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This work analyzes the appearance of wide-spread deka-MeV solar energetic proton (SEP) events, in particular the arrival of the first protons within ≈ 4.5 – 45 MeV measured at Earth–Sun L1, and their relationship with their relative solar source longitude. The definition of "wide-spread SEP event" for this study refers to events that are observed as a 25 MeV proton intensity increase at near 1 AU locations that are separated by at least 130∘ in solar longitude. Many of these events are seen at all three of the spacecraft, STEREO (Solar-Terrestrial Relations Observatory) A, STEREO B, and SOHO (Solar and Heliospheric Observatory), and may therefore extend far beyond 130∘ in longitude around the Sun. A large subset of these events have already been part of a study by Richardson et al. (Solar Phys., 289, 3059, 2014). The event source region identifications draw from this study; more recent events have also been added. Our focus is on answering two specific questions: (1) What is the maximum longitude over which SEP protons show energy dispersion, i.e., a clear sign of arrival of higher-energy protons before those of lower energy? (2) What implications can be drawn from the ensemble of events observed regarding either direct magnetic connectivity to shocks and/or cross-field transport from the site of the eruption in the onset phase of the event? [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]

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]

The recent 2009 solar-minimum period was characterized by a record-setting high Galactic cosmic-ray flux observed at Earth. This, along with the unexpected low heliospheric magnetic-field magnitude, caused this period to be characterized as unusual compared with previous minimum epochs. In this work, selected solar-activity proxies and corresponding cosmic-ray observations for the past five solar cycles are compared with each other, and we identify those that showed unusual behaviour during the 2009 solar-minimum modulation period. Using a state-of-the-art numerical-modulation model, the proton-intensity spectra for the past solar minima are reproduced to establish which of the transport processes might be considered the main cause of this unusually high cosmic-ray flux. It is found that diffusion was more prominent during 2009 so that drift effects on the modulation of cosmic rays in the heliosphere were less evident than during previous solar-polarity epochs. However, particle drifts still occurred and because of these drift effects, the proton spectrum is predicted to be even higher during the coming A>0 solar-minimum period. [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]

A modified Anderson–Newns (A–N) model for calculating the work function and the charge transfer of Cs-O-adsorbed graphene surface with the coverage of adsorbed particles is proposed. The calculation of the length of adsorption bond λ is optimized. The work function and the amount of charge transfer for different coverage of Cs-O molecules are calculated, and the calculated results variations are in reasonable agreement with the experimental data. As coverage θ increases, the amount of charge transfer Z decreases and the work function φ first decreases to a certain value and then increases slightly. When θ = 0.8, the work function φ reaches a minimum value of 0.7. [ABSTRACT FROM AUTHOR]

Voyager 1 and 2 observations could improve a model of the heliosphere that includes the supersonic solar wind and heliosheath as far as local interstellar space. This enables us to construct a simple model of the propagation of galactic cosmic-ray particles (GCR) in the heliosphere and its magnetic fields. Solutions of the cosmic-ray transport equation in an spherical force-field approximation (Gleeson and Urch in Astrophys. Space Sci. 25:387, 1973) are generalized, and then they are modified in a second-order approximation assuming a small GCR streaming (GCR anisotropy) as a smallness parameter. GCR reacceleration on shock waves is not considered in our model. This idealized approach still yields additional insight into the process of GCR distribution in the real heliosphere. The energy and spatial distribution of the GCR intensity is investigated in separate regions of the heliosphere. The GCR energy streaming is estimated, and the anisotropy in the GCR angular distribution is computed for particle kinetic energies from 100 MeV up to 10 GeV. [ABSTRACT FROM AUTHOR]

Global gradients for cosmic-ray (CR) protons in the heliosphere are computed with a comprehensive modulation model for the recent prolonged solar minimum of Cycle 23/24. Fortunately, the PAMELA ( Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics) and Ulysses/KET ( Kiel Electron Telescope) instruments simultaneously observed proton intensities for the period between July 2006 and June 2009. This provides a good opportunity to compare the basic features of the model with these observations, including observations from Voyager-1 in the outer heliosphere, beyond $50~\mbox{AU}$ . Radial and latitudinal gradients are calculated from measurements, with the latter possible because Ulysses changed its position significantly in the heliocentric meridional plane during this period. The modulation model is set up for the conditions that prevailed during this unusual solar-minimum period to gain insight into the role that particle drifts played in establishing the observed gradients for this period. Four year-end PAMELA proton spectra were reproduced with the model, from 2006 to 2009, followed by corresponding radial profiles that were computed along the Voyager-1 trajectory, and compared to available observations. It is found that the computed intensity levels are in agreement with solar-minimum observations from Voyager-1 at multiple energies. The model also reproduces the steep intensity increase observed when Voyager-1 crossed the heliopause region. Good agreement is found between computed and observed latitudinal gradients, so that we conclude that the model gives a most reasonable representation of modulation conditions from the Earth to the heliopause for the period from 2006 to 2009. As a characteristic feature of CR drifts, the most negative latitudinal gradient is computed for 2009, with a value of $-0.15~\%\,\mbox{degree}^{-1}$ around $600~\mbox{MV}$ . The maximum radial gradient in the inner heliosphere (as covered by Ulysses) also occurs in this range, with the highest value of $4.25~\%\,\mbox{AU}^{-1}$ in 2009. [ABSTRACT FROM AUTHOR]

With the cosmic ray observations made by the Voyager 1 spacecraft outside the dominant modulating influence of the heliosphere, the comparison of computed galactic spectra with experimental data at lower energies is finally possible. Spectra for specifically protons, helium and carbon nuclei, computed by galactic propagation models, can now be compared with observations at low energies from Voyager 1 and at high energies from the PAMELA space detector at Earth. We set out to reproduce the Voyager 1 observations in the energy range of 6 MeV/nuc to 60 MeV/nuc, and the PAMELA spectrum above 50 GeV/nuc, using the GALPROP code, similarly to our previous study for Voyager 1 electrons. By varying the galactic diffusion parameters in the GALPROP plain diffusion model, specifically the rigidity dependence of spatial diffusion, and then including reacceleration, we compute spectra simultaneously for galactic protons, helium and carbon. We present new local interstellar spectra, with expressions for the energy range of 3 MeV/nuc to 100 GeV/nuc, which should be of value for solar modulation modeling. [ABSTRACT FROM AUTHOR]

After a prolonged and deep solar minimum at the end of Cycle 23, the current Solar Cycle 24 is one of the lowest cycles. These two periods of deep minimum and mini-maximum are separated by a period of increasing solar activity. We study the cosmic-ray intensity variation in relation with the solar activity, heliospheric plasma and magnetic field parameters, including the heliospheric current sheet, during these three periods (phases) of different activity level and nature: (a) a deep minimum, (b) an increasing activity period, and (c) a mini-maximum. We use neutron monitor data from stations located around the globe to study the rigidity dependence on modulation during the two extremes, i.e., minimum and maximum. We also study the time lag between the cosmic-ray intensity and various solar and interplanetary parameters separately during the three activity phases. We also analyze the role of various parameters, including the current sheet tilt, in modulating the cosmic-ray intensity during the three different phases. Their relative importance and the implications of our results are also discussed. [ABSTRACT FROM AUTHOR]

By means of an analysis of data from eight neutron monitor (NM) stations with different geomagnetic cutoff rigidities, we found an unusual latitudinal effect observed in the cosmic-ray (CR) modulation during the last solar cycles. Since the beginning of the ground-based cosmic-ray monitoring, it is known that the solar-cycle modulation is more evident in data from high latitude than from the medium and low latitudes, showing an expected geomagnetic cutoff rigidity effect. However, a more detailed look shows a new latitudinal effect in cycle 24: while the magnitude of the solar modulation in the low-latitude data remains the same for the last three solar minima, the last solar minimum caused a more intense peak in the polar NM data than in the previous cycles. After correcting the data for the geomagnetic changes of the period, we found an anomalous solar modulation in the last cycle. This suggests a weaker heliospheric modulation at low-energy particles (responsible for the NM counting in polar sites) now than in the previous cycles, while there is no significant difference of the modulation for the more energetic part of the CR spectrum. Our result can be associated with changes of the solar wind turbulence, which would corroborate some recent studies about the last solar minimum phase, and indicates that this new solar modulation feature is still present in the current solar maximum stage. [ABSTRACT FROM AUTHOR]

We studied the relationship between the power-law exponent γ on the rigidity R of the spectrum of galactic cosmic-ray (GCR) intensity variation ( δD( R)/ D( R)∝ R) and the exponents ν and ν of the power spectral density (PSD) of the B and B components of the interplanetary magnetic field (IMF) turbulence (PSD∼ f, where f is the frequency). We used the data from neutron monitors and IMF for the period of 1968 - 2002. The exponents ν and ν were calculated in the frequency interval Δ f= f− f=3×10 Hz of the resonant frequencies ( f=1×10 Hz, f=4×10 Hz) that are responsible for the scattering of GCR particles with the rigidity range detected by neutron monitors. We found clear inverse correlations between γ and ν or ν when the time variations of the resonant frequencies were derived from in situ measurements of the solar wind velocity U and IMF strength B during 1968 - 2002. We argue that these inverse relations are a fundamental feature in the GCR modulation that is not restricted to the analyzed years of 1968 - 2002. [ABSTRACT FROM AUTHOR]

Many tropical rainforests harbour species-rich assemblages of frogs and, consequently, of tadpoles. These larvae are often morphologically highly diverse, especially in their oral structures. Whether this might represent an important axis of ecological partitioning in frog assemblages remains an untested hypothesis. In general, it is poorly known how diverse tadpole assemblages are organised. Using information from Madagascar's remarkably species-rich stream tadpole assemblages, we analysed the distribution and co-occurrence of 44 species. We also assessed the importance of phylogenetic history and eco-morphological adaptation for habitat selection at two functional and two spatial levels. We show that both rare and common species exist in most morphological clusters and phylogenetic groups of tadpoles. Habitat characteristics of the streams and surrounding forest influence species composition. Whereas there is a general trend in preferring wide and deep streams without a steep slope for most species, some of the morphological clusters separate along specific habitat variables. Stream choice is influenced both by phylogenetic history and morphological adaptation. Within streams, tadpoles partition microhabitat mainly according to their morphological cluster but without phylogenetic signal. Species dissimilarities of habitat selection on both spatial scales are not correlated. We found no evidence for competition in the tadpole assemblages studied. [ABSTRACT FROM AUTHOR]

A group of representative species of the genus Puya was studied to determine if there are allometric relationships between vegetative and floral parts, whether these relationships correlate with their pollination system and if plant size is correlated with elevation and latitude. Fifty-three species representing the morphological variation and distribution of the genus were studied. Total plant height, as well as leaf, inflorescence, petal and sepal length were measured and these data subjected to univariate and multivariate analyses. To test for correlation between plant size and altitudinal and latitudinal distribution, ANOVAs were performed. When the pollination system of a species is known, additional multivariate and univariate analyses were also performed. The results indicate that the characters studied are correlated with a size component, exhibiting positive allometry for sepal and petal length and negative allometry for leaf length. Inflorescence length is an isometric character. There was no significant correlation between plant size and altitudinal or latitudinal distribution. The ANOVAs show that the only character correlated to pollinator type was petal length. Small plants with small flowers are correlated to pollinators such as insects, while medium to large plants with medium to large-sized flowers are correlated with pollinators such as birds and bats. Large plants have small flowers, that are more evident and attract more pollinators. [ABSTRACT FROM AUTHOR]

The kinetics of 5-hydroxytryptamine (5-HT) release into the portal system after efferent electrical vagal stimulation were studied in an in vivo model. Blood samples were drawn from cats before, during and after vagal nerve stimulation, and portal plasma levels of 5-HT were measured. Portal plasma concentration of 5-HT rose during stimulation. After termination of stimulation, the plasma levels returned to steady state values and were used to calculate half-life and elimination rate constant. When pharmacokinetic principles were applied, the plasma half-life (T1/2) was determined to be 1.32 min and the elimination rate constant (k), 0.5246 min. Pharmacokinetic principles also were applied to data from earlier in vitro studies using exogenously administered 5-HT, and a half-life of 1.03 min and a k of 0.67 min were calculated. Therefore, it appears that exogenously administered 5-HT and neurogenically released endogenous 5-HT are metabolized at a similar rate, both having a short half-life. [ABSTRACT FROM AUTHOR]

The structure of GCR intensity and its changes during the solar magnetic cycle are analyzed by numerically solving its transport equation. We propose a research method that allows us to use the intermediate results from numerical calculations, to resolve the intensity of galactic cosmic rays into components caused by sunspot and magnetic solar cycles, and to monitor the changes in energy in different parts of the heliosphere and different phases of the cycle. A method for dividing intensity into its components associated with the main physical processes determining the modulation of galactic cosmic rays is also proposed. [ABSTRACT FROM AUTHOR]