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The Sun is the largest reservoir of matter in the solar system, which formed 4.6 Gyr ago from the protosolar nebula. Data from space missions and theoretical models indicate that the solar wind carries a nearly unfractionated sample of heavy isotopes at energies of about 1 keV/amu from the Sun into interplanetary space. In anticipation of results from the Genesis mission’s solar-wind implanted samples, we revisit solar wind isotopic abundance data from the high-resolution CELIAS/MTOF spectrometer on board SOHO. In particular, we evaluate the isotopic abundance ratios 15N/14N, 17O/16O, and 18O/16O in the solar wind, which are reference values for isotopic fractionation processes during the formation of terrestrial planets as well as for the Galactic chemical evolution. We also give isotopic abundance ratios for He, Ne, Ar, Mg, Si, Ca, and Fe measured in situ in the solar wind.

We analyze suprathermal ions and plasma wave spectra upstream of interplanetary shocks driven by coronal mass ejection events. In particular, we analyze the competition between two processes: (1) the upstream wave generation by suprathermal protons accelerated at the shock, and (2) the cascading of wave energy in the inertial range of solar wind turbulence. We derive the cascading timescale from the comparison of particle and turbulent wave spectra with theory and conclude that amplified solar wind turbulence upstream of interplanetary traveling shocks is better described by Iroshnikov-Kraichnan-type rather than Kolmogorov-type wave diffusion.

This article presents an integrated analytical model on the injection efficiencies of the different ion species of the Anomalous component of the Cosmic Rays (ACRs) at the solar wind termination shock. We find that the injection into diffusive (first-order Fermi) acceleration is dominated by parallel ion diffusion and not by perpendicular diffusion unless the angle Ψ between the shock normal and the heliospheric magnetic field is almost exactly 90° (89.3° < T 90°). In steady state the threshold speed for injection into first-order Fermi acceleration at a not exactly perpendicular solar wind termination shock - with the Parker shock angle Ψ 89.3° - adjusts itself self-consistently. Increased anisotropic ACR flux amplifies Alfvenic turbulence which in turn suppresses parallel diffusion. It therefore increases the injection threshold and decreases the ACR flux until equilibrium is reached. For this equilibrium situation, we estimate the injection efficiencies of different species of suprathermal ions at the termination shock. We consider the following pre-acceleration processes: 1) momentum diffusion in compressional (ion-acoustic and magnetosonic) turbulence in the upstream supersonic solar wind and adiabatic cooling during convection to the termination shock; 2) reflection, transmission, and acceleration in the electric potential of the termination shock; and 3) momentum diffusion (stochastic or second-order Fermi acceleration) in the subsonic solar wind downstream of the termination shock in the inner heliosheath region. Our model results are compared to data from instruments on board the SOHO, ACE, Ulysses, and Voyager spacecraft.

Using data of the Highly Suprathermal Time-Of-Flight sensor of the Charge, Element, and Isotope Analysis System on board the Solar and Heliospheric Observatory spacecraft located at Lagrangian point L1 near Earth, we have measured proton spectra in the energy range 60 keV-2 MeV associated with the Bastille Day coronal mass ejection of 2000 July 14-16. For the same event, the power spectral densities of the magnetic field fluctuations in the solar wind have been measured with the magnetometer on board the Advanced Composition Explorer in the frequency range from about 0.05 mHz to 0.5 Hz. Within 0.11 AU upstream of the main shock, the flux of protons in the energy range 150 keV-2 MeV decreases much more rapidly with distance from the shock than is expected from diffusion in typical solar wind magnetic turbulence. In the same upstream region, the excitation of hydromagnetic waves in the frequency range 0.25-3 mHz and with power spectral density levels of up to 100 times the typical levels in the ambient solar wind is observed.

The distribution functions of suprathermal ions in the energy range 35–2000 keV/amu associated with the interplanetary coronal mass ejection of 14–16 July 2000 are analyzed. The ion spectra agree with a theoretical model on momentum diffusion in two-dimensional magnetohydrodynamic turbulence.

The distribution functions of suprathermal ions associated with the two interplanetary coronal mass ejections in the time period of April 9–12, 2001, are analyzed. The data on ions in the energy range 35–2000 keV/amu were recorded by the (Highly) Suprathermal Time-of-Flight (HSTOF/STOF) Spectrometer on board the Solar and Heliospheric Observatory (SOHO) at 1 AU. While the instrument passes the event the ion spectra undergo changes that correpond to the local plasma properties. In particular, there are significant differences between the spectra and the spatial distribution of singly charged interstellar 4 He + pick-up ions and of solar wind 4 He 2+ ions, respectively.

In the years 2004 and 2007, the instruments onboard the Voyager 1&2 spacecraft delivered unprecedented data on the structure of the solar wind termination shock. This shock has been assumed to be responsible for the acceleration of the anomalous component of cosmic rays (ACRs) from a pick‐up ion seed population derived from the interstellar neutral gas penetrating the heliosphere. In this article, we present model results on the evolution of solar wind turbulence and suprathermal tails with heliocentric distance to support the hypothesis that stochastic acceleration all over the heliosphere but in particular in the heliosheath is an important process to energize the ACRs if not the most important one.

Neutral hydrogen atoms, which give rise to the prominent so lar Ly-alpha corona, are closely coup led to the emerging solar-wind plasma. The density ratio of neutral hydrogen to protons is minute, ~10-6; therefore, the neutral atoms are tracers in the solar wind. In-situ observations of the neutral atoms, their flight paths (imag ing), density, and velocity distribu tions are a new tool to the understanding of the Ly-alpha corona, i.e. setting limits on the plasma velocity distribution along the solar magnetic field lines. The other goal of the neutral solar- wind instrumentation is the in-situ observation of the interactions between solar wind plasma and dust grains near the Sun. We will discuss the science objectives and the potential "zero charge" solar-wind instrument envelope onboard Solar Orbiter.

The observations of magnetic field fluctuations and suprathermal ion spectra upstream of interplanetary shocks driven by coronal mass ejections (CMEs) give information on two time scales: (1) the eddy turn‐over time scale i.e. the non‐linear cascading time scale of solar wind turbulence, and (2) the growth time scale for waves amplified by energetic protons accelerated at the shock. These two time scales scale differently with wave number. From an analysis of data from the ACE magnetometer and the suprathermal particle sensor SOHO/STOF we derive the solar‐wind eddy turn‐over time.

The observations on magnetic field fluctuations and suprathermal ion spectra near the shocks driven by the coronal mass ejections during the time periods of the Bastille Day 2000 event and the Halloween 2003 events are summarized.

Diffusive shock acceleration process is regarded as one of the most important processes for astrophysical particle acceleration. We treat an ESP (energetic storm particle) event associated with an interplanetary shock (IPS) arrived at 1AU about 28 hours after a large flare/CME event happened in 14 July 2000 (known as the Bastille event). Using the magnetic field data from Geotail (X=24.9 Re, Y=7.4Re, Z=-1.8Re), and flux data of protons (~ several×10 2 keV) from SOHO (X=2.2Re, Y=-67.8Re, Z=12.3Re), we study the wave-particle interaction in the upstream region of this IPS.

We present SOHO/CELIAS/HSTOF data on suprathermal H, He, CNO, and Fe ions in the energy range 0.035–2 MeV/amu associated with the Bastille Day coronal mass ejection event, July 14–16, 2000. We observe a complicated evolution of the spectra in the plasma upstream from the strong interplanetary shock on July 15, in the downstream turbulent compression region, and in the magnetic cloud following the compression region. The spectra of suprathermal H, CNO, and Fe ions from the solar wind source fit a scheme of ordering by their charge‐to‐mass (Q/A) ratio. This scheme suggests that the ions are stochastically accelerated in the turbulence region downstream from the shock and then injected into first‐order Fermi acceleration. The suprathermal He flux consists of solar wind 4He2+ ions matching the Q/A‐ordering scheme, and an additional component.

Since the launch of the Solar and Heliospheric Observatory (SOHO) on Dec. 2, 1995, the Suprathermal Time‐Of‐Flight (STOF) energetic particle sensor of the Charge, Element and Isotope Analysis System (CELIAS) has observed gradual and impulsive solar particle events from solar activity cycle minimum to maximum. The instrument CELIAS/STOF has the capability of detecting energetic ions and determine the mass, energy and charge of each particle. We report on the measurements of the detected energetic particle events from 1996 to 2001, i.e. the velocity dispersion of energetic He ions in the energy/charge range between 30 and 800 keV/nuc. For energetic particle events we analyse the velocity dispersion of the suprathermal He and O ions (78 and 43 events, resp.) and estimate the onset time of the solar event and set limits on the propagation length along the connecting magnetic field line.

A model for the acceleration and transport of suprathermal ions associated with interplanetary coronal mass ejections (CMEs) is presented. The combined mechanisms of stochastic acceleration in the turbulence near interplanetary shocks, first‐order Fermi acceleration, stationary spatial diffusion in field irregularities of magnetic clouds, and time‐dependent propagation in the upstream solar wind are described. Ions from the bulk solar wind are considered as source populations of suprathermal ions. The results of the model are compared to the spectra of suprathermal ions observed with SOHO/CELIAS/HSTOF during the Bastille Day CME of 14–16 July 2000.

[1] The Solar and Heliospheric Observatory/Charge, Element, and Isotope Analysis System/(Highly) Suprathermal Time of Flight ((H)STOF) mass spectrometer measures the elemental composition and the charge state distribution of ions with suprathermal energies in the range 10–4000 keV amu−1 from above the solar wind particle distribution up to low-energy flare particle energies. We analyze the time period around the large coronal mass ejection event on 2–3 May 1998. Using data from (H)STOF, we study the charge state distribution of He, the CNO group, and Fe. In addition, we investigate the energy dependence of the mean ionic charge state of Fe in the energy-per-nucleon range 12–100 keV amu−1. Furthermore, we also report energy spectra of H+, He++, and He+ and the variations in the elemental abundance ratios He/H, He/CNO, and Fe/CNO. These observations greatly extend the energy range in which particles associated with this time period have been measured. Because of their elevated energies, suprathermal particles are the prime seed population for further acceleration in gradual events. We identify interstellar pickup ions as an important nonsolar seed population. The observed low mean ionic charge states of Fe and the small Fe/CNO ratio are typical for large gradual events. The energy dependence of the Fe charge states may be a result of the presence of different iron populations or of the thermal history of the accelerated material. The temporal variations of Fe/CNO and He/CNO indicate a stronger confinement of low-rigidity particles at the acceleration site.