Performance of ERNE in particle flux anisotropy measurement     

E. Riihonen  J. Torsti  A. Anttila  J. Kuusela  M. Lumme  E. Valtonen 《Annales Geophysicae》1996,14(5):503-509

The HED particle detector of the ERNE experiment to be flown on the SOHO spacecraft is unique compared to the earlier space-born detectors in its high directional resolution (better than 2°, depending on the track inclination). Despite the fixed view cone due to the three-axis stabilization of the spacecraft, the good angular and temporal resolution of the detector provides a new kind of opportunity for monitoring in detail the development of the anisotropies pertaining, for example, to the onset of SEP events, or passage of shock fronts related to gradual events. In order to optimize the measurement parameters, we have made a preflight simulation study of the HED anisotropy measurement capabilities. The purpose was to prove the feasibility of the selected measurement method and find the physical limits for the HED anisotropy detection. The results show HED to be capable of detecting both strong anisotropies related to impulsive events, and smoother anisotropies associated with gradual events.  相似文献   

Anomalous Cosmic-Ray Helium,Nitrogen and Oxygen in 1996 – Measurements of the ERNE Instrument on-board SOHO     

Torsti  J.  Valtonen  E.  Anttila  A.  Vainio  R.  Mäkelä  P.  Riihonen  E.  Teittinen  M. 《Solar physics》1997,170(1):193-204

The energy spectra of the anomalous components of helium, nitrogen and oxygen have been measured by the ERNE experiment on board the SOHO spacecraft. During February 28–April 30, 1996, the maximum intensity of anomalous helium was found to be 3.8 × 10^-5 cm^-2 sr^-1 s^-1 (MeV nucl^-1)^-1 in the energy range 10–15 MeV nucl^-1. During the period January 26–April 30, 1996, the maximum oxygen intensity was 1.2 × 10^-5 cm^-2 sr^-1 s^-1 (MeV nucl^-1)^-1 at 4–7 MeV nucl^-1, and the maximum nitrogen intensity 1.7 × 10^-6 cm^-2 sr^-1 s^-1 (MeV nucl^-1)^-1 at 4–9 MeV nucl^-1. These peak intensities are at the same level as two solar cycles ago in 1977, but significantly higher than in 1986. This gives observational evidence for a 22-year solar modulation cycle. A noteworthy point is that the spectra of anomalous nitrogen and oxygen appear to be somewhat broader than in 1977.  相似文献   

First Energetic Particle Events Observed by the ERNE Instrument     

Torsti  J.  Valtonen  E.  Kocharov  L. G.  Vainio  R.  Riihonen  E.  Anttila  A.  Laitinen  T.  Teittinen  M.  Kuusela  J. 《Solar physics》1997,170(1):179-191

The energetic particle instrument ERNE on-board SOHO started its observations on December 15, 1995. The low-energy sensor of ERNE, LED, is capable of measuring particles in the energy range from 1 to 10 MeV nucl^-1. From the beginning of the year 1996 until May 22, 1996, LED-observations included four energetic particle events above threshold intensities. An energetic particle event caused by a corotating interaction region that accelerated protons upto 10 MeV, was observed during January 20–25. Another similar particle event occured on May 6–12. The events were separated by four solar rotation periods. They had similar time profiles, but the one in May had a harder spectrum and a lower intensity level. The ⁴He-to-proton ratios were in accordance with the solar wind value. Energetic particles observed during April 22–23 and May 14–17 were accelerated at the Sun. The first one was apparently an outcome from an active region observed on the west limb by telescopes on-board SOHO. Protons were detected at energies from 1 to 10 MeV. For this event, the⁴He-to-proton ratio in the range 1.5–5 MeV nucl^-1 was 3%. No ³He ions were detected. The period of May 14–15 was, in contrast, extremely ³He-rich: it had a³He-to-proton ratio of 1.5 ± 0.6 and a ³He-to- ^4He ratio as high as 8. The period of May 14–17 comprised at least three individual, one-day-long events. The first two events were ³He-rich, while the last one seemed to have a normal composition.  相似文献   

Scientific Analysis within SEPServer – New Perspectives in Solar Energetic Particle Research: The Case Study of the 13 July 2005 Event     

O. E. Malandraki  N. Agueda  A. Papaioannou  K.-L. Klein  E. Valtonen  B. Heber  W. Dr?ge  H. Aurass  A. Nindos  N. Vilmer  B. Sanahuja  A. Kouloumvakos  S. Braune  P. Preka-Papadema  K. Tziotziou  C. Hamadache  J. Kiener  V. Tatischeff  E. Riihonen  Y. Kartavykh  R. Rodríguez-Gasén  R. Vainio 《Solar physics》2012,281(1):333-352

Solar energetic particle (SEP) events are a key ingredient of solar?Cterrestrial physics both for fundamental research and space weather applications. Multi-satellite observations are an important and incompletely exploited tool for studying the acceleration and the coronal and interplanetary propagation of the particles. While STEREO uses for this diagnostic two identical sets of instrumentation, there are many earlier observations carried out with different spacecraft. It is the aim of the SEPServer project to make these data and analysis tools available to a broad user community. The consortium will carry out data-driven analysis and simulation-based data analysis capable of deconvolving the effects of interplanetary transport and solar injection from SEP observations, and will compare the results with the electromagnetic signatures. The tools and results will be provided on the web server of the project in order to facilitate further analysis by the research community. This paper describes the data products and analysis strategies with one specific event, the case study of 13 July 2005. The release time of protons and electrons are derived using data-driven and simulation-based analyses, and compared with hard X-ray and radio signatures. The interconnection of the experimental and the simulation-based results are discussed in detail.  相似文献   

Energetic particle experiment ERNE     

J. Torsti  E. Valtonen  M. Lumme  P. Peltonen  T. Eronen  M. Louhola  E. Riihonen  G. Schultz  M. Teittinen  K. Ahola  C. Holmlund  V. Kelhä  K. Leppälä  P. Ruuska  E. Strömmer 《Solar physics》1995,162(1-2):505-531

The Energetic and Relativistic Nuclei and Electron (ERNE) experiment will investigate the solar atmosphere and the heliosphere by detecting particles produced in various kinds of energy release processes. ERNE is at the upper end in energy among the SOHO particle instruments. The instrument will measure the energy spectra of elements in the range Z=1–30. The energy coverage varies dependent on the particle species from a few MeV/n up to a few hundred MeV/n and electrons from 2 to 50 MeV. At high energies, ERNE records also the direction of the incident particles for accurate measurements of the pitch angle distribution of the ambient flux within the viewing cone. Especially the isotope identification capability has been one of the instrument design goals, thus providing new data regarding various fundamental questions in solar physics.  相似文献   

Energetic particle investigation using the ERNE instrument     

J. Torsti  E. Valtonen  L. Kocharov  M. Lumme  T. Eronen  M. Louhola  E. Riihonen  G. Schultz  M. Teittinen  R. Vainio  A. Anttila  J. Kuusela 《Annales Geophysicae》1996,14(5):497-502

During solar flares and coronal mass ejections, nuclei and electrons accelerated to high energies are injected into interplanetary space. These accelerated particles can be detected at the SOHO satellite by the ERNE instrument. From the data produced by the instrument, it is possible to identify the particles and to calculate their energy and direction of propagation. Depending on variable coronal/interplanetary conditions, different kinds of effects on the energetic particle transport can be predicted. The problems of interest include, for example, the effects of particle properties (mass, charge, energy, and propagation direction) on the particle transport, the particle energy changes in the transport process, and the effects the energetic particles have on the solar-wind plasma. The evolution of the distribution function of the energetic particles can be measured with ERNE to a better accuracy than ever before. This gives us the opportunity to contribute significantly to the modeling of interplanetary transport and acceleration. Once the acceleration/transport bias has been removed, the acceleration-site abundance of elements and their isotopes can be studied in detail and compared with spectroscopic observations.  相似文献   

Solar energetic particle fluences from SOHO/ERNE     

Eino Valtonen  Esa Riihonen  Iiro-Ville Lehtinen 《Acta Geophysica》2009,57(1):116-124

We have calculated integral fluences of solar protons and helium nuclei at 19 energy thresholds between 1.6 and 90 MeV/n from the SOHO/ERNE measurements during the years 1996–2005. We have also calculated fluences of oxygen and iron in the energy range from 10 up to a few hundred MeV/n for nineteen solar energetic particle (SEP) events. These are the first results of the work aiming at a full employment of the ERNE data in investigating the fluence distributions of SEP events over the entire solar activity cycle 23 and in deriving the total dose received on-board SOHO during its mission. Some instrumental problems are identified and future developments are presented.  相似文献