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A mini‐neutron monitor (MNM) was installed at the German Antarctic Neumayer III station, measuring the variation of galactic cosmic rays and searching for Forbush Decreases (FDs) caused by solar activities. Running continuously from 2014 until the end of 2017, the long‐term stability of the detector could be investigated. After correcting the air pressure and normalization to the 27 days running mean averages of the SANAE and TERA Neutron Monitors (NMs), the daily running mean count rates are compared with the SANAE and TERA NMs also installed in Antarctica. For most of the 14 FDs with magnitudes greater than 3, taken from the list compiled by the IZMIRAN group (http://spaceweather.izmiran.ru/eng/dbs.html), the three detectors show consistent particle flux variation, although the average rate of the MNM is more than a hundred times smaller. The light and low‐cost MNM is an ideal alternative to heavy and old NMs, especially at high altitudes and remote environments. Plain Language Summary: A mini‐neutron monitor (MNM) was installed at the German Antarctic Neumayer III station from 2014 till the end of 2017, measuring the variation of galactic cosmic rays and investigating its sensitivity by searching for Forbush decreases (FDs). The data were successfully corrected for pressure and normalized to the long‐term trend utilizing 27‐day running mean averages of the weighted mean of SANAE and TERA NMs. A comparison with the SANAE and Terre Adelie NMs on the basis of daily running mean averages reveals a difference of about 1% for each combination. Utilizing the IZMIRAN FD catalog, we showed that the sensitivity of the MNM is large enough to investigate FDs with amplitudes above 3%, making the MNM a useful instrument for space weather investigations. Key Points: Measurements of Galactic Cosmic Rays by a mini‐neutron monitor (MNM) at the German Antarctic Research Station from 2014 to 2017 are presentedThe measurements were successfully corrected for pressure and normalized to the weighted mean of the SANAE and TERA Neutron MonitorWe show that Forbush Decreases with amplitudes above 3% in Magnitude identified by the IZMIRAN database can be identified with the MNM too [ABSTRACT FROM AUTHOR]

The processes responsible for the acceleration of solar energetic particles (SEPs) are still not well understood, including whether SEP electrons and protons are accelerated by common or separate processes. Using a numerical particle transport model that includes both pitch-angle and perpendicular spatial diffusion, we simulate, among other quantities, the onset delay for MeV electrons and protons and compare the results to observations of SEPs from widely separated spacecraft. Such observations have previously been interpreted, in a simple scenario assuming no perpendicular diffusion, as evidence for different electron and proton sources. We show that, by assuming a common particle source together with perpendicular diffusion, we are able to simultaneously reproduce the onset delays for both electrons and protons. We argue that this points toward a common accelerator for these particles. Moreover, a relatively broad particle source is required in the model to correctly describe the observations. This is suggestive of diffusive shock acceleration occurring at large shock structures playing a significant role in the acceleration of these SEPs. [ABSTRACT FROM AUTHOR]

Both the recent 2009 and 2020 solar minima were classified as unusually quiet and characterized with unusually high galactic cosmic-ray (GCR) levels. However, unlike the trends from previous decades, in which anomalous cosmic-ray (ACR) and GCR levels strongly agreed, the ACR intensities did not reach such high, record-setting levels. This discrepancy between the behavior of GCRs and ACRs is investigated in this work by simulating the acceleration and transport of GCR and ACR oxygen under different transport conditions. After using recent observations to constrain any remaining free parameters present in the model, we show that less turbulent conditions are characterized by higher GCR fluxes and lower ACR fluxes, due to less efficient ACR acceleration at the solar wind termination shock. We offer this as an explanation for the ACR/GCR discrepancy observed during 2009 and 2020, when compared to previous solar cycles. [ABSTRACT FROM AUTHOR]

The Integrated Science Investigation of the Sun instrument suite onboard NASA’s Parker Solar Probe mission continues to measure solar energetic particles and cosmic rays closer to the Sun than ever before. Here, we present the first observations of cosmic rays into 0.1 au (21.5 solar radii), focusing specifically on oxygen from ∼2018.7 to ∼2021.2. Our energy spectra reveal an anomalous cosmic-ray-dominated profile that is comparable to that at 1 au, across multiple solar cycle minima. The galactic cosmic-ray-dominated component is similar to that of the previous solar minimum (Solar Cycle 24/25 compared to 23/24) but elevated compared to the past (Solar Cycle 20/21). The findings are generally consistent with the current trend of unusually weak solar modulation that originated during the previous solar minimum and continues today. We also find a strong radial intensity gradient: 49.4 ± 8.0% auâˆ'1 from 0.1 to 0.94 au, for energies of 6.9â€"27 MeV nucâˆ'1. This value agrees with that measured by Helios nearly 45 yr ago from 0.3 to 1.0 au (48% ± 12% auâˆ'1; 9â€"29 MeV nucâˆ'1) and is larger than predicted by models. The large anomalous cosmic-ray gradients observed close to the Sun by the Parker Solar Probe Integrated Science Investigation of the Sun instrument suite found here suggest that intermediate-scale variations in the magnetic field’s structure strongly influence cosmic-ray drifts, well inside 1 au. [ABSTRACT FROM AUTHOR]

The Earth‐Sun Lagrangian point 4 is a meta‐stable location at 1 AU from the Sun, 60° ahead of Earth's orbit. It has an uninterrupted view of the solar photosphere centered on W60, the Earth's nominal magnetic field connection to the Sun. Such a mission on its own would serve as a solar remote sensing observatory that would oversee the entire solar radiation hemisphere with significant relevance for protecting Moon and Mars explorers from radiation exposure. In combination with appropriately planned observatories at L1 and L5, the three spacecraft would provide 300° longitude coverage of photospheric magnetic field structure, and allow continuous viewing of both solar poles, with >3.6° elevation. Ideally, the L4 and L5 missions would orbit the Sun with a 7.2° inclination out of the heliographic equator, 14.5° out of the ecliptic plane. We discuss the impact of extending solar magnetic field observations in both longitude and latitude to improve global solar wind modeling and, with the development of local helioseismology, the potential for long‐term solar activity forecasting. Such a mission would provide a unique opportunity for interplanetary and interstellar dust science. It would significantly add to reliability of operational observations on fast coronal mass ejections directed at Earth and for human Mars explorers on their round‐trip journey. The L4 mission concept is technically feasible, and is scientifically compelling. Plain Language Summary: This work describes the advantages of placing a spacecraft at a point 60° ahead of Earth in its orbit, which offers advantages for viewing areas on the surface of the Sun that hold critical clues about solar ionizing radiation that may affect astronauts on/at the moon or on the way to and from Mars. We describe that a combination of missions ahead and behind the Earth in its orbit would provide additional benefits, even more so if injected in an orbital plane that is tilted by ∼14°. Solar remote sensing observations from these platforms would significantly improve models of the magnetic field and solar wind of the Sun and in the inner solar system, by covering more solar surface area in longitude, but also of the polar regions. This would help us better understand when solar eruptions affect the Earth's magnetosphere. Other benefits, including long‐term advance forecasting of solar activity and the understanding of dust populations in the near‐Sun environment are also discussed. An analysis of launch capabilities shows that such a mission concept, even launching both suggested missions together, is feasible. Key Points: First thorough analysis of advantages of Earth‐Sun L4 location as observation platform, and combination of L4/L5 at moderate inclinationThe L4 view of solar radiation hemisphere is ideal for forecasting/warning Earth‐Moon system and Mars journey of solar energetic particlesCombination of L4/L5 observations would boost inner‐heliosphere solar wind modeling and validation, and long‐term solar activity forecasting [ABSTRACT FROM AUTHOR]

NASA's Parker Solar Probe mission continues to travel closer to the Sun than any prior human-made object, with an expected closest approach of <10 solar radii (<0.046 au) by 2024. On board, the Integrated Science Investigation of the Sun instrument suite makes unprecedented in situ measurements of energetic particles in the near-Sun environment. The current low level of solar activity offers a prime opportunity to measure cosmic rays closer to the Sun than ever before. We present the first observations of anomalous cosmic rays in to 36 solar radii (0.166 au), focusing specifically on helium. Our results indicate a strong radial intensity gradient of ∼25 ± 5%/au over energies of ∼4 to ∼45 MeV/nuc. These values are larger than prior observations, further out in the heliosphere, and come at a unique time in our understanding and modeling of particle transport and acceleration, particularly as both Voyagers have crossed the heliopause and IBEX has accumulated a full solar cycle of observations. Thus, continued measurements of cosmic rays by Parker Solar Probe will play a critical role in linking past observations with our present knowledge and significantly advancing our understanding of cosmic ray transport in the heliosphere. [ABSTRACT FROM AUTHOR]

Context. Jovian electrons serve an important role in test-particle distribution in the inner heliosphere. They have been used extensively in the past to study the (diffusive) transport of cosmic rays in the inner heliosphere. With new limits on the Jovian source function, that is, the particle intensity just outside the Jovian magnetosphere, and a new set of in-situ observations at 1 AU for cases of both good and poor magnetic connection between the source and observer, we revisit some of these earlier simulations. Aims. We aim to find the optimal numerical set-up that can be used to simulate the propagation of 6 MeV Jovian electrons in the inner heliosphere. Using such a setup, we further aim to study the residence (propagation) times of these particles for different levels of magnetic connection between Jupiter and an observer at Earth (1 AU). Methods. Using an advanced Jovian electron propagation model based on the stochastic differential equation approach, we calculated the Jovian electron intensity for different model parameters. A comparison with observations leads to an optimal numerical setup, which was then used to calculate the so-called residence (propagation) times of these particles. Results. Through a comparison with in-situ observations, we were able to derive transport parameters that are appropriate for the study of the propagation of 6 MeV Jovian electrons in the inner heliosphere. Moreover, using these values, we show that the method of calculating the residence time applied in the existing literature is not suited to being interpreted as the propagation time of physical particles. This is due to an incorrect weighting of the probability distribution. We applied a new method, where the results from each pseudo-particle are weighted by its resulting phase-space density (i.e. the number of physical particles that it represents). We thereby obtained more reliable estimates for the propagation time. [ABSTRACT FROM AUTHOR]

We address the effect of particle scattering on the energy spectra of solar energetic electron events using (i) an observational and (ii) a modeling approach. (i) We statistically study observations of the STEREO spacecraft, using directional electron measurements made with the Solar Electron and Proton Telescope in the range of 45–425 keV. We compare the energy spectra of the anti-Sunward propagating beam with that of the backward-scattered population and find that, on average, the backward-scattered population shows a harder spectrum with the effect being stronger at higher energies. (ii) We use a numerical solar energetic particle (SEP) transport model to simulate the effect of particle scattering (both in terms of pitch angle and perpendicular to the mean field) on the spectrum. We find that pitch-angle scattering can lead to spectral changes at higher energies (E > 100 keV) and further away from the Sun (r > 1 au), which are also often observed. At lower energies, and closer to the Sun, the effect of pitch-angle scattering is much more reduced, so that the simulated energy spectra still resemble the injected power-law functions. When examining pitch-angle-dependent spectra, we find, in agreement with the observational results, that the spectra of the backward-propagating electrons are harder than that of the forward (from the Sun) propagating population. We conclude that Solar Orbiter and Parker Solar Probe will be able to observe the unmodulated omnidirectional SEP electron spectrum close to the Sun at higher energies, giving a direct indication of the accelerated spectrum. [ABSTRACT FROM AUTHOR]

Context. Since the Pioneer 10 flyby of Jupiter it has become well known that electrons of Jovian origin dominate the lower MeV range of charged energetic particles in the inner heliosphere. Aims. Because the Jovian source can be treated as point-like in numerical models, many attempts to investigate charged particle transport in the inner heliosphere have utilized Jovian electrons as test particles. The reliability of the derived parameters for convective and diffusive transport processes are therefore highly dependent on an accurate estimation of the Jovian source spectrum. In this study we aim to provide such an estimation . Methods. In this study we have proposed a new electron source spectrum, specified at the boundary of the Jovian magnetosphere, fitted to flyby measurements by Pioneer 10 and Ulysses, with a spectral shape also in agreement with measurements at Earth's orbit by Ulysses, Voyager 1, ISEE and SOHO. Results. The proposed spectrum is consistent with all previous theoretical suggestions, but deviates considerably in the lower MeV range which was inaccessible to those studies. [ABSTRACT FROM AUTHOR]

We study the temporal intensity profile, or pulse shape, of cosmic ray ground-level enhancements (GLEs) by calculating the rise (τr) and decay (τd) times for a small subset of all available events. Although these quantities show very large inter-event variability, a linear dependence of τd ≈ 3.5τr is found. We interpret these observational findings in terms of an interplanetary transport model, thereby including the effects of scattering (in pitch-angle) as these particles propagate from (near) the Sun to Earth. It is shown that such a model can account for the observed trends in the pulse shape, illustrating that interplanetary transport must be taken into account when studying GLE events, especially their temporal profiles. Furthermore, depending on the model parameters, the pulse shape of GLEs may be determined entirely by interplanetary scattering, obscuring all information regarding the initial acceleration process, and hence making a classification between impulsive and gradual events, as is traditionally done, superfluous. [ABSTRACT FROM AUTHOR]

Permutation entropy analysis is a relatively recent addition to the palette of techniques used to study spacecraft observations of heliospheric magnetic field fluctuations at Earth, allowing one to characterize the underlying processes driving the observed fluctuations. This study investigates the effects of data averaging, data gaps, and underlying periodicities on the results of such an analysis, utilizing synthetic data sets and thereby developing efficient treatments for each of these effects. Furthermore, WIND spacecraft observations are employed to validate the results of an earlier permutation entropy analysis by Weck et al. (2015, https://doi.org/10.1103/PhysRevE.91.023101), confirming the results of that study and showing how dat averaging effects can significantly affect the results so acquired. Lastly, as a novel application of this technique, Advanced Composition Explorer spacecraft data taken from 1998 to 2008 are analyzed to investigate whether the permutation entropy so calculated displays a solar cycle dependence. It is shown that although solar cycle dependencies have been reported for observed turbulence quantities such as the magnetic variance, there is no significant dependence discernible in the permutation entropy, and therefore in the underlying processes driving the turbulence. Key Points: Permutation entropy analysis can provide useful insights when analyzing spacecraft observations of magnetic turbulence in the solar windThis method is thoroughly characterized here, considering the effects (among others) of data gaps and averagingWe consider solar cycle effects on the permutation entropy calculated from data and find no significant solar cycle dependence [ABSTRACT FROM AUTHOR]

The spatial diffusion of cosmic rays in turbulent magnetic fields can, in the most general case, be fully anisotropic, i.e., one has to distinguish three diffusion axes in a local, field-aligned frame. We reexamine the transformation for the diffusion tensor from this local to a global frame, in which the Parker transport equation for energetic particles is usually formulated and solved. Particularly, we generalize the transformation formulae to allow for an explicit choice of two principal local perpendicular diffusion axes. This generalization includes the "traditional" diffusion tensor in the special case of isotropic perpendicular diffusion. For the local frame, we describe the motivation for the choice of the Frenet--Serret trihedron, which is related to the intrinsic magnetic field geometry. We directly compare the old and the new tensor elements for two heliospheric magnetic field configurations, namely the hybrid Fisk and Parker fields. Subsequently, we examine the significance of the different formulations for the diffusion tensor in a standard three-dimensional model for the modulation of galactic protons. For this, we utilize a numerical code to evaluate a system of stochastic differential equations equivalent to the Parker transport equation and present the resulting modulated spectra. The computed differential fluxes based on the new tensor formulation deviate from those obtained with the "traditional" one (only valid for isotropic perpendicular diffusion) by up to 60% for energies below a few hundred MeV depending on heliocentric distance. [ABSTRACT FROM AUTHOR]

It is generally accepted that the solar wind is significantly heated beyond ∼10 AU by the turbulent decay of pickup ion generated Alfvénic fluctuations. Here, we present a detailed and general calculation of the pickup ion ionization frequencies, and we evaluate these quantities within the solar wind termination shock along the stagnation line. For this supersonic solar wind region, inside of the solar wind termination shock, our results compare well with earlier estimates of these frequencies. When, in the future, turbulence transport models are extended into the heliosheath, the methodology outlined in this paper can be used to calculate ionization frequencies in this hot and dense plasma region where the resulting calculations become more complex. [ABSTRACT FROM AUTHOR]

We present a newly developed numerical modulation model to study the transport of galactic and Jovian electrons in the heliosphere. The model employs stochastic differential equations (SDEs) to solve the corresponding transport equation in five dimensions (time, energy, and three spatial dimensions) which is difficult to accomplish with the numerical schemes used in finite difference models. Modeled energy spectra for galactic electrons are compared for the two drift cycles to observations at Earth. Energy spectra and radial intensity profiles of galactic and Jovian electrons are compared successfully to results from previous studies. In line with general drift considerations, it is found that most 100 MeV electrons observed at Earth enter the heliosphere near the equatorial regions in the A > 0 cycle, while they enter mainly over the polar regions in the A < 0 cycle. Our results indicate that 100 MeV electrons observed at Earth originate at the heliopause with ~600 MeV undergoing adiabatic cooling during their transport to Earth. The mean propagation time of these particles varies between ~180 and 300 days, depending on the drift cycle. For 10 MeV Jovian electrons observed at Earth, a mean propagation time of ~40 days is obtained. During this time, the azimuthal position of the Jovian magnetosphere varies by ~1°. At a 50 AU observational point, the mean propagation time of these electrons increases to ~370 days with an azimuthal position change of Jupiter of ~20°. The SDE approach is very effective in calculating these propagation times. [ABSTRACT FROM AUTHOR]

Two of the paradigms in modeling the transport of galactic cosmic rays are that the modulation boundary is the heliopause and that the local interstellar spectra are identical to the galactic cosmic ray spectra. Here we demonstrate that the proton spectrum is already modulated due to an altered interstellar diffusion in the outer heliosheath as a consequence of the heliospheric "obstacle" in the interstellar flow. The main modulation effect however is adiabatic energy losses during a "confinement time" of cosmic rays inside the heliosphere. [ABSTRACT FROM AUTHOR]

In this paper, we demonstrate the applicability of the data‐driven solar energetic particle (SEP) model, SOlar‐wind with FIeld‐lines and Energetic‐particles (SOFIE), to simulate the acceleration and transport processes of SEPs and make forecast of the energetic proton flux at energies ≥10 MeV that will be observed near 1 AU. The SOFIE model is built upon the Space Weather Modeling Framework developed at the University of Michigan. In SOFIE, the background solar wind plasma in the solar corona and interplanetary space is calculated by the Stream‐Aligned Aflvén Wave Solar‐atmosphere Model(‐Realtime) driven by the near‐real‐time hourly updated Global Oscillation Network Group solar magnetograms. In the background solar wind, coronal mass ejections (CMEs) are launched by placing an force‐imbalanced magnetic flux rope on top of the parent active region, using the Eruptive Event Generator using Gibson‐Low model. The acceleration and transport processes are modeled by the Multiple‐Field‐Line Advection Model for Particle Acceleration. In this work, nine SEP events (Solar Heliospheric and INterplanetary Environment challenge/campaign events) are modeled. The three modules in SOFIE are validated and evaluated by comparing with observations, including the steady‐state background solar wind properties, the white‐light image of the CMEs, and the flux of solar energetic protons, at energies of ≥10 MeV. Plain Language Summary: In this paper, we describe a physics‐based solar energetic particle (SEP) model, called Solar‐wind with FIeld‐lines and Energetic‐particles (SOFIE). This model is designed to simulate the acceleration and transport processes of SEPs in the solar atmosphere and interplanetary space. SOFIE is built on the Space Weather Modeling Framework developed at the University of Michigan. There are three modules in the SOFIE model, the background solar wind module, the coronal mass ejection (CME) initiation and propagation module, and the particle acceleration and transport module. The background solar wind plasma in the solar corona and interplanetary space is modeled by the Stream‐Aligned Aflvén Wave Solar‐atmosphere Model(‐Realtime) driven by the near‐real‐time hourly updated Global Oscillation Network Group solar magnetograms. In the background solar wind, the CMEs are launched by placing an force‐unbalanced magnetic flux rope on top of the active region, using the Eruptive Event Generator using Gibson‐Low configuration. The acceleration and transport processes are then modeled by the Multiple‐Field‐Line Advection Model for Particle Acceleration. Using SOFIE, we modeled nine historical SEP events. The performance of the model and its capability in making space radiation prediction is discussed. Key Points: The >10 MeV energetic protons can be predicted using the physics‐based model SOlar‐wind with FIeld‐lines and Energetic‐particles (SOFIE)The background of the acceleration and transport processes of energetic protons are resolved using data driven magnetohydrodynamic modelThe default and free parameters of the SOFIE model are evaluated [ABSTRACT FROM AUTHOR]

This paper reviews recent publications that describe mathematical models with stochastic differential equations (SDEs) and applications in various fields. The purpose of this paper is to briefly describe Rosenbrock-type methods for approximate solution of SDEs. It shows how the performance of the numerical methods can be improved and the accuracy of calculations can be increased without increasing the implementation complexity too much. The paper also proposes a new Rosenbrock-type method for SDEs with multiplicative non-commutative noise. Its testing is carried out by modeling rotational diffusion. [ABSTRACT FROM AUTHOR]

Ongoing observing projects like the James Webb Space Telescope and future missions offer the chance to characterize Earth-like exoplanetary atmospheres. Thereby, M dwarfs are preferred targets for transit observations, for example, due to their favorable planet–star contrast ratio. However, the radiation and particle environment of these cool stars could be far more extreme than what we know from the Sun. Thus, knowing the stellar radiation and particle environment and its possible influence on detectable biosignatures—in particular, signs of life like ozone and methane—is crucial to understanding upcoming transit spectra. In this study, with the help of our unique model suite INCREASE, we investigate the impact of a strong stellar energetic particle event on the atmospheric ionization, neutral and ion chemistry, and atmospheric biosignatures of TRAPPIST-1e. Therefore, transit spectra for six scenarios are simulated. We find that a Carrington-like event drastically increases atmospheric ionization and induces substantial changes in ion chemistry and spectral transmission features: all scenarios show high event-induced amounts of nitrogen dioxide (i.e., at 6.2 μ m), a reduction of the atmospheric transit depth in all water bands (i.e., at 5.5–7.0 μ m), a decrease of the methane bands (i.e., at 3.0–3.5 μ m), and depletion of ozone (i.e., at ∼9.6 μ m). Therefore, it is essential to include high-energy particle effects to correctly assign biosignature signals from, e.g., ozone and methane. We further show that the nitric acid feature at 11.0–12.0 μ m, discussed as a proxy for stellar particle contamination, is absent in wet-dead atmospheres. [ABSTRACT FROM AUTHOR]

In this work, we perform a statistical study of magnetic field fluctuations in the solar wind at 1 au using permutation entropy and complexity analysis and the investigation of the temporal variations of the Hurst exponents. Slow and fast wind, magnetic clouds, interplanetary coronal mass ejection (ICME)-driven sheath regions, and slow–fast stream interaction regions (SIRs) have been investigated separately. Our key finding is that there are significant differences in permutation entropy and complexity values between the solar wind types at larger timescales and little difference at small timescales. Differences become more distinct with increasing timescales, suggesting that smaller-scale turbulent features are more universal. At larger timescales, the analysis method can be used to identify localised spatial structures. We found that, except in magnetic clouds, fluctuations are largely anti-persistent and that the Hurst exponents, in particular in compressive structures (sheaths and SIRs), exhibit a clear locality. Our results shows that, in all cases apart from magnetic clouds at the largest scales, solar wind fluctuations are stochastic, with the fast wind having the highest entropies and low complexities. Magnetic clouds, in turn, exhibit the lowest entropy and highest complexity, consistent with them being coherent structures in which the magnetic field components vary in an ordered manner. SIRs, slow wind and ICME sheaths are intermediate in relation to magnetic clouds and fast wind, reflecting the increasingly ordered structure. Our results also indicate that permutation entropy–complexity analysis is a useful tool for characterising the solar wind and investigating the nature of its fluctuations. [ABSTRACT FROM AUTHOR]

In this work, a model for calculating the galactic cosmic rays (GCRs) radiation dose rate is developed. The model is based on a GCR modulation model, which is established by Shen and Qin, and the fluence‐dose conversion coefficients (FDCCs) published by the International Commission on Radiological Protection (ICRP). With the model, the radiation absorbed dose rate of GCRs near the lunar surface over long time periods is calculated and compared with the observation data from the Cosmic Ray Telescope for the Effects of Radiation and the Lunar Lander Neutron and Dosimetry. First, the energy spectrum of GCRs at 1 AU in the ecliptic, where the lunar orbit is located, is computed using the GCR modulation model. Then, using the FDCCs of ICRP 123, the absorbed dose rates of 15 human organs/tissues at the lunar orbit position are calculated to represent the general absorbed dose rate of the body (in water). Furthermore, considering the albedo radiation (excluding neutrons) and using the water‐silicon conversion coefficients, the total absorbed dose rates of GCRs near the lunar surface (in silicon) are calculated, it is shown that our modeling results generally agree with the observations from spacecraft. This work is useful for future manned space exploration to the Moon or other celestial bodies in the solar system. Plain Language Summary: The radiation absorbed dose rate is a fundamental quantity for evaluating the space radiation environment. In our study, we develop a time‐varying and spatial‐varying model to calculate the radiation dose rates of the galactic cosmic rays (GCRs). With the model, we calculate the radiation absorbed dose rate of GCRs near the lunar surface (excluding neutrons) over long time periods and compare it with the observation data from the Cosmic Ray Telescope for the Effects of Radiation and the Lunar Lander Neutron and Dosimetry. The results show that our modeling results generally agree with the observations from spacecraft. This research is important for evaluating the space radiation environment for future human space exploration to the Moon or other planets similar to the Moon in our solar system. Key Points: We develop a time‐varying and spatial‐varying model to calculate the radiation dose rates of cosmic raysReproduce the absorbed dose rate of galactic cosmic rays near the lunar surface (2010–2022) and compare with the observation of Cosmic Ray Telescope for the Effects of Radiation and Lunar Lander Neutron and Dosimetry [ABSTRACT FROM AUTHOR]

Solar flare electron acceleration is an efficient process, but its properties (mechanism, location) are not well constrained. Via hard X-ray (HXR) emission, we routinely observe energetic electrons at the Sun, and sometimes we detect energetic electrons in interplanetary space. We examine if the plasma properties of an acceleration region (size, temperature, density) can be constrained from in situ observations, helping to locate the acceleration region in the corona, and infer the relationship between electrons observed in situ and at the Sun. We model the transport of energetic electrons, accounting for collisional and non-collisional effects, from the corona into the heliosphere (to 1.0 au). In the corona, electrons are transported through a hot, over-dense region. We test if the properties of this region can be extracted from electron spectra (fluence and peak flux) at different heliospheric locations. We find that cold, dense coronal regions significantly reduce the energy at which we see the peak flux and fluence for distributions measured out to 1.0 au, the degree of which correlates with the temperature and density of plasma in the region. Where instrument energy resolution is insufficient to differentiate the corresponding peak values, the spectral ratio of [7–10) to [4–7) keV can be more readily identified and demonstrates the same relationship. If flare electrons detected in situ are produced in, and/or transported through, hot, over-dense regions close to HXR-emitting electrons, then this plasma signature should be present in their lower-energy spectra (1–20 keV), observable at varying heliospheric distances with missions such as Solar Orbiter. [ABSTRACT FROM AUTHOR]

In this work, we perform a statistical study of magnetic field fluctuations in the solar wind at 1 au using permutation entropy and complexity analysis. Slow and fast wind, magnetic clouds, interplanetary coronal mass ejection (ICME)-driven sheath regions and slow-fast stream interaction regions (SIRs) have been investigated separately. Our key finding is that there are significant differences in permutation entropy and complexity values between the solar wind types at larger timescales and little difference at small timescales. Differences become more distinct with increasing timescale, suggesting that smaller-scale turbulent features are more universal. At larger timescales, the analysis method can be used to identify localized spatial structures. We found that fluctuation properties in compressive structures (sheaths and SIRs) exhibit a clear locality. Our results shows that, in all cases apart from magnetic clouds at largest scales, solar wind fluctuations are stochastic with the fast wind having the highest entropies and low complexities. Magnetic clouds in turn exhibit the lowest entropy and highest complexity, consistent with them being coherent structures in which the magnetic field components vary in an ordered manner. SIRs, slow wind and ICME sheaths are intermediate to magnetic clouds and fast wind, reflecting the increasingly ordered structure. Our results also indicate that permutation entropy – complexity analysis is a useful tool for characterizing the solar wind and investigating the nature of its fluctuations. [ABSTRACT FROM AUTHOR]

A common task in oceanography is to model the vertical movement of particles such as microplastics, nanoparticles, mineral particles, gas bubbles, oil droplets, fish eggs, plankton, or algae. In some cases, the distribution of the vertical rise or settling velocities of the particles in question can span a wide range, covering several orders of magnitude, often due to a broad particle size distribution or differences in density. This requires numerical methods that are able to adequately resolve a wide and possibly multi-modal velocity distribution. Lagrangian particle methods are commonly used for these applications. A strength of such methods is that each particle can have its own rise or settling speed, which makes it easy to achieve a good representation of a continuous distribution of speeds. An alternative approach is to use Eulerian methods, where the partial differential equations describing the transport problem are solved directly with numerical methods. In Eulerian methods, different rise or settling speeds must be represented as discrete classes, and in practice, only a limited number of classes can be included. Here, we consider three different examples of applications for a water column model: positively buoyant fish eggs, a mixture of positively and negatively buoyant microplastics, and positively buoyant oil droplets being entrained by waves. For each of the three cases, we formulate a model for the vertical transport based on the advection–diffusion equation with suitable boundary conditions and, in one case, a reaction term. We give a detailed description of an Eulerian and a Lagrangian implementation of these models, and we demonstrate that they give equivalent results for selected example cases. We also pay special attention to the convergence of the model results with an increasing number of classes in the Eulerian scheme and with the number of particles in the Lagrangian scheme. For the Lagrangian scheme, we see the 1/Np convergence, as expected for a Monte Carlo method, while for the Eulerian implementation, we see a second-order (1/Nk2) convergence with the number of classes. [ABSTRACT FROM AUTHOR]

The multitude of recent multi-point spacecraft observations of solar energetic particle (SEP) events has made it possible to study the longitudinal distribution of SEPs in great detail. SEPs, even those accelerated during impulsive events, show a much wider than expected longitudinal extent, bringing into question the processes responsible for their transport perpendicular to the local magnetic field. In this paper, we examine some aspects of perpendicular transport by including perpendicular diffusion in a numerical SEP transport model that simulates the propagation of impulsively accelerated SEP electrons in the ecliptic plane. We find that (1) the pitch-angle dependence of the perpendicular diffusion coefficient is an important, and currently mainly overlooked, transport parameter. (2) SEP intensities are generally asymmetric in longitude, being enhanced toward the west of the optimal magnetic connection to the acceleration region. (3) The maximum SEP intensity may also be shifted (parameter dependently) away from the longitude of best magnetic connectivity at 1 AU. We also calculate the maximum intensity, the time of maximum intensity, the onset time, and the maximum anisotropy as a function of longitude at Earth's orbit and compare the results, in a qualitative fashion, to recent spacecraft observations. [ABSTRACT FROM AUTHOR]

We examine the East‐West asymmetry of the peak intensity in energetic storm particle (ESP) events using the improved Particle Acceleration and Transport in the Heliosphere model. We find that injection efficiency peaks east of the nose of coronal mass ejection shock where the shock exhibits a quasi‐parallel geometry. We show that the peak intensity at the eastern flank is generally larger than that at the western flank and it positively correlates with the injection efficiency. We also examine this asymmetry for heavy ions, which depends sensitively on the ion energy. Comparison between the modeling results with the measurements of ESP events at 1 au shows a reasonable agreement. We suggest that the injection efficiency can be a primary factor leading to the East‐West asymmetry of the peak intensity in ESP events. Additionally, the charge‐to‐mass (Q/A) dependence of the maximum particle energy affects this asymmetry for heavy ions. Plain Language Summary: Energetic storm particle (ESP) events occur when coronal mass ejection‐driven shocks pass a spacecraft, leading to abrupt increases in particle intensity and posing severe radiation hazards to astronauts and spacecraft. These enhancements are usually interpreted as the result of a local particle acceleration process. Therefore, in‐situ measurements of ESP events provide a great opportunity to investigate the shock acceleration mechanism. Recent observations from multiple spacecraft show an East‐West asymmetry in the peak intensity of ESP events, with significantly different intensities observed on the eastern and the western shock flank. In this study, we use the 2D improved Particle Acceleration and Transport in the Heliosphere model to investigate the East‐West asymmetry of particle intensity in ESP events. We find that the injection efficiency, which depends on the shock geometry, is the key parameter responsible for this East‐West asymmetry. Key Points: East‐West Asymmetry of particle intensity is often found in energetic storm particle events. We propose continuous shock acceleration can lead to this asymmetryContinuous acceleration depends on shock geometry and through this, the injection efficiency plays a central role for this asymmetryWe simulate this asymmetry using the improved Particle Acceleration and Transport in the Heliosphere model and compared our simulation results with observations [ABSTRACT FROM AUTHOR]

Interplanetary shocks are large-scale heliospheric structures often caused by eruptive phenomena at the Sun, and represent one of the main sources of energetic particles. Several interplanetary (IP) shock crossings by spacecraft at 1 au have revealed enhanced energetic-ion fluxes that extend far upstream of the shock. Surprisingly, in some shock events ion fluxes with energies between 100 keV and about 2 MeV acquire similar values (which we refer to as "overlapped" fluxes), corresponding to flat energy spectra in that range. In contrast, closer to the shock the fluxes are observed to depend on energy. In this work, we analyze three IP-shock-related energetic particle events observed by the Advanced Composition Explorer spacecraft where flat ion energy spectra were observed upstream of the shock. We interpret these observations via a velocity-filter mechanism for particles in a given energy range. In particular, ions with velocity parallel to the local magnetic field larger than the speed of the upstream plasma, in the reference frame of the shock, can easily propagate back upstream, while lower-energy ions tend to be confined to the shock front, thus reducing their fluxes far upstream and giving rise to flat energy spectra. The velocity-filter mechanism has been corroborated from observations of particle flux anisotropy by the Solid-State Telescope of Wind/3DP. [ABSTRACT FROM AUTHOR]

Particles measured in large gradual solar energetic particle events are believed to be predominantly accelerated at shocks driven by coronal mass ejections (CMEs). Ion charge state and composition analyses suggest that the origin of the seed particle population for the mechanisms of particle acceleration at CME‐driven shocks is not the bulk solar wind thermal material, but rather a suprathermal population present in the solar wind. This suprathermal population could result from remnant material accelerated in prior solar flares and/or preceding CME‐driven shocks. In this work, we examine the distribution of this suprathermal particle population in the inner heliosphere by combining a magnetohydrodynamic simulation of the solar wind and a Monte Carlo simulation of particle acceleration and transport. Assuming that the seed particles are uniformly distributed near the Sun by solar flares of various magnitudes, we study the longitudinal distribution of the seed population at multiple heliocentric distances. We consider a nonuniform background solar wind, consisting of fast and slow streams that lead to compression and rarefaction regions within the solar wind. Our simulations show that the seed population at a particular location (e.g., 1 au) is strongly modulated by the underlying solar wind configuration. Corotating interaction regions and merged interactions regions can strongly alter the energy spectra of the seed particle populations. In addition, cross‐field diffusion plays an important role in mitigating strong variations of the seed population in both space and energy. Plain Language Summary: Large solar energetic particle (SEP) events are a major concern of space weather. During these events, particles are accelerated to very high energies at shock waves driven by coronal mass ejections (CMEs). While the CMEs in these events are often similar in morphology and speed, the intensity of the accelerated particles can differ significantly from one event to another. One possible reason for these large variations may be attributed to the variability of the underlying seed population that gets injected into the acceleration mechanism occurring at the CME‐driven shock. To be efficiently accelerated at a CME‐driven shock, particles need an initial speed larger than the speed of the shock wave. For this reason, it is often assumed that the seed population originates from the suprathermal population, rather than the bulk solar wind. These suprathermal particles can be generated near the Sun by, for example, micro and nano flares. In this work, we use the three‐dimensional magnetohydrodynamic model EUHFORIA and the particle transport and acceleration model PARADISE to examine how solar wind structures affect the distribution of these suprathermal particles at different heliocentric distances. We find that the variation of the solar wind speed at the inner boundary can lead to a significant longitudinal variation of the suprathermal population in the inner heliosphere. Our study may offer an explanation for the variation of particle intensity in large SEP events. Key Points: Seed particle populations in large solar energetic particle (SEP) events may originate from flare remnantsWe examine the distribution of seed particles in the inner heliosphere by combining a magnetohydrodynamic (MHD) solar wind code and a particle transport codeWe obtain the longitudinal profile of the seed population at 1 au and show that the perpendicular diffusion coefficient is a key parameter [ABSTRACT FROM AUTHOR]

The equilibrium theory of island biogeography and its quantitative consideration of origination and extinction dynamics as they relate to island area and distance from source populations have evolved over time and enriched theory related to many disciplines in spatial ecology. Indeed, the island focus was catalytic to the emergence of landscape ecology and macroecology in the late 20th century. We integrate concepts and perspectives of island biogeography, landscape ecology, macroecology, and metacommunity ecology, and show how these disciplines have advanced the understanding of variation in abundance, biodiversity, and composition of bat communities. We leverage the well‐studied bat fauna of the islands in the Caribbean to illustrate the complex interplay of ecological, biogeographical, and evolutionary processes in molding local biodiversity and system‐wide structure. Thereafter, we highlight the role of habitat loss and fragmentation, which is increasing at an accelerating rate during the Anthropocene, on the structure of local bat communities and regional metacommunities across landscapes. Bat species richness increases with the amount of available habitat, often forming nested subsets along gradients of patch or island area. Similarly, the distance to and identity of sources of colonization influence the richness, composition, and metacommunity structure of islands and landscape networks. [ABSTRACT FROM AUTHOR]

Energetic electrons of Jovian origin have been observed for decades throughout the heliosphere, as far as 11 au, and as close as 0.5 au, from the Sun. The treatment of Jupiter as a continuously emitting point source of energetic electrons has made Jovian electrons a valuable tool in the study of energetic electron transport within the heliosphere. We present observations of Jovian electrons measured by the EPI-Hi instrument in the Integrated Science Investigation of the Sun instrument suite on Parker Solar Probe at distances within 0.5 au of the Sun. These are the closest measurements of Jovian electrons to the Sun, providing a new opportunity to study the propagation and transport of energetic electrons to the inner heliosphere. We also find periods of nominal connection between the spacecraft and Jupiter in which expected Jovian electron enhancements are absent. Several explanations for these absent events are explored, including stream interaction regions between Jupiter and Parker Solar Probe and the spacecraft lying on the opposite side of the heliospheric current sheet from Jupiter, both of which could impede the flow of the electrons. These observations provide an opportunity to gain a greater insight into electron transport through a previously unexplored region of the inner heliosphere. [ABSTRACT FROM AUTHOR]

We study anisotropic magnetohydrodynamic (MHD) turbulence in the slow solar wind measured by Parker Solar Probe (PSP) and Solar Orbiter (SolO) during its first orbit from the perspective of variance anisotropy and correlation anisotropy. We use the Belcher & Davis approach (M1) and a new method (M2) that decomposes a fluctuating vector into parallel and perpendicular fluctuating vectors. M1 and M2 calculate the transverse and parallel turbulence components relative to the mean magnetic field direction. The parallel turbulence component is regarded as compressible turbulence, and the transverse turbulence component as incompressible turbulence, which can be either Alfvénic or 2D. The transverse turbulence energy is calculated from M1 and M2, and the transverse correlation length from M2. We obtain the 2D and slab turbulence energy and the corresponding correlation lengths from those transverse turbulence components that satisfy an angle between the mean solar wind flow speed and mean magnetic field θ UB of either (i) 65° < θ UB < 115° or (ii) 0° < θ UB < 25° (155° < θ UB < 180°), respectively. We find that the 2D turbulence component is not typically observed by PSP near perihelion, but the 2D component dominates turbulence in the inner heliosphere. We compare the detailed theoretical results of a nearly incompressible MHD turbulence transport model with the observed results of PSP and SolO measurements, finding good agreement between them. [ABSTRACT FROM AUTHOR]

The permutation entropy analysis technique is here employed to study Voyager 2 observations of heliospheric field fluctuations from ∼6 AU to ∼34 AU for the first time. The properties of the technique, especially regarding the classification of a given process as either chaotic or stochastic, are illustrated in some detail and it is indicated how the technique is best applied and interpreted to the data set in question. Proceeding from this, conclusions are made regarding the stochasticity of the processes driving turbulence as a function of radial distance from the Sun, which is here found to increase with distance toward a value theoretically associated with Brownian motion, exceeding that value depending on the data bin size considered. At larger radial distances, however, it is argued that this trend may be influenced by a strongly declining signal‐to‐noise ratio. Intriguingly, this technique also serves to identify intervals of anomalously moderate to low stochasticity, which are briefly investigated here. Plain Language Summary: Analyzing spacecraft data measuring the Sun's magnetic field using the permutation entropy analysis technique allows on to ascertain whether the processes generating fluctuations in the magnetic field are chaotic (more deterministic) or stochastic (more random). This study presents for the first time the results of such an analysis of Voyager spacecraft data, and shows that fluctuations in the Sun's magnetic field, out to a distance of approximately 34 AU (near Pluto's orbit), appear to be primarily stochastic in nature. However, we identify a fair number of intervals with low permutation entropy, that could correspond to interesting phenomena that require further analysis. This raises the intriguing possibility that the permutation entropy analysis technique may serve as a useful tool in identifying intervals of interest to scientists in large data sets. Key Points: Permutation entropy analysis is here, for the first time, applied to Voyager dataPermutation entropy is found to imply that the driving processes for heliospheric magnetic field (HMF) turbulence are predominantly stochasticPermutation entropy is found to increase with heliocentric radial distance, although this effect may be influenced by instrumental uncertainties at the largest radial distances considered here [ABSTRACT FROM AUTHOR]

It has been noted that in large solar energetic particle (SEP) events, the peak intensities show an East‐West asymmetry with respect to the source flare locations. Using the 2D improved Particle Acceleration and Transport in the Heliosphere (iPATH) model, we investigate the origin of this longitudinal trend. We consider multiple cases with different solar wind speeds and eruption speeds of the coronal mass ejections (CMEs) and fit the longitudinal distributions of time‐averaged fluence by symmetric/asymmetric Gaussian functions with three time intervals of 8, 24 and 48 hr after the flare onset time respectively. The simulation results are compared with a statistical study of three‐spacecraft events. We suggest that the East‐West asymmetry of SEP fluence and peak intensity can be primarily caused the combined effect of an extended shock acceleration process and the evolution of magnetic field connection to the shock front. Our simulations show that the solar wind speed and the CME speed are important factors determining the East‐West fluence asymmetry. Plain Language Summary: Large solar energetic particle (SEP) events are quite common during the solar maximum period when the solar activity is high. In these events, particles can be accelerated to relatively high energies at shock waves driven by coronal mass ejections (CMEs) in large SEP events. These energetic particles are the leading concern of astronaut safety and are a central topic of space weather studies. The intensity and the maximum particle energy, as well as the spectral shape of energetic particles vary significantly from one event to another. In particular, an interesting feature of these events is the so‐called East‐West asymmetry, where the intensity of energetic particles are not symmetric with respect to the source flare location and the peak intensity is shifted to the west of the source location. Using the 2D improved Particle Acceleration and Transport in the Heliosphere model, we examine this East‐West asymmetry. Model results clearly show this asymmetry and suggest that its origin arises from the history of shock acceleration and magnetic connection. We also discuss the role of the background solar wind speed and the CME speed as key parameters organizing this asymmetry. Key Points: The time‐averaged fluence of solar energetic particles shows an East‐West asymmetry with respect to the source flare locationsUsing the improved Particle Acceleration and Transport in the Heliosphere model, we find the asymmetry is a result of the effects of shock acceleration history and the geometry of the magnetic fieldThe background solar wind speed and the coronal mass ejection speed are key factors affecting this asymmetry [ABSTRACT FROM AUTHOR]

Spectral hardening has been identified in solar flare hard X-ray observations for several decades and remains a puzzle. We examine spectral hardening under the diffusive shock acceleration mechanism using numerical simulations. The hardening is related to the finite width of the shock and is controlled by the shock PĂ©clet number. We implement two different types of Monte Carlo simulations. The first is based on the backward stochastic differential equation method, where the Parker transport equation is solved by casting it to a set of stochastic different equations, and by following the trajectories of individual quasiparticles. In the second approach, we follow real particles and particles are assumed to move freely between scatterings from magnetic turbulence in the plasma. The scattering is modeled as either large-angle hard-sphere elastic collision, or small-angle pitch-angle scattering. We show that the results from these two approaches agree well with each other and agree with analytical results. We also use a Pan-spectrum form to fit the resulting spectra. [ABSTRACT FROM AUTHOR]

Exoplanets are as diverse as they are fascinating. They vary from ultrahot Jupiter‐like low‐density planets to presumed gas‐ice‐rock mixture worlds such as GJ 1214b or worlds as LHS 1140b, which features twice the Earth's bulk density. Regarding the great diversity of exoplanetary atmospheres, much remains to be explored. For a few selected objects such as GJ1214b, Proxima Centauri b, and the TRAPPIST‐1 planets, the first observations of their atmospheres have already been achieved or are expected in the near future with the launch of the James Webb Space Telescope envisaged in October 2021. However, in order to interpret these observations, model studies of planetary atmospheres that account for various processes—such as atmospheric escape, outgassing, climate, photochemistry, as well as the physics of air showers and the transport of stellar energetic particles and galactic cosmic rays through the stellar astrospheres and planetary magnetic fields—are necessary. Here, we present our model suite INCREASE, a planned extension of the model suite discussed in Herbst, Grenfell, et al. (2019). [ABSTRACT FROM AUTHOR]

An ad hoc analytical calculation is presented to infer the duration of injection of 20 MeV protons in 21 selected western solar energetic particle (SEP) events. We convolve the solution of diffusion equation with a “triangle” source to model the time-intensity profiles over the onset and the peaking phase. The effects of “corotating” flux tubes and of solar wind convection are neglected. To accommodate these simplifications, only western events whose associated flares erupted between W15 and W90 are selected. The time-intensity profiles of these events are reconstructed from the timescales presented in Kahler (2005) and Kahler (2013) using the modified Weibull function. From the linear relation between the logarithm of the peak intensity and the logarithm of the fluence of 27â€"37 MeV protons presented in Kahler & Ling, we derive an optimal radial mean free path (λ mfp) of 0.08 au and adopt this value to fit all selected events. The inferred duration of injection for the selected events, which in general increases with the initial speed of the associated coronal mass ejection (CME) (V cme), is less than 1 hr for V cme < 1000 km sâˆ'1 and varies from a few to ∼10 hr for 1000 km sâˆ'1 < V cme < 2000 km sâˆ'1. We then estimate the distance that the associated CMEs have traveled over the duration of injection. Most CMEs in selected events have traveled to less than 60 solar radii by the time the majority of accelerated particles have been injected into the interplanetary space. [ABSTRACT FROM AUTHOR]

Novel insights into the behavior of the diffusion coefficients of charged particles in the inner heliosphere are of great importance to any study of the transport of these particles and are especially relevant with regard to the transport of low-energy electrons. The present study undertakes an exhaustive investigation into the diffusion parameters needed to reproduce low-energy electron intensities as observed at Earth, using a state-of-the-art 3D cosmic ray transport code. To this end, the transport of Jovian electrons is considered, as Jupiter represents the predominant source of these particles in the inner heliosphere, and because a careful comparison of model results with observations taken during periods of good and poor magnetic connectivity between Earth and Jupiter allows for conclusions to be drawn as to both parallel and perpendicular diffusion coefficients. This study then compares these results with the predictions made by various scattering theories. Best-fit parameters for parallel and perpendicular mean free paths at 1 au fall reasonably well within the span of observational values reported by previous studies, but best-fit radial and rigidity dependences vary widely. However, a large number of diffusion parameters lead to reasonable to-good fits to observations, and it is argued that considerable caution must be exercised when comparing theoretical results for diffusion coefficients with diffusion parameters calculated from particle transport studies. [ABSTRACT FROM AUTHOR]

Density irregularities are responsible for the scattering of radio waves in the solar wind and astrophysical plasmas. These irregularities significantly affect the inferred physical properties of radio sources, such as size, direction, and intensity. We present here a theory of angular broadening due to the scattering of radio waves by density irregularities that improves the existing formalism used to investigate radio wave scattering in the outer heliosphere and the very local interstellar medium. The model includes an inner scale and both latitudinal and radial dependencies for the density fluctuation spectra and propagation paths for the radiation both near and out of the ecliptic plane. Based on the pickup-ion-mediated solar wind model (PUI model) of Zank et al., we estimate the turbulence and solar wind quantities for the high-latitude fast solar wind. The predictions include the density variance, inner/dissipation scale, velocity correlation length, mean magnetic field, and proton temperature. The density turbulence amplitude is estimated in two ways. First, a simple scaling technique is used to extend the theoretical predictions of the PUI model for the high-latitude wind beyond the heliospheric termination shock. Second, the solar wind and turbulence quantities are calculated near the ecliptic plane using plasma and magnetometer data from the Voyager 2 spacecraft over the period 1977â€"2018. Based on the turbulence models and observations, we calculate the scattering angle of the radio sources in the high-latitude and near-ecliptic wind. Finally, we compare the numerical results with the analytic predictions from Cairns and Armstrong et al. and the observed source sizes. [ABSTRACT FROM AUTHOR]

It was recently shown that, owing to the turbulent nature of the solar wind, the interplanetary magnetic field lines can be well described by stochastic Parker spirals. These are realizations of Brownian diffusion on a sphere of increasing radius, superimposed on the angular drift due to the solar rotation. In this work, we present a model for the transport of solar energetic particles along stochastic Parker spirals in the inner heliosphere. The transport model is governed by a set of four stochastic differential equations for the heliographic position of the guiding centers and the cosine of the pitch angle between the velocity vector and the Parker field. The model accounts for the role played by the combination of pitch angle scattering and magnetic focusing in the interplanetary medium. The effects of the dynamical evolution of the turbulence are included in the model by taking the field line angular diffusivity to be a function of the radial distance from the Sun. The heliolongitudinal distribution of particles propagating along stochastic Parker spirals is given by the wrapped Gaussian distribution. This angular distribution can also well be represented by the von Mises distribution that interpolates between the Gaussian distribution at small angular spread and the uniform distribution at large distances from the acceleration region of energetic particles in the aftermath of a solar eruption. [ABSTRACT FROM AUTHOR]

Very local interstellar spectra (vLIS's) for protons and total Helium (He) were observed in situ by Voyager 1 below about 340 MeV/ since it had moved across the heliopause (HP). Together with high precision PAMELA and AMS observations at the Earth, we previously reported on new vLIS calculated from 1 MeV to 100 GeV for protons, electrons, total He, Oxygen, Carbon, and Boron. We now follow this up to report on the vLIS's for positrons and for the isotopes He-3, He-4, and Deuteron (H-2) by combining computations with the galactic propagation code, GALPROP, and our 3D modulation model for GCRs in the heliosphere as done previously. Similarly, we also have computed updates of the vLIS's for antiprotons and antideuteron. We assume that the modulation processes between the HP and the Earth for protons and other GCR nuclei are essentially similar, which is also the case for electrons and positrons, except for particle drifts of oppositely charged particles. The procedures followed to obtain these updates are summarized and a compilation of the mentioned vLIS's is presented. [ABSTRACT FROM AUTHOR]