A three-dimensional plasma and energetic particle investigation for the wind spacecraft

This instrument is designed to make measurements of the full three-dimensional distribution of suprathermal electrons and ions from solar wind plasma to low energy cosmic rays, with high sensitivity, wide dynamic range, good energy and angular resolution, and high time resolution. The primary scientific goals are to explore the suprathermal particle population between the solar wind and low energy cosmic rays, to study particle accleration and transport and wave-particle interactions, and to monitor particle input to and output from the Earth's magnetosphere.Three arrays, each consisting of a pair of double-ended semi-conductor telescopes each with two or three closely sandwiched passivated ion implanted silicon detectors, measure electrons and ions above 20 keV. One side of each telescope is covered with a thin foil which absorbs ions below 400 keV, while on the other side the incoming <400 keV electrons are swept away by a magnet so electrons and ions are cleanly separated. Higher energy electrons (up to 1 MeV) and ions (up to 11 MeV) are identified by the two double-ended telescopes which have a third detector. The telescopes provide energy resolution of E/E0.3 and angular resolution of 22.5°×36°, and full 4 steradian coverage in one spin (3 s).Top-hat symmetrical spherical section electrostatic analyzers with microchannel plate detectors are used to measure ions and electrons from 3 eV to 30 keV. All these analyzers have either 180° or 360° fields of view in a plane, E/E0.2, and angular resolution varying from 5.6° (near the ecliptic) to 22.5°. Full 4 steradian coverage can be obtained in one-half or one spin. A large and a small geometric factor analyzer measure ions over the wide flux range from quiet-time suprathermal levels to intense solar wind fluxes. Similarly two analyzers are used to cover the wide range of electron fluxes. Moments of the electron and ion distributions are computed on board.In addition, a Fast Particle Correlator combines electron data from the high sensitivity electron analyzer with plasma wave data from the WAVE experiment (Bougeretet al., in this volume) to study wave-particle interactions on fast time scales. The large geometric factor electron analyzer has electrostatic deflectors to steer the field of view and follow the magnetic field to enhance the correlation measurements.     

Interplanetary acceleration of low-energy protons as observed during the 25 september 1978 shock event

ISEE-3 observations of a long-lasting low-energy proton intensity increase during the 25 September 1978 shock event are presented as an example for interplanetary particle acceleration in association with shock waves. The observations are discussed in the light of current models for particle acceleration. The particular shape of the time intensity behaviour of the particle intensity increase, the existence of a shock spike and the observed particle distributions indicate that the particles are accelerated at the shock by the induced electric field $\text{E}\text{= ?}\text{1}\text{c}\text{V}\text{×}\text{B}$.     

Reduction of aliasing ambiguities through phase relations

A method for digital determination of a single frequency from a sine wave sampled at less than the Nyquist rate is discussed. The method makes use of phase shift information to eliminate the aliasing ambiguity. Multiple sampled data are required to eliminate ambiguity completely. Computer modeling using simulated data corrupted by uncorrelated Gaussian noise was used to verify the approach. The results demonstrate that the frequency of an input sine wave can be correctly identified. This approach can be applied to electronic warfare (EW) receivers to increase their input bandwidth     

Reactant jetting in unstable detonation

We note the common existence of a supersonic jet structure locally embedded within a surrounding transonic flow field in the hitherto unrelated phenomena of unstable gaseous detonation and hypervelocity blunt body shock wave interaction. Extending prior results that demonstrate the consequences of reduced endothermic reaction rate for the supersonic jet fluid in the blunt body case, we provide an explanation for observations of locally reduced OH PLIF signal in images of the keystone reaction zone structure of weakly unstable detonations. Modeling these flow features as exothermically reacting jets with similarly reduced reaction rates, we demonstrate a mechanism for jetting of bulk pockets of unreacted fluid with potentially differing kinetic pathways into the region behind the primary detonation front of strongly unstable mixtures. We examine the impact of mono-atomic and diatomic diluents on transverse structure. The results yield insight into the mechanisms of transition and characteristic features of both weakly and strongly unstable mixtures.     

The evolution of the anomalous component of the cosmic rays during the Ulysses mission

We have studied the evolution of the anomalous cosmic ray component at ULYSSES using observations of the quiet time helium fluxes obtained with the COSPIN Low Energy Telescope during the years from launch in October 1990 to the latest data in 1994. Shown are preliminary results of measurements in the energy range from 4.0 to 19 MeV/n. Following the drop in solar activity in late 1991, the low energy cosmic ray helium flux started to increase and continue to rise until the end of 1993, signifying the appearance of the anomalous component at ULYSSES.     

Energetic Ions Observed at Low to High Latitudes in the Southern Heliosphere During Declining and Rising Solar Activity

We present and compare observations of energetic protons during the two first transits of the Ulysses spacecraft from low to high latitudes in the southern heliosphere. Protons in the energy range 1.8–3.8 MeV from the COSPIN experiment are studied for global trends and in relation to some ambient structures in the solar wind (corotating interaction region, forward/reverse shock). The global trends show the large dependence on the heliospheric condition and solar activity, including indications of a larger ambient particle population during the rising phase of solar activity and more efficient solar wind particle accelerators during the declining phase. More enhancements in the proton flux intensity are time associated with forward shocks than reverse contrary to first pass. Recurrent structures are found even during the second transit. Some latitude dependent periodicities are observed that could relate to the differential solar rotation. This revised version was published online in August 2006 with corrections to the Cover Date.     

Propagation of upstream protons in the near-earth solar wind

The propagation of energetic protons (35–1600 keV) from the Earth's magnetosphere to the ISEE-3 spacecraft located about 240 earth radii (R_E) upstream in the solar wind is used as a tool to study the interaction between these protons and the solar wind. In this preliminary study we present proton pitch angle distributions seen at different times during the development of upstream events that occur in relatively quiet interplanetary conditions. In general a highly anisotropic sunward flow is seen at the beginning of the events. During the course of the events pitch angle distributions may vary between streaming along the field lines (peaked around 0° pitch angle), a uniform intensity between 0° and 90°, and a peaked distribution around a preferred pitch angle that is often near 90°.     

CIR Associated Energetic Particles in the Inner and Middle Heliosphere

Energetic particles associated with Corotating Interaction Regions (CIRs) are observed throughout the inner and middle heliosphere, showing large positive (>100%/AU) radial intensity gradients. Their appearance at 1 AU is associated with the appearance of fast, recurrent solar wind streams. At several AU, CIR energetic particles are accelerated at shocks which propagate away from the interface of fast and slow solar wind streams. CIR energy spectra at 1 AU cover the range >35 keV to several MeV/amu; the spectra steepen above ∼1 MeV/amu, and show no turnover even at the lowest energies. The ion composition of CIRs is similar to solar material, but with significant differences that might be due to properties of the seed population and/or the acceleration process. This paper summarizes properties of energetic particles in CIRs as known through the early 1990s, prior to the launch of the Ulysses, and WIND spacecraft, whose new results are presented in Kunow, Lee et al. (1999) in this volume. This revised version was published online in August 2006 with corrections to the Cover Date.     

The Solar Electron and Proton Telescope for the STEREO Mission

The Solar Electron and Proton Telescope (SEPT), one of four instruments of the Solar Energetic Particle (SEP) suite for the IMPACT investigation, is designed to provide the three-dimensional distribution of energetic electrons and protons with good energy and time resolution. This knowledge is essential for characterizing the dynamic behaviour of CME associated and solar flare associated events. SEPT consists of two dual double-ended magnet/foil particle telescopes which cleanly separate and measure electrons in the energy range from 30–400 keV and protons from 60–7?000 keV. Anisotropy information on a non-spinning spacecraft is provided by the two separate telescopes: SEPT-E looking in the ecliptic plane along the Parker spiral magnetic field both towards and away from the Sun, and SEPT-NS looking vertical to the ecliptic plane towards North and South. The dual set-up refers to two adjacent sensor apertures for each of the four view directions: one for protons, one for electrons. The double-ended set-up refers to the detector stack with view cones in two opposite directions: one side (electron side) is covered by a thin foil, the other side (proton side) is surrounded by a magnet. The thin foil leaves the electron spectrum essentially unchanged but stops low energy protons. The magnet sweeps away electrons but lets ions pass. The total geometry factor for electrons and protons is 0.52 cm²?sr and 0.68 cm²?sr, respectively. This paper describes the design and calibration of SEPT as well as the scientific objectives that the instrument will address.     

STEREO IMPACT Investigation Goals, Measurements, and Data Products Overview

The IMPACT (In situ Measurements of Particles And CME Transients) investigation on the STEREO mission was designed and developed to provide multipoint solar wind and suprathermal electron, interplanetary magnetic field, and solar energetic particle information required to unravel the nature of coronal mass ejections and their heliospheric consequences. IMPACT consists of seven individual sensors which are packaged into a boom suite, and a SEP suite. This review summarizes the science objectives of IMPACT, the instruments that comprise the IMPACT investigation, the accommodation of IMPACT on the STEREO twin spacecraft, and the overall data products that will flow from the IMPACT measurements. Accompanying papers in this volume of Space Science Reviews highlight the individual sensor technical details and capabilities, STEREO project plans for the use of IMPACT data, and modeling activities for IMPACT (and other STEREO) data interpretation.