low voltage grids protection against surge currents and overvoltages. For practical research of the narrow gap plasma of spark gaps, high-speed camera recordings are used in modified transparent test models. In this test setup, current densities of 1010 A/m2 are generated. In order to optimize and automate the evaluation process of camera recordings, an image analysis tool is developed further in this contribution. After basic image improvement and segmentation, this research optimizes a detection algorithm for plasma location and distribution. As a result, the known plasma distribution gives access to significantly more information about the plasma behaviour and the spatial distribution of radiation

Online zu Gott?!

Gehen Kirche und liturgisches Leben überhaupt digital und, wenn ja, wie? Diese simple Frage wurde mit Beginn der Corona-Pandemie zuletzt noch drängender und verlangt im Hinblick auf gottesdienstliche und gottesdienstähnliche Feierformen in Rundfunk und Internet nach differenzierten Antworten sowie einer vertieften (liturgie-) wissenschaftlichen Reflexion – ein theologisches Feld, das in diesem Band neu vermessen wird