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We doubt whether the “Energetic Neutral Atom (ENA) ribbon” signals, especially the peak ones, scanned remotely by IBEX-Hi at the lunar resonance orbit, are really from the heliopause, which involves assessing the scale of solar wind particle energy loss throughout the solar system. The ENA imaging simulation results at the Earth’s orbit show that the scale of the planetary magnetosphere with a telemetry distance of AU magnitude is too small to contribute to the IBEX-Hi ribbon. However, the simulated effective ENA differential fluxes provide a reference for the physical scale evaluation of the huge magnetic structure in the heliopause. The ENA differential flux of the “ENA emission cone” generated by the charge exchange between the solar wind ion flow and local neutral gas near the Earth’s orbit is also comparable to the measured peak of the IBEX-Hi ribbon, which may be the main ENA emission source of the ribbon’s measured peak. The 2D ENA imaging measurements at the Lagrange points proposed here can be used to investigate the ENA ribbon origination by using the energy spectral lag vs the disparity of the ENA images.

Context. Upflows in the corona are of importance, as they may contribute to the solar wind. There has been considerable interest in upflows from active regions (ARs). The coronal upflows that are seen at the edges of active regions have coronal elemental composition and can contribute to the slow solar wind. The sources of the upflows have been challenging to determine because they may be multiple, and the spatial resolution of previous observations is not yet high enough. Aims. In this article, we analyse coronal upflows in AR 12960 that are unusually close to the sunspot umbra. We analyse their properties, and we attempt to determine if it is possible that they feed into the slow solar wind. Methods. We analysed the activity in the upflow region in detail using a combination of Solar Orbiter EUV images at high spatial and temporal resolution, Hinode/EUV Imaging Spectrometer data, and observations from instruments on board the Solar Dynamics Observatory. This combined dataset was acquired during the first Solar Orbiter perihelion of the science phase, which provided a spatial resolution of 356 km for two pixels. Doppler velocity, density, and plasma composition determinations, as well as coronal magnetic field modelling, were carried out to understand the source of the upflows. Results. We observed small magnetic fragments, called moving magnetic features (MMFs), moving away from the sunspot in the active region. Specifically, they moved towards the sunspot from the edge of the penumbra where a small positive polarity connects to the umbra via small-scale and very dynamic coronal loops. At this location, small dark grains are evident and flow along penumbral filaments in continuum images. The magnetic field modelling showed small low-lying loops anchored close to the umbral magnetic field. The high-resolution data of the Solar Orbiter EUV Imagers showed the dynamics of these small loops, which last on time scales of only minutes. The edges of these small loops are the location of the coronal upflow that has photospheric abundance., Astronomy & Astrophysics, 675, ISSN:0004-6361, ISSN:1432-0746

We analyze periods with elevated >40 MeV proton intensities observed near Earth over a time span of 43 yr (1973-2016) that coincide with the passage of interplanetary (IP) shocks. Typically, elevated proton intensities result from large solar energetic particle (SEP) events. The IP shocks observed during these elevated-intensity periods may or may not be related to the origin of the SEP events. By choosing those cases when the shocks can be confidently associated with the solar eruption that generated the SEP event, we analyze the components of these SEP events that are localized in the vicinity of the shock (so-called 'energetic storm particles', ESPs), focusing on those events where the ESP component exceeds 40 MeV. We examine the interdependence of these high-energy ESPs with (i) the properties of the solar eruptions that generated the shocks and the SEP events, and (ii) the parameters of the shocks at their arrival at 1 au. The solar eruptions at the origin of the shocks producing >40 MeV proton ESP intensity enhancements are within ±50° longitude of central meridian and are associated with fast coronal mass ejections (plane-of-sky speeds ≳1000 km s−1). The ESP events with the largest >40 MeV proton intensity increases tend to occur when there are structures such as intervening IP coronal mass ejections and other unrelated shocks present in the solar wind through which the shock is propagating. Among the various local shock parameters considered, only the shock speed shows a certain degree of correlation with the observed ESP intensity increase.

Radial diffusion has been established as one of the most important mechanisms contributing to both the acceleration and loss of relativistic electrons in the outer radiation belt, as well as to the supply of particles to the inner radiation belt. In the framework of the “SafeSpace” project, we have used 9 years (2011–2019) of multi-point magnetic and electric field measurements from THEMIS A, D and E satellites to create a database of radial diffusion coefficients (DLL) and ultra-low-frequency (ULF) wave power spectral densities (PSDs) spanning an L∗ range from 3 to 8. In this work we investigate the dependence of the DLL on the various solar wind parameters, geomagnetic indices and coupling functions, as well as the L-shell, during the solar cycle 24. Moreover, we discuss the uncertainties introduced on the estimation of DLL time series by the partial azimuthal coverage provided by in situ measurements. Furthermore, we investigate, via a superposed analysis, the dependence of the DLL on solar wind drivers. We show, for the first time to the best of our knowledge, that the interplanetary coronal mass ejection (ICME)-driven disturbances accompanied by high solar wind pressure values combined with intense magnetospheric compression can produce DLLB values comparable to or even greater than the ones of DLLE. This feature cannot be captured by semi-empirical models and introduces a significant energy dependence on the DLL. Finally, we show the advantages of using DLL time series by means of numerical simulations of relativistic electron fluxes performed with the Salammbô code and significant deviations in the predictions of several semi-empirical models depending on the level of geomagnetic activity and L-shell.

Solar wind (SW) quantities, referred to as coupling parameters (CPs), are often used in statistical studies devoted to the analysis of SW–magnetosphere–ionosphere couplings. Here, the CPs and their limitations in describing the magnetospheric response are reviewed. We argue that a better understanding of SW magnetospheric interactions could be achieved through estimations of the energy budget in the magnetosheath (MS), which is the interface region between the SW and magnetosphere. The energy budget involves the energy transfer between scales, energy transport between locations, and energy conversions between electromagnetic, kinetic, and thermal energy channels. To achieve consistency with the known multi-scale complexity in the MS, the energy terms have to be complemented with kinetic measures describing some aspects of ion–electron scale physics.

The underlying dynamics of solar processes are a topic of considerable interest, because the events on the surface of the Sun directly affect the environment of our planet. Certain ‘storms’ that erupt in the outer layers of the Sun can propel masses of electrically charged plasma into the solar system. If the path of that material crosses Earth’s orbit, it can disrupt our societal electronic and satellite resources. Observing and analyzing these events is a first step toward predicting them and hardening our equipment against them. This work reviews how solar scientists collect and view this data on coronal mass ejections.

Context. The origin of the slow solar wind is still an open issue. One possibility that has been suggested is that upflows at the edge of an active region can contribute to the slow solar wind. Aims. We aim to explain how the plasma upflows are generated, which mechanisms are responsible for them, and what the upflow region topology looks like. Methods. We investigated an upflow region using imaging data with the unprecedented temporal (3 s) and spatial (2 pixels = 236 km) resolution that were obtained on 30 March 2022 with the 174 channel of the Extreme-Ultraviolet Imager (EUI)/High Resolution Imager (HRI) on board Solar Orbiter. During this time, the EUI and Earth-orbiting satellites (Solar Dynamics Observatory, Hinode, and the Interface Region Imaging Spectrograph, IRIS) were located in quadrature (∼92), which provides a stereoscopic view with high resolution. We used the Hinode/EIS (Fe XII) spectroscopic data to find coronal upflow regions in the active region. The IRIS slit-jaw imager provides a high-resolution view of the transition region and chromosphere. Results. For the first time, we have data that provide a quadrature view of a coronal upflow region with high spatial resolution. We found extended loops rooted in a coronal upflow region. Plasma upflows at the footpoints of extended loops determined spectroscopically through the Doppler shift are similar to the apparent upward motions seen through imaging in quadrature. The dynamics of small-scale structures in the upflow region can be used to identify two mechanisms of the plasma upflow: Mechanism I is reconnection of the hot coronal loops with open magnetic field lines in the solar corona, and mechanism II is reconnection of the small chromospheric loops with open magnetic field lines in the chromosphere or transition region. We identified the locations in which mechanisms I and II work., Astronomy & Astrophysics, 673, ISSN:0004-6361, ISSN:1432-0746

The radio signal transmitted by the Mars Express (MEX) spacecraft was observed regularly between the years 2013-2020 at X-band (8.42 GHz) using the European Very Long Baseline Interferometry (EVN) network and University of Tasmania's telescopes. We present a method to describe the solar wind parameters by quantifying the effects of plasma on our radio signal. In doing so, we identify all the uncompensated effects on the radio signal and see which coronal processes drive them. From a technical standpoint, quantifying the effect of the plasma on the radio signal helps phase referencing for precision spacecraft tracking. The phase fluctuation of the signal was determined for Mars' orbit for solar elongation angles from 0 - 180 deg. The calculated phase residuals allow determination of the phase power spectrum. The total electron content (TEC) of the solar plasma along the line of sight is calculated by removing effects from mechanical and ionospheric noises. The spectral index was determined as $-2.43 \pm 0.11$ which is in agreement with Kolomogorov's turbulence. The theoretical models are consistent with observations at lower solar elongations however at higher solar elongation ($>$160 deg) we see the observed values to be higher. This can be caused when the uplink and downlink signals are positively correlated as a result of passing through identical plasma sheets., The paper has 13 figures and one table. It has been accepted for publication in PASA and the article will receive its DOI in a week's time

Cosmic rays measured through neutron monitors on Earth’s surface have a strong correlation with the number of sunspots on the solar photosphere. Other indices that affect the dynamics of the heliosphere and distortions in the Earth’s geomagnetic field also exhibit significant correlations. Typically, studies focus on these indices individually or combine some into a smaller set of estimators. This study uses Structural Equation Modeling to examine relationships between a broad range of parameters of solar dynamics and cosmic ray intensity (measured by the Moscow neutron monitor) across several solar cycles from 1976 to present day. The study also classifies these indices into three distinct contributions: Photosphere, Solar Wind and Terrestrial Geomagnetic Field Distortions. Regression models were built for all solar cycles and the complete cosmic ray series from 1976 to the present, resulting in good estimators with calculated p-values below 0.05 (95% confidence). Relationships among all contributions were determined using their estimators.

The recently published Interstellar Probe (ISP) study report describes a pragmatic mission concept with a launch window that starts in 2036 and is expected to reach several hundreds of astronomical units past the heliopause within a time frame of ≥50 years (https://interstellarprobe.jhuapl.edu/Interstellar-Probe-MCR.pdf). Following the ISP report, this paper, that will also be accessible from the Bulletin of the AAS (BAAS) in the framework of the Decadal Survey for Solar and Space Physics (Heliophysics) 2024–2033 (Dialynas et al., A future Interstellar Probe on the dynamic heliosphere and its interaction with the very local interstellar medium: In-situ particle and fields measurements and remotely sensed ENAs, 2022a), aims to highlight the importance of studying the physics of the interactions pertaining to the expanding solar wind that meets the plasma, gas and dust flows of the very local interstellar medium, forming the complex and vast region of our astrosphere. We focus on three fundamental open science questions that reveal the dynamical nature of the heliosphere A) Where are the heliosphere boundaries and how thick is the heliosheath B) Is there a “missing” pressure component towards exploring the dynamics of the global heliosheath and its interaction with the very local interstellar medium C) Why does the shape and size of the global heliosphere appear different in different Energetic Neutral Atom energies? We argue that these questions can only be addressed by exploiting a combination of in-situ charged particle, plasma waves and fields measurements with remotely sensed Energetic Neutral Atoms that can be measured simultaneously from the instruments of a future Interstellar Probe mission, along its trajectory from interplanetary space through the heliosheath and out to the very local interstellar medium., Frontiers in Astronomy and Space Sciences, 10, ISSN:2296-987X

This paper bestows 3-phase grid interfaced solar-wind hybrid renewable energy system (RES), feeding three-phase loads. The proposed system includes solar photovoltaic, permanent magnet based synchronous generator (PMSG), DC-DC converter, maximum power point tracker (MPPT) based on incremental conductance, three phases IGBT based voltage source converter (VSC), with a third order generalized integrator (TOGI) control technique. This control technique bestows multifunctional capabilities as harmonic mitigations, load balancing, and reactive power compensation. A fundamental component of load current is extracted by TOGI based controller, and further it is utilized to provide switching pulses to VSC for power quality enrichment. The fuzzy logic-based controller is used for loss computation of VSC as well as for maintaining DC link voltage. Moreover, fuzzy logic provides better dynamic performance compared to conventional PI controller. The results are presented in many aspects for linear and nonlinear loads such as, intermittent nature of solar and wind as well as disturbances in the system. A comparative analysis between proposed TOGI based controller and conventional control algorithm has been presented. Test results are performed by using MATLAB/ Simulink environment and demonstrate, AC-grid current is maintained within the IEEE-519 standard.

Absorption level by riometer was estimated at high-latitudes during four moderate magnetic storms that occurred in 2018 and were similar by several features. The data of riometer absorption at 30 MHz was obtained from Sodankyla Geophysical Observatory in Finland (67.36°N, 26.63°E). Particle precipitations were estimated by POES satellite data. According to our results, the character of development of the magnetic disturbance and the similarity/difference of Space Weather parameter variations (IMF magnitude, solar wind parameters, Dst variation) did not played the leading role in the absorption peak value. The absorption level in the auroral oval during the considered similar moderate magnetic disturbances depended on the combination of factors: simultaneous electron bursts of particular energies, the number of precipitating particles in these bursts and the moment of the storm at which such precipitation bursts occurred. The highest absorption was caused by the large electron precipitations with energies of >40 keV and >130 keV that occurred just after the maximal storm development at the very beginning of the recovery phase of the storm.

The aim of this study is to estimate the peculiarities of the bioefficacy of geomagnetic activity in the period of the COVID-19 pandemic (March–April, 2020) and reveal the specific factors of space weather that impact the sensitivity of the myocardium of healthy volunteers to geomagnetic activity in the given period. The bioefficacy of geomagnetic activity has been studied in healthy volunteers for the first time. There were persons whose initial myocardium disorder was caused by the COVID-19 pandemic. The study continued for 2 months (March–April, 2020) with the daily control of the T-wave coefficient in the electrocardiogram phase portrait, the daily Kp index of the geomagnetic activity, dynamical solar wind pressure, Bz components of the interplanetary magnetic field, and solar radiation with the wave length of 10.7 cm. Two types of responses of the cardiovascular system were revealed—immediate (typical for cardio-sensitive volunteers) and delayed (for cardio-insensitive persons). The analysis of the extended spectrum of the space-weather parameters made it possible for the first time to determine the combination and the value of geophysical features of geomagnetic activity that cause delayed response (for 1–2 days) in cardio-insensitive persons: the daily Kp index over 20 relative units, the dynamical solar wind pressure over 2.0 nPa, and the negative value of Bz components of the interplanetary magnetic field.

Wave–particle interactions are fundamental processes in space plasma, and some plasma waves, including electrostatic solitary waves (ESWs), are recognised as broadband noises (BBNs) in the electric field spectral data. Spacecraft observations in recent decades have detected BBNs around the Moon, but the generation mechanism of the BBNs is not fully understood. Here, we study a wake boundary traversal with BBNs observed by Kaguya, which includes an ESW event previously reported by Hashimoto et al. Geophys Res Lett 37:L19204 10.1029/2010GL044529 (2010). Focusing on the relation between BBNs and electron pitch-angle distribution functions, we show that upward electron beams from the nightside lunar surface are effective for the generation of BBNs, in contrast to the original interpretation by Hashimoto et al. Geophys Res Lett 37:L19204 10.1029/2010GL044529 (2010) that high-energy electrons accelerated by strong ambipolar electric fields excite ESWs in the region far from the Moon. When the BBNs were observed by the Kaguya spacecraft in the wake boundary, the spacecraft’s location was magnetically connected to the nightside lunar surface, and bi-streaming electron distributions of downward-going solar wind strahl component and upward-going field-aligned beams (at $$\sim$$ ∼ 124 eV) were detected. The interplanetary magnetic field was dominated by a positive $$B_Z$$ B Z (i.e. the northward component), and strahl electrons travelled in the antiparallel direction to the interplanetary magnetic field (i.e. southward), which enabled the strahl electrons to precipitate onto the nightside lunar surface directly. The incident solar wind electrons cause negative charging of the nightside lunar surface, which generates downward electric fields that accelerate electrons from the nightside surface toward higher altitudes along the magnetic field. The bidirectional electron distribution is not a sufficient condition for the BBN generation, and the distribution of upward electron beams seems to be correlated with the BBNs. Ambipolar electric fields in the wake boundary should also contribute to the electron acceleration toward higher altitudes and further intrusion of the solar wind ions into the deeper wake. We suggest that solar wind ion intrusion into the wake boundary is also an important factor that controls the BBN generation by facilitating the influx of solar wind electrons there. Graphical Abstract

The linear scaling of the mixed third-order moment of the magnetohydrodynamic fluctuations is used to estimate the energy transfer rate of the turbulent cascade in the expanding solar wind. In 1976 the Helios 2 spacecraft measured three samples of fast solar wind originating from the same coronal hole, at different distance from the sun. Along with the adjacent slow solar wind streams, these represent a unique database for studying the radial evolution of turbulence in samples of undisturbed solar wind. A set of direct numerical simulations of the MHD equations performed with the Lattice-Boltzmann code FLAME is also used for interpretation. We show that the turbulence energy transfer rate decays approximately as a power law of the distance, and that both the amplitude and decay law correspond to the observed radial temperature profile in the fast wind case. Results from magnetohydrodynamic numerical simulations of decaying magnetohydrodynamic turbulence show a similar trend for the total dissipation, suggesting an interpretation of the observed dynamics in terms of decaying turbulence, and that multi-spacecraft studies of the solar wind radial evolution may help clarifying the nature of the evolution of the turbulent fluctuations in the ecliptic solar wind., In press on Astron. Astrophys

Interplanetary scintillation (IPS) analysis is an effective technique for remotely sensing solar-wind disturbances, such as stream-interaction regions (SIRs) and coronal mass ejections (CMEs), which are the main drivers of space weather. Here, we employed 327-MHz IPS observations conducted at the Institute of Space–Earth Environmental Research, Nagoya University for the period of 1997 – 2019 to determine IPS indices that represent the density-fluctuation level of the inner heliosphere. We then compared these indices with the solar-wind density and speed measured near the Earth. Consequently, we found weak but significant positive correlations between the IPS indices and both the solar-wind density and speed gradient at a time lag of 0 days. This suggests that an increase in IPS indices corresponds to the arrival of the compression region associated with SIR or CME at the Earth, which is consistent with model calculations. Significant negative correlations were observed between the IPS and disturbance storm time (Dst) indices at a time lag of a few days; however, the correlations were too weak to enable reliable predictions of space weather. Possible reasons for these weak correlations are also discussed. Using the IPS indices, we determined the solar-cycle variation in the occurrence rate of solar-wind disturbances for the analysis period. The occurrence rates exhibited two maxima corresponding to the solar maximum and minimum, which are generally consistent with the combined effects of CME and SIR. The lower occurrence rates in Cycle 24 than in Cycle 23 reflect a weaker solar activity. These results suggest that the proposed IPS indices are useful for studying the long-term characteristics of solar-wind disturbances.

Hematite, a ferric mineral with diagnostic features in the visible and infrared spectral range, has recently been discovered in the polar regions of the Moon by the Chandrayaan-1 Moon Mineralogy Mapper (M3). The oxygen involving the oxidization process producing lunar hematite is supposed to originate from the Earth’s upper atmosphere, and hematite with different ages may have preserved information on the oxygen evolution of the Earth’s atmosphere in the past billions of years. The discovery of lunar hematite may provide insight into the understanding of the oxidation products on the Moon and other airless bodies. In this work, we analyze hematite abundance distribution in the lunar polar regions, showing that the content of hematite on the lunar surface increases with latitude, and is positively correlated with surface water abundance. We suggest that the latitude dependence of hematite is derived from the latitude dependence of water, which indicates that water may play an essential role in the formation of hematite. The correlation between hematite and the optical maturity parameter (OMAT) was analyzed and a significant positive correlation was observed, which suggests that the hematite in the polar regions is the result of gradual and persistent oxidation reactions. In addition, based on the analysis of oxygen particles in the Earth wind, it was found that O+ and O2+ are much more abundant, suggesting that low-energy O+ or O2+ ions escaping from the upper atmosphere of the Earth may play a crucial role in the formation of hematite in the lunar polar regions.

The Sun reveals itself in the 385.8–2.439-nHz band of polar (φSun>|70°|) fast (>700 km·s−1) solar wind’s decade-scale dynamics as a globally completely vibrating and resonating revolving-field magnetoalternator rather than just a proverbial engine (as obscurely yet commonly referred to). Thus North–South separation of 1994–2008 Ulysses 7–2.5·109-erg base energies reveals Gauss–Vaníček spectral signatures of a ≥99%-significant Sun-borne global sharp Alfvén resonance (AR), Pi=PS/i, i=2…n, i∈ℤ ∧ n∈א, imprinted into the winds to the order n=100+ and co-triggered by the PS=~11-yr Schwabe (global) mode northside, the mode’s ~10-yr degeneration equatorially, and a ~9-yr degeneration southside. The overwhelming (anisotropy moderating) and deterministic (with Φ≫12 fidelity) AR is found accompanied by an also sharp symmetrical antiresonance, P-, whose both N/S tailing harmonics P-17 are the well-known PR=~154-day Rieger period from which the wind’s folded Rieger resonance (RR) sprouts, dominating the 30–180-days critical band of planetary dynamics and space weather. PR gets its value from being the tri-band resonance response of the Sun to its three global vibration degenerations, i.e., PR=PS/3/3/3. The Sun is a typical ~3-dB-attenuated ring system of differentially rotating and contrarily (out-of-phase) vibrating conveyor belts and layers with a continuous spectrum, patterns complete in both parities, and resolution better than 81.3 nHz (S) and 55.6 nHz (N) in lowermost frequencies (≲2 μHz in most modes). Unlike a resonating motor engine restrained from separating its casing, the freely resonating Sun exhausts the wind in an axial shake-off at highly coherent, discrete wave modes generated in the Sun, so to understand solar-type stars, only global decadal scales matter. The wind is transported effortlessly to distances beyond L1 in the form of a guided resonating flux of alternating fast-slow jets blanketing and flapping quasiperiodically (locally transiently) about the ecliptic rather than forming turbulently random flux tubes or ropes as held previously. Base energies of the solar-wind mechanism can multiply ~102-fold or more via frequency demultiplication and thus supply the known minimum input energy of ~102–104 W∙m−2 required for balancing the chromosphere and corona losses to radiation and supersonic wind. The result verified both against remote data and the experiment, so it instantly replaces dynamo with magnetoalternator and advances standard stellar models for the known universe, improving fundamental understanding of billions of trillions of solar-type stars. Deciphering the RR as solar in origin completes the knowledge of stellar wind dynamics. Gauss–Vaníček spectral analysis revolutionizes planetary and space sciences by rigorously simulating multiple spacecraft or entire fleet formations from a single spacecraft and physics by enabling direct computations of nonlinear global dynamics (renders spherical approximation obsolete)., HIGHLIGHTS: • Least-squares spectra of Ulysses total polar magnetometer data resemble well-known concepts from engineering • The first complete recovery of the Sun's global vibration (resonance & antiresonance) • Globally resonating Sun conclusively exposed operating as a magnetoalternator instead of dynamo • Sun conclusively revealed exhausting solar wind in an axial shake-off and into heliosphere coherently beyond L1 • Well-known & solar system-dominant Rieger period decisively (twice; hemispherically) deciphered as solar in origin • Now completely known global vibration improves Standard Stellar Models of billions of trillions of solar-type stars • Accurately computed vibration of solar wind enables macroscopic space weather forecasting and event prediction • First application of rigorous Gauss-Vaniček Spectral Analysis (GVSA) by least squares in global heliophysics • GVSA revolutionizes space physics by rigorously simulating multiple spacecraft/fleets from a single spacecraft • GVSA revolutionizes physics by enabling direct computations of nonlinear global dynamics (rendering spherical approximation obsolete)., {"references":["Abreu, J.A., Beer, J., Ferriz-Mas, A., McCracken, K.G., Steinhilber, F. 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Unser Sonnensystem ist trotz seiner Leere eine raue Umgebung. Auf die Oberflächen gesteinsförmiger Himmelskörper wirkt ständig eine Vielzahl von Einflüssen ein und führt zum einen zu einer Veränderung dieser und zum anderen zum Freisetzen von Material. Dies ist darauf zurückzuführen, dass Planetenoberflächen kontinuierlich durch von der Sonne emittierte, energetische Teilchen – dem Sonnen- wind – getroffen und aufgrund der verursachte Ionenzerstäubung abgetragen werden. In weiterer Folge führt dieses zerstäubte Material zur Bildung einer dünnen Schicht erhöhter Dichte um Planeten und Monde, der Exosphäre. Um die Bildung der Exosphäre nachvollziehen zu können, ist es daher von entscheidender Bedeutung, die Wechselwirkung der Ionen des Sonnenwindes mit den Oberflächen von gesteinsförmigen Himmelskörpern zu verstehen. Dazu gehört auch, die Auswirkungen von oft nicht berücksichtigten Eigenschaften wie Kristallstruktur und Oberflächenrauigkeit auf den Zerstäubungsprozess bei Mineralien einzugrenzen, da typischerweise flache, amorphe Proben im Hinblick auf ihre Zerstäubungsausbeute diskutiert werden. Hierzu wurden Experimente mit verschiedenen Ionenspezies und Probenmaterialien durchgeführt, wodurch die Wechselwirkung der Sonnenwind- Ionen mit Planetenoberflächen im Detail untersucht werden konnte.Das magnesium- und eisenreiche Pyroxen Augit ((Ca,Mg,Fe)2[Si2O6]) wurde in Form dünner Schichten mit 4 keV He+ und mit 2 keV H2+ Ionen bestrahlt und die Zerstäubungsausbeuten in Abhängigkeit vom Einfallswinkel für beide Projektile gemessen. Darüber hinaus wurde auch die Implantation von He während den Bestrahlungsphasen eingehend untersucht. Es konnten zum einen verschiedene Regime in Bezug auf die netto Implantation sowie zum anderen eine lokale Konzentration von 10 at.% an implantiertem He in der gesättigten Probe festgestellt werden. Anschließende Thermodesorptionsspektroskopie haben in Kombination mit einer Mikrowaagen-Technik gezeigt, dass ein erhitzen der Proben auf 530 K dazu führt, dass das gesamte implantierte He wieder aus den Proben entfernt wird. Dies liegt im Bereich der Temperaturschwankungen auf der Oberfläche des Planeten Merkur, die von 100 K bis zu 700 K reichen können.Mit Hilfe eines neuartigen Versuchsaufbaus mit zwei Mikrowaagen war auch ein Vergleich des Zerstäubens von amorphen und kristallinen Phasen für planetare Analogmaterialien möglich – wobei zusätzlich auch die Winkelverteilungen des emittierten Materials untersucht werden konnte. Zu diesem Zweck wurden Proben aus Wollastonit (CaSiO3) und Enstatit (MgSiO3) als amorphe, dünne Filme und als polykristalline, gepresste Mineralpellets hergestellt und Bestrahlungen mit 4 keV He+ und 2 keV Ar+ Ionen unter verschiedenen Einfallswinkeln durchgeführt. Im Falle der Wollastonit-Proben wurden nahezu identische Zerstäubungsausbeuteniii2für die beiden Probentypen gefunden, während sich bei dem Enstatit-Pellet eine deutlich geringere Ausbeuten im Vergleich zu den entsprechenden Dünnschichten zeigten. Begleitende Simulationen zur Zerstäubung von rauen Oberflächen unter Verwendung von Aufnahmen der Pelletoberflächen – erstellt mittels Rasterkraft- mikroskopie – stimmen gut mit diesem experimentell beobachteten Verhalten überein. Daraus kann gefolgert werden, dass es im untersuchten Fluenzbereich keine Auswirkun- gen der Kristallstruktur auf den Zerstäubungsprozess gibt. Dies bedeutet auch, dass die mit amorphen Proben gewonnenen Daten für die Abschätzung des Zerstäubens für Himmelskörper angewendet werden können, für die Berechnung jedoch die Oberflächenrauigkeit berücksichtigt werden muss.Erweiternd zu den Ergebnissen mit Analogmaterialien wurden auch reale Mondproben – aus dem Bestand des von der Apollo 16 Mission der NASA zur Erdegebrachten Materials – hinsichtlich der entsprechenden Zerstäubungsausbeute beiIonenbestrahlung untersucht. Für die Experimente wurden sowohl molekularer Wasserstoff (H +) mit einer kinetischen Energie von 2 keV als auch 4 keV He+ Ionen 2 verwendet, um das Zerstäuben von gepresste Mineralpellets mit polykristalliner Struktur und einer gewissen Oberflächenrauigkeit mit dem von flachen, amorphen Dünnschichten zu verglichen. Auch in diesem weniger idealisierten Szenario sind die Simulationen – unter der Annahme, dass die Oberflächenrauigkeit der einzige relevante Unterschied für den Zerstäubungsprozess ist – in der Lage, die experimentellen Ergebnisse zu reproduzieren. Dies bedeutet, dass die Berücksichtigung der tatsächlichen Oberflächentopologie (Rauheit) und der Oberflächenzusammensetzung für eine genaue Beschreibung der Zerstäubung von gesteinsförmigen Himmelskörpern ausreichen könnte., The space between planets and bodies in our solar system is almost empty – but nevertheless a very harsh environment. A wide range of effects continuously impacts on the surfaces of rocky celestial bodies, leading to modifications and liberation of material. Due to the emission of energetic particles from the sun – the solar wind – surfaces are constantly eroded by ion sputtering. The sputtered material leads to the formation of a tenuous layer around planets and moons with increased density, the exosphere. It is therefore crucial to understand the interaction of solar wind ions with the surfaces of rocky bodies in order to be able to comprehend the exosphere formation. This also includes constraining the effects of often hidden properties, like crystal structure and surface roughness on the sputtering process for minerals, as typically flat, amorphous samples are discussed with regard to their sputter yield. Experiments with different ion species and sample materials were carried out, investigating the interaction of the solar wind ions with rocky body surfaces in detail.Therefore the magnesium and iron rich pyroxene augite ((Ca,Mg,Fe)2[Si2O6]) was irradiated with He+ ions at a kinetic energy of 4 keV and H + ions at 2 keV in the form of thin films. Thereby, the sputter yields in dependence of the incidence angle could be measured for both projectiles. Furthermore, the implantation of He upon impact was studied extensively. Different regimes with respect to the net implan- tation flux could be seen as well as a concentration of 10 at.% of implanted He in the saturated sample. Subsequent thermal desorption spectroscopy measurements in combination with a microbalance technique have shown, that all implanted He is removed from the samples when heating them to 530 K. This is in the range of Mercury’s temperature variations, which can reach from 100 K up to 700 K.By means of a novel experimental setup including two microbalances, also a com- parison of the sputtering of amorphous and crystalline phases for planetary analogs was possible – additionally allowing to probe the angular distributions of the sput- tered material. For this purpose, wollastonite (CaSiO3) and enstatite (MgSiO3) samples were prepared as amorphous thin films and as polycrystalline pressed mineral pellets. Measurements were performed with 4 keV He+ and 2 keV Ar+ ions, impinging under varying angles of incidence. In the case of the wollastonite samples, almost identical sputter yields for the two types of samples were ob- tained, whereas significantly smaller yields were measured for the enstatite pellet compared to the respective thin films. Accompanying simulations of sputtering of rough surfaces using atomic force microscope images of the pellet surfaces as inputs agree well with this experimentally observed behavior. It is therefore concluded, that no effects of crystal structure are present in the investigated fluence regime.i2This also implies that data obtained with amorphous samples can be used for the estimation of sputtering on celestial bodies. Furthermore, the necessity of taking surface roughness into account when calculating sputtering on realistic planetary surfaces has been shown.Expanding on the results with analog materials, real lunar samples returned toEarth by the NASA Apollo 16 mission have been investigated regarding the according sputter yields upon ion irradiation. Molecular hydrogen (H +) at a kinetic 2energy of 2keV as well as 4keV He+ ions were used for the experiments. Again, pressed mineral pellets with poly-crystalline structure and certain surface rough- ness were compared to flat amorphous thin films. Also in this less idealized scenario, simulations are able to reproduce experimental results under the assump- tion, that surface roughness is the only relevant difference for sputtering. This means, that it might be sufficient to consider actual surface topology (roughness) and surface composition for an accurate description of the sputtering behavior of rocky celestial bodies.

In this study we examine the radial dependence of the inertial and dissipation range indices, as well as the spectral break separating the inertial and dissipation range in power density spectra of interplanetary magnetic field fluctuations using {\it Parker Solar Probe} data from the fifth solar encounter between $\sim$0.1 and $\sim$0.7 au. The derived break wavenumber compares reasonably well with previous estimates at larger radial distances and is consistent with gyro-resonant damping of Alfv\'enic fluctuations by thermal protons. We find that the inertial scale power law index varies between approximately -1.65 and -1.45. This is consistent with either the Kolmogorov (-5/3) or Iroshnikov-Kraichnan (-3/2) values, has a very weak radial dependence with a possible hint that the spectrum becomes steeper closer to the Sun. The dissipation range power law index, however, has a clear dependence on radial distance (and turbulence age), decreasing from -3 near 0.7 au (4 days) to -4 [$\pm$0.3] at 0.1 au (0.75 days) closer to the Sun., Comment: Accepted for publication in ApJ

Solar-wind 3-D reconstruction tomography based on interplanetary scintillation (IPS) studies provides fundamental information for space-weather forecasting models, and gives the possibility to determine heliospheric column densities. Here we compare the time series of Solar-wind column densities derived from long-term observations of pulsars, and the Solar-wind reconstruction provided by the UCSD IPS tomography. This work represents a completely independent comparison and validation of these techniques to provide this measurement, and it strengthens confidence in the use of both in space-weather analyses applications., Comment: Published in Journal of Advances in Space Research

Context.The fast solar wind is known to emanate from polar coronal holes.Aims.This Letter reports the first estimate of the expansion rate of polar coronal flows performed by the Metis coronagraph on board Solar Orbiter.Methods.By exploiting simultaneous measurements in polarized white light and ultraviolet intensity of the neutral hydrogen Lyman-αline, it was possible to extend observations of the outflow velocity of the main component of the solar wind from polar coronal holes out to 5.5 R⊙, the limit of diagnostic applicability and observational capabilities.Results.We complement the results obtained with analogous polar observations performed with the UltraViolet Coronagraph Spectrometer on board the SOlar and Heliospheric Observatory during the previous full solar activity cycle, and find them to be satisfactorily reproduced by a magnetohydrodynamic turbulence model.Conclusions.This suggests that the dissipation of 2D turbulence energy is a viable mechanism for coronal plasma heating and the subsequent acceleration of the fast solar wind.

Context. Coronal upflows in the quiet Sun are seen in a wide range of features, including jets and filament eruptions. The in situ measurements from Parker Solar Probe within â 0.2 au have demonstrated that the solar wind is highly structured, showing abrupt and near-ubiquitous magnetic field reversals (i.e., switchbacks) on different timescales. The source of these structures has been associated with supergranular structures on the solar disc. This raises the question of whether there are additional small coronal features that contribute energy to the corona and produce plasma that potentially feeds into the solar wind. Aims. During the Solar Orbiter first science perihelion, high-resolution images of the solar corona were recorded using the Extreme Ultraviolet High Resolution Imager (HRIEUV) from the Extreme Ultraviolet Imager (EUI). The Hinode spacecraft was also observing at the same location providing coronal spectroscopic measurements. Combining the two datasets allows us to determine the cause of the weak upflows observed in the quiet Sun and the associated activity. Methods. We used a multi-spacecraft approach to characterise regions of upflows. The upflows were identified in the Feâ ¯XII emission line by the Hinode EUV Imaging Spectrometer (EIS). We then used imaging data from the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory (SDO/AIA) and the High Resolution Imagers (HRI) from EUI on board the Solar Orbiter to identify coronal features and magnetic field data from the SDO Helioseismic and Magnetic Imager (HMI). Interface Region Imaging Spectrograph (IRIS) observations were also used to understand the photospheric and chromospheric driving mechanisms. Results. We have identified two regions of coronal upflows in the quiet Sun, with respective sizes and lifetimes of (20 Mm2, 20 min) and (180 Mm2, several hours), which are contrasting dynamic events. Both examples show weak flux cancellation, indicating that the source of the upflows and enhancements is related to the magnetic field changes. The first event, a larger upflow region, shows velocities of up to 8.6 km s1 at the footpoint of a complex loop structure. We observe several distinct extreme ultraviolet (EUV) features including frequent loop brightenings and plasma blobs travelling along closed coronal loops. The second upflow region has velocities of up to 7.2 km s1. Within it, a complex EUV feature that lasts for about 20 min can be seen. This main feature has several substructures. During its appearance, a clear mini-filament eruption takes place at its location, before the EUV feature disappears. Conclusions. Two features, with contrasting properties, show upflows with comparable magnitudes. The first event, a complex loop structure, shares several similarities with active region upflows. The second one, a complex small-scale feature that could not have been well resolved with previous instruments, triggered a cascade of events, including a mini-filament that lead to a measurable upflow. This is remarkable for an EUV feature that many instruments can barely resolve. The complexity of the two events, including small loop brightenings and travelling plasma blobs for the first and EUV small-scale loops and mini-filament for the second one would not have been identifiable as the sources of upflow without an instrument with the spatial resolution of HRIEUV at this distance to the Sun. These results reinforce the importance of the smallest-scale features in the Sun and their potential relevance for and impact on the solar corona and the solar wind., Astronomy & Astrophysics, 674, ISSN:0004-6361, ISSN:1432-0746

Solar wind measurements carried out by NASA’s Wind spacecraft before, during, and after the passing of an interplanetary coronal mass ejection (ICME), detected on 12 – 14 September 2014, have been used in order to examine several properties of magnetohydrodynamic (MHD) turbulence. Spectral indices and flatness scaling exponents of magnetic field, velocity, and proton density measurements were obtained, and provided a standard description of the characteristics of turbulence within different sub-regions of the ICME and its surroundings. This analysis was followed by the validation of the third-order moment scaling law for isotropic, incompressible MHD turbulence in the same sub-regions, which confirmed the fully developed nature of turbulence in the ICME plasma. The energy transfer rate was also estimated in each ICME sub-region and in the surrounding solar wind. An exceptionally high value was found within the ICME sheath, accompanied by enhanced intermittency, possibly related to the powerful energy injection associated with the arrival of the ICME.

Parker Solar Probe and Solar Orbiter data are used to investigate the radial evolution of magnetic turbulence between $0.06 ~ \lesssim R ~\lesssim 1$ au. The spectrum is studied as a function of scale, normalized to the ion inertial scale $d_{i}$. In the vicinity of the Sun, the inertial range is limited to a narrow range of scales and exhibits a power-law exponent of, $\alpha_{B} = -3/2$, independent of plasma parameters. The inertial range grows with distance, progressively extending to larger spatial scales, while steepening towards a $\alpha_{B} =-5/3$ scaling. It is observed that spectra for intervals with large magnetic energy excesses and low Alfv\'enic content steepen significantly with distance, in contrast to highly Alfv\'enic intervals that retain their near-Sun scaling. The occurrence of steeper spectra in slower wind streams may be attributed to the observed positive correlation between solar wind speed and Alfv\'enicity., Comment: Accepted to APJ letters with minor revisions

Global changes in the state of the ionosphere-thermosphere system depend to a large extent on the energy input from the solar wind and magnetosphere, which occurs in the high-latitude regions. On the one hand energy is deposited in the form of Joule heating causing changes in the thermosphere composition and circulation. On the other hand, imposed electric fields change plasma transport. Joule heating is closely related to changes in the solar wind dynamic pressure, because it can cause a compression of the magnetosphere driving currents in the magnetosphere, and the currents transfer electromagnetic energy into the ionosphere. The enhancement of plasma convection in the polar ionosphere is related to the intensification of the convection electric field, which is driven by the solar wind sweeping across the open magnetic field lines of the polar magnetosphere. These changes are most significant during storm conditions, caused e.g. by coronal mass ejections and corotating interaction regions. The storm related energy release in the high-latitude ionosphere is impacting the thermosphere-ionosphere system on a global scale.However, the solar wind impact causes a regular every day variability of the polar ionosphere, too. We are investigating how the solar wind variability in time scales of days and weeks is reflected in the ionosphere variability at Tromso, which is located in Scandinavia at 70°N, 19°E. We use cross correlation analysis of total electron content with solar wind merging electric field and dynamic pressure data. It can be shown that in timescales of days and weeks, the magnitude of correlation between TEC and solar wind reaches similar values to the correlation of TEC and F10.7. However, the results show that the correlation between TEC and solar wind parameters depends strongly on local time, season and solar cycle. There is a clear annual cycle in the variability of the correlation coefficient, with higher correlation values in winter than in summer. The positive correlation in winter close to local midnight hours is related to precipitation effects increasing the electron densities. During summer in solar maximum condition, clear negative correlation values are retrieved. These are considered to be caused by increased convection.

The accurate reconstruction of the plasma and magnetic field parameters in the ambient interplanetary medium is fundamental to reproduce the interplanetary propagation of solar disturbances such as solar energetic particles (SEPs), stream and corotating interaction regions (SIRs and CIRs), and coronal mass ejections (CMEs), both for understanding the physics of these phenomena and for applications in space weather forecasting. The small-scale features of the ambient solar wind, in fact, affect the evolution, arrival times, and geo-effectiveness of solar transients. The Reverse In situ and MHD Approach (RIMAP) is a hybrid analytical-numerical method to reconstruct the heliosphere on the ecliptic plane from in situ measurements acquired by spacecraft with heliocentric orbits. RIMAP uses the in situ measurements as boundary conditions for a MHD simulation based on the PLUTO code, combining ballistic and MHD approaches in order to preserve the small-scale variability of the solar wind flow lines and thus offering a structured, realistic background medium for modelling the propagation of solar eruptions. In this dissertation, after an introduction about the main topics and models of heliospheric physics and the magnetohydrodynamics equations, we present the detailed description of the novelties of the RIMAP model, and its application to the measurements acquired by spacecraft at 1 AU in correspondence of solar minima configurations. Then, one of these reconstructions is used as a background medium to propagate an interplanetary CME. The perturbation is modelled as a spheroidal, homogeneous plasma cloud without internal magnetic flux rope. We use an artificial, passive tracer to quantify the mixing at 1 AU between ambient solar wind material and the one with coronal eruption origins, in order to evaluate the fraction of plasma measured in situ that can be traced back to its sources on the Sun. The RIMAP reconstruction is also carried out using measurements acquired by NASA’s Parker Solar Probe (PSP) during its seventh solar encounter, in January 2021, between 20 and 40 solar radii. This was the time of the first quadrature between PSP and ESA-NASA’s Solar Orbiter (SolO), which at the time was orbiting the Sun around 0.5 AU and providing remote sensing observations of the solar corona via the Metis coronagraph. The RIMAP reconstruction connects density and wind speed estimates inferred from the coronal features observed by Metis/SolO between 3 and 6 solar radii to the measurements acquired by PSP at 21.5 solar radii along the corresponding plasma streamline. Thus, the magnetic connection between the inner corona and the super Alfvénic wind is reconstructed with a high degree of accuracy with a detailed data-driven MHD simulation. Finally, we describe the possible future developments of the RIMAP technique such as the extension to a two-fluids treatment, the testing of different models of magnetized coronal mass ejections, the simulation of solar wind switchbacks, and the extension to full three-dimensional boundaries, using coronagraphic observations to infer the input parameters.

We present simulation results of a gradual solar energetic particle (SEP) event detected on 2021 October 9 by multiple spacecraft, including BepiColombo (Bepi) and near-Earth spacecraft such as the Advanced Composition Explorer (ACE). A peculiarity of this event is that the presence of a high speed stream (HSS) affected the low-energy ion component ($\lesssim 5$ MeV) of the gradual SEP event at both Bepi and ACE, despite the HSS having only a modest solar wind speed increase. Using the EUHFORIA (European Heliospheric FORecasting Information Asset) magnetohydrodynamic model, we replicate the solar wind during the event and the coronal mass ejection (CME) that generated it. We then combine these results with the energetic particle transport model PARADISE (PArticle Radiation Asset Directed at Interplanetary Space Exploration). We find that the structure of the CME-driven shock was affected by the non-uniform solar wind, especially near the HSS, resulting in a shock wavefront with strong variations in its properties such as its compression ratio and obliquity. By scaling the emission of energetic particles from the shock to the solar wind compression at the shock, an excellent match between the PARADISE simulation and in-situ measurements of $\lesssim 5$ MeV ions is obtained. Our modelling shows that the intricate intensity variations observed at both ACE and Bepi were influenced by the non-uniform emission of energetic particles from the deformed shock wave and demonstrates the influence of even modest background solar wind structures on the development of SEP events., Comment: 13 pages, 7 figures, accepted for publication in The Astrophysical Journal

Database of THEMIS observation of magnetopause crossings created for and used in: Grimmich, N., Plaschke, F., Archer, M. O., Heyner, D., Mieth, J. Z. D., Nakamura, R. and Sibeck, D. G.: Study of Extreme Magnetopause Distortions under Varying Solar Wind Conditions, submitted to JGR-Space Physics. See section 3 of that publication for a detailed description of the identification process.

We have analyzed the dynamics of solar wind and interplanetary magnetic field (IMF) parameters during the development of 933 isolated geomagnetic storms, observed over the period from 1964 to 2010. The analysis was carried out using the epoch superposition method at intervals of 48 hrs before and 168 hrs after the moment of Dst minimum. The geomagnetic storms were selected by the type of storm commencement (sudden or gradual) and by intensity (weak, moderate, and strong). The dynamics of the solar wind and IMF parameters was compared with that of the Dst index, which is an indicator of the development of geomagnetic storms. The largest number of storms in the solar activity cycle is shown to occur in the years of minimum average values (close in magnitude to 1) of the solar wind parameter β (β is the ratio of plasma pressure to magnetic pressure). We have revealed that the dynamics of the Dst index is similar to that of the β parameter. The duration of the storm recovery phase follows the characteristic recovery time of the β parameter. We have found out that during the storm main phase the β parameter is close to 1, which reflects the maximum turbulence of solar wind plasma fluctuations. In the recovery phase, β returns to background values β~2‒3.5. We assume that the solar wind plasma turbulence, characterized by the β parameter, can play a significant role in the development of geomagnetic storms.

Studying the direction of the solar wind flow is a topical problem of space weather forecasting. As a rule, the quiet and uniform solar wind propagates radially, but significant changes in the solar wind flow direction can be observed, for example, in compression regions before the interplanetary coronal mass ejections (Sheath) and Corotating Interaction Regions (CIR) that precede high-speed streams from coronal holes. In this study, we perform a statistical analysis of the longitude (φ) and latitude (θ) flow direction angles and their variations on different time scales (30 s and 3600 s) in solar wind large-scale streams of different types, using WIND spacecraft data. We also examine the relationships of the value and standard deviations SD of the flow direction angles with various solar wind parameters, regardless of the solar wind type. We have established that maximum values of longitude and latitude angle modulus, as well as their variations, are observed for Sheath, CIR, and Rare, with the probability of large deviations from the radial direction (>5°) increasing. The dependence on the solar wind type is shown to decrease with scale. We have also found that the probability of large values of SD(θ) and SD(φ) increases with increasing proton temperature (Tp) in the range 5–10 eV and with increasing proton velocity (Vp) in the range 400–500 km/s.

In this paper, we examine the relationship of the SME index with magnetic storm characteristics and interplanetary medium parameters during the main phase of magnetic storms caused by CIR and ICME events. Over the period 1990–2017, 107 magnetic storms driven by (64) CIR and (43) ICME events have been selected. In contrast to AE and Kp, a stronger correlation is shown to exist between the average SME index (SMEaver) and interplanetary medium parameters during the magnetic storm main phase. Close correlation coefficients between SMEaver and the SW electric field (southward IMF Bz) have been obtained for CIR and ICME events. SMEaver has been found to increase with the rate of magnetic storm development and |Dstmin|. For CIR and ICME events, no difference has been revealed between SMEaver and |Dstmin| in linear regression equations. Keywords: magnetic storm, SME index, Dst index, solar wind, electric field

We analyze the time-variation of cosmic ray intensity during the periods when large and sudden disturbances occur and last for several days. We consider periods when there are sudden decreases of ≥5% in the galactic cosmic ray (GCR) intensity records. For the analysis, in addition to cosmic-ray intensity data, we utilize several solar wind plasma and field parameters. Time variation of changes in GCR intensity have been compared with simultaneous changes in solar wind plasma and field parameters, in order to gain insight about the physical processes responsible for large-amplitude cosmic ray disturbances. We utilize not only data about changes in the magnitude of some of the plasma and magnetic field parameters but also the parameters which provide information about the turbulent or quite (non-turbulent) nature of the parameters. Moreover, we also utilize the magnitude of a number of plasma and field parameters and their various products, during cosmic ray decrease of various magnitudes. The magnitudes of various plasma and field parameters and their various products including some newly tried products are subjected to correlation analysis with the magnitude of cosmic-ray decreases. We identify plasma and field parameters and their products which best correlates with cosmic-ray decreases. We provide an empirical relation that can be useful to estimate the amplitude of Forbush decreases using interplanetary plasma and field observations. Our results provide further insight about the physical processes playing important role during large cosmic ray disturbances in the heliosphere. Our results further demonstrate that large-amplitude Forbush decreases in GCR intensity occur due to passage of enhanced and turbulent magnetic field structure, consistent with the model that Forbush decreases are mainly due to scattering of cosmic ray particles by enhanced turbulent magnetic field regions in the heliosphere.

In this paper, we present an analysis of how alpha–proton drift speeds (the difference between the magnitudes of alpha and bulk proton speeds) are constrained in the inner heliosphere using observations from the WIND and twin HELIOS spacecraft. The solar wind is separated based on its bulk proton speed into the fast wind (>600 km/s) and slow wind (

The Wang–Sheeley–Arge (WSA) solar wind (SW) model is based on the idea that weakly expanding coronal magnetic field tubes are associated with sources of fast SWs and vice versa. A parameter called the “flux tube expansion” (FTE) is used to determine the degree of expansion of magnetic tubes. The FTE is calculated based on the coronal magnetic field model, usually in the potential approximation. The second input parameter for the WSA model is the great circle distance from the base of the open magnetic field line in the photosphere to the boundary of the corresponding coronal hole (DCHB). These two coronal magnetic field parameters are related by an empirical relationship with the solar wind velocity near the Sun. The WSA model has shortcomings and does not fully explain the solar wind formation mechanisms. In the present work, we model various coronal magnetic field parameters in the potential-field source-surface (PFSS) approximation from a long series of magnetographic observations: the Solar Telescope-magnetograph for Operative Prognoses (STOP) (Kislovodsk Mountain Astronomical Station), the Helioseismic and magnetic imager (SDO/HMI), and data from the Wilcox Solar Observatory (WSO). Our main goal is to identify correlations between the coronal magnetic field parameters and the observed SW velocity in order to use them for modeling SW. We found that the SW velocity correlates relatively well with some geometric properties of the magnetic tubes, including the force line length, the latitude of the force line footpoints, and the DCHB. We propose a formula for calculating the SW velocity based on these parameters. The presented relationship does not use FTE and showed a better correlation with observations compared to the WSA model.

The isotopic composition of water in Earth’s oceans is challenging to recreate using a plausible mixture of known extraterrestrial sources such as asteroids—an additional isotopically light reservoir is required. The Sun’s solar wind could provide an answer to balance Earth’s water budget. We used atom probe tomography to directly observe an average ~1 mol% enrichment in water and hydroxyls in the solar-wind-irradiated rim of an olivine grain from the S-type asteroid Itokawa. We also experimentally confirm that H+ irradiation of silicate mineral surfaces produces water molecules. These results suggest that the Itokawa regolith could contain ~20 l m−3 of solar-wind-derived water and that such water reservoirs are probably ubiquitous on airless worlds throughout our Galaxy. The production of this isotopically light water reservoir by solar wind implantation into fine-grained silicates may have been a particularly important process in the early Solar System, potentially providing a means to recreate Earth’s current water isotope ratios. Water and hydroxyl enrichment in the solar-wind-irradiated rim of an olivine grain from asteroid Itokawa suggests that its regolith could contain ~20 l m−3 of water from solar wind—a potential water source for airless planetary bodies.

Magnetosphere-ionosphere energy transfer and AE fluctuations are studied using a cellular automata model of terrestrial magnetosphere based on the concept of self-organised criticality (SOC). The m...

The solar wind plasma is characterized by unequal effective kinetic temperatures defined in perpendicular and parallel directions with respect to the ambient magnetic field. For electrons, the excessive perpendicular temperature anisotropy leads to quasi-parallel electromagnetic electron cyclotron (or whistler) instability and aperiodic electron-mirror instability with oblique wave vectors. The present paper carries out a direct side-by-side comparison of quasi-linear (QL) theory and particle-in-cell (PIC) simulation of combined mirror and cyclotron instabilities acting upon the initially anisotropic electron temperatures, and find that the QL theory satisfactorily encapsulates the non-linear aspect of the combined instability effects. However, a discrepancy between the present study and a previous PIC simulation result is also found, which points to the need for further investigation to resolve such an issue.

This paper formulates a velocity moment-based quasi-linear theory that combines the impacts of weakly unstable proton–cyclotron- (or, equivalently, electromagnetic ion cyclotron) and proton-mirror instabilities on the solar wind plasma initially characterized by an excessive perpendicular proton temperature anisotropy. The present formalism is an alternative to the existing model in that the weakly unstable modes are characterized by analytical formalism that involves the assumption of weak growth rate and/or fluid-theoretical dispersion relation, in place of numerical root-finding method based on the transcendental plasma dispersion function. This results in an efficient numerical platform for analyzing the quasi-linear development of the said instabilities. Such a formalism may be useful in the larger context of global solar wind modelling effort where an efficient calculation of self-consistent wave–particle interaction process is called for. A direct comparison with spacecraft observations of solar wind proton data distribution shows that the present weak growth rate formalism of quasi-linear calculation produces results that are consistent with the observation.

To build the hybrid energy transmission line with the HTS cables and liquid hydrogen pipelines is one of the solutions to the carbon emission problem. However, geomagnetic storms caused by solar wind can generate Geomagnetic Induced Current (GIC) and Pipe-Soil Potentials (PSP) offset in hydrogen-electricity hybrid transmission line, which will threaten the safe operation of the hybrid energy system. In order to evaluate GIC and PSP effects of hydrogen-electricity hybrid transmission line accurately, the mechanism of GIC generation in hydrogen-electricity hybrid transmission line is researched in this paper based on the structure of hydrogen-electricity hybrid transmission line and the occurrence process of geomagnetic storm. Then, the GIC calculation model of buried transmission line is established according to the Distributed Source Transmission Line (DSTL) theory. Finally, an example analysis is carried out, the calculation results are verified using the monitoring data, the influence of GIC on the hydrogen-electricity hybrid transmission line is recognized, and two prevention methods of GIC effect are obtained.

Solar wind induces the escape of ions from the ionospheric shell of an unmagnetized planet, Venus. To analyze the dynamics of ions due to the escape process, the modeling of ion-acoustic waves (IAWs) is scrutinized for an interaction between an upper ionospheric plasma of Venus constituting mobile electrons with two kinds of positive ions, viz, H + and O + and the solar-wind which is composed of highly energized electrons and protons. The Sagdeev pseudopotential is examined for wave breaking phenomena. Employing the concept of phase plane analysis, the formulated autonomous dynamical systems are examined for all feasible nonlinear and supernonlinear periodic waves. To support the existence of nonlinear and supernonlinear waves, the graph of the total energy function is plotted in three-dimensional space. A typical set of Venusian plasma parameters are used to discuss the analytical solutions of the dynamical system by the method of Jacobi elliptic function. Effect of traveling wave velocity on the plot of the total energy function and the wave solutions are discussed.

A shock wave can be formed by continuous mass loading of the solar wind by the newly formed cometary ions. The formation of ion acoustic shocklets has thus been studied in a plasma of solar and cometary electrons, described by kappa distribution functions with different temperatures and spectral indices, a drifting H 3 O + ion component and a pair of oppositely charged oxygen ion components. The Korteweg-deVries-Burger’s equation which describes weakly nonlinear waves in a dissipative medium has been derived for the above plasma composition using the momentum, continuity and Poisson’s equations and studied for parameters observed at the inner shock region of comet Halley. We find that the spectral index of the cometary electrons plays a key role in the formation, speed of propagation and width of the shock wave, which has been interpreted as a “shocklet”, whose strength decreases as the spectral indices increase or as the suprathermal distribution relaxes to a Maxwellian distribution, with a buildup of colder electrons. Also, all three components of ions contribute to the formation of shocklets; thus bringing out the additive nature of the contributions of various types of ions to their formation. This study could aid the understanding of in-situ measurements of shock waves in cometary plasmas.

This paper presents the Total Electron Content variability, during the solar cycle 23 maximum under geomagnetic fluctuating activity conditions from 2000 to 2002 at Niamey station (lat. :13°28’N ; long : 2°10’E) in Niger. A comparative study of TEC profiles variation under quiet and fluctuating geomagnetic activity conditions allowed us to analyze the effects of fluctuations in solar wind on equatorial ionosphere. Our investigation argues on that the solar cycle 23 maximum is mostly characterized by a non-effect of fluctuating winds on the ionosphere for equatorial region. Key words: Seasonal variability, total electron content, fluctuating activity.

Magnetic fields provide an important probe of the thermal, material, and structural history of planetary and sub-planetary bodies. Core dynamos are a potential source of magnetic fields for differentiated bodies, but evidence of magnetization in undifferentiated bodies requires a different mechanism. Here we study the amplified field provided by the stellar wind to an initially unmagnetized body using analytic theory and numerical simulations, employing the resistive MHD AstroBEAR adaptive mesh refinement (AMR) multiphysics code. We obtain a broadly applicable scaling relation for the peak magnetization achieved once a wind advects, piles-up, and drapes a body with magnetic field, reaching a quasi-steady state. We find that the dayside magnetic field for a sufficiently conductive body saturates when it balances the sum of incoming solar wind ram, magnetic, and thermal pressures. Stronger amplification results from pileup by denser and faster winds. Careful quantification of numerical diffusivity is required for accurately interpreting the peak magnetic field strength from simulations, and corroborating with theory. As specifically applied to the Solar System, we find that early solar wind-induced field amplification is a viable source of magnetization for observed paleointensities in meteorites from some undifferentiated bodies. This mechanism may also be applicable to other Solar System bodies, including metal-rich bodies to be visited in future space missions such as the asteroid (16) Psyche., 12 pages, 6 figures, accepted by MNRAS

This article presents the derivation of semianalytic solutions to a new 1-D photoelectron sheath model near the lunar surface. The plasma species include the cold solar wind protons, drifting Maxwellian solar wind electrons, and Maxwellian photoelectrons emitted from the surface. The semianalytic model is then numerically solved to obtain profiles of quantities of interest as functions of the vertical distance from the surface. A fully-kinetic 3-D finite-difference (FD) particle-in-cell (PIC) code is then utilized to simulate the 1-D photoelectron sheath and the results agree well with the numerical solution to the semianalytic model. A $\kappa $ -distribution for solar wind electrons is also implemented to the FD-PIC code to compare with the Maxwellian distribution. Results show that photoelectron sheath may reach as high as close to 100 m above the illuminated flat lunar surface near the terminator region and up to about 50 m near the equator region. Our results show that under average solar wind condition, the photoelectron sheath profiles obtained with Maxwellian and $\kappa $ -distribution (with $\kappa = 4.5$ ) are very close for 1-D numerical results.

Dispatchable renewable generation is essential for 100% renewables power system. It is in the interest of both power system operators and customers since it reduces the need for flexibility and reserve. To this end, battery energy storage systems (BESS) are proposed for integration in the renewable power plant. This paper presents the optimal dispatch unit for a dispatchable hybrid solar‐wind power plant with BESS framework. It achieves optimal dispatchable renewable generation (from dispatchable hybrid renewable (solar‐wind) power plant with BESS, DHRB, operator perspective), subject to operational limits, by exploiting the synergy of wind and solar energy and combining it with storage capability of BESS using two different operation strategies, maximisation of revenues and maximisation of renewables harvesting. A continuous BESS degradation model is incorporated in the proposed rolling‐algorithm‐based‐optimal dispatch unit to improve the accuracy of results. The applicability of the proposed methodology and the performance of the operation strategies are demonstrated using a case study and the operation strategies are compared. Further, the effect of BESS size on its degradation and dispatchable power in a hybrid solar‐wind power plant with BESS are investigated through BESS lifetime. An indicative economic analysis is carried out to provide ground for the extra investment on and sizing of BESS for a dispatchable hybrid renewable power plant.