In backtracing simulations, which are widely employed to determine cosmic-ray particle trajectories in the geomagnetic field, the atmosphere is typically approximated as an artificial sharp boundary at some low altitude where the traced trajectory terminates. In this paper, we extend beyond this simplified assumption and investigate two realistic physical processes that terminate cosmic-ray particle propagation in the atmosphere: Bethe-Bloch energy loss mechanisms and hard scattering interactions with atmospheric atoms using total cross sections based on the Glauber-Gribov formalism. The former mechanism dominates at low rigidities (for protons below $\sim0.57$~GV), while the latter becomes dominant at higher rigidities. Consequently, we introduce two dimensionless variables up to detailed numerical criteria: the relative rigidity shift due to Bethe-Bloch effects ($Δ\mathfrak{R}/\mathfrak{R}$), and the expected number of hard scattering events ($\langle N\rangle$). Using the corrected US Standard Atmosphere 1976 model, we demonstrate that the altitude dependence can be factorized as approximately $\exp(-0.14h/\textrm{km})$. Additionally, the effect of the local curvature radius of the trajectory near perigee can be similarly factorized. Our calculations indicate that the simplified sharp-boundary altitude should be at least $50$ km with $Δ\mathfrak{R}/\mathfrak{R}+\langle N\rangle\lesssim1$ for protons, increasing by more than $15$ km for heavy nuclei such as iron.
Abstract We present a new theoretical framework to describe the rapid and spatially localized loss of energetic particles in planetary radiation belts, focusing on interactions between gas giant magnetospheres and their moons. Observations show that flux depletions—known as microsignatures—often refill on timescales comparable to a single drift period, which conflicts with traditional quasi‐linear radial diffusion models that assume slow, gradual transport and predict refilling only over many drift periods. To resolve this inconsistency, we develop a drift‐kinetic model that explicitly captures localized losses occurring on timescales similar to the azimuthal drift period. We demonstrate that such localized loss regions can synchronize the azimuthal Fourier modes of the particle distribution function, producing apparent refilling through phase‐space synchronization rather than diffusion. The resulting governing equations are mathematically equivalent to a generalized Kuramoto model, widely used to describe synchronization phenomena. This framework provides a first‐principles, non‐diffusive explanation for the evolution of microsignatures near moons, highlighting synchronization as a fundamental yet overlooked mechanism in magnetized plasma environments.
Abstract Using combined MHD/test particle simulations, we further explore characteristics of ion (proton) acceleration tailward of a near‐tail reconnection site related to tailward moving plasmoids. In this paper we focus on local features, addressing specifically energy‐time spectrograms, directional fluxes and phase space distributions, in comparison to some typical ion observations made by the “Acceleration, Reconnection, Turbulence and Electrodynamics of the Moon's Interaction with the Sun” mission near the plasma sheet boundary layer (PSBL) and in the central plasma sheet (CPS). In agreement with the observations, the simulations show boundary populations consisting of a core and an accelerated tailward beam, which decreases in speed but increases in intensity. While the core is found to be of PSBL or lobe origin the beam ions tend to include also origins in the central plasma sheet. Farther inward from the boundary, similar core/beam populations can also be found, both predominantly originating from the outer CPS. The rise in energetic ion fluxes is found to result from acceleration at or near the near‐tail reconnection site. In contrast to the boundary populations, CPS distributions within the tailward moving plasmoid tend to be more isotropic, shifted by their bulk flow speed, again in agreement with observations.
Magnetic reconnection is an explosive process that accelerates particles to high energies in Earth's magnetosphere, offering a unique natural laboratory to study this phenomenon. This study investigates how well data-driven fully kinetic simulations can reproduce the ion and electron energy distributions observed during a reconnection event by the Magnetospheric Multiscale (MMS) mission.We performed fully kinetic 2D simulations initialized with plasma parameters derived from the MMS event and compared the resulting ion and electron energy distributions with observations. Key numerical and physical parameters were systematically varied to assess their influence on the resulting particle spectra. The simulations capture the overall shape and evolution of nonthermal energy distributions for both species, but generally underestimate the very high-energy tail of the electron spectrum. Variations in numerical parameters have negligible effects on the resulting spectra, while the initial upstream temperatures instead play a more pronounced role in reproducing the observed distributions.We present a novel analysis of data-driven fully kinetic simulations of MR, showing that key aspects of particle acceleration can be captured, while also highlighting the limitations of 2D simulations and the need for more realistic (e.g., 3D) setups to reproduce the observed particle energization accurately.
Kp-Index is a very important factor for determining how the Sun's magnetic field is affecting the Earth's magnetic field and help us prepare for the worst (like solar or geomagnetic storms). Currently there are around thirteen observation centers to determine the worldwide Kp index. Huge data is generated from all the observation centers which is then used to determine several factors, but the observatories are concentrated in places like North America and Europe only. To eliminate the data dependency from a very limited geographical periphery we can use a constellation of satellites in LEO which can log in data continuously and provide a real time and accurate Kp index which can help humanity for tackling with the impending issues from our nearest star in a better way. The constellation of the satellites will be deployed in the Low Earth Orbit(LEO) and continuously log the geomagnetic data and provide a constant stream of data, which will be more diverse given the area coverage made by one satellite. This is essentially a boon as more the data we can have better geomagnetic data and the Kp index will be all encompassing which can help in better mapping of any solar-catastrophe.
AbstractThe analytical theory is presented that describes the propagation of power lines emission (PLE) with frequency of 50/60 Hz in the heights range from the Earth surface to the magnetosphere. Validation of the theory is made by the comparison with earlier published results of numerical modeling. It is shown that the actual source of emission is a magnetic dipole formed by the power line current and by the secondary image current in the ground. The emission is propagating to the lower boundary of ionosphere, where its main part is reflected back, but some of the energy (a few percent) penetrates into the ionosphere. There it is transformed into a quasi‐flat whistler wave. The generation of current in ground and the reflection from the ionosphere are the main factors that reduce the emission into space. In the ionosphere wave fronts propagate approximately vertically, and the energy propagates in a certain direction that depends on the geomagnetic field inclination. Thus, the ionosphere acts as a focusing system that collects PLE into a unidirectional beam. The PLE intensity does not change with altitude within the total range of ionospheric heights. In the magnetosphere PLE is transformed to both magnetosonic and Alfvén waves and the emission splits into two rays: one propagates along the wave vector and the other one—along the geomagnetic field lines. A set of analytical solutions is presented allowing determining the change in PLE parameters with altitude depending on the source parameters and ionospheric conditions.
Claudio Corti, Peter Sadowski, Nikolay Nikonov
et al.
Galactic cosmic rays (GCRs) are affected by solar modulation while they propagate through the heliosphere. The study of the time variation of GCR spectra observed at Earth can shed light on the underlying physical processes, specifically diffusion and particle drifts. We combine a state-of-the art 3D numerical model of GCR transport in the heliosphere with a neural-network-accelerated Markov chain Monte Carlo to constrain the rigidity and time dependence of the global transport coefficients, using precise GCR data from the PAMELA and AMS-02 experiments between 2006 and 2019.
We face unprecedented resource stresses in the 21st Century such as global climate disruptions, freshwater scarcity, expanding energy demands, and the threat of global pandemics. Historically, societies have relieved resource stress by increasing trade, innovating technologically, expanding territorially, regulating, redistributing, making alliances, creating new economic models, training new skills, as well as conducting war. Do we continue depleting our already strained resources leading to more regulation, redistribution, alliances, new economics, and war or do we grow our resources using innovation, expansion, new economics, and new skills? We present the argument for evolving space development using asteroid mining as the primary activity for frontier expansion aided by Low Earth Orbit (LEO), Moon, and Mars waystations. Forecast space weather is a necessary technology baseline for developing this pathway. All activity off Earth will require a fundamental knowledge of how the energetics of space will affect technological progress. We discuss the critical elements this space economy expansion, including technical feasibility and infrastructure development, economic and geopolitical viability complete with the US National Space Weather Program dialogue, ethical and legal considerations, and risk management. This discussion helps us understand how a space economy is feasible with the aggregation of many existing and new technologies into more advanced systems engineering projects.
Alexandra Roosnovo, Anton V. Artemyev, Xiao-Jia Zhang
et al.
Certain forms of solar wind transients contain significant enhancements of dynamic pressure and may effectively drive magnetosphere dynamics, including substorms and storms. An integral element of such driving is the generation of a wide range of electromagnetic waves within the inner magnetosphere, either by compressionally heated plasma or by substorm plasma sheet injections. Consequently, solar wind transient impacts are traditionally associated with energetic electron scattering and losses into the atmosphere by electromagnetic waves. In this study, we show the first direct measurements of two such transient-driven precipitation events as measured by the low-altitude Electron Losses and Fields Investigation (ELFIN) CubeSats. The first event demonstrates storm-time generated electromagnetic ion cyclotron waves efficiently precipitating relativistic electrons from >300 keV to 2 MeV at the duskside. The second event demonstrates whistler-mode waves leading to scattering of electrons from 50 keV to 700 keV on the dawnside. These observations confirm the importance of solar wind transients in driving energetic electron losses and subsequent dynamics in the ionosphere.
On November 3-4 2021, an interplanetary coronal mass injection (ICME) hits the magnetosphere, sparking a strong G3-class geomagnetic storm and auroras as far south as California and New Mexico. All detectors of the SEVAN network registered a Forbush decrease (FD) of 5-10 percentdeep in 1 minute time series of count rates. We present the results of a comparison of Fd registered on mountain altitudes on Aragats (Armenia), Lomnicky Stit (Slovakia), Musala (Bulgaria), and at sea level DESY (Hamburg, Germany), and in Mileshovka, Czechia. We present as well purity and barometric coefficients of different coincidences of SEVAN detector layers on Aragats. We demonstrate disturbances of the near-surface electric (NSEF) and geomagnetic fields at the arrival of the ICME on Earth.
Catalin Negrea, Costel Munteanu, Marius Mihai Echim
In this study, we investigate the global ionospheric impact of high-speed solar wind streams/corotating interaction regions (HSS/CIR). A series of ten such events are identified between December 1st 2007 and April 29th 2008, characterized in the frequency domain by the main spectral peaks corresponding to 27, 13.5, 9 and 6.75 days. The spectra of solar wind magnetic field, speed and proton density, as well as those of the geomagnetic indices AE and SYM-H are solely dominated by these features. By contrast, the ionospheric NmF2 and to a lesser extent the hmF2 spectra have a much more complex structure, with secondary peaks adding to or replacing the main ones. We argue that this is evidence of the nonlinear nature of the magnetosphere-ionosphere coupling, highlighted particularly in the NmF2 ionospheric response. Additionally, we show that hmF2 is more closely correlated than NmF2 to all parameters describing the solar wind and geomagnetic activity. Finally, the ionospheric response shows higher correlation with Bz than any other solar wind parameter, and higher with SYM-H than AE, indicating that for the low-frequency part of the spectrum, high-latitude Joule heating and particle precipitation play a secondary role to that of prompt penetration electric fields in dictating the ionospheric response to geomagnetic activity, in the case of this sequence of HSS/CIR events.
Based on in-situ measurements by Wind spacecraft from 2005 to 2015, this letter reports for the first time a clearly scale-dependent connection between proton temperatures and the turbulence in the solar wind. A statistical analysis of proton-scale turbulence shows that increasing helicity magnitudes correspond to steeper magnetic energy spectra. In particular, there exists a positive power-law correlation (with a slope $\sim 0.4$) between the proton perpendicular temperature and the turbulent magnetic energy at scales $0.3 \lesssim kρ_p \lesssim 1$, with $k$ being the wavenumber and $ρ_p$ being the proton gyroradius. These findings present evidence of solar wind heating by the proton-scale turbulence. They also provide insight and observational constraint on the physics of turbulent dissipation in the solar wind.
We use $Δ$SYM-H to capture the variation in the SYM-H index during the main phase of a geomagnetic storm. We define great geomagnetic storms as those with $Δ$SYM-H $\le$ -200 nT. After analyzing the data that were not obscured by solar winds, we determined that 11 such storms occurred during solar cycle 23. We calculated time integrals for the southward interplanetary magnetic field component I(B$_s$), the solar wind electric field I(E$_y$), and a combination of E$_y$ and the solar wind dynamic pressure I(Q) during the main phase of a great geomagnetic storm. The strength of the correlation coefficient (CC) between $Δ$SYM-H and each of the three integrals I(B$_s$) (CC = 0.74), I(E$_y$) (CC = 0.85), and I(Q) (CC = 0.94) suggests that Q, which encompasses both the solar wind electric field and the solar wind dynamic pressure, is the main driving factor that determines the intensity of a great geomagnetic storm. The results also suggest that the impact of B$_s$ on the great geomagnetic storm intensity is much more significant than that of the solar wind speed and the dynamic pressure during the main phase of associated great geomagnetic storm. How to estimate the intensity of an extreme geomagnetic storm based on solar wind parameters is also discussed.
AbstractPhotos of a spectacular optical phenomenon, nicknamed STEVE, show finely structured, purple‐colored, east‐west arcs spanning the sky. These purple Sub‐auroral Arc Emissions are associated with Sub‐Auroral Ion Drifts, often accompanied by separate green arcs frequently displaying magnetic field aligned rays suggesting charge particle excitation. Both types of these arcs and polar auroras appear in some photos. Splitting the images into red, green, and blue channels allowed comparison of color ratios of the three phenomena. Wavelength calibration of the camera verified that the dominant atmospheric auroral emissions, 630.0 nm O(1D), O(1S) 557.7 nm, and N2+1N bands, were cleanly separated in the red, green, and blue channels of the camera. In the absence of a spectrogram the ratios between the color channels were interpreted in terms of possible excitation mechanisms. The purple arcs contained an excess of blue, presumably N2+1N intensity. This excess production could be due to the excitation of N2+ ions that were ionized through charge exchange with O+. The green companion arcs appear to be purely green (557.7) with almost no blue and minimal red suggesting excitation by low‐energy electrons excitation at altitudes >100 and <150 km.
AbstractThe spatial distribution and amplitudes of electron phase space holes observed in the plasma environment near Earth's Moon are presented. When the Moon is in the solar wind, the overwhelming majority of holes in its vicinity occur in its wake, and we attribute them to an instability caused by distortion of the electron distribution by the wake, as predicted by theory. Approximately 30% of these wake holes are statistically correlated with observed magnetic discontinuities nearby, which implies that external effects can influence and trigger these wake instabilities, yet the wake is the determining factor. When the Moon is deep in the Earth's magnetotail, and no detectable lunar wake is present, the hole occurrence is greatly reduced and is distributed approximately homogeneously about the Moon, implicating a different production mechanism. Near the boundary of the magnetotail, homogeneously occurring holes are more frequent, showing that other instabilities associated with the magnetopause region are also active. These results demonstrate ways in which the Earth's Moon is a unique plasma physics laboratory where plasma wake physics and electron instabilities can be studied in detail.
Michael W. Liemohn, Viviane Pierrard, Natalia Yu Ganushkina
et al.
AbstractThe Editors of the Journal of Geophysical Research Space Physics would like to honor and thank the 2018 manuscript reviewers for the journal. This is a large‐scale, community‐wide effort for which 1,358 scientists submitted 3,027 reviews in 2018. We understand that this is a volunteer task and we greatly appreciate your time and effort to fulfill this service role back to the research community.
Rehan Siddiqui, Rajinder K. Jagpal, Sanjar M. Abrarov
et al.
The description, imagery and interpretation of cloud scenes by remote sensing datasets from Earth-orbiting satellites have become a great debate for several decades. Presently, there are many models for cloud detection and its classifications have been reported. However, none of the existing models can efficiently detect the clouds within the small band of shortwave upwelling radiative wavelength flux (SWupRF) in the spectral range from 1100 to 1700 nm. Therefore, in order to detect the clouds more effectively, a method known as the radiance enhancement (RE) can be implemented (Siddiqui et al., 2015). This article proposes new approaches how with RE and SWupRF methods to distinguish cloud scenes by space orbiting Argus 1000 micro-spectrometer utilizing the GENSPECT line-by-line radiative transfer model (Quine and Drummond, 2002; Siddiqui, 2017). This RE approach can also be used within the selected wavelength band for the detection of combustion-originated aerosols due to seasonal forest fires.
Abstract. Observations of the terrestrial ion transport and budget in the magnetosphere are reviewed, with stress on low energy ions in the high-altitude polar region and inner magnetosphere, for which Cluster significantly improved the knowledge. Outflowing ions from the ionosphere are classified into three types in terms of energy: (1) as cold ions refilling the plasmasphere faster than Jeans escape, (2) as cold supersonic ions such as the polar wind, and (3) as suprathermal ions energized by wave-particle interaction or parallel potential acceleration. Majority of the suprathermal ions are further energized at higher altitudes becoming hot with much higher velocity than the escape velocity even for heavy ions. This makes heavy ions in this category more abundant than cold refilling or cold supersonic flow. The immediate destination of these terrestrial ions varies from the plasmasphere, the inner magnetosphere including those entering to the ionosphere in the other, the magnetotail, and the solar wind (magnetosheath and cusp/plasma mantle). Due to time variable return from the magnetotail, ions with different routes and energy meet in the inner magnetosphere, making it a zoo of different types of ions in both energy and energy distribution. This zoo is not yet completely entangled, and includes many unanswered phenomena such as mass-dependent energization although the mass-independent drift theory is well justified. Nearly half of heavy ions in this zoo also finally escape to space, mainly due to magnetopause shadowing (overshooting of ion drift beyond the magnetopause) and charge exchange near the mirror altitude where the exospheric neutral density is the highest. The amount of heavy ions mixing with the solar wind is already the same or larger than that into the magnetotail, and is large enough to directly extract the solar wind kinetic energy in the cusp/plasma mantle through the mass-loading effect and drive the cusp current system. Considering the past solar and solar wind conditions, ion escape might have even influenced the evolution of the terrestrial biosphere.
Based on now historical magnetic and plasma data and available wave spectra from the AMPTE-IRM spacecraft, and on as well historical Equator-S high-cadence magnetic field observations of mirror modes in the magnetosheath near the dayside magnetopause, we present some observational evidence for a recent theoretical evaluation by Noreen et al. (2017) of the contribution of a global electron temperature anisotropy to the evolution of mirror modes in the high-temperature anisotropic collisionless plasma of the magnetosheath causing a separate electron mirror branch. These old data most probably indicate that signatures of this electron effect on mirror modes had indeed been observed already long ago in magnetic and wave data though had not been recognised as such. Unfortunately either poor time resolution or complete lack of plasma data would have inhibited the confirmation of the notoriously required pressure balance in the electron branch for unambiguous confirmation of a separate electron mirror mode. If confirmed by future high-resolution observations, in both cases the large mirror mode amplitudes suggest that mirror modes escape quasilinear saturation being in a state of weak kinetic plasma turbulence.
AbstractQuasi‐linear diffusion coefficients are considered for highly oblique whistler mode waves, which exhibit a singular “resonance cone” in cold plasma theory. The refractive index becomes both very large and rapidly varying as a function of wave parameters, making the diffusion coefficients difficult to calculate and to characterize. Since such waves have been repeatedly observed both outside and inside the plasmasphere, this problem has received renewed attention. Here the diffusion equations are analytically treated in the limit of large refractive index μ. It is shown that a common approximation to the refractive index allows the associated “normalization integral” to be evaluated in closed form and that this can be exploited in the numerical evaluation of the exact expression. The overall diffusion coefficient formulas for large μ are then reduced to a very simple form, and the remaining integral and sum over resonances are approximated analytically. These formulas are typically written for a modeled distribution of wave magnetic field intensity, but this may not be appropriate for highly oblique whistlers, which become quasi‐electrostatic. Thus, the analysis is also presented in terms of wave electric field intensity. The final results depend strongly on the maximum μ (or μ∥) used to model the wave distribution, so realistic determination of these limiting values becomes paramount.