T. Eronen

Energetic and relativistic nuclei and electron experiment of the SOHO mission

Abstract The design of the ERNE experiment of the ESA and NASA collaborative SOHO mission is described. ERNE will investigate the sun by measuring energetic particles. Starting from the design objectives, as determined by the scientific goals of the experiment, and from the adopted basic solutions, the design and structure of the instrument are presented in detail. The fundamental technical aspects encountered in building a space instrument are briefly considered. The methods of implementation of scientifically the most important parts of the instrument, the sensors for measuring energetic particles and the associated electronics, are thoroughly explained. Both hardware and software are examined. The pre-flight calibrations of the instrument are described and the performance of the instrument in space is demonstrated.

A silicon microstrip tracker in space: Experience with the AMS silicon tracker on STS-91

SummaryThe Alpha Magnetic Spectrometer (AMS) is designed as an independent module for installation on the International Space Station (ISS) in the year 2003 for an operational period of three years. The principal scientific objectives include the searches for antimatter and dark matter in cosmic rays. The AMS tracker uses silicon microstrip sensors to reconstruct charged-particle trajectories. A first version of the AMS, equipped with 2.1 m2 of silicon sensors and a permanent magnet, was flown on the NASA space shuttle Discovery duringJune 2–12, 1998. In this contribution, we describe the detector and present results of the tracker performance duringthe flight.

Erne observations of energetic particle fluxes

Abstract The observations of the ERNE instrument on-board the SOHO 1 spacecraft are analysed. The main period under study is from the beginning of May till mid-October 1996. Only very small energetic particle events were observed. A comparison of the ERNE measurements with energetic particle observations during the two previous solar minima indicates that the flux levels of protons during the first half of 1996 are exceptionally low. The daily counting rates of quiet-time protons and 4He in the energy range 13–100 MeV/nucleon show statistically significant variations with time. Following two energetic particle events in July and August, anticorrelations were found between enhancements of low energy protons in the range 1.5–8 MeV, possibly accelerated in a corotating interaction region, and the modulation of high energy protons and helium above 13 MeV/nucleon. The period of the observed anticorrelations coincide with the solar rotation period.

Solar energetic particle abundance measurement by ERNE on board Soho

As one of the scientific experiments on-board Soho ERNE will be responsible for measurement of the solar energetic particle flux. In addition to this, special emphasis has been put on determining the isotope abundance ratios in the particle flux and the high isotopic resolution has been one goal in both instrument design as well as in development of the on-board data acquisition software and the methods of data analysis on the ground. Results from accelerator tests in GANIL are presented here. The isotopic resolution varies with particle type and energy; e.g., mass resolution of carbon isotopes is σm = 0.19 amu at the energy 15 MeV/nucleon and resolution of silicon is σm = 0.20 amu at 40 MeV/nucleon.

ESTIMATION OF HIGH ENERGY SOLAR PARTICLE TRANSPORT PARAMETERS DURING THE GLE's IN 1989

ABSTRACT Analysis of five ground level enhancements in 1989 is carried out for the observations of the Lomnicky Stit and Oulu neutron monitors. The objective of the analysis is the estimation of the particle transport parameters in the solar corona and in the interplanetary space at relativistic proton energies. For the September 29 and October 24 flares the observations at both stations reveal fine structures which can be interpreted as a double injection process into IP space.

Specialized detector techniques and electronics of the ERNE instrument onboard SOHO

ERNE is designed to study the composition and energy spectra of particles encountered in interplanetary space in the energy range from 1 MeV/n to well beyond 500 MeV/n. Several innovative ideas had to be incorporated in the design of the instrument in order to fulfill the scientific requirements. Position-sensitive strip detectors are used in the High Energy Detector (HED) for determining particle trajectories. Integrated interstrip capacitances were designed to allow for a very simple read-out technique from the two edges of each detector. The event recognition, signal multiplexing and control of the pulse height analysis are based on a gate array technique. The versatility of the gate array also allowed an elegant realization of a number of other functions and instrument control tasks. By using the gate array a very compact structure of the digital control electronics was achieved.

Scientific performance of ERNE sensors

Abstract The Energetic and Relativistic Nuclei and Electron experiment of the SOHO mission contains two sensors LED and HED. The energy ranges of the sensors are of the order of 1–10 MeV/n and 13–540 MeV/n, respectively. One of the design goals was good charge resolution of nuclei in the charge range 1–30. The isotopic resolution of light elements (LED) and all nuclei (HED) were also important objectives. Up to now, first models of the sensors have been built, and their performance has been tested in accelerator runs and by using an alpha particle source. First results of the test measurements are given.

Search of periodic scintillations in cosmic radiation in the range 2–50 mHz

Abstract Neutron monitor measurements using 10-second recording intervals were started at Oulu in September 1987. A special analysis method based on the power spectra was adopted to compensate for the relative low statistics associated with short recording intervals. The preliminary result based on the analysis of 6274 one-hour length data records strongly indicates the existence of periodic scintillations in the whole frequency range 2–50 mHz.