Hasil untuk "Geomagnetism"

Murchana Khusroo, Yimnasangla

Solitary structures, commonly known as solitons, are a class of nonlinear plasma waves that are abundantly found in near-Earth plasmas and planetary magnetospheres. They are nonlinear, localized plasma waves that maintain their shape and velocity over time and distance. While their occurrence in various space plasma environments has been extensively reported, their observation during geomagnetic storms, large-scale disturbances driven by interactions between the solar wind and Earth's magnetosphere, remains limited. In this study, we present a comparative investigation of magnetosonic soliton signatures during geomagnetic storms associated with Solar Cycles 24 and 25. Using high-resolution in-situ magnetic field measurements from the Cluster II mission, we systematically examine the plasma conditions favorable for soliton generation and their evolution during storm-time dynamics. A comprehensive multi-diagnostic observational framework, incorporating several state-of-the-art analytical techniques, is developed to reliably detect and characterize magnetosonic solitons. The results demonstrate that solitary structures in both storms predominantly occur during the early storm intervals, prior to the main phase, suggesting that they may serve as potential precursor signatures of enhanced geomagnetic activity.

Kevin Cann

Bruehl & Villarroel (2025) reported a correlation (p = 0.008, 2.6 sigma) between atmospheric nuclear weapon tests and photographic plate transient detection rates in the Palomar Observatory Sky Survey (POSS-I) archive, independently replicated by Doherty (2026) using negative binomial regression with weather controls. I identify geomagnetic storm activity, measured by the planetary Kp index, as an additional independent variable modulating transient rates in the same dataset. Transient detection rates follow a monotonic dose-response across five Kp intensity bins, from 17.4% during geomagnetically quiet periods to 2.4% at Kp 8-9 (Cochran-Armitage trend: Z = -3.391, p = 0.0007). Nuclear test days are not geomagnetically quieter than the baseline; they are slightly more storm-influenced. A multivariate logistic regression including Kp and lunar-phase controls strengthens the nuclear-transient correlation from 2.6 sigma (p = 0.009, OR = 1.53) to 3.1 sigma (p = 0.002, OR = 1.70). The dose-response rules out emulsion defects and spectrally inert orbital debris as the primary transient source, indicating a population physically coupled to the radiation belt environment at geosynchronous altitude. A self-contained reproduction script is provided as supplementary material.

Evangelos Paouris, Angelos Vourlidas, Manolis K. Georgoulis et al.

The first severe (G4) geomagnetic storm of Solar Cycle 25 occurred on 23-24 April 2023, following the arrival of a Coronal Mass Ejection (CME) on 23 April. The characteristics of this CME, measured from coronagraphs (speed and mass), did not indicate that it would trigger such an intense geomagnetic storm. In this work, our aim is to understand why this CME led to such a geoeffective outcome. Our analysis spans from the source active region to the corona and inner heliosphere through 1 au using multiwavelength, multi-viewpoint remote sensing observations and in situ data. We find that rotation and possibly deflection of the CME resulted in an axial magnetic field nearly parallel to the ecliptic plane during the Earth encounter, which might explain the storm's severity. Additionally, we find that imaging away from the Sun-Earth line is crucial in hindcasting the CME Time-of-Arrival at Earth. The position (0.39 au) and detailed images from the SoloHI telescope onboard the Solar Orbiter mission, in combination with SOHO and STEREO images, helped decisively with the three-dimensional (3D) reconstruction of the CME.

Foteini Vervelidou, Alex Delacroix, Laura Domine et al.

Witness reports of Unidentified Aerial Phenomena (UAP) occasionally associate UAP sightings with local electromagnetic interferences, such as spinning magnetic compasses onboard aircraft or sudden malfunctions of mechanical vehicles. These reports have motivated the incorporation of a magnetometer into the instrumentation suite of the Galileo Project (GP), a Harvard-led scientific collaboration whose aim is to collect and analyze multi-sensor data that collectively could help elucidate the nature of UAP. The goal of the GP magnetometry investigation is to identify magnetic anomalies that cannot be readily explained in terms of a natural or human-made origin, and analyze these jointly with the data collected from the other modalities. These include an ensemble of visible and infrared cameras, a broadband acoustic system and a weather-monitoring system. Here, we present GP's first geomagnetic variometer station, deployed at the GP observatory in Colorado, USA. We describe the calibration and deployment of the instrumentation, which consists of a vector magnetometer and its data acquisition system, and the collection and processing of the data. Moreover, we present and discuss examples of the magnetic field data obtained over a period of 6 months, including data recorded during the May 2024 G5 extreme geomagnetic storm. We find that the data meet and even surpass the requirements laid out in GP's Science Traceability Matrix. Key to the evaluation of our data is the proximity of the variometer station to the USGS magnetic observatory in Boulder, Colorado. By comparing the two sets of data, we find that they are of similar quality. Having established the proper functioning of the first GP variometer station, we will use it as the model for variometer stations at future GP observatories.

Hui Wu, Yuan Yang, Weiyu Chang et al.

Objective: Depression has become disabling disease in the world. Geomagnetic storm is closely related to depression behavior, and melatonin is an important factor in the pathogenesis of depression. This study observed the effects of different intensities of geomagnetic storm on melatonin in depressed rats. Aim to provides a theoretical basis for the prevention and treatment of depression and other melatonin related mental illnesses during geomagnetic storms. Methods: In this study, rats with chronic unpredictable mild stress (CUMS) were exposed to geomagnetic storms of different intensities for 7 days. The depressive behavior of CUMS rats was determined via the weigh, sucrose preference test, elevated plus maze test, novelty-suppressed feeding test and open field test. Then, through the use of kits, qPCR analysis, immunofluorescence staining and western blot analysis of melatonin synthesis, melatonin metabolism and melatonin receptor pathway related indicators. Performed to explore the effects of different intensities of geomagnetism on CUMS rats and the related molecular mechanisms. Results: The reults showed moderate geomagnetic storms (50 nT) protected against depressive behaviors in CUMS rats by increasing melatonin synthesis and metabolism and MT1 receptor pathway activity, while a extreme geomagnetic storms (500 nT) and shielding from geomagnetic storms (0 nT) inhibited melatonin synthesis and metabolism and the MT1 receptor pathway and aggravated injury. Conclusions: In this study we found moderate geomagnetic storms (50 nT) protected against depressive behaviors in CUMS rats, while a extreme geomagnetic storms (500 nT) and shielding from geomagnetic storms (0 nT) aggravated injury.

David Gubbins

The Macau satellites differ from their predecessors in their orbits: MSS-1 (Macau Science Satellite-1) is in low inclination and the planned MSS-2 will be in highly elliptical orbits. This paper reviews the fundamental advantages and disadvantages of the different possible magnetic measurements: the component (declination, intensity, etc.) and location (satellite, ground, etc.). When planning a survey the choice of component is the "What?" question; the choice of location the "Where?" question. Results from potential theory inform the choice of measurement and data analysis. For example, knowing the vertical component of magnetic field provides a solution for the full magnetic field everywhere in the potential region. This is the familiar Neumann problem. In reality this ideal dataset is never available. In the past we were restricted to declination data only, then direction only, then total intensity only. There have also been large swathes of Earth’s surface with no measurements at all (MSS-1 is restricted to latitudes below \begin{document}$ 41^\circ $\end{document}). These incomplete datasets throw up new questions for potential theory, questions that have some intriguing answers. When only declination is known uniqueness is provided by horizontal intensity measurements on a single line joining the dip-poles. When only directions are involved uniqueness is provided by a single intensity measurement, at least in principle. Paleomagnetic intensities can help. When only total intensity is known, as was largely the case in the early satellite era, uniqueness is provided by a precise location of the magnetic equator. Holes in the data distribution is a familiar problem in geophysical studies. All magnetic measurements sample, to a greater or lesser extent, the potential field everywhere. There is a trade-off between measurements close to the source, good for small targets and high resolution, and the broader sample of a distant measurement. The sampling of a measurement is given by the appropriate Green’s function of the Laplacian, which determines both the resolution and scope of the measurement. For example, radial and horizontal measurements near the Earth’s surface give a weighted average of the radial component over a patch of the core surface beneath the measurement site about \begin{document}$ 30^\circ $\end{document} in radius. The patch is smaller for shallower surfaces, for example from satellite to ground. Holes in the data distribution do not correspond to similar holes at the source surface; the price paid is in resolution of the source. I argue that, in the past, we have been too reluctant to take advantage of incomplete and apparently hopeless datasets.

Sten Odenwald, Hilarie Davis, Christina Milotte et al.

Simple magnetometers are the gateway instruments for exploring the geomagnetic field that can be used by hobbyists and teachers alike to monitor and study a variety of space weather phenomena. This article provides designs for four different instruments that can be built for under <inline-formula> <tex-math notation="LaTeX">${\$}50$ </tex-math></inline-formula>, yet have the sensitivity to detect the diurnal ionospheric Sq variation, and geomagnetic disturbances due to the arrival of solar coronal mass ejections. A comparison of the data from these instruments against contemporaneous data from the Fredericksburg Magnetic Observatory reveal the accuracy of these instruments. Also provided is an example of how these instruments have been used in high school Earth Science and Astronomy classes to improve student learning and scientific curiosity.

Hao Ding

Surface geomagnetic observations and length of day variations (dLOD) have played an important role in interpreting the long-period motions of the Earth's core. Focusing on the 5-30yr period band, we use the optimal sequence estimation method to analyze the global geomagnetic vertical observations, and newly find that the about 6yr/8.6yr signals, the about7.6yr/13.6yr/22.5yr signals, the about 15.4yr and about 18.6yr signals respectively have the Y2,2, Y2,-2, Y2,-1 and Y2,0 spatial patterns; in which, the about 7.6yr/8.6yr/13.6yr/15.4yr/18.6yr signals are clearly detected for the first time. We also find that the five Y2,+/-2-related "equivalent" excitation signals have good phase consistency with the corresponding signals in the dLOD, and they have the same about 0.042 amplitude scaling factor. Determining the physical mechanisms behind those seven signals still leaves many unresolved problems, and our new findings make those problems more complicated. As a preliminary thought, we suggest the five Y2,+/-2-related signals may be originated from the Magnetic-Archimedes-Coriolis waves

Kalpesh Ghag, Anil Raghav, Ankush Bhaskar et al.

Interplanetary Coronal Mass Ejections (ICMEs) are prominent drivers of space weather disturbances and mainly lead to intense or extreme geomagnetic storms. The reported studies suggested that the planar ICME sheath and planar magnetic clouds (MCs) cause extreme storms. Here, we investigated the severe two-step geomagnetic storm ($Dst \sim -187$ nT) of 25$^{th}$ solar cycle. Our analysis demonstrates flattened (pancaked) ICME structures, i.e., quasi-planar magnetic structures (PMS). The study corroborates our earlier reported finding that the less adiabatic expansion in quasi-PMS transformed ICME enhanced the strength of the southward magnetic field component. It contributes to the efficient transfer of plasma and energy in the Earth's magnetosphere to cause the observed severe storm.

Paul Baki, Babatunde Rabiu, Christine Amory-Mazaudier et al.

Space weather science has been a growing field in Africa since 2007. This growth in infrastructure and human capital development has been accompanied by the deployment of ground-based observing infrastructure, most of which was donated by foreign institutions or installed and operated by foreign establishments. However, some of this equipment is no longer operational due to several factors, which are examined in this paper. It was observed that there are considerable gaps in ground-based space-weather-observing infrastructure in many African countries, a situation that hampers the data acquisition necessary for space weather research, hence limiting possible development of space weather products and services that could help address socio-economic challenges. This paper presents the current status of space weather science in Africa from the point of view of some key leaders in this field, focusing on infrastructure, situation, human capital development, and the research landscape.

Erwan Thebault, Lydie-Sarah Gailler

UAVs represent a tremendous opportunity to perform geophysical and repeated experiments, particularly in volcanic contexts. Their ability to be deployed rapidly and fly at various altitudes and the fact that they are easy to operate despite complex field conditions make them attractive for magnetic surveys. Detailed maps of the magnetic field in turn bring key constraints on the rocks’ composition, thermal anomalies, intrusive systems, and crustal contrast evolution. Yet, raw magnetic field measurements require careful processing to minimize directional, positional, and crossover errors. Moreover, stitching together adjacent or overlapping surveys acquired at different times and altitudes is not a trivial task. Therefore, it is challenging in remote areas to directly evaluate the consistency of a survey and to ascertain the success of the field mission. In this paper, we present a fast algorithm allowing for a quick-look modeling of scalar magnetic intensity measurements. The approach relies on rectangular harmonic analysis (RHA). The field measurements are automatically corrected for a global main field. Then, they are projected along this main field and modeled in terms of RHA functions. The software can exploit the quality indices provided with data and a procedure is applied to mitigate the effect of outliers. Maps for the scalar and the vector anomaly fields are readily built on an interpolated regular grid leveled at a constant altitude. In order to assess the modeling and the inversion procedures, analyses are carried out with synthetic measurements derived from a high-resolution global lithospheric magnetic field model estimated on the French aeromagnetic grid and at UAV locations with some added nonrandom noise. These analyses indicate that RHA is efficient for first-order and direct mapping of the crustal magnetic field structures measured by UAVs but that it could be applied on airborne and marine magnetic intensity data covering dense and large geographical extensions.

Nithin Sivadas, David Sibeck, Varsha Subramanyan et al.

Extreme space weather events on Earth occur during intervals of strong solar wind driving. The solar wind drives plasma convection and currents in the near-Earth space environment. For low values of the driver, the Earth's response is linear, estimated by parameters such as the polar cap index based on ground magnetometer activity. Curiously, for extreme solar wind driving, the Earth's response appears not to increase beyond a saturation limit. Theorists have advanced a host of explanations for this saturation effect, but there is no consensus. Here, we demonstrate that the saturation is a manifestation of the regression to the mean effect resulting from random uncertainty in the time and magnitude of solar wind measurements. Our results reveal that data analysis underpinning the saturation theories is non-linearly biased; hence, the theories must be validated against the correct solar wind data. Correcting for the uncertainties reveals that the Earth's response to solar wind driving is linear throughout, and the impact of extreme geomagnetic storms can be twice as large as previously thought. We show that regression to the mean is a fundamental property of the relationship between measurement and the truth, where the truth corresponding to the measurement is closer to the mean. This effect is particularly pronounced for uncertain measurements of extreme values and is likely to manifest across various fields, from extreme climate studies to chronic medical pain.

Afroditi Nasi, Christos Katsavrias, Ioannis A. Daglis et al.

During July to October of 2019, a sequence of isolated Corotating Interaction Regions (CIRs) impacted the magnetosphere, for four consecutive solar rotations, without any interposed Interplanetary Coronal Mass Ejections. Even though the series of CIRs resulted in relatively weak geomagnetic storms, the net effect of the outer radiation belt during each disturbance was different, depending on the electron energy. During the August-September CIR group, significant multi-MeV electron enhancements occurred, up to ultra-relativistic energies of 9.9 MeV in the heart of the outer Van Allen radiation belt. These characteristics deemed this time period a fine case for studying the different electron acceleration mechanisms. In order to do this, we exploited coordinated data from the Van Allen Probes, the Time History of Events and Macroscale Interactions during Substorms Mission (THEMIS), Arase and Galileo satellites, covering seed, relativistic and ultra-relativistic electron populations, investigating their Phase Space Density (PSD) profile dependence on the values of the second adiabatic invariant K, ranging from near-equatorial to off equatorial mirroring populations. Our results indicate that different acceleration mechanisms took place for different electron energies. The PSD profiles were dependent not only on the μ value, but also on the K value, with higher K values corresponding to more pronounced local acceleration by chorus waves. The 9.9 MeV electrons were enhanced prior to the 7.7 MeV, indicating that different mechanisms took effect on different populations. Finally, all ultra-relativistic enhancements took place below geosynchronous orbit, emphasizing the need for more Medium Earth Orbit (MEO) missions.

Amélie Cohu, Matias Tramontini, Antoine Chevalier et al.

Muon tomography or muography is an innovative imaging technique using atmospheric muons. The technique is based on the detection of muons that have crossed a target and the measurement of their attenuation or deviation induced by the medium. Muon flux models are key ingredients to convert tomographic and calibration data into the 2D or 3D density maps of the target. Ideally, they should take into account all possible types of local effects, from geomagnetism to atmospheric conditions. Two approaches are commonly used: semi-empirical models or Monte Carlo simulations. The latter offers the advantage to tackle down many environmental and experimental parameters and also allows the optimization of the nearly horizontal muons flux, which remains a long-standing problem for many muography applications. The goal of this paper is to identify through a detailed simulation what kind of environmental and experimental effects may affect the muography imaging sensitivity and its monitoring performance. The results have been obtained within the CORSIKA simulation framework, which offers the possibility to tune various parameters. The paper presents the simulation’s configuration and the results obtained for the muon fluxes computed in various conditions.

Minseok Ryu, Harsha Nagarajan, Russell Bent

Severe geomagnetic disturbances (GMDs) increase the magnitude of the electric field on the Earth's surface (E-field) and drive geomagnetically-induced currents (GICs) along the transmission lines in electric grids. These additional currents can pose severe risks, such as current distortions, transformer saturation and increased reactive power losses, each of which can lead to system unreliability. Several mitigation actions (e.g., changing grid topology) exist that can reduce the harmful GIC effects on the grids. Making such decisions can be challenging, however, because the magnitude and direction of the E-field are uncertain and non-stationary. In this paper, we model uncertain E-fields using the distributionally robust optimization (DRO) approach that determines optimal transmission grid operations such that the worst-case expectation of the system cost is minimized. We also capture the effect of GICs on the nonlinear AC power flow equations. For solution approaches, we develop an accelerated column-and-constraint generation (CCG) algorithm by exploiting a special structure of the support set of uncertain parameters representing the E-field. Extensive numerical experiments based on "epri-21" and "uiuc-150" systems, designed for GMD studies, demonstrate (i) the computational performance of the accelerated CCG algorithm, (ii) the superior performance of distributionally robust grid operations that satisfy nonlinear, nonconvex AC power flow equations and GIC constraints, in comparison with standard stochastic programming-based methods during the out-of-sample testing.

A. Bershadskii

The role of the moments of helicity distribution in rotating turbulence has been studied using the notion of helical distributed chaos. Results of the direct numerical simulations, laboratory experiments and geophysical observations have been used in this investigation. It is shown, in particular, that even for the cases when the global helicity is equal to zero at least even moments are usually non-zero (due to the appearance of the local spatial regions with strong negative and positive helicity) and can play a significant role in the rotating turbulence as adiabatic invariants. Rotating buoyancy driven thermal convection (Rayleigh-Bénard and Rayleigh-Taylor, the former also for the magnetohydrodynamics) is also studied, and applications of this approach to the convection zone of massive stars and to the geomagnetic dynamo have been discussed in this context.

Gurbax Singh Lakhina, Satyavir Singh, Rajith Rubia et al.

Occurrence of electrostatic solitary waves (ESWs) is ubiquitous in space plasmas, e.g., solar wind, Lunar wake and the planetary magnetospheres. Several theoretical models have been proposed to interpret the observed characteristics of the ESWs. These models can broadly be put into two main categories, namely, Bernstein–Green–Kruskal (BGK) modes/phase space holes models, and ion- and electron- acoustic solitons models. There has been a tendency in the space community to favor the models based on BGK modes/phase space holes. Only recently, the potential of soliton models to explain the characteristics of ESWs is being realized. The idea of this review is to present current understanding of the ion- and electron-acoustic solitons and double layers models in multi-component space plasmas. In these models, all the plasma species are considered fluids except the energetic electron component, which is governed by either a kappa distribution or a Maxwellian distribution. Further, these models consider the nonlinear electrostatic waves propagating parallel to the ambient magnetic field. The relationship between the space observations of ESWs and theoretical models is highlighted. Some specific applications of ion- and electron-acoustic solitons/double layers will be discussed by comparing the theoretical predictions with the observations of ESWs in space plasmas. It is shown that the ion- and electron-acoustic solitons/double layers models provide a plausible interpretation for the ESWs observed in space plasmas.

I. M. Chertok

More than 140 isolated non-recurrent geomagnetic storms (GMSs) of various intensities from extreme to weak are considered, which are reliably identified with solar eruptive sources (coronal mass ejections, CMEs). The analysis aims to obtain a possibly complete picture of the relationship between the transit time of propagation of CMEs and interplanetary coronal mass ejections (ICMEs) from the Sun to the Earth (more precisely, the time interval dtp from the moment of an eruption until the peak of the corresponding GMS) and the maximum intensity of this GMS, as measured by the disturbance storm time geomagnetic index Dst. Two groups of events are singled out: one includes GMSs, the source of which was an eruption from an active region (AR events), the other GMSs caused by filament eruptions from quiescent areas of the Sun located outside ARs (QS events). The distribution of the large number of the analyzed events on a dtp - Dst plane confirms and substantially clarifies the known regularities. The AR events are characterized by a shorter transit time (dtp ~ 1-4 days) and much stronger GMSs (Dst up to -600 nT mainly) in comparison with the QS events (dtp ~ 3-5 days, Dst > -200 nT). For events of both groups, the shorter transit time of CMEs/ICMEs, the more intense GMSs; in particular, for AR events when dtp declines from 4 to 1 day, Dst decreases on average from -100 to -470 nT and can reach -900 nT. From the point of view of the nature of GMSs and their sources on the Sun, the obtained results mean that both the speed of CMEs/ICMEs and the strength of the magnetic field transferred by them are largely determined by the parameters of the corresponding eruptions, in particular, by the eruptive magnetic flux and the released energy.

Hermann Lühr, Yun‐Liang Zhou

Abstract Thanks to mapping missions, like Ørsted, CHAMP, and Swarm, we have gained a detailed understanding of the geomagnetic field. High‐resolution models like POMME, GRIMM, or CHAOS are able to describe the main parts of the Earth's magnetic field reliably. These models represent well contributions from the core and crustal fields. But their validity of describing magnetospheric field effects is limited to low activity periods (Kp ~ 0–2). Here, we study the differences between CHAMP magnetic observations and the predictions from CHAOS‐6‐x9, a recent version, outside this validity range. Systematic residuals appear at times of elevated activity. Mean amplitudes at the equator grow up to 12 nT around 20 hr magnetic local time for magnetic activity around Kp = 4.7. Negative residuals are obtained in the evening to midnight sector and positive ones in the morning. A seasonal dependence of the magnetospheric currents causes more negative deflections of the residuals in the winter than in the summer hemisphere. This hemispheric asymmetry cannot be accounted for by a degree 1 spherical harmonics function. A surprising observation is that the residuals show a clear longitude dependent pattern, which changes with local time. The analysis reveals that this feature can be interpreted as a Universal Time dependence of the residuals with a peak‐to‐peak amplitude of about 8 nT and a period of 12 hr at an activity level of Kp = 4.7. All these results call for a better parameterization of the magnetospheric current effects in a geomagnetic field model that is reliable at least up to moderate activity levels.

S. Marsal, J. M. Torta, F. J. Pavón‐Carrasco et al.

Abstract The equivalent source method of Spherical Elementary Current Systems (SECS) has contributed valuable results for spatial magnetic interpolation purposes where no observations are available, as well as for modeling equivalent currents both in the ionosphere and in the subsurface, thus providing a separation between external and internal sources. It has been successfully applied to numerous Space Weather (SW) events, whereas some advantages have been reported over other techniques such as Fourier or Spherical (Cap) Harmonic Analysis. Although different modalities of SECS exist (either 1‐D, 2‐D, or 3‐D) depending on the number of space dimensions involved, the method provides a sequence of instantaneous pictures of the source current. We present an extension of SECS consisting in the introduction of a temporal dependence in the formulation based on a cubic B‐splines expansion. The technique thus adds one dimension, becoming 4‐D in general (e.g., 3‐D + t), and its application is envisaged for, though not restricted to, the analysis of past events including heterogeneous geomagnetic data sets, such as those containing gaps, different sampling rates or diverse data sources. A synthetic model based on the SW Modeling Framework is used to show the efficacy of the extended scheme. We apply this method to characterize the current systems of past and significant SW events producing geomagnetically induced currents, which we exemplify with an outstanding geomagnetic sudden commencement occurred on 24 March 1991.