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Nature Geoscience, Published online: 17 February 2025; doi:10.1038/s41561-025-01650-2

Rapid deposition of early-generation oxidation products substantially reduces the formation of late-generation atmospheric compounds, according to a deposition framework based on physicochemical properties and chemical modelling.

Publication date: Available online 3 February 2025

Source: Advances in Space Research

Author(s): Lin M.M. Myint, Septi Perwitasari, Michi Nishioka, Susumu Saito, Rungnapa Kaewthongrach, Pornchai Supnithi

Publication date: 1 February 2025

Source: Advances in Space Research, Volume 75, Issue 3

Author(s): Yunong Shang, Changxuan Wen, Yang Sun, Hao Zhang, Yang Gao

Publication date: 1 February 2025

Source: Advances in Space Research, Volume 75, Issue 3

Author(s): Xun Liu, Hashem Ashrafiuon, Sergey G. Nersesov

Publication date: 1 February 2025

Source: Advances in Space Research, Volume 75, Issue 3

Author(s): Mohamed Elamine Galloua, Shuai Li, Jiahao Cui

Publication date: 1 February 2025

Source: Advances in Space Research, Volume 75, Issue 3

Author(s): Zilong Chen, Haichao Gui, Rui Zhong

Publication date: 1 February 2025

Source: Advances in Space Research, Volume 75, Issue 3

Author(s): Lei Liu, Yong Liu

Publication date: 1 February 2025

Source: Advances in Space Research, Volume 75, Issue 3

Author(s): Xiang Chen, Chengpan Tang, Wujiao Dai, Xiaogong Hu, Liucheng Chen, Zhongying Zhang, Xinhui Zhu, Mingzhe Li

From late July to October 2022, residents of the Manu'a Islands in American Samoa felt the earth shake several times a day, raising concerns of an imminent volcanic eruption or tsunami.

The cool conditions which have allowed ice caps to form on Earth are rare events in the planet's history and require many complex processes working at once, according to new research.

El Niño and La Niña are climate phenomena that are generally associated with wetter and drier winter conditions in the Southwestern United States, respectively. In 2023, however, a La Niña year proved extremely wet in the Southwest instead of dry.

While most look for ways to avoid the steady rain falling from atmospheric rivers, some take advantage of the unwieldy weather patterns to improve forecasts and to help control, and ultimately modernize, the complex labyrinth of waterways hydrating California.

In this study, two Category 3 carbonaceous particles (RB-CV-0008 and RB-CV-0031) among more than 700 Hayabusa-returned particles were analyzed by molecular imaging using desorption electrospray ionization–high...

Vulcanian eruptions, characterized by intermediate magma compositions, pose significant hazards due to their potential for both magmatic and phreatomagmatic fragmentation. The Young Ciremai volcano located in ...

Abstract

While integer ambiguity resolution (IAR) enables GNSS to achieve real-time sub-centimeter-level positioning in open-sky environments, it can be easily hindered if the involved receivers are situated in areas with limited satellite visibility, such as in dense city environments. In such GNSS-challenged cases, commercial Low Earth Orbit (LEO) communication satellites can potentially augment GNSS by providing additional measurements. However, LEO satellites often lack code measurements, mainly transmitting satellite-specific frequency-varying carrier phase signals. This contribution aims to study the ambiguity-resolved baseline positioning performance of such phase-only signals, addressing the extent to which LEO constellations can realize near real-time positioning in standalone and GNSS-combined modes. Through a simulation platform, we analyze the distinct response of each LEO constellation (Iridium, Globalstar, Starlink, OneWeb, and Orbcomm) to IAR under various circumstances. Although achieving single-receiver high-precision positioning can be challenged by inaccuracies in the LEO satellite orbit products, the relative distance between two receivers can help overcome this limitation. As a result, centimeter-level relative positioning over short baselines can be made possible, even with a satellite elevation cut-off angle of 50 degrees, making it suitable for GNSS-challenged environments. This can be achieved with high-grade receiver clocks over very short baselines ( \(\sim \) 5 km) and access to decimeter-level orbit products.

Abstract

The prerequisite for achieving highly reliable Wide-Lane (WL) ambiguity resolution (AR) is the accurate determination of phase fractional cycle biases (FCB) on both the receiver and satellite side. It is generally assumed that the observation signal biases on the receiver side are stable, and receiver FCBs can be expressed using a single parameter over a period. However, due to the influence of satellite signal distortion and multipath errors, the receiver-dependent pseudorange biases (RDPB) may be inconsistent for different observed satellites at a certain receiver, which is called inconsistent RDPB (IRDPB) in this study. To improve the WL AR performance in GNSS network processing, we propose an optimized FCB estimation method with IRDPB corrected by the receiver individual. Utilizing data from 490 stations with four receiver types, the effect of the proposed WL FCB is verified in terms of ambiguity residual distribution and ambiguity fixed rate by comparing it with the original FCB and FCB with IRDPB corrected by receiver type. The proposed method improves the proportions of WL residuals within ± 0.1 cycles by 13.7%–20.5% for GPS, BDS-2 and BDS-3 compared to the original FCB. Compared to FCB corrected with receiver-type IRDPB, the number of stations with the proportions of residuals within ± 0.1 cycles in the percentage range (80,100] are improved by more than 130 for GPS, BDS-2 and BDS-3. Using the proposed FCB, the GNSS stations can obtain reliable real-time WL fixing solution. The result also shows that the influence of IRDPB varied with receiver types and GNSS systems. Galileo was less affected by IRDPB than GPS and BDS-2/3, and Trimble Alloy receivers suffer more significant IRDPB than the other three types of receivers.

SummaryBeamforming (BF) has been demonstrated to extract multi-mode surface wave dispersion curves from ambient seismic noise. However, due to the limited sampling of the array and the complex distribution of the noise sources, the dispersion image generated by the array-based technique is usually contaminated by aliasing or artifacts. According to seismic interferometry (SI) theory, the Green's function (GF) in the time domain can be retrieved using the noise cross-correlation function (NCF). The Fourier transform of NCFs, i.e. the spatial coherence function, is related to the imaginary part of the frequency domain GF. For the vertical component of the surface wave, it corresponds to the zero-order Bessel function of the first kind, i.e. the standing wave containing propagating waves in two directions described by positive and negative vector wavenumber. In array techniques based on wavefield transforms, it is common to adopt the propagating wave instead of the standing wave to eliminate the aliasing associated with the negative wavenumber, i.e. to replace the Bessel function using the Hankel function or to construct a complete GF via the Hilbert transform. In this paper, we quantitatively analyze the characteristics of three types of aliasing, i.e. the aliasing associated with the period extension of the positive wavenumber, the aliasing associated with the negative wavenumber and those associated with the constant wavenumber. The theoretical representations of different imaging conditions are derived for the finite sampling of the wavefield. A new BF imaging condition is then proposed to remove the crossed artifacts, a type of aliasing associated with the negative wavenumber. The new imaging condition relies only on the computed NCFs and does not require reconstruction of the complete GF via the Hilbert transform. The advantage of random sampling in removing artifacts is illustrated. A random array design scheme is suggested by investigating the array performance of the random array and the array designed using tiles of the Hat family newly discovered in the field of monotile aperiodic tiling. We show the artifacts associated with the constant wavenumber, which are usually manifested as a straight line in the dispersion image of the frequency-velocity domain, also known as radial artifacts, can be eliminated by windowing the NCFs.

SummaryNumerical models of geothermal reservoirs typically depend on hundreds or thousands of unknown parameters, which must be estimated using sparse, noisy data. However, these models capture complex physical processes, which frequently results in long run-times and simulation failures, making the process of estimating the unknown parameters a challenging task. Conventional techniques for parameter estimation and uncertainty quantification, such as Markov chain Monte Carlo (MCMC), can require tens of thousands of simulations to provide accurate results and are therefore challenging to apply in this context. In this paper, we study the ensemble Kalman inversion (EKI) algorithm as an alternative technique for approximate parameter estimation and uncertainty quantification for geothermal reservoir models. EKI possesses several characteristics that make it well-suited to a geothermal setting; it is derivative-free, parallelisable, robust to simulation failures, and in many cases requires far fewer simulations to provide an accurate characterisation of the posterior than conventional uncertainty quantification techniques such as MCMC. We illustrate the use of EKI in a reservoir modelling context using a combination of synthetic and real-world case studies. Through these case studies, we also demonstrate how EKI can be paired with flexible parametrisation techniques capable of accurately representing prior knowledge of the characteristics of a reservoir and adhering to geological constraints, and how the algorithm can be made robust to simulation failures. Our results demonstrate that EKI provides a reliable and efficient means of obtaining accurate parameter estimates for large-scale, two-phase geothermal reservoir models, with appropriate characterisation of uncertainty.

Abstract

Magnetic reconnection converts magnetic field energy into particle energy by breaking and reconnecting magnetic field lines. Magnetic reconnection is a kinetic process that generates a wide variety of kinetic waves via wave-particle interactions. Kinetic waves have been proposed to play an important role in magnetic reconnection in collisionless plasmas by, for example, contributing to anomalous resistivity and diffusion, particle heating, and transfer of energy between different particle populations. These waves range from below the ion cyclotron frequency to above the electron plasma frequency and from ion kinetic scales down to electron Debye length scales. This review aims to describe the progress made in understanding the relationship between magnetic reconnection and kinetic waves. We focus on the waves in different parts of the reconnection region, namely, the diffusion region, separatrices, outflow regions, and jet fronts. Particular emphasis is placed on the recent observations from the Magnetospheric Multiscale (MMS) spacecraft and numerical simulations, which have substantially increased the understanding of the interplay between kinetic waves and reconnection. Some of the ongoing questions related to waves and reconnection are discussed.

Abstract

The Analyzer for Cusp Electrons (ACE) instruments on the Tandem Reconnection and Cusp Electrodynamics Reconnaissance Satellites (TRACERS) mission provide measurements of electron velocity distribution functions from two closely spaced spacecraft in a low Earth orbit that passes through the magnetospheric cusp. The precipitating and upward-going electrons provide a sensitive probe of the magnetic field line topology and electrostatic potential structure, as well as revealing dynamic processes. ACE measurements contribute to the top-level TRACERS goals of characterizing the spatial and temporal variation of magnetic reconnection at the terrestrial magnetopause and its relationship to dynamic structures in the cusp. ACE utilizes a classic hemispheric electrostatic analyzer on a spinning platform to provide full angular coverage with 10 degree by 7 degree resolution. ACE can measure electrons over an energy range of 20-13,500 electron volts, with fractional energy resolution of 19%. ACE provides 50 ms cadence measurements of the electron velocity distribution, enabling sub-kilometer spatial resolution of cusp boundaries and other structures.