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We examine variations in energetic storm particle (ESP) heavy ion peak intensities and energy spectra at CME-driven interplanetary shocks. We focus on their dependence with heliolongitude relative to the source region of their associated CMEs, and with CME speed, for events observed in Solar Cycle 24 at the STEREO-A, STEREO-B, and/or ACE spacecraft. We find that observations of ESP events at 1 au are organized by longitude relative to their CME solar source. The ESP event longitude distribution also showed organization with CME speed. The near-Sun CME speeds (V i ) for these events ranged from ∼560 to 2650 km sâˆ'1 while the average CME transit speeds to 1 au were significantly slower. The angular width of the events had a clear threshold at V i of ∼1300 km sâˆ'1, above which events showed significantly larger angular extension compared to events with speeds below. High-speed events also showed larger heavy ion peak intensities near the nose of the shock compared to the flanks while their spectral index was smaller near the nose and larger near the flanks. This organization for events with V i < 1300 km sâˆ'1 was not as clear. These ESP events were observed over a narrower range of longitudes though the heavy ion peak intensities still appeared largest near the nose of the shock. Their heavy ion spectra showed no clear organization with longitude. These observations highlight the impact of spacecraft position relative to the CME source longitude and V i on the properties of ESP events at 1 au. [ABSTRACT FROM AUTHOR]

The last solar minimum, which extended into 2009, was especially deep and prolonged. Since then, sunspot activity has gone through a very small peak while the heliospheric current sheet achieved large tilt angles similar to prior solar maxima. The solar wind fluid properties and interplanetary magnetic field (IMF) have declined through the prolonged solar minimum and continued to be low through the current mini solar maximum. Compared to values typically observed from the mid-1970s through the mid-1990s, the following proton parameters are lower on average from 2009 through day 79 of 2013: solar wind speed and beta (∼11%), temperature (∼40%), thermal pressure (∼55%), mass flux (∼34%), momentum flux or dynamic pressure (∼41%), energy flux (∼48%), IMF magnitude (∼31%), and radial component of the IMF (∼38%). These results have important implications for the solar wind's interaction with planetary magnetospheres and the heliosphere's interaction with the local interstellar medium, with the proton dynamic pressure remaining near the lowest values observed in the space age: ∼1.4 nPa, compared to ∼2.4 nPa typically observed from the mid-1970s through the mid-1990s. The combination of lower magnetic flux emergence from the Sun (carried out in the solar wind as the IMF) and associated low power in the solar wind points to the causal relationship between them. Our results indicate that the low solar wind output is driven by an internal trend in the Sun that is longer than the ∼11 yr solar cycle, and they suggest that this current weak solar maximum is driven by the same trend. [ABSTRACT FROM AUTHOR]

Recent in situ observations of the solar wind show that charge states (e.g., the O7+/O6+ and C6+/C5+ abundance ratios) and α-particle composition evolved through the extended, deep solar minimum between solar cycles 23 and 24 (i.e., from 2006 to 2009). Prior investigations have found that both particle flux and magnetic field strength gradually decreased over this period of time. In this study, we find that (for a given solar wind speed) the coronal electron temperature (as derived from O7+/O6+ and C6+/C5+ measurements from ACE) likewise decreased during this minimum. We use the Schwadron & McComas solar wind scaling law to show that cooler coronal electron temperatures are naturally associated with lower particle fluxes because downward heat conduction must be reduced to keep the average energy loss per particle fixed. The results of the scaling law should apply to all solar wind models and suggest that the evolution of the solar wind is linked to the solar dynamo, which caused the coronal magnetic field strength to decrease in the deep, extended minimum. We utilize the scaling law to project coronal electron temperatures backward in time throughout the space age and find that these temperatures have been decreasing in successive temperature maxima since 1987 but were increasing in successive temperature maxima from 1969 to 1987. Thus, we show how the solar wind scaling law relates solar wind properties observed at 1 AU back to coronal electron temperatures throughout the space age. [ABSTRACT FROM AUTHOR]