Cosmological parameters from SDSS and WMAP

We measure cosmological parameters using the three-dimensional power spectrum P(k) from over 200,000 galaxies in the Sloan Digital Sky Survey (SDSS) in combination with WMAP and other data. Our results are consistent with a ``vanilla'' flat adiabatic Lambda-CDM model without tilt (n=1), running tilt, tensor modes or massive neutrinos. Adding SDSS information more than halves the WMAP-only error bars on some parameters, tightening 1 sigma constraints on the Hubble parameter from h~0.74+0.18-0.07 to h~0.70+0.04-0.03, on the matter density from Omega_m~0.25+/-0.10 to Omega_m~0.30+/-0.04 (1 sigma) and on neutrino masses from <11 eV to <0.6 eV (95%). SDSS helps even more when dropping prior assumptions about curvature, neutrinos, tensor modes and the equation of state. Our results are in substantial agreement with the joint analysis of WMAP and the 2dF Galaxy Redshift Survey, which is an impressive consistency check with independent redshift survey data and analysis techniques. In this paper, we place particular emphasis on clarifying the physical origin of the constraints, i.e., what we do and do not know when using different data sets and prior assumptions. For instance, dropping the assumption that space is perfectly flat, the WMAP-only constraint on the measured age of the Universe tightens from t0~16.3+2.3-1.8 Gyr to t0~14.1+1.0-0.9 Gyr by adding SDSS and SN Ia data. Including tensors, running tilt, neutrino mass and equation of state in the list of free parameters, many constraints are still quite weak, but future cosmological measurements from SDSS and other sources should allow these to be substantially tightened.Comment: Minor revisions to match accepted PRD version. SDSS data and ppt figures available at http://www.hep.upenn.edu/~max/sdsspars.htm

Oxygen production from dissociation of Europa’s water-ice surface

Jupiter’s moon Europa has a predominantly water-ice surface that is modified by exposure to its space environment. Charged particles break molecular bonds in surface ice, thus dissociating the water to ultimately produce H2 and O2, which provides a potential oxygenation mechanism for Europa’s subsurface ocean. These species are understood to form Europa’s primary atmospheric constituents. Although remote observations provide important global constraints on Europa’s atmosphere, the molecular O2 abundance has been inferred from atomic O emissions. Europa’s atmospheric composition had never been directly sampled and model-derived oxygen production estimates ranged over several orders of magnitude. Here, we report direct observations of H2+ and O2+ pickup ions from the dissociation of Europa’s water-ice surface and confirm these species are primary atmospheric constituents. In contrast to expectations, we find the H2 neutral atmosphere is dominated by a non-thermal, escaping population. We find 12 ± 6 kg s−1 (2.2 ± 1.2 × 1026 s−1) O2 are produced within Europa’s surface, less than previously thought, with a narrower range to support habitability in Europa’s ocean. This process is found to be Europa’s dominant exogenic surface erosion mechanism over meteoroid bombardment

Energetic Electron Observations by Parker Solar Probe/ISo˙IS during the First Widespread SEP Event of Solar Cycle 25 on 2020 November 29

At the end of 2020 November, two coronal mass ejections (CMEs) erupted from the Sun and propagated through the interplanetary medium in the direction of Parker Solar Probe while the spacecraft was located at ∼0.81 au. The passage of these interplanetary CMEs (ICMEs) starting on November 29 (DOY 334) produced the largest enhancement of energetic ions and electrons observed by the Integrated Science Investigation of the Sun (ISo˙IS) energetic particle instrument suite on board Parker Solar Probe during the mission's first eight orbits. This was also the first spatially widespread solar energetic particle event observed in solar cycle 25. We investigate several key characteristics of the energetic electron event including the time profile and anisotropy distribution of near-relativistic electrons as measured by ISo˙IS's low-energy Energetic Particle Instrument (EPI-Lo) and compare these observations with contextual data from the Parker Solar Probe Fields Experiment magnetometer. These are the first electron anisotropy measurements from ISo˙IS/EPI-Lo, demonstrating that the instrument can successfully produce these measurements. We find that the electron count rate peaks at the time of the shock driven by the faster of the two ICMEs, implying that the shock parameters of this ICME are conducive to the acceleration of electrons. Additionally, the angular distribution of the electrons during the passage of the magnetic clouds associated with the ICMEs shows significant anisotropy, with electrons moving primarily parallel and antiparallel to the local magnetic field as well as bidirectionally, providing an indication of the ICME's magnetic topology and connectivity to the Sun or magnetic structures in the inner heliosphere. © 2021. The Author(s). Published by the American Astronomical Society..Open access articleThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Meteoroids as One of the Sources for Exosphere Formation on Airless Bodies in the Inner Solar System

AbstractThis manuscript represents a review on progress made over the past decade concerning our understanding of meteoroid bombardment on airless solar system bodies as one of the sources of the formation of their exospheres. Specifically, observations at Mercury by MESSENGER and at the Moon by LADEE, together with progress made in dynamical models of the meteoroid environment in the inner solar system, offer new tools to explore in detail the physical phenomena involved in this complex relationship. This progress is timely given the expected results during the next decade that will be provided by new missions such as DESTINY+, BepiColombo, the Artemis program or the Lunar Gateway

Juno Observations of Plasma Waves Associated with the Io Footprint Tail

The Juno spacecraft has crossed magnetic flux tubes associated with the Io auroral footprint tail at a variety of downtail distances from the Io footprint spot. The Juno radio and plasma wave instrument (Waves) detects large amplitude electromagnetic waves during many of these crossings. These emissions are usually detected for just a few seconds to tens of seconds and high resolution Wave burst data show that peak amplitudes of these waves can reach about 1 V/m for the electric field and a few nT for the magnetic field. However, on the recent perijove 12 northern crossing, the Waves instrument detected an intense funnel shaped emission lasting for many minutes with intense lower frequency emission at the funnel apex. Initial analysis of these emissions suggest that these waves are propagating upward from Jupiter. The emission frequencies are well below the electron cyclotron frequency and the upper frequency appears to be cutoff at the electron plasma frequency, with an additional change in intensity also observed at the proton cyclotron frequency. We will discuss the details of these waves and examine possible wave modes

Evidence of Injection Driven Aurora at Jupiter during Juno Perijove 5

Injections in Jupiter's magnetosphere are a dynamic process associated with the inward transport of hot plasma, containing ions and electrons with energies into the keV or even MeV. Previous studies have demonstrated a relationship between electron injections observed in Jupiter's equatorial magnetosphere and transient aurora near Jupiter's main emission [e.g. Mauk et al. 2002]. Here, we present observations from several instruments on Juno between ~03:00 to 05:00 UT on DOY 86 2017 that link electron injection signatures observed at high-latitudes to bright UV emissions near Jupiter's main aurora. These injections, observed at magnetic latitudes of ~50oN and jovicentric distances of ~5.5 – 8 jovian radii (1 RJ ~ 71,400 km), were identified by sudden intensity depletions and enhancements in the low ( 50 keV) energy electrons. They are likely connected to several transient UV emission features observed at jovigraphic latitudes of ~55o – 60oN, lasting for tens of minutes, with high color ratios consistent with an energetic electron source. These combined observations allow us to directly compare the measured in-situ properties of electrons associated with injection events (pitch angle distributions, characteristic energy, energy flux) to the remote observations of the UV emissions that they produce

What kind of training is required to help language students use metaphor-based strategies to work out the meaning of new vocabulary? Que tipo de treinamento é necessário para ajudar estudantes de idiomas a usar estratégias baseadas em metáforas para adivinhar o significado de vocabulário novo?

A study is described, which compared the benefits of two different training approaches in the use of metaphor-based vocabulary guessing strategies for foreign language learners. A group-based, step-by-step approach was compared with a more autonomous approach. The findings suggest that the type of training received affects the students' ability to use these strategies, but not their tendency to use them. The students who participated in the autonomous approach were significantly more successful at using metaphor-based vocabulary guessing strategies than the students who had received the group training. The difference was particularly marked in terms of their successful use of interactive images.<br>É descrito um estudo que compara os benefícios de duas abordagens diferentes de treinamento no uso de estratégias de adivinhação de vocabulário baseadas em metáforas para estudantes de línguas estrangeiras. Uma abordagem passo-a-passo, de grupo, é comparada com outra, mais autônoma. Os resultados sugerem que o tipo de treinamento recebido afeta a capacidade dos alunos usarem essas estratégias, mas não sua tendência em usá-las. Alunos que participaram da abordagem autônoma foram significativamente melhor sucedidos no uso de estratégias de adivinhação de vocabulário baseadas em metáforas do que os alunos que receberam treinamento em grupo. A diferença foi particularmente acentuada em relação a seu sucesso no uso de imagens interativas

Time evolution of stream interaction region energetic particle spectra in the inner heliosphere

We analyze an energetic proton event associated with a stream interaction region (SIR) that was observed at Parker Solar Probe on day 320 of 2018 when the spacecraft was just 0.34 AU from the Sun. Using the Integrated Science Investigation of the Sun instrument suite, we perform a spectral analysis of the event and show how the observed spectra evolve over the course of the event. We find that the spectra from the first day of the event are much more consistent with local acceleration at a weak compression, while spectra from later on are more typical of SIR-related events in which particles accelerated at distant shocks dominate. After the first day, the spectra remain approximately constant, which indicates that the modulation of energetic particles during transit from the presumed source region is weaker than previously thought. We argue that these observations can be explained by a sub-Parker spiral magnetic field structure connecting the spacecraft to a source region in the SIR that is relatively close to the Sun. We further propose that acceleration at weak, pre-shock compressions likely plays an important role in observations of SIR-related events in the inner heliosphere and that future modelling of such events should consider acceleration all along the compression region, not just at the distant shock region. © ESO 2021.Immediate accessThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]