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Abstract

The Europa Clipper mission will explore Europa and investigate its habitability utilizing a set of five remote-sensing instruments that cover the electromagnetic spectrum from thermal infrared to ultraviolet wavelength, four in-situ fields and particles instruments, a dual-frequency radar, and a gravity and radio science investigation. Key mission objectives include to produce high-resolution images of Europa’s surface, determine its composition, look for signs of recent or ongoing activity, measure the thickness of the icy shell, search for subsurface lakes, and determine the depth and salinity of Europa’s ocean. The Europa Clipper Mission Plan integrates the above investigations in a way that allows for the simultaneous acquisition of complimentary datasets (i.e., datasets at the regional scale, distributed globally across Europa) utilizing a complex network of flybys while in Jupiter orbit. About 50 flybys of Europa—with closest-approach altitudes varying from several thousand kilometers to as low as 25 kilometers—will be executed over an approximately 4.3-year prime mission. We present an overview of the mission design, which is driven by the complex scientific goals of the mission but also influenced by launch vehicle capabilities, the intense Jovian radiation environment, varying thermal environment, and dependency on precise planet and moon flybys to manage the orbit. We describe the interplanetary and Jovian orbit design, Mission Plan, and Navigation Plan, and forecast performance against mission requirements to date.

Abstract

The stochastic representation of an uncertain shape model allows the dynamic evaluation of its induced gravity signal. This can be also applied for representing a time variable gravity field to model mass changes. The algorithm for estimating variations in gravitational potential is extended for the case of second-order derivatives. Two different harmonic synthesis formulas are used to derive the sought variations: one expressed in spherical coordinates using the traditional associated Legendre functions (ALF) and their derivatives up to the second order, while the other expressed in Cartesian coordinates by including the derived Legendre functions (DLF). The obtained variations are compared in terms of convergence with gravity signal differences referring to the specific shape changes using the line integral analytical approach for three asteroid shape models. Both approaches provide results that differ from the analytical method at a 1E−1 level, while the differences between them are at the 1E−15 level. The obtained results are highly influenced by the geometry of the examined shape model, with the ALF approach providing variations with closer agreement with the analytical method only for the almost spherical shape. Both harmonic synthesis expressions can be used to derive accurate results, as they differ at a very low level, and one can choose based on the convenience of their algorithmic characteristics.

Abstract

Effective angular momentum (EAM) forecasts are widely used as an important input for predicting both polar motion and dUT1. So far, model predictions for atmosphere, ocean, and terrestrial hydrosphere utilized in Earth rotation research reach only 6-days into the future. GFZ’s oceanic and land-surface model forecasts are forced with operational 6-day high-resolution deterministic numerical weather predictions provided by the European Centre for Medium-range Weather Forecasts. Those atmospheric forecasts extend also further into the future with a reduced sampling rate of just 6 h but the prediction skill decreases rapidly after roughly one week. To decide about publishing 10-day instead of 6-day model-based EAM forecasts, we generated a test set of 454 individual 10-day forecasts and used it with GFZ’s EAM Predictor method to calculate Earth rotation predictions. Using 10-day instead of 6-day EAM forecasts leads to slight improvements in y-pole and dUT1 predictions for 10 to 30 days ahead. By introducing additional neural network models trained on the errors of the EAM forecasts when compared to their subsequently available analysis runs, Earth rotation prediction can be enhanced even further. A reduction of the mean absolute errors for polar motion and length-of-day prediction at a forecast horizon of 10 days of 26.8% in x-pole, 15.5% in y-pole, 27.6% in dUT1, and 47.1% in \(\Delta \) LOD is achieved. This test application successfully demonstrates the potential of the extended EAM forecasts for Earth rotation prediction although the success rate has to be further improved to arrive at robust routine predictions. GFZ publishes from October 2024 onwards raw uncorrected 10-day instead of 6-day EAM forecasts at www.gfz-potsdam.de/en/esmdata for the individual contributions of atmosphere, ocean, and terrestrial hydrosphere. Users interested in the summarized effect of all subsystems are advised to use the 90-day combined EAM forecast product that also makes use of the presented corrections to the EAM forecasts.

Abstract

GPS flex power can improve anti-jamming capability by enhancing the transmitting power of individual signals. However, during the active periods of GPS flex power in 2020, it was found that the accuracy of kinematic orbit for GRACE-FO satellites is decreased. In this paper, the impact of flex power on kinematic orbit determination of GRACE-FO is investigated. With the analysis of 30-day epoch-differenced geometry-free combinations of phase, i.e., \(\:\varDelta\:{{\Phi\:}}_{\text{G}\text{F}}\) and signal-to-noise ratio (SNR) for GRACE-FO satellites, a new strategy which considers the impact of flex power on the continuity of ambiguity is put forward to improve the kinematic orbit of GRACE-FO. After considering flex power, the 3D root-mean-square (RMS) of GRACE-C and GRACE-D are reduced to 4.10 and 4.42 cm, with improvements of 36% and 21%, respectively. The improvements of SLR validation are 34% and 14% for GRACE-C and GRACE-D. The above results prove the effectiveness of the proposed strategy.

Abstract

Signal anti-jamming has always been a difficult problem in GNSS (global navigation satellite system) signal processing. There are many GNSS anti-jamming techniques in the existing research, which can achieve good results if the interferences are sparsely distinguishable in some signal feature domains. Specifically, the single antenna based anti-jamming techniques cannot deal with wideband Gaussian noise interference because it is not sparse in time or frequency domain, while the only effective method currently is using multiple antennas to apply the space array processing (SAP) technique since the wideband Gaussian noise interference is sparse in the spatial domain. However, when the incoming directions of the different interferences are not less than that of antennas, the interferences are not sparse to the array anymore, and the SAP anti-jamming performance would decrease drastically. In this paper, a LSTM (long short-term memory) deep neural network (DNN) based algorithm is proposed to enhance the array anti-jamming performance in this situation. The proposed network estimates the interferences as an integrity by exploring the non-linear relationship of the array data received by antennas. Especially, a new loss function is designed exclusively for GNSS anti-jamming problem. The proposed DNN method is verified in the simulation that two wideband Gaussian interferences with JSR (jamming to signal ratio) 50 dB can be eliminated by using two antennas’ data, and the interference cancellation ratio improvement is about 24 dB compared to some other widely used classical SAP algorithms.

Nature Geoscience, Published online: 12 February 2025; doi:10.1038/s41561-025-01646-y

Natural gradients across surface ocean regions show that changes in carbonate chemistry projected for ocean alkalinity enhancement could promote the proliferation of calcifying phytoplankton. This shift would increase an alkalinity sink, thus reducing the efficiency of ocean alkalinity enhancement as a CO2 removal method.

Nature Geoscience, Published online: 12 February 2025; doi:10.1038/s41561-025-01644-0

Intensive ocean alkalinity enhancement will cause a proliferation of calcifying organisms, which reduces its effectiveness as a carbon sequestration approach, according to an analysis of coccolithophore sensitivity to natural carbonate chemistry variability.

Abstract

The dynamics of the Earth’s outer radiation belt, filled by energetic electron fluxes, is largely controlled by electron resonant interactions with electromagnetic whistler-mode waves. The most coherent and intense waves resonantly interact with electrons nonlinearly, and the observable effects of such nonlinear interactions cannot be described within the frame of classical quasi-linear models. This paper provides an overview of the current stage of the theory of nonlinear resonant interactions and discusses different possible approaches for incorporating these nonlinear interactions into global radiation belt simulations. We focus on observational properties of whistler-mode waves and theoretical aspects of nonlinear resonant interactions between such waves and energetic electrons. We consider only sufficiently energetic particles, which can be treated as test particles and do not have a significant feedback to the waves. The review covers two main regimes of nonlinear resonant wave-particle interactions: the regime of long wave-packets, historically better studied, and the regime of short wave-packets, actively investigated more recently based on refined spacecraft observations.

Abstract

An International Space Science Institute (ISSI) workshop was convened to assess recent rapid advances in studies of magnetic reconnection made possible by the NASA Magnetospheric Multiscale (MMS) mission and to place them in context with concurrent advances in solar physics by the Parker Solar Probe, astrophysics, planetary science and laboratory plasma physics. The review papers resulting from this study focus primarily on results obtained by MMS, and these papers are complemented by reports of advances in magnetic reconnection physics in these other plasma environments. This paper introduces the topical collection “Magnetic Reconnection: Explosive Energy Conversion in Space Plasmas”, in particular introducing the new capabilities of the MMS mission used in majority of the articles in the collection and briefly summarizing the advances obtained from MMS.

Nature Geoscience, Published online: 11 February 2025; doi:10.1038/s41561-024-01633-9

Rhabdophane contains high concentrations of the rare earth elements, yet Tobias Bamforth argues that it remains underappreciated as a significant host of these critical metals.

Nature Geoscience, Published online: 11 February 2025; doi:10.1038/s41561-025-01651-1

Sustained monitoring is essential for assessing volcanic hazards. Integration with igneous petrology is key to linking monitoring data to underlying magmatic processes.

The triggering mechanism of the substorm onset has been a major issue in magnetospheric research. Various models have been proposed so far. To understand the causal relationship of magnetotail processes associ...

Abstract

The geodetic community commonly challenges the composite hypotheses in the statistical testing of mathematical models. Since the composite hypotheses are not specified as opposed to their simple counterparts, they require a prior estimation of the model parameters. However, if the mathematical models are ill-conditioned, the regularized estimation is often applied for the parameters of interest. Due to the biased property, the regularized estimation does not rigorously originate in the principle of maximum likelihood (ML) estimation, which was the base for developing the theory of the generalized likelihood ratio (GLR) test. Since the regularized estimator of the parameters of interest is consequently inconsistent with the ML one, one cannot construct the GLR test, which is the uniformly most powerful invariant (UMPI) test. So far, only the bias correction approach has been suggested to solve this problem. In this contribution, an implicit representation of the regularized mathematical model is proposed. It eliminates the complete impact of regularized estimation on a mathematical model and delivers the misclosures analytically free from the influence of regularization. Thus, one can construct the GLR test, which belongs to the UMPI family, and then formulate the test statistic in terms of misclosures.

Abstract

This short article highlights unsolved problems of magnetic reconnection in collisionless plasma. Advanced in-situ plasma measurements and simulations have enabled scientists to gain a novel understanding of magnetic reconnection. Nevertheless, outstanding questions remain concerning the complex dynamics and structures in the diffusion region, cross-scale and regional couplings, the onset of magnetic reconnection, and the details of particle energization. We discuss future directions for magnetic reconnection research, including new observations, new simulations, and interdisciplinary approaches.

Nature Geoscience, Published online: 10 February 2025; doi:10.1038/s41561-025-01647-x

The rigid-body motion of Earth’s wandering inner core has now been reliably tracked over the past 20 years. With this knowledge, we can compare seismic recordings obtained when the inner core returns to the same position after moving for several years. More is changing than just the inner core position; the soft outermost inner core probably deforms.

Nature Geoscience, Published online: 10 February 2025; doi:10.1038/s41561-025-01642-2

Earth’s inner core has both changed its relative rotation rate and deformed in the past few decades, according to an analysis of seismic waves recorded when the inner core occupied the same relative location owing to its changing rotation rate.

Abstract

The seismo-electromagnetic studies have been in progress since 1998 at Agra station. In the present paper, ionospheric GPS-TEC, ground-based ULF/VLF measurements were investigated in light of four strong earthquakes (M ≥ 6.8) that occurred around the Indian subcontinent in different periods. These three datasets are processed by using advanced signal-processing techniques in time and frequency domains. To analyze these datasets, a period of 16 days (including the day of the earthquake) was considered. For each day, only one minute of data was taken into account, with the time of the earthquake being the midpoint of that minute. The precursors are obtained in all the datasets considered before the occurrence of earthquakes. In TEC, ULF, and VLF data, significant changes are observed 2 to 15, 2 to 7, and 5 to 13 days before earthquakes, respectively. Significant results are obtained in time and frequency domains and the variations of solar and magnetic storm activities have also been examined thoroughly to check the validity of these variations. Further, these variations are interpreted in terms of lithosphere-atmosphere-ionosphere coupling mechanisms available in the literature.

Abstract

This study investigates Pc5 pulsations during the St. Patrick’s Day geomagnetic storm of March 17, 2015, using ground-based magnetic data from the SER station in Chile (29.827° S, 71.261° W), satellite observations, and geomagnetic indices. Pc5 pulsations, with frequencies of 1.67–6.67 mHz, are influenced by various factors, including the Kelvin–Helmholtz instability, field line resonance effects, and solar wind dynamics. During this storm ignificant variations in solar wind parameters were observed, with positive correlations between Pc5 pulsations and parameters like temperature, density, speed, and pressure, especially during the main and recovery phases Pc5 pulsations exhibited large amplitudes during the storm, potentially driven by magnetospheric MHD waveguide/cavity mode and induced by the substantial compression of the geomagnetic field from the solar wind. Our results show the appearance of Pc5 pulsations at low latitudes and strong correlations between solar wind parameters and Pc5 signals during all storm phases, with maximum correlation coefficients of 0.98.

Abstract

The occurrence of geomagnetic storms and the variation in the geomagnetic storm indices during the ascending phase of solar cycle 24 has been examined. The parameters considered for this study includes; IMF Bz (nT), solar wind speed ( \({{{v}}_{x}}\) , in km/s), Dst index (nT), Aurora Electroject (AE, AU and AL indices in nT), and sunspot number. The datasets span from 2010 to 2012. Results of the study reveals that; the frequency of occurrence of geomagnetic storms increases with the increase in solar activity. Six (6) geomagnetic storms were recorded in 2010 (with sunspot number, Rz = 16.5), 13 storms in 2012 (with sunspot number Rz = 55.7), and 17 storms occurred in 2012 (with sunspot number, Rz = 57.5) giving a total of 36 geomagnetic storm events for the entire period. The performed study demonstrates that an increase in the speed and density of the solar wind coincided with the decrease in the Dst index in 58% cases (in 21 out of 36 geomagnetic storms). However, in some cases, there was a sharp simultaneous increase in both the speed and density of the solar wind that fell on the recovery phase of the storm. This also in most cases coincided with the sharp north-south fluctuations in the IMF Bz. These variations cannot be unconnected with the nature of the drivers of such geomagnetic storms. It is evident that the behavior of the solar wind speed during geomagnetic storm events can provide meaningful insight on the underlying mechanisms and processes that drive the geomagnetic storm.

Nature Geoscience, Published online: 10 February 2025; doi:10.1038/s41561-024-01629-5

Diverse lithospheric rocks show nanoporosity that changes the geochemistry of fluids and rock reactivity during fluid–rock interactions, according to a study including electron microscopy, molecular dynamics and thermodynamic modelling.