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The Atmosphere-Space Interactions Monitor (ASIM) was designed to monitor Terrestrial Gamma-ray Flashes (TGFs) and Transient Luminous Events (TLEs) from space, enabling the study of how these phenomena are related. In this paper, we present observations of 17 TGFs with accompanying Elves. TGFs are short and highly energetic bursts of gamma photons associated with lightning discharges, whereas Elves are TLEs that are observed as concentric rings of ultraviolet (UV) and visible light at ionospheric altitudes, produced by the excitation of N2 molecules when an electromagnetic pulse (EMP) hits the base of the ionosphere. Elves were identified when optical detections in the UV band could be clearly distinguished from other optical signals from lightning strokes. The TGFs they accompanied had short durations and were associated with particularly high peak current lightning. Lightning sferics associated with these events were detected by the global lightning network GLD360 and the World Wide Lightning Location Network (WWLLN), and they were, with the exception of one event, observed over ocean or coastal regions. It is likely that these events were associated with Energetic In-cloud Pulses (EIPs). We show that short duration TGFs tend to be associated with higher peak currents than long duration TGFs.

Terrestrial Gamma ray Flashes (TGFs) are short flashes of high energy photons, produced by thunderstorms. When interacting with the atmosphere, they produce relativistic electrons and positrons, and a part gets bounded to geomagnetic field lines and travels large distances in space. This phenomenon is called a Terrestrial Electron Beam (TEB). The Atmosphere-Space Interactions Monitor (ASIM) mounted on-board the International Space Station detected a new TEB event on March 24, 2019, originating from the tropical cyclone Johanina. Using ASIM's low energy detector, the TEB energy spectrum is resolved down to 50 keV. We provide a method to constrain the TGF source spectrum based on the detected TEB spectrum. Applied to this event, it shows that only fully developed Relativistic Runaway Electron Avalanche spectra are compatible with the observation. More specifically, assuming a TGF spectrum urn:x-wiley:00948276:media:grl62333:grl62333-math-0001, the compatible models have ϵ ≥ 6.5 MeV (E is the photon energy and ϵ is the cut-off energy). We could not exclude models with ϵ of 8 and 10 MeV. publishedVersion

We report the first Terrestrial Electron Beam detected by the Atmosphere‐Space Interactions Monitor. It happened on 16 September 2018. The Atmosphere‐Space Interactions Monitor Modular X and Gamma ray Sensor recorded a 2 ms long event, with a softer spectrum than typically recorded for Terrestrial Gamma ray Flashes (TGFs). The lightning discharge associated to this event was found in the World Wide Lightning Location Network data, close to the northern footpoint of the magnetic field line that intercepts the International Space Station location. Imaging from a GOES‐R geostationary satellite shows that the source TGF was produced close to an overshooting top of a thunderstorm. Monte‐Carlo simulations were performed to reproduce the observed light curve and energy spectrum. The event can be explained by the secondary electrons and positrons produced by the TGF (i.e., the Terrestrial Electron Beam), even if about 3.5% to 10% of the detected counts may be due to direct TGF photons. A source TGF with a Gaussian angular distribution with standard deviation between 20.6° and 29.8° was found to reproduce the measurement. Assuming an isotropic angular distribution within a cone, compatible half angles are between 30.6° and 41.9°, in agreement with previous studies. The number of required photons for the source TGF could be estimated for various assumption of the source (altitude of production and angular distribution) and is estimated between 1017.2 and 1018.9 photons, that is, compatible with the current consensus.

In a genome alignment of five individuals of the ascomycete fungus Zymoseptoria pseudotritici , a close relative of the wheat pathogen Z. tritici (synonym Mycosphaerella graminicola ), we observed peculiar diversity patterns. Long regions up to 100 kb without variation alternate with similarly long regions of high variability. The variable segments in the genome alignment are organized into two main haplotype groups that have diverged ∼3% from each other. The genome patterns in Z. pseudotritici are consistent with a hybrid speciation event resulting from a cross between two divergent haploid individuals. The resulting hybrids formed the new species without backcrossing to the parents. We observe no variation in 54% of the genome in the five individuals and estimate a complete loss of variation for at least 30% of the genome in the entire species. A strong population bottleneck following the hybridization event caused this loss of variation. Variable segments in the Z. pseudotritici genome exhibit the two haplotypes contributed by the parental individuals. From our previously estimated recombination map of Z. tritici and the size distribution of variable chromosome blocks untouched by recombination we estimate that the hybridization occurred ∼380 sexual generations ago. We show that the amount of lost variation is explained by genetic drift during the bottleneck and by natural selection, as evidenced by the correlation of presence/absence of variation with gene density and recombination rate. The successful spread of this unique reproductively isolated pathogen highlights the strong potential of hybridization in the emergence of pathogen species with sexual reproduction.

We present the results of using the statistical model of field-aligned currents (FACs) based on satellite data and the numerical model of the electric potential distribution in order to detect the asymmetric part in FAC structures and ionospheric plasma convection controlled by the IMF azimuthal (B y ) component at different seasons of the year. These structures can be identified by plotting diagrams, which represent differences in corresponding maps for opposite signs of IMF B y . Circular near-pole current symmetric about the noon meridian and corresponding convection vortices around the pole have been obtained for the summer and equinox periods. It is difficult to detect distinct structures under winter conditions, and the current is most intense on the morning side. A two-cell convection system with the foci in the afternoon and postmid-night sectors is created in the electric potential difference diagrams. Thus, qualitatively different FAC and convection patterns exist during the solstice in opposite hemispheres. The value of the electric potential originating in the near-pole region under the action of the B y component and a change in the potential under the action of additional factors have been estimated.

We compare the SuperDARN convection patterns with the predictions of a new numerical model of the global distribution of ionospheric electric potentials. The model utilizes high-precision statistical maps of field-aligned currents (FAC) derived from measurements made by polar-orbiting low-altitude satellites. Both the solar and auroral precipitation contributions are included in order to derive the ionospheric conductance. Taking into account the electrodynamic coupling of the opposite hemispheres, the model allows one to obtain the convection patterns developed simultaneously in both hemispheres for given input parameters. SuperDARN, with its database containing global northern and southern convection maps, provides the unique opportunity to compare the model predictions of electric fields with observations. In the present study we focus on the effect of significant interhemispheric asymmetry governed by the IMF clock angle and solar zenith angle. We calculate the convection patterns for specific cases caused by the sign of BY and season and demonstrate the capability of the FAC-based model reproduce the radar observations. The simulation confirms that the solar zenith angle should be linked to the IMF clock angle to fully characterize the convection patterns. The model predicts that the cross-polar cap potential drop is regularly larger in the winter hemisphere than in the summer hemisphere.

A new approach for modeling the global distribution of ionospheric electric potentials utilizing high-precision maps of field-aligned currents (FACs) derived from measurements by the Orsted and Magsat satellites as input to a comprehensive numerical scheme is presented. We simulate the universal time (UT) effect in convection patterns caused by variation of solar luminosity and its effect on ionospheric conductivity. A rather complicated dependence of the convection patterns on the combination of UT and IMF clock angle is found. We consider different seasons and IMF conditions and find an increase of the daily variation in the cross-polar potential drop (UPC) at the equinoxes and a decrease at the solstices. Under equinoctial and zero IMF conditions the UPC can vary by a factor of two, while the convection cells keep their shape. The model predicts that the summer UPC can be smaller or larger than the winter UPC depending on the combination of UT and IMF clock angle. If a UT control of the FAC is introduced to the model, the UPC does not vary more than 10% over the course of the day.

We report an investigation of interior crisis in extended spatiotemporal systems exemplified by the Kuramoto–Sivashinsky equation. We show that unstable periodic orbits and their associated invariant stable and unstable manifolds in the Poincare hyperplane can effectively characterize the global bifurcation dynamics of high-dimensional systems. In particular, we introduce a new technique to characterize the high-dimensional homoclinic tangency responsible for an interior crisis using the stable manifolds of a chaotic saddle.

We report on field-aligned currents (FAC) ob- tained from precise magnetic field measurements made on- board the Orsted and Magsat satellites when the interplan- etary magnetic field (IMF) was near zero. We found that Region 1/Region 2 currents persist through southward IMF, IMF - 0, and northward IMF; also the central area of both the northern and southern polar caps is always filled with FACs, even during slightly southward IMF. A statis- tical distribution of the latter currents resembles the day- side NBZ system with the downward/upward currents at post-noon/pre-noon hours, discovered earlier from Magsat observations. We hypothesize that the quasi-viscous inter- action of the solar wind with the magnetospheric lobes may cause a sunward convection of the lobes' field lines through the bunch's core, effectively mapping the FACs of NBZ-type down to the near-pole area.

In this letter, we report geomagnetic observations over Greenland and Antarctica during May 11, 1999, when the solar wind almost disappeared. Greenland magnetometers show no magnetic activity in the nominal auroral zone but disturbances reached-200 nT at higher latitudes; however, conjugate observations in Antarctica show much weaker activity -40 nT. Analyzed data provide evidence that the cusp current system could be extended far to the dusk (dawn) in the northern (southern) polar region. This is consistent with the Orsted satellite observations, where field-aligned currents were detected near cusp, over the northem geomagnetic pole, and in the nightside polar cap; however, almost no were detected over the southern polar cap. We conclude that the low-density solar wind quieted activity at auroral latitudes ("loading-unloading" processes); but the "directly-driven" convection observed over both polar caps was mainly unaffected by the significant inflation of the magnetosphere.

It is not generally realized that genetics has finally solved the age-old problem of the reason for the existence (i.e. the function) of sexuality and sex, and that only geneticists can properly answer the question, “Is sex necessary?” ▪ Abstract Optimality arguments and modifier theory are reviewed as paradigms for the study of the evolution of recombination. Optimality criteria (such as maximization of mean fitness) may agree with results from models developed in terms of the evolution of recombination at modifier loci. Modifier models demonstrate, however, that equilibrium mean fitness can decrease during the evolution of recombination rates and is not always maximized. Therefore, optimality arguments do not successfully predict the conditions under which increased or decreased recombination will evolve. The results from modifier models indicate that decreased recombination rates are usually favored when the population is initially near a polymorphic equilibrium with linkage disequilibrium. When the population is subject to directional selection or to deleterious mutations, increased recombination may be favored under certain conditions, provided that there is negative epistasis among alleles.

The genetic mechanism underlying an ‘Optimal outcrossing distance’ in plants (sensu Price and Waser) is discussed. Monte Carlo simulations of a population subdivided as a one-dimensional stepping-stone are used to evaluate possible genetic mechanisms. A simple genetic model with two types of unlinked loci, underdominant and partially dominant, with multiplicative effects on fitness, is found to create an ‘Optimal outcrossing distance’ under a wide range of parameter values. The results are compared to, and discussed in relation to a two-locus epistatic model, previously investigated by Campbell and Waser, and found to give very similar results.

We study a population exposed to a lethal infectious disease. Host response is carried at one locus with two alleles while the pathogen occurs in two variants. Based on an Si-type epidemic model we derive explicit equations for the dynamics of each genotype. By assuming small variations in both host and disease, we obtain a separation in time scales between epidemic and evolutionary processes. This allows us to describe explicitly the changes in host and disease gene frequencies. The resulting model has a rich behaviour including multiple stable states and oscillations. However, in the oscillatory situation the model is degenerate excluding the possibility of limit cycles. We show that the degeneracy can only be removed by frequency dependent selection in the pathogen, for example by including direct interaction of virus in a free-living stage. The qualitative conclusions extend to an SIR-type epidemic model, where recovery with immunity from the disease is possible.

The periodic orbit quantization on the anisotropic Kepler problem is tested. By computing the stability and action of some 2000 of the shortest periodic orbits, the eigenvalue spectrum of the anisotropic Kepler problem is calculated. The aim is to test the following claims for calculating the quantum spectrum of classically chaotic systems: (1) Curvature expansions of quantum mechanical zeta functions offer the best semiclassical estimates; (2) the real part of the cycle expansions of quantum mechanical zeta functions cut at appropriate cycle length offer the best estimates; (3) cycle expansions are superfluous; and (4) only a small subset of cycles (irreducible cycles) suffices for good estimates for the eigenvalues. No evidence is found to support any of the four claims.

Selection due to differential viability is studied in an n-locus two-allele model using a set indexation that allows the simplicity of the one-locus two-allele model to be carried to multi-locus models. The existence condition is analyzed for polymorphic equilibria with linkage equilibrium: Robbins' equilibria. The local stability condition is given for the Robbins' equilibria on the boundaries in the generalized non-epistatic selection regimes of Karlin and Liberman (1979). These generalized non-epistatic regimes include the additive selection model, the multiplicative selection model and the multiplicative interaction model, and their symmetric versions cover all the symmetric viability models.

[1] A model of field-aligned currents is derived from high-precision magnetic field measurements from the Orsted and Magsat satellites, being parameterized by the interplanetary magnetic field strength and direction for summer, winter and equinox. The high-precision data allow the model to be determined directly by a simple 2-D curl technique combined with fitting of spherical harmonic functions. New elements of the model are: (a) the FAC patterns are determined separately for both polar regions, resolving the seasonal dependence of interhemispheric asymmetries, (b) the IMF ∼ 0, ground-state patterns are also resolved; these elements are obtained for the first time. From the model, the total upward/downward currents have been determined for various IMF conditions. The ratio of the summer/winter currents is ∼1.35 and the equinox currents ∼1. The model allows FAC mapping for IMF |B| ≤ 12 nT, except during magnetic storms and substorms.

[1] In this paper we report on field-aligned currents inferred from high-precision three-component geomagnetic field observations made on board the Danish satellite Orsted over polar regions. Because of a slow drift in local time of the satellite orbit through the “noon-midnight” sector, we were able to study the seasonal dependence of the dynamic properties of the dayside and nightside field-aligned current systems over the Northern and Southern Hemispheres. We find an average over-the-pole distance between dayside and nightside currents of 32° during summer but 37° during winter and 36° during equinox. The decrease in the size of the summer polar cap is caused by a shift of both daytime and nighttime current systems to higher magnetic latitudes. For comparison, the dawn-dusk cross-polar distance of the Region 1/Region 2 field-aligned currents has been determined from high-precision data observed by Magsat, a satellite flown in 1979–1980 in a “dawn-dusk” orbit. The latter results show that the dawn-dusk distance between R1/R2 currents exhibits little seasonal dependence and amounts to ∼34° for all seasons in both polar caps. The seasonal dependence is confirmed for the high-latitude field-aligned intensities; they are larger by a factor of 1.5–1.8 in the sunlit (summer) polar cap in comparison with the winter hemisphere. Our results suggest that the R1/R2 and dayside field-aligned currents are well balanced between the pairs of downward/upward currents for all seasons as well as between hemispheres during equinox. We were not able to confirm results reported in earlier studies that the net currents tend to increase with an enhancement of ionospheric conductivity caused by the solar illumination or substorm activity.

Single gene models for the evolution of rates of selfing and sib mating in the presence of an inbreeding depression of fitness are treated. In models in which the genetic constitution of the male gamete pool available for random mating is not affected by prior inbreeding, an allele which increases the rate of inbreeding will succeed, provided the inbreeding depression is not too large. The opposite result holds when the proportion of male genotypes available for random mating are reduced according to their rate of prior inbreeding.

Sufficient conditions for protected polymorphism at an autosomal locus in a diploid organism are developed for a Levene model with explicit modeling of the population dynamics. Levene's condition for protected polymorphism, formulated in terms of weighted harmonic means of relative genotypic fitnesses, is only strictly valid for components of selection that are not immediately relevant for the regulation of the population size in the subpopulations. Global regulation of the population size produces Dempster's condition for protected polymorphism in terms of weighted arithmetic means of absolute genotypic fitnesses. The general condition for protection of an allele may be written in the same form as Levene's condition, but then the weights of the subpopulations depend on the fitnesses in the various habitats. The model allows for marginal habitats that cannot sustain a population if left isolated.

A symmetric viability model for two loci with two alleles at one locus and m alleles at the other is suggested and analyzed. The analysis of the equilibria is complete if the two loci are absolutely linked, while if recombination is allowed the analysis is incomplete. The dynamics of the mode! resemble those of the two locus two allele model, namely that for loose linkage there will be no correlation between the loci and for tight linkage there may be strong correlation. The major caveats to this are: 1. The equilibria stable for tight linkage may belong to an array of different structures dependent on the selection and the number of alleles. 2. If both loci are overdominant in viability, the stable equilibria always contain all alleles segregating in the population; otherwise, the stable equilibria may only be two locus two allele high complementarity equilibria for tight linkage. 3. For intermediate linkage values and special selection values the boundary two locus two allele high complementarity equilibria may be stable simultaneously with the totally polymorphic central point at which there is no association between the loci.

SUMMARYThis paper is devoted to the study of the effects of population subdivision on the evolution of two linked loci. Two simple deterministic models of population subdivision without selection are investigated. One is a finite linear ‘stepping stone’ model and the other is a finite linear stepping stone chain of populations stretching between two large populations of constant genetic constitution. At equilibrium in the first model the gene frequencies in each population are equal and there is linkage equilibrium in each population. The rate of decay to zero of the linkage disequilibrium functions is the larger of (1 –c) and, where λ1is the rate of convergence of the gene frequencies to equilibrium and c is the recombination frequency. In the second model at equilibrium there will be a linear cline in gene frequencies connecting the two large constant populations. This cline will be accompanied by a ‘cline’ of linkage disequilibria. The rate of convergence to this equilibrium cline is independent of the recombination frequency, and, in fact, the gene frequencies and the linkage disequilibria converge to equilibrium at the same rate.

Two unlinked polymorphisms of a marine teleost, one in hemoglobin and one in esterase, show parallel clines through Danish waters, while two unlinked phosphoglucosemutase polymorphisms maintain constant gene frequencies. It is argued that the clinal and the constant polymorphisms cannot be accounted for simultaneously by random genetic drift of selectively neutral genes. It is therefore concluded that selection is responsible for at least one of the two classes of geographical patterns, be it the clinal, the constant, or both.