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In a previous study (Cane and Richardson, J. Geophys. Res. 108 (A4), SSH6-1, 2003 ), we investigated the occurrence of interplanetary coronal mass ejections in the near-Earth solar wind during 1996 – 2002, corresponding to the increasing and maximum phases of solar cycle 23, and provided a “comprehensive” catalog of these events. In this paper, we present a revised and updated catalog of the ≈300 near-Earth ICMEs in 1996 – 2009, encompassing the complete cycle 23, and summarize their basic properties and geomagnetic effects. In particular, solar wind composition and charge state observations are now considered when identifying the ICMEs. In general, these additional data confirm the earlier identifications based predominantly on other solar wind plasma and magnetic field parameters. However, the boundaries of ICME-like plasma based on charge state/composition data may deviate significantly from those based on conventional plasma/magnetic field parameters. Furthermore, the much studied “magnetic clouds”, with flux-rope-like magnetic field configurations, may form just a substructure of the total ICME interval.

We summarize the response of the galactic cosmic ray (CGR) intensity to the passage of the more than 300 interplanetary coronal mass ejections (ICMEs) and their associated shocks that passed the Earth during 1995 – 2009, a period that encompasses the whole of Solar Cycle 23. In ∼ 80% of cases, the GCR intensity decreased during the passage of these structures, i.e. , a “Forbush decrease” occurred, while in ∼ 10% there was no significant change. In the remaining cases, the GCR intensity increased. Where there was an intensity decrease, minimum intensity was observed inside the ICME in ∼ 90% of these events. The observations confirm the role of both post-shock regions and ICMEs in the generation of these decreases, consistent with many previous studies, but contrary to the conclusion of Reames, Kahler, and Tylka ( Astrophys. J. Lett . 700 , L199, 2009 ) who, from examining a subset of ICMEs with flux-rope-like magnetic fields (magnetic clouds) argued that these are “open structures” that allow free access of particles including GCRs to their interior. In fact, we find that magnetic clouds are more likely to participate in the deepest GCR decreases than ICMEs that are not magnetic clouds.

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.

In the current paradigm for the modulation of galactic cosmic rays (GCRs), diffusion is taken to be the dominant process during solar maxima while drift dominates at minima. Observations during the recent solar minimum challenge the pre-eminence of drift at such times. In 2009, the ∼2 GV GCR intensity measured by the Newark neutron monitor increased by ∼5% relative to its maximum value two cycles earlier even though the average tilt angle in 2009 was slightly larger than that in 1986 (∼20° vs. ∼14°), while solar wind B was significantly lower (∼3.9 nT vs. ∼5.4 nT). A decomposition of the solar wind into high-speed streams, slow solar wind, and coronal mass ejections (CMEs; including post-shock flows) reveals that the Sun transmits its message of changing magnetic field (diffusion coefficient) to the heliosphere primarily through CMEs at solar maximum and high-speed streams at solar minimum. Long-term reconstructions of solar wind B are in general agreement for the ∼1900-present interval and can be used to reliably estimate GCR intensity over this period. For earlier epochs, however, a recent 10 Be-based reconstruction covering the past ∼10 4 years shows nine abrupt and relatively short-lived drops of B to ≲0 nT, with the first of these corresponding to the Spörer minimum. Such dips are at variance with the recent suggestion that B has a minimum or floor value of ∼2.8 nT. A floor in solar wind B implies a ceiling in the GCR intensity (a permanent modulation of the local interstellar spectrum) at a given energy/rigidity. The 30–40% increase in the intensity of 2.5 GV electrons observed by Ulysses during the recent solar minimum raises an interesting paradox that will need to be resolved.

In-situ measurements of interplanetary coronal mass ejections (ICMEs) display a wide range of properties. A distinct subset, “magnetic clouds” (MCs), are readily identifiable by a smooth rotation in an enhanced magnetic field, together with an unusually low solar wind proton temperature. In this study, we analyze Ulysses spacecraft measurements to systematically investigate five possible explanations for why some ICMEs are observed to be MCs and others are not: i) An observational selection effect; that is, all ICMEs do in fact contain MCs, but the trajectory of the spacecraft through the ICME determines whether the MC is actually encountered; ii) interactions of an erupting flux rope (FR) with itself or between neighboring FRs, which produce complex structures in which the coherent magnetic structure has been destroyed; iii) an evolutionary process, such as relaxation to a low plasma- β state that leads to the formation of an MC; iv) the existence of two (or more) intrinsic initiation mechanisms, some of which produce MCs and some that do not; or v) MCs are just an easily identifiable limit in an otherwise continuous spectrum of structures. We apply quantitative statistical models to assess these ideas. In particular, we use the Akaike information criterion (AIC) to rank the candidate models and a Gaussian mixture model (GMM) to uncover any intrinsic clustering of the data. Using a logistic regression, we find that plasma- β , CME width, and the ratio O 7 / O 6 are the most significant predictor variables for the presence of an MC. Moreover, the propensity for an event to be identified as an MC decreases with heliocentric distance. These results tend to refute ideas ii) and iii). GMM clustering analysis further identifies three distinct groups of ICMEs; two of which match (at the 86 % level) with events independently identified as MCs, and a third that matches with non-MCs (68 % overlap). Thus, idea v) is not supported. Choosing between ideas i) and iv) is more challenging, since they may effectively be indistinguishable from one another by a single in-situ spacecraft. We offer some suggestions on how future studies may address this.

The angle (θBn) between the normal to an interplanetary shock front and the upstream magnetic field direction, though often thought of as a property “of the shock,” is also determined by the configuration of the magnetic field immediately upstream of the shock. We investigate the interplanetary circumstances of 105 near‐Earth quasi‐perpendicular shocks during 1996–2005 identified by θBn ≥ 80° and/or by evidence of shock drift particle acceleration. Around 87% of these shocks were driven by interplanetary coronal mass ejections (ICMEs); the remainder were probably the forward shocks of corotating interaction regions. For around half of the shocks, the upstream field was approximately perpendicular to the radial direction, either east‐west or west‐east or highly inclined to the ecliptic. Such field directions will give quasi‐perpendicular configurations for radially propagating shocks. Around 30% of the shocks were propagating through, or closely followed, ICMEs at the time of observation. Another quarter were propagating through the heliospheric plasma sheet (HPS), and a further quarter occurred in slow solar wind that did not have characteristics of the HPS. Around 11% were observed in high‐speed streams, and 7% in the sheaths following other shocks. The fraction of shocks found in high‐speed streams is around a third of that expected based on the fraction of the time when such streams were observed at Earth. Quasi‐perpendicular shocks are found traveling through ICMEs around 2–3 times more frequently than expected. In addition, shocks propagating through ICMEs are more likely to have larger values of θBn than shocks outside ICMEs.

Previous studies have discussed the identification of interplanetary coronal mass ejections (ICMEs) near the Earth based on various solar wind signatures. In particular, methods have been developed of identifying regions of anomalously low solar wind proton temperatures ( T p ) and plasma compositional anomalies relative to the composition of the ambient solar wind that are frequently indicative of ICMEs. In this study, similar methods are applied to observations from the Ulysses spacecraft that was launched in 1990 and placed in a heliocentric orbit over the poles of the Sun. Some 279 probable ICMEs are identified during the spacecraft mission, which ended in 2009. The identifications complement those found independently in other studies of the Ulysses data, but a number of additional events are identified. The properties of the ICMEs detected at Ulysses and those observed near the Earth and in the inner heliosphere are compared.

The phase scintillation index was obtained from L1 GPS data collected with the Canadian High Arctic Ionospheric Network (CHAIN) during years of extended solar minimum 20082010. Phase scintillation occurs predominantly on the dayside in the cusp and in the nightside auroral oval. We set forth a probabilistic forecast method of phase scintillation in the cusp based on the arrival time of either solar wind corotating interaction regions (CIRs) or interplanetary coronal mass ejections (ICMEs). CIRs on the leading edge of high-speed streams (HSS) from coronal holes are known to cause recurrent geomagnetic and ionospheric disturbances that can be forecast one or several solar rotations in advance. Superposed epoch analysis of phase scintillation occurrence showed a sharp increase in scintillation occurrence just after the arrival of high-speed solar wind and a peak associated with weak to moderate CMEs during the solar minimum. Cumulative probability distribution functions for the phase scintillation occurrence in the cusp are obtained from statistical data for days before and after CIR and ICME arrivals. The probability curves are also specified for low and high (below and above median) values of various solar wind plasma parameters. The initial results are used to demonstrate a forecasting technique on two example periods of CIRs and ICMEs.

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?

The C-S-H gels present in both water- and alkali-activated hardened pastes of white Portland cement/blast-furnace slag blends have been studied by solid-state 29Si magic angle spinning nuclear magnetic resonance (NMR) spectroscopy and analytical transmission electron microscopy (TEM). Structural data are obtained by NMR for the semi-crystalline C-S-H gels in the alkali-activated systems and extended to the nearly amorphous gels in the water-activated systems by peak broadening; unambiguous chemical analyses are determined in the TEM. The following conclusions apply to both the semi-crystalline and nearly amorphous C-S-H gels: (1) aluminium substitutes for silicon at tetrahedral sites; (2) aluminium only substitutes for silicon in the central tetrahedron of pentameric silicate chains; (3) the results strengthen confidence in dreierkette-based models for the structure of C-S-H. Compositional similarities suggest that these conclusions will be true for OPC/slag blends, and possibly also for OPC/pulverized fuel ash blends indicating that the same structural model applies to C-S-H gels in a wide range of hardened cement pastes.