Observations of Anomalous Cosmic Rays at 1 AU

Anomalous cosmic rays (ACRs) provide a sensitive probe of the access of energetic particles to the inner heliosphere, varying in intensity by more than two orders of magnitude during the course of the solar cycle. New data which are becoming available from the Advanced Composition Explorer (ACE) can provide a detailed record of ACR intensity and spectral changes on short (~ 1 day) time scales during the approach to solar maximum, which will help address issues of ACR modulation and transport. The elemental and isotopic composition of ACRs provides important information on the source or sources of these particles, while their ionic charge state composition and its energy dependence serves as a diagnostic of their acceleration time scale. We review measurements of the ACR elemental, isotopic, and charge state composition and spectra as determined at 1 AU by SAMPEX, ACE, Wind, and other spacecraft. These results are important input to models of the acceleration, modulation, and transport of ACRs

The Solar Energetic Particle Event of 6 May 1998

The abundances of elements from helium to iron have been measured in more than a dozen moderate to large solar energetic particle (SEP) events using the Solar Isotope Spectrometer (SIS) on-board the Advanced Composition Explorer (ACE). Time variations within some of these events and from event to event have been reported previously. This paper presents an analysis of the event of 6 May 1998, for which relatively time-independent abundance ratios are found. This event has been considered to be an example of an impulsive event, a gradual event, and as a hybrid of the two. Difficulties with classifying this event are discussed

Variable fractionation of solar energetic particles according to first ionization potential

The average composition of solar energetic particles (SEPs), like the solar corona, is known to be depleted in elements with first ionization potential (FIP) more than ~10 eV by a factor of approximately four. We examine evidence for event to event variations in the FIP-related fractionation of SEPs, following up a 1994 study by Garrard and Stone. In a survey of 46 SEP events from 1974 to 1999 the deduced FIP-fractionation varies by a factor of ~2 from event to event, with no apparent relation to charge-to-mass dependent fractionation patterns in these same events. These results are compared to similar variations observed in the solar wind

The Coronal Isotopic Composition as Determined Using Solar Energetic Particles

Solar energetic particles (SEPs), like the solar wind, provide a direct sample of the Sun. Although SEP abundances show a variable amount of mass fractionation, it is possible to develop methods of correcting for it in order to deduce the composition of the corona. Using high-resolution measurements from the Solar Isotope Spectrometer on the Advanced Composition Explorer, we have studied the isotopic composition of 10 abundant elements from C to Ni in 32 large SEP events from late 1997 to the end of 2001 at energies >15 MeV/nucleon. We show that various isotopic and elemental enhancements are correlated with each other, discuss the first order corrections used to account for the variability, and obtain estimated coronal abundances. We compare the coronal values and their uncertainties inferred from SEPs with those that are available from solar wind and meteoritic measurements and find generally good agreement. We include C and Ni isotopic abundances, for which no solar wind measurements have yet been reported

The Isotopic Composition of Solar Energetic Particles

Since the launch of ACE in August 1997, the Solar Isotope Spectrometer (SIS) has observed 11 large solar particle events in which elemental and isotopic composition was determined over a large energy range. The composition of these events has raised many issues and challenged generally accepted characterizations of solar energetic particle (SEP) events. In particular, ^3He/^4He enhancements have been observed in several large events as well as enhancements of heavy ions typically associated with smaller impulsive events. The isotopic composition varies substantially from event to event (a factor of 3 for ^(22)Ne/^(20)Ne) with enhancements and depletions that are generally correlated with elemental composition. This correlation suggests that the isotopic enhancements may be related to the Q/M fractionation typically evident in the elemental composition of SEP events. However, there are also significant deviations from this pattern, which may imply that wave-particle resonances or other mass fractionation processes may be involved. We review the recent isotopic observations made with ACE and discuss their implications for particle acceleration and transport

The Cosmic-Ray Contribution to LiBeB: Interpretation of LiBeB Abundances from CRIS

The bulk of galactic Li, Be, and B (LiBeB) abundances is believed to be created during energetic inelastic collisions of cosmic-ray and interstellar medium (ISM) nuclei. Additional sources such as big bang nucleosynthesis or neutrino-driven spallation within Type II supernovae may also add a small contribution. However, measurements of the elemental ratios Be/H, B/H, and Fe/H in old, low-metallicity halo stars indicate an overabundance of LiBeB that can not be accounted for by fragmentation of cosmic-ray CNO. This interpretation assumes that the ISM in any epoch serves as a source of material both for star formation and for cosmic rays, which contribute fragmentation material in later epochs. We have simulated cosmic-ray transport using a simple model and present an interpretation of the abundance measurements from the Cosmic Ray Isotope Spectrometer (CRIS) during the past three years. We will discuss the implications on cosmic-ray LiBeB production at lower energies

How Common is Energetic ^3He in the Inner Heliosphere?

Using data from the SIS and ULEIS instruments on the Advanced Composition Explorer (ACE) we have identified periods during which energetic ^3He is present in near-Earth interplanetary space between November 1997 and May 2002. The data, which cover the energy intervals 0.2–1 MeV/nuc (ULEIS) and 4.5–16.3 MeV/nuc (SIS), show that ^3He is present a significant fraction of the time, as would be required if these suprathermal particles were the major source of the ^3He being accelerated by shocks in the interplanetary medium. Specifically, we find that energetic ^3He is present at least ~ 60% of the time, and perhaps significantly more often

Project 8 Phase III Design Concept

We present a working concept for Phase III of the Project 8 experiment, aiming to achieve a neutrino mass sensitivity of $2~\mathrm{eV}$ ($90~\%$ C.L.) using a large volume of molecular tritium and a phased antenna array. The detection system is discussed in detail.Comment: 3 pages, 3 figures, Proceedings of Neutrino 2016, XXVII International Conference on Neutrino Physics and Astrophysics, 4-9 July 2016, London, U