Recent Observational Developments Research Articles

Recent developments in tornado theory and observations.

This article critically reviews research on tornado theory and observations over the last decade. From the theoretical standpoint, the major advances have come through improved numerical-simulation models of supercell convective storms, which contain the tornado's parent circulation. These simulations are carried out on a large domain (to capture the supercell's circulation system), but with high grid resolution and improved representations of sub-grid physics (to capture the tornado). These simulations offer new insights into how and why tornadoes form in some supercells, but not others. Observational advances have come through technological improvements of mobile Doppler radars capable of rapid scanning and dual-polarization measurements, which offer a much more accurate view of tornado formation, tornado structure, and the tornado's place within its parent supercell.

Cosmological constraints on curved quintessence

Dynamical dark energy has gained renewed interest due to recent theoretical and observational developments. In the present paper, we focus on a string-motivated dark energy set-up, and perform a detailed cosmological analysis of exponential quintessence with potential V = V 0 e λϕ -, allowing for non-zero spatial curvature. We first gain some physical intuition into the full evolution of such a scenario by analysing the corresponding dynamical system. Then, we test the model using a combination of Planck CMB data, DESI BAO data, as well as recent supernovae datasets. For the model parameter λ, we obtain a preference for nonzero values: λ = 0.48+0.28 -0.21, 0.68+0.31 -0.20, 0.77+0.18 -0.15 at 68% C.L. when combining CMB+DESI with Pantheon+, Union3 and DES-Y5 supernovae datasets respectively. We find no significant hint for spatial curvature. We discuss the implications of current cosmological results for the exponential quintessence model, and more generally for dark energy in string theory.

From apparent attenuation towards physics-based source terms – a perspective on spectral wave modeling in ice-covered seas

Numerical modeling of waves in sea ice covered regions of the oceans is important for many applications, from short-term forecasting and ship route planning up to climate modeling. In spite of a substantial progress in wave-in-ice research that took place in recent years, spectral wave models – the main tool for wave modeling at regional and larger scales – still don’t capture the underlying physics and have rather poor predictive skills. This article discusses recent developments in wave observations and spectral wave modeling in sea ice, identifies problems and shortcomings of the approaches used so far, and sketches future directions that, in the opinion of the author, have the potential to improve the performance of wave-in-ice models.

Control of Seismicity Migration in Earthquake Swarms by Injected Fluid Volume and Aseismic Crack Propagation

AbstractThe evolution of fluid injection‐induced seismicity, generally characterized through the number of events or their seismic moment, depends on, among other factors, the injected fluid volume. Migration of seismicity is observed during those sequences and might be caused by a range of mechanisms: fluid pressure diffusion, fluid‐induced aseismic slip propagating along a stimulated fault, interactions between earthquakes. Recent theoretical and observational developments underline the important effect on seismicity migration of structural parameters, like fault criticality, or injection parameters, like flow rate or pressurization rate. Here, we analyze two well‐studied injection‐induced seismic sequences at the Soultz‐sous‐Fôret and Basel geothermal sites, and find that the evolution of the seismicity front distance primarily depends on the injected fluid volume. Based on a fracture mechanics model, we develop new equations relating seismicity migration to injected fluid volume and frictional and structural properties of the fault. We find that the propagation of a fluid‐induced aseismic slip front along the stimulated fault, triggering seismicity, explains well the observations made on the two sequences. This model allows us to constrain parameters describing the seismicity front evolution and explains the diversity of migration patterns observed in injection‐induced and natural earthquake swarms.

The evolution of 21st century sea-level projections from IPCC AR5 to AR6 and beyond

AbstractSea-level science has seen many recent developments in observations and modelling of the different contributions and the total mean sea-level change. In this overview, we discuss (1) the evolution of the Intergovernmental Panel on Climate Change (IPCC) projections, (2) how the projections compare to observations and (3) the outlook for further improving projections. We start by discussing how the model projections of 21st century sea-level change have changed from the IPCC AR5 report (2013) to SROCC (2019) and AR6 (2021), highlighting similarities and differences in the methodologies and comparing the global mean and regional projections. This shows that there is good agreement in the median values, but also highlights some differences. In addition, we discuss how the different reports included high-end projections. We then show how the AR5 projections (from 2007 onwards) compare against the observations and find that they are highly consistent with each other. Finally, we discuss how to further improve sea-level projections using high-resolution ocean modelling and recent vertical land motion estimates.

Constraints on the contributions to the observed binary black hole population from individual evolutionary pathways in isolated binary evolution

ABSTRACT Gravitational waves from merging binary black holes can be used to shed light on poorly understood aspects of massive binary stellar evolution, such as the evolution of massive stars (including their mass-loss rates), the common envelope phase, and the rate at which massive stars form throughout the cosmic history of the Universe. In this paper, we explore the correlated impact of these phases on predictions for the merger rate and chirp mass distribution of merging binary black holes, aiming to identify possible degeneracies between model parameters. In many of our models, a large fraction (more than 70 per cent of detectable binary black holes) arise from the chemically homogeneous evolution scenario; these models tend to overpredict the binary black hole merger rate and produce systems that are on average too massive. Our preferred models favour enhanced mass-loss rates for helium rich Wolf–Rayet stars, in tension with recent theoretical and observational developments. We identify correlations between the impact of the mass-loss rates of Wolf–Rayet stars and the metallicity evolution of the Universe on the rates and properties of merging binary black holes. Based on the observed mass distribution, we argue that the $\sim 10{{\ \rm per\ cent}}$ of binary black holes with chirp masses greater than 40 M⊙ (the maximum predicted by our models) are unlikely to have formed through isolated binary evolution, implying a significant contribution (>10 per cent) from other formation channels such as dense star clusters or active galactic nuclei. Our models will enable inference on the uncertain parameters governing binary evolution in the near future.

Quantum Conductance in Memristive Devices: Fundamentals, Developments, and Applications (Adv. Mater. 32/2022)

Quantum Conductance In article number 2201248, Gianluca Milano, Ilia Valov, and co-workers review the state-of-the-art of quantum conductance effects in memristive devices. Besides analyzing fundamental physicochemical phenomena and electronic ballistic transport in nanofilaments, recent developments in experimental observation of quantum effects in memristive devices and related challenges are discussed. Representing suitable platforms for investigating quantum phenomena at room temperature, future perspectives of memristive devices in quantum and neuromorphic systems are envisioned.

The Double Detonation of a Double-degenerate System, from Type Ia Supernova Explosion to its Supernova Remnant

Type Ia supernovae (SNe) are believed to be caused by the thermonuclear explosion of a white dwarf (WD), but the nature of the progenitor system(s) is still unclear. Recent theoretical and observational developments have led to renewed interest in double-degenerate models, in particular the “helium-ignited violent merger” or “dynamically driven double-degenerate double-detonation” (D6). In this paper we take the output of an existing D6 SN model and carry it into the supernova remnant (SNR) phase up to 4000 yr after the explosion, past the time when all the ejecta have been shocked. Assuming a uniform ambient medium, we reveal specific signatures of the explosion mechanism and spatial variations intrinsic to the ejecta. The first detonation produces an ejecta tail visible at early times, while the second detonation leaves a central density peak in the ejecta that is visible at late times. The SNR shell is off-center at all times, because of an initial velocity shift due to binary motion. The companion WD produces a large conical shadow in the ejecta, visible in projection as a dark patch surrounded by a bright ring. This is a clear and long-lasting feature that is localized, and its impact on the observed morphology is dependent on the viewing angle of the SNR. These results offer a new way to diagnose the explosion mechanism and progenitor system using observations of a Type Ia SNR.

Updated constraints on superconducting cosmic strings from the astronomy of fast radio bursts

In this article we update constraints on superconducting cosmic strings (SCSs) in the light of the recent observational developments of fast radio bursts (FRBs) astronomy. Assuming strings follow an exponential distribution characterized by a current, we show that two parameters in our context, which are the characteristic tension (Gmu ) and a parameter which describes the aforementioned exponential distribution (I_c), can be constrained by FRB experiments. Particularly, we investigate data sets from Parkes and ASKAP. We looked at a parameter space where Gmu sim [10^{-17}, 10^{-12}] and I_csim [10^{-1}, 10^{2}] GeV, and found our results show that Parkes jointly with ASKAP can constrain the parameter space for SCSs.

Relativistic Aspects of Accreting Supermassive Black Hole Binaries in Their Natural Habitat: A Review

In this review a summary is given on recent theoretical work, on understanding accreting supermassive black hole binaries in the gravitational wave (GW)-driven regime. A particular focus is given to theoretical predictions of properties of disks and jets in these systems during the gravitational wave driven phase. Since a previous review by Schnittman 2013, which focussed on Newtonian aspects of the problem, various relativistic aspects have been studied. In this review we provide an update on these relativistic aspects. Further, a perspective is given on recent observational developments that have seen a surge in the number of proposed supermassive black hole binary candidates. The prospect of bringing theoretical and observational efforts closer together makes this an exciting field of research for years to come.

EN LA BÚSQUEDA DE LOS "ELUSIVOS" AGUJEROS NEGROS DE MASA INTERMEDIA

Ultra-Luminous X-ray sources (ULXs) are accreting black holes for which their X-ray properties have been seen to be different to the case of stellar-mass black hole binaries. For most of the cases their intrinsic energy spectra are well described by a cold accretion disc (thermal) plus a curved high-energy emission components. The mass of the black hole (BH) derived from the thermal disc component is usually in the range of 100-10^5 solar masses, which have led to the idea that this can represent strong evidence of the Intermediate Mass Black Holes (IMBH), proposed to exist by theoretical studies but with no firm detection (as a class) so far. Recent theoretical and observational developments are leading towards the idea that these sources are instead compact objects accreting at an unusual super-Eddington regime instead. On the other hand, gravitational waves have been seen to be a useful tool for finding (some of these) IMBHs. We give a brief overview about the recent advent of the discovery of gravitational waves and their relationship with these so far elusive IMBHs.

Submesoscale processes promote seasonal restratification in the Subantarctic Ocean

AbstractTraditionally, the mechanism driving the seasonal restratification of the Southern Ocean mixed layer (ML) is thought to be the onset of springtime warming. Recent developments in numerical modeling and North Atlantic observations have shown that submesoscale ML eddies (MLE) can drive a restratifying flux to shoal the deep winter ML prior to solar heating at high latitudes. The impact of submesoscale processes on the intraseasonal variability of the Subantarctic ML is still relatively unknown. We compare 5 months of glider data in the Subantarctic Zone to simulations of a 1‐D mixing model to show that the magnitude of restratification of the ML cannot be explained by heat, freshwater, and momentum fluxes alone. During early spring, we estimate that periodic increases in the vertical buoyancy flux by MLEs caused small increases in stratification, despite predominantly down‐front winds that promote the destruction of stratification. The timing of seasonal restratification was consistent between 1‐D model estimates and the observations. However, during up‐front winds, the strength of springtime stratification increased over twofold compared to the 1‐D model, with a rapid shoaling of the MLD from >200 m to <100 m within a few days. The ML stratification is further modified under a negative Ekman buoyancy flux during down‐front winds, resulting in the destruction of ML stratification and deepening of the MLD. These results propose the importance of submesoscale buoyancy fluxes enhancing seasonal restratification and mixing of the Subantarctic ML.

The AGN Jet Model of the Fermi Bubbles

AbstractThe nature and origin of the Fermi bubbles detected in the inner Galaxy remain elusive. In this paper, we briefly discuss some recent theoretical and observational developments, with a focus on the AGN jet model. Analogous to radio lobes observed in massive galaxies, the Fermi bubbles could be naturally produced by a pair of opposing jets emanating nearly along the Galaxy’s rotation axis from the Galactic center. Our two-fluid hydrodynamic simulations reproduce quite well the bubble location and shape, and interface instabilities at the bubble surface could be effectively suppressed by shear viscosity. We briefly comment on some potential issues related to our model, which may lead to future progress.

Dark matter indirect searches: Multi-wavelength and anisotropies

If dark matter is made of particles governed by weak-scale physics, they may annihilate or decay to leave observable signatures in high-energy gamma-ray sky. In addition, any charged particles produced by the same process will also give low-frequency photons through successive electromagnetic interactions. Plenty of data from modern astrophysical measurements of various wavelengths, especially gamma rays, enabled new analysis techniques to search for these dark matter signatures with an unprecedented sensitivities. Since it is very likely that signatures of dark matter annihilation or decay is hidden in the gamma-ray data, one should fully utilize all available data including: (1) energy spectrum of all wavelengths ranging from radio to very-high-energy gamma rays; (2) spatial clustering probed with the angular power spectrum of the gamma-ray background; (3) cross correlation between the gamma-ray distribution with nearby galaxy catalogs; and (4) gamma-ray-flux distribution. I will review recent theoretical and observational developments in all these aspects, and discuss prospects for the future towards discovery of dark matter as an elementary particle in physics beyond the standard model.

Dawes Review 4: Spiral Structures in Disc Galaxies

AbstractThe majority of astrophysics involves the study of spiral galaxies, and stars and planets within them, but how spiral arms in galaxies form and evolve is still a fundamental problem. Major progress in this field was made primarily in the 1960s, and early 1970s, but since then there has been no comprehensive update on the state of the field. In this review, we discuss the progress in theory, and in particular numerical calculations, which unlike in the 1960s and 1970s, are now commonplace, as well as recent observational developments. We set out the current status for different scenarios for spiral arm formation, the nature of the spiral arms they induce, and the consequences for gas dynamics and star formation in different types of spiral galaxies. We argue that, with the possible exception of barred galaxies, spiral arms are transient, recurrent and initiated by swing amplified instabilities in the disc. We suppose that unbarredm= 2 spiral patterns are induced by tidal interactions, and slowly wind up over time. However the mechanism for generating spiral structure does not appear to have significant consequences for star formation in galaxies.

New developments, plasma physics regimes and issues for the Ignitor experiment

The scientific goal of the Ignitor experiment is to approach, for the first time, the ignition conditions of a magnetically confined D–T plasma. The IGNIR collaboration between Italy and Russia is centred on the construction of the core of the Ignitor machine in Italy and its installation and operation within the Triniti site (Troitsk). A parallel initiative has developed that integrates this programme, involving the study of plasmas in which high-energy populations are present, with ongoing research in high-energy astrophysics, with a theory effort involving the National Institute for High Mathematics, and with INFN and the University of Pisa for the development of relevant nuclear and optical diagnostics. The construction of the main components of the machine core has been fully funded by the Italian Government. Therefore, considerable attention has been devoted towards identifying the industrial groups having the facilities necessary to build these components. An important step for the Ignitor programme is the adoption of the superconducting MgB2 material for the largest poloidal field coils (P14) that is compatible with the He-gas cooling system designed for the entire machine. The progress made in the construction of these coils is described. An important advance has been made in the reconfiguration of the cooling channels of the toroidal magnet that can double the machine duty cycle. A facility has been constructed to test the most important components of the ICRH system at full scale, and the main results of the tests carried out are presented. The main physics issues that the Ignitor experiment is expected to face are analysed considering the most recent developments in both experimental observations and theory for weakly collisional plasma regimes. Of special interest is the I-regime that has been investigated in depth only recently and combines advanced confinement properties with a high degree of plasma purity. This is a promising alternative to the high-density L-regime that had been observed by the Alcator experiment and whose features motivated the Ignitor project. The provisions that are incorporated in the machine design, and in that of the plasma chamber in particular, in order to withstand or prevent the development of macroscopic instabilities with deleterious amplitudes are presented together with relevant analyses.

The Role of Earth Observation on Environmental Management in Africa

The success of environmental management and protection lies on the availability of adequate information to support intervention measures. Such information acts as a prerequisite to predict the future and, subsequently, to validate the accuracy of those predictions. In this paper, we illustrate the potential of earth observation, more precisely remote sensing in measuring and monitoring environmental variables that are crucial for the management of the earth’s resources. Recent developments in earth observation and the sources of remote sensing data for Africa are detailed. Examples of available sensors and their potential applications, including the newly launched SumbandilaSat South African sensor, are detailed in the paper.

From Observations to Forecasts – Part 3. Key principles and recent developments in satellite observations

On 1 April 1960, two and a half years after the launch of the first satellite, Sputnik-1, the Television InfraRed Observation Satellite (TIROS-1) became the first meteorological satellite. Since then, meteorology has been at the forefront of Earth observation. In 1963, the World Weather Watch programme was set up by the World Meteorological Organization (WMO) to establish a satellite observation network of (nominally) five geostationary and two polar orbiting meteorological satellites. The first geostationary meteorological observations started in 1966, followed by the launch of a series of meteorological satellites to observe and monitor our atmosphere (see Brugge and Stuttard, 2003). Key to the success of satellite observations was the ability to acquire routine synoptic-scale observations of the Earth and its atmosphere at relatively fine resolutions. By interpreting the imagery and monitoring any changes, these observations have provided crucial information to aid our understanding and knowledge of meteorological and atmospheric processes. Furthermore, the longevity of such observations now allows such data to be used on climatological timescales. Meteorological satellites provide observations of the Earth from low-Earth orbits or from geostationary orbits: observations taken by satellite sensors in these orbits complement each other to provide global im agery on a routine basis. Figure 1 shows the current operational meteorological satellites of the Global Observing System (GOES).

Real-Time Eruption Magnitude Estimation from Far-Field Geodetic Data: A Proposal for Volcanic Early Warning

Recent developments in dense geodetic observation of volcanoes have enabled us to handle data in real-time. Monitoring agencies detect volcano unrest using numerous instruments and quickly broadcast volcanic activity alerts but based on little quantitative information. Residents on volcanoes seek predictive, practical, and reliable alerts including place, time, and magnitude directly linked to disaster mitigation activities. A strategy I proposed in this study answers the question of the magnitude of a foreseen eruption. Far-field displacements by geodetic instruments provide the signals of deflating magma reservoirs, and may give predictive maximum magnitude Mvpof a looming eruption. This may play an important role in antidisaster measures because it is the parameter most determinate for evacuation. Continuous monitoring of Mvpmay also yield valuable information for judging the termination of an eruption because its stagnation indicates magma feeding disconnection from reservoir to shallower part. I believe that predictive volcanic early warnings with quantitative Mvpcan provide truly effective, practical information to residents and local governments potentially affected by active volcanoes.

GEMS at the Galactic Cosmic-Ray Source

Galactic cosmic rays probably predominantly originate from shock-accelerated gas and dust in superbubbles. It is usually assumed that the shock-accelerated dust is quickly destroyed by sputtering. However, it may be that some of the dust can survive bombardment by the high-metallicity gas in the superbubble interior, and that some of that dust has been incorporated into solar system materials. Interplanetary dust particles (IDPs) contain enigmatic submicron components called GEMS (Glass with Embedded Metal and Sulfides). These GEMS have properties that closely match those expected of a population of surviving shock-accelerated dust at the GCR source (Westphal and Bradley in Astrophys. J. 617:1131, 2004). In order to test the hypothesis that GEMS are synthesized from shock-accelerated dust in superbubbles, we plan to measure the relative abundances of Fe, Zr, and Mo isotopes in GEMS using the new Resonance Ionization Mass Spectrometer at Argonne National Laboratory. If GEMS are synthesized from shock-accelerated dust in superbubbles, they should exhibit isotopic anomalies in Fe, Zr and Mo: specificially, enhancements in the r-only isotopes 96Zr and 100Mo, and separately in 58Fe, should be observed. We review also recent developments in observations of GEMS, laboratory synthesis of GEMS-like materials, and implications of observations of GEMS-like materials in Stardust samples.