216 research outputs found
The Space Environment and Atmospheric Joule Heating of the Habitable Zone Exoplanet TOI700-d
We investigate the space environment conditions near the Earth-size planet
TOI~700~d using a set of numerical models for the stellar corona and wind, the
planetary magnetosphere, and the planetary ionosphere. We drive our simulations
using a scaled-down stellar input and a scaled-up solar input in order to
obtain two independent solutions. We find that for the particular parameters
used in our study, the stellar wind conditions near the planet are not very
extreme -- slightly stronger than that near the Earth in terms of the stellar
wind ram pressure and the intensity of the interplanetary magnetic field. Thus,
the space environment near TOI700-d may not be extremely harmful to the
planetary atmosphere, assuming the planet resembles the Earth. Nevertheless, we
stress that the stellar input parameters and the actual planetary parameters
are unconstrained, and different parameters may result in a much greater effect
on the atmosphere of TOI700-d. Finally, we compare our results to solar wind
measurements in the solar system and stress that modest stellar wind conditions
may not guarantee atmospheric retention of exoplanets.Comment: accepted to Ap
Stellar energetic particles in the magnetically turbulent habitable zones of TRAPPIST-1-like planetary systems
Planets in close proximity to their parent star, such as those in the
habitable zones around M dwarfs, could be subject to particularly high doses of
particle radiation. We have carried out test-particle simulations of ~GeV
protons to investigate the propagation of energetic particles accelerated by
flares or travelling shock waves within the stellar wind and magnetic field of
a TRAPPIST-1-like system. Turbulence was simulated with small-scale
magnetostatic perturbations with an isotropic power spectrum. We find that only
a few percent of particles injected within half a stellar radius from the
stellar surface escape, and that the escaping fraction increases strongly with
increasing injection radius. Escaping particles are increasingly deflected and
focused by the ambient spiralling magnetic field as the superimposed turbulence
amplitude is increased. In our TRAPPIST-1-like simulations, regardless of the
angular region of injection, particles are strongly focused onto two caps
within the fast wind regions and centered on the equatorial planetary orbital
plane. Based on a scaling relation between far-UV emission and energetic
protons for solar flares applied to M dwarfs, the innermost putative habitable
planet, TRAPPIST-1e, is bombarded by a proton flux up to 6 orders of magnitude
larger than experienced by the present-day Earth. We note two mechanisms that
could strongly limit EP fluxes from active stars: EPs from flares are contained
by the stellar magnetic field; and potential CMEs that might generate EPs at
larger distances also fail to escape.Comment: 17 pages, 12 figures, ApJ in pres
Building an endangered language resource in the classroom: Universal dependencies for Kakataibo
In this paper, we launch a new Universal Dependencies treebank for an endangered language from Amazonia: Kakataibo, a Panoan language spoken in Peru. We first discuss the collaborative methodology implemented, which proved effective to create a treebank in the context of a Computational Linguistic course for undergraduates. Then, we describe the general details of the treebank and the language-specific considerations implemented for the proposed annotation. We finally conduct some experiments on part-of-speech tagging and syntactic dependency parsing. We focus on monolingual and transfer learning settings, where we study the impact of a Shipibo-Konibo treebank, another Panoan language resourc
Frustrated charge order and cooperative distortions in ScV6Sn6
Here we study the stability of charge order in the kagome metal ScV6Sn6.
Synchrotron x-ray diffraction measurements reveal high-temperature, short-range
charge correlations at the wave vectors along q=(1/3,1/3,1/2) whose inter-layer
correlation lengths diverge upon cooling. At the charge order transition, this
divergence is interrupted and long-range order freezes in along
q=(1/3,1/3,1/3), as previously reported, while disorder enables the charge
correlations to persist at the q=(1/3,1/3,1/2) wave vector down to the lowest
temperatures measured. Both short-range and long-range charge correlations
seemingly arise from the same instability and both are rapidly quenched upon
the introduction of larger Y ions onto the Sc sites. Our results validate the
theoretical prediction of the primary lattice instability at q=(1/3,1/3,1/2),
and we present a heuristic picture for viewing the frustration of charge order
in this compound
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