> 25 MeV Proton Events Observed by the High Energy Telescopes on the STEREO A and B Spacecraft and/or at Earth During the First ∼ Seven Years of the STEREO Mission

Using observations from the High Energy Telescopes (HETs) on the STEREO A and B spacecraft and similar observations from near-Earth spacecraft, we summarize the properties of more than 200 individual >?25 MeV solar proton events, some detected by multiple spacecraft, that occurred from the beginning of the STEREO mission in October 2006 to December 2013, and provide a catalog of these events and their solar sources and associations. Longitudinal dependencies of the electron and proton peak intensities and delays to onset and peak intensity relative to the solar event have been examined for 25 three-spacecraft particle events. Expressed as Gaussians, peak intensities fall off with longitude with σ=47±14^° for 0.7?–?4 MeV electrons, and σ=43±13^° for 14?–?24 MeV protons. Several particle events are discussed in more detail, including one on 3 November 2011, in which ～?25 MeV protons filled the inner heliosphere within 90 minutes of the solar event, and another on 7 March 2012, in which we demonstrate that the first of two coronal mass ejections that erupted from an active region within ～?1 hour was associated with particle acceleration. Comparing the current Solar Cycle 24 with the previous cycle, the first >?25 MeV proton event was detected at Earth in the current solar cycle around one year after smoothed sunspot minimum, compared with a delay of only two months in Cycle 23. Otherwise, solar energetic particle event occurrence rates were reasonably similar during the rising phases of Cycles 23 and 24. However, the rate declined in 2013, reflecting the decline in sunspot number since the peak in the northern-hemisphere sunspot number in November 2011. Observations in late 2013 suggest that the rate may be rising again in association with an increase in the southern sunspot number.     

Spatial dispersion of Faraday rotation and its connexion with mode coupling

It is shown that the lack of linear polarization in the microwave radiation of solar bursts (reported in a earlier paper) may be explained by spatial dispersion of Faraday rotation. The maximum source diameter s without noticeable destruction of linear polarization is determined by the electron density and the magnetic field strength in the volume, where the linear polarization is generated. In the case where linear polarization is produced by the radiation source, s is smaller than only 20 km. In the other case where linear polarization is produced by mode coupling in a quasi-transverse magnetic field in the corona, the s-values are found to range from 10 to 6000 km, which is still much smaller than the generally adopted sizes of microwave burst sources. The second case has been investigated for several models of magnetic fields.     

Episodic absorption in the outflow of the old nova V603 Aquilae

We report on the time-dependent behaviour of ultraviolet spectral lines in Hubble Space Telescope Goddard High-Resolution Spectrograph data of the classical nova V603 Aql. In particular, episodic blueshifted absorption (extending to ∼−2500 km s⁻¹) is present, with a variability time-scale down to ∼1 min. The data provide a rare opportunity to study the rapid evolution of absorption structures that may be associated with accretion-disc winds in cataclysmic variables. At least three absorption events are recorded (at blueward velocities only) over ∼5 h, each lasting ∼10–15 min. The derived velocity, acceleration and optical depth properties provide an empirical picture of stochastically variable structures in the outflow, with no evidence for short-term (less than ∼1 h) cyclic or modulated behaviour in the overall absorption properties. In contrast, the emission components of the ultraviolet resonance lines are very stable in velocity and strength in this low-inclination system. On at least two occasions there is an intriguing short-term 'flare' in the ultraviolet continuum flux (of up to ∼40 per cent). Though there is no clear one-to-one relation in these data between the continuum fluctuations and the occurrence of the absorption events, the time-scales for the two variable phenomena are essentially the same. The irregular absorption episodes in the ultraviolet data of V603 Aql presently defy a clear physical interpretation. Their overall characteristics are discussed in the context of instabilities in radiation-pressure-driven disc winds.     

Computational reproducibility in geoscientific papers: Insights from a series of studies with geoscientists and a reproduction study

Reproducibility is a cornerstone of science and thus for geographic research as well. However, studies in other disciplines such as biology have shown that published work is rarely reproducible. To assess the state of reproducibility, specifically computational reproducibility (i.e. rerunning the analysis of a paper using the original code), in geographic research, we asked geoscientists about this topic using three methods: a survey (n = 146), interviews (n = 9), and a focus group (n = 5). We asked participants about their understanding of open reproducible research (ORR), how much it is practiced, and what obstacles hinder ORR. We found that participants had different understandings of ORR and that there are several obstacles for authors and readers (e.g. effort, lack of openness). Then, in order to complement the subjective feedback from the participants, we tried to reproduce the results of papers that use spatial statistics to address problems in the geosciences. We selected 41 open access papers from Copernicus and Journal of Statistical Software and executed the R code. In doing so, we identified several technical issues and specific issues with the reproduced figures depicting the results. Based on these findings, we propose guidelines for authors to overcome the issues around reproducibility in the computational geosciences.     

Holocene environmental change at Lake Njulla (999 m a.s.l.), northern Sweden: a comparison with four small nearby lakes alongan altitudinal gradient

We assess Holocene environmental change at alpine Lake Njulla(68°22N, 18°42E, 999 m a.s.l.) innorthernmost Sweden using sedimentary remains of chironomid head capsules anddiatoms. We apply regional calibration sets to quantitatively reconstruct meanJuly air temperature (using chironomids and diatoms) and lake-water pH(using diatoms). Both chironomids and diatoms infer highest temperatures(1.7–2.3°C above present-day estimates, includinga correction for glacio-isostatic land up-lift by0.6°C) during the early Holocene (c.9,500–8,500 cal. yrs BP). Diatoms suggest a decreasing lake-waterpH trend (c. 0.6 pH units) since the early Holocene. Usingdetrended canonical correspondence analysis (DCCA), we compare the Holocenedevelopment of diatom communities in Lake Njulla with four other nearby lakes(Lake 850, Lake Tibetanus, Vuoskkujávri, Vuolep Njakajaure) locatedalong an altitudinal gradient. All five lakes show similar initial DCCA scoresafter deglaciation, suggesting that similar environmental processes such ashigh erosion rates and low light availability associated with high summertemperature appear to have regulated the diatom community, favouring highabundances of Fragilaria species. Subsequently, the diatomassemblages develop in a directional manner, but timing and scale ofdevelopment differ substantially between lakes. This is attributed primarily todifferences in the local geology, which is controlling the lake-waterpH. Imposed on the basic geological setting, site-specific processessuch as vegetation development, climate, hydrological setting andin-lake processes appear to control lake development in northernSweden.     

Climatic significance of seasonal trace element and stable isotope variations in a modern freshwater tufa

We present a continuous ∼14-yr-long (1985 to 1999) high-resolution record of trace element (Mg, Sr, Ba, U) and stable isotope (δ¹³C, δ¹⁸O) variations in a modern freshwater tufa from northwestern Queensland, Australia. By utilizing the temperature dependence of the δ¹⁸O signal, an accurate chronology was developed for the sampled profile, which allowed a comparison of the chemical records with hydrological and meteorological observations. As a consequence, it was possible to constrain the relevant geochemical processes relating climate variables, such as temperature and precipitation, to their chemical proxies in the tufa record. Temperatures calculated from the Mg concentrations of the tufa samples provide close approximations of average annual water temperature variations. Furthermore, we demonstrate that temporal changes in (Mg/Ca)_water can be estimated using an empirically derived equation relating (Mg/Ca)_water to the (Sr/Ba) ratio measured in the tufa samples. By means of this relationship, it is theoretically possible to determine the (Mg/Ca) ratio of paleowaters, and hence to derive reliable estimates of former water temperatures from the Mg concentrations of fossil tufas from the study area. Sympathetic variations in Sr, Ba, and δ¹³C along the sampled profile record changes in water chemistry, which are most probably caused by variable amounts of calcite precipitation within the vadose zone of the karst aquifer. This process is thought to be markedly subdued whenever the amount of wet-season precipitation exceeds a given threshold. Accordingly, distinct minima in Sr, Ba, and δ¹³C are interpreted to reflect years with above-average rainfall. The pronounced seasonal and annual variability of the U concentration along the profile is thought to primarily record changes in the U flux from the soil to the water table. We suggest that during intensive rain events U is transported to the phreatic zone by complexing organic colloids, giving rise to conspicuous U maxima in the tufa after above-average wet seasons. This study demonstrates the potential of freshwater tufas to provide valuable information on seasonal temperature and rainfall variations. If tufa deposits turn out to be reasonably resistant to secondary processes, combined investigation of speleothems and tufas from the same area could become a promising approach in future research. While speleothems offer continuous records of long-term paleoenvironmental changes, tufas could provide high-resolution time windows into selected periods of the past.     

Cosmological evolution of the Fanaroff–Riley type II source population

By combining a model for the evolution of the radio luminosity of an individual source with the radio luminosity function, we perform a multidimensional Monte Carlo simulation to investigate the cosmological evolution of the Fanaroff–Riley type II (FR II) radio galaxy population by generating large artificial samples. The properties of FR II sources are required to evolve with redshift in the artificial samples to fit the observations. Either the maximum jet age or the maximum density of the jet environment or both evolve with redshift. We also study the distribution of FR II source properties as a function of redshift. From currently available data we cannot constrain the shape of the distribution of environment density or age, but jet power is found to follow a power-law distribution with an exponent of approximately −2. This power-law slope does not change with redshift out to   z = 0.6  . We also find the distribution of the pressure in the lobes of FR II sources to evolve with redshift up to   z ∼ 1.2  .     

Reasons for Spatial Microdistributions of Foraminifers in an Intertidal Pool (Northern Adriatic Sea)

Abstract. The spatial microdistribution of foraminifers was tested by the method of quadratic samplings on 2 sample grids in an intertidal pool of the northernmost Adriatic sea. Abundant species of foraminifers exhibit patchy distributions throughout; the distribution-patterns of some species correspond nearly completely. Using statistical methods (regression- and correlation-analyses) correlations to abiotic and biotic factors (water depth, exposure rate, seagrass, benthonic algae) were ascertained. The significant correlations of the foraminiferal frequencies to blue-green algae and/or diatoms enable an interpretation of these connexions as food dependences. Several foraminiferal species seem to have specific diets.