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There is a growing appreciation that the environmental conditions that we call space weather impact the technological infrastructure that powers the coupled economies around the world. With that comes the need to better shield society against space weather by improving forecasts, environmental specifications, and infrastructure design. [...] advanced understanding of space weather requires a coordinated international approach to effectively provide awareness of the processes within the Sun-Earth system through observation-driven models. This roadmap prioritizes the scientific focus areas and research infrastructure that are needed to significantly advance our understanding of space weather of all intensities and of its implications for society. Advancement of the existing system observatory through the addition of small to moderate state-of-the-art capabilities designed to fill observational gaps will enable significant advances. Such a strategy requires urgent action: key instrumentation needs to be sustained, and action needs to be taken before core capabilities are lost in the aging ensemble. We recommend advances through priority focus (1) on observation-based modeling throughout the Sun-Earth system, (2) on forecasts more than 12 hrs ahead of the magnetic structure of incoming coronal mass ejections, (3) on understanding the geospace response to variable solar-wind stresses that lead to intense geomagnetically-induced currents and ionospheric and radiation storms, and (4) on developing a comprehensive specification of space climate, including the characterization of extreme space storms to guide resilient and robust engineering of technological infrastructures. The roadmap clusters its implementation recommendations by formulating three action pathways, and outlines needed instrumentation and research programs and infrastructure for each of these. [...], In press for Advances of Space Research: an international roadmap on the science of space weather, commissioned by COSPAR and ILWS (63 pages and 4 figures)

This review focuses on the processes that energize and trigger major solar flares and flux-rope destabilizations. Numerical modeling of specific solar regions is hampered by uncertain coronal-field reconstructions and by poorly understood magnetic re- connection; these limitations result in uncertain estimates of field topology, energy, and helicity. The primary advances in understanding field destabilizations therefore come from the combination of generic numerical experiments with interpretation of sets of observations. These suggest a critical role for the emergence of twisted flux ropes into pre-existing strong field for many, if not all, of the active regions that pro- duce M- or X-class flares. The flux and internal twist of the emerging ropes appear to play as important a role in determining whether an eruption will develop predom- inantly as flare, confined eruption, or CME, as do the properties of the embedding field. Based on reviewed literature, I outline a scenario for major flares and erup- tions that combines flux-rope emergence, mass draining, near-surface reconnection, and the interaction with the surrounding field. Whether deterministic forecasting is in principle possible remains to be seen: to date no reliable such forecasts can be made. Large-sample studies based on long-duration, comprehensive observations of active regions from their emergence through their flaring phase are needed to help us better understand these complex phenomena., Comment: in press for Advances in Space Research

We report on our efforts to model the ambient solar wind out to 1 AU around the time of the May 12, 1997 halo coronal mass ejection (CME) and to identify its coronal source regions. We use the simple physics and empirical based Wang–Sheeley–Arge (WSA) model driven by two different sets of updated photospheric field synoptic maps to accomplish this: daily updated maps from Mount Wilson Solar Observatory and updated SOHO/MDI maps constructed with the Schrijver et al. flux transport data assimilation algorithm. The results generated by the WSA model are then compared with the WIND satellite observations near Earth, as well as with each other. We find that the model describes the observed ambient solar wind stream structure around the time of the May 12, 1997 CME generally well, except for the ejecta itself. Our results suggest that the source of the high-speed stream that followed the CME is a coronal hole extension located south of the Sun's equator. We conclude that the northern active region associated with the May 12th CME did not play a role in the formation of the small southern coronal hole extension that produced the high-speed stream, which followed and eventually compressed the ICME from behind. Overall, this analysis suggests how the solar wind context of CME-related events can be analyzed and understood using coronal and solar wind models.

We derive phase differences between irradiance and full-disk velocity variations for l=0, 1, and 2 modes with order ranging from 11 up to 30 (1.8–4.3mHz). We use irradiance measurements from the IPHIR instrument flown on the PHOBOS mission to Mars during the second half of 1988, and simultaneous velocity measurements obtained at Tenerife. The IPHIR instrument measures broad-band irradiance fluctuations and the derived phase differences are therefore typical of the deep layers of the photosphere. We select three one week intervals from the 155 day observing interval of PHOBOS 2 for which simultaneous good quality velocity data are available. We find a smooth variation of the phase difference between irradiance at 500nm (5nm FWHM) and velocity from about 70° at 1.8mHz to 145° at 2.5mHz, while it remains roughly constant at 145° degrees up to at least 3.5mHz, and possibly up to 4.3mHz. We also show that the phase differences between the green (500nm) and red (865nm) channels does not differ significantly from zero below 3mHz, while a small difference of about 10° may exist at higher frequencies.

We analyze the solar irradiance data gathered by the IPHIR experiment on the USSR planetary mission to Phobos during 160 days of the cruise phase to Mars of PHOBOS II, launched on 12 July 1988. We use two methods to ‘clean’ the data from the unexpected effects caused by the variable pointing. Both methods yield spectra of the green and red passbands in the range of the solar 5-minute p-mode oscillations with a very high signal-to-noise ratio. The consistency of the four spectra demonstrates the effectiveness of the ‘cleaning’ and allows to determine highly accurate p-mode frequencies. For the low-frequency analysis another, independent method is applied which produces reasonable power spectra in the range from 0.1 to 200 μHz. Interesting features of the medium-term variability of the solar spectral irradiance are revealed. No evidence was found for solar g modes, possibly because the solar or the pointing noise prevents their disclosure.

We observed the late-type stars Capella, σ2 CrB, λ And, AD Leo, GL494, GL569 and Procyon with different combinations of three instruments aboard EXOSAT : the low-energy channel multiplier array (LE), the medium-energy proportional counters (ME), and the transmission grating spectrometer (TGS). We derive crude temperature information on the coronae of these stars from the photometric data, using one- and two-temperature models of optically thin, thermal plasmas. We compare the results with 2-T fits and differential emission measure analyses of three grating observations and with simulations for mixtures of two plasma components with varying emission measure ratios. But for Procyon, all sources have a strong, hot component between 10 and 25 MK. The TGS spectra of Capella and σ2 CrB reveal a cooler component with comparable emission measure around 5 MK. The emission from the corona of Procyon is dominated by a very cool (0.6 MK) component, with an additional contribution from a 2–3 MK component.

Hydrophilic and hydrophobic regions were predicted for Elapid neuro- and cardiotoxins. The contribution of these regions to the retention times of neuro- and cardiotoxins on hydrophobic-interaction HPLC was assessed from the known surface accessibilities of amino acid side-chains within these regions. Differences in retention times between neuro- and cardiotoxins on hydrophobic-interaction HPLC could be attributed to differences in hydrophobicity of regions 6-12 and 22-26 between these two types of toxins. Smaller differences in retention times between cardiotoxins were due to the variable hydrophobicities of regions 1-4 and 26-36.

The active late-type stars Capella (α Aur G6III+F9III) and σ2 CrB (F6V+GV) (X-ray candidate emitters underlined) were observed with the EXOSAT Transmission Grating Spectrometer (TGS) in the region 10–200 A. We have made an analysis of the differential emission measure (DEM) distribution. The derived DEM peaks between 3 and 7 MK and above 10 MK. The results disagree with models for static loops as developed by Rosner, Tucker and Vaiana [1, hereafter referred to as RTV ]: the contrast in emission between the maximal and lower temperatures in the loop is larger than predicted by the RTV model. Other models which predict DEM distributions falling off more steeply towards lower temperatures are briefly discussed: e.g. quasi-static loops with varying cross-sectional area or dynamic loops with strong downward flows.

A sample of 52 stars containing dwarfs and giants is subjected to a multidimensional factor analysis. The parameters used are the soft X-ray flux at the stellar surface Fx, the Ca II H+K line-core flux FH+K, the stellar radius and mass. We find a high correlation between Fx and the Ca II H+K excess flux ΔFH+K obtained by subtracting an observational lower-limit flux from FH+K. We conclude that the lower-limit Ca II flux is uncorrelated with the stellar X-ray emission. The common-factor analysis shows that, for the present sample, Fx depends only on ΔFH+K, and not on the stellar radius or mass. All stars included in our analysis follow the relation Fx ∝ Δ1.4H+K over almost four decades in Fx.

Electron cloud sizes have been calculated for gas mixtures containing Ar, Xe, CO2, CH4, and N2 for drifts through a constant electric field. The transport coefficients w and D/μ are in good agreement with experimental data of various sources for pure gases. Results of measurements, also performed in this work, for Ar + CO2, Ar + CH4, and Ar + Xe + CO2 mixtures are in fair agreement with the calculated cloud sizes. For a large number of useful gas mixtures calculated electron cloud sizes are presented and discussed, most of which are given for the first time. A suggestion is made for an optimal gas mixture for an X-ray position sensitive proportional counter for medium and low energies.