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11.
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
12.
M. Lumme M. Nieminen J. J. Torsti E. Vainikka J. Peltonen E. Valtonen H. Arvela 《Solar physics》1986,107(1):183-194
Particle fluxes and pitch angle distributions of relativistic solar protons at Earth's orbit have been determined by Monte Carlo calculations. The analysis covers two hours after the release of the particles from the Sun and total of 8 × 106 particle trajectories were simulated. The pitch angle scattering was assumed to be isotropic and the scattering mean free path was varied from 0.1 to 4 AU.The intensity-time profiles after a delta-like injection from the Sun show that the interplanetary propagation is clearly non-diffusive at scattering mean-free paths above 0.5 AU. All pitch angle distributions have a steady minimum at 90 °, and they become similar about 20 min after the arrival of first particles.As an application, the solar injection profile and the interplanetary scattering mean-free path of particles that gave rise to the GLE on 7 May, 1978 were determined. In contrast to the values of 3–5 AU published by other authors, the average scattering mean-free path was found to be about 1 AU. 相似文献
13.
Torsti Jarmo Kocharov Leon Laivola Jarno Chertok Ilya Thompson Barbara J. 《Solar physics》2003,214(1):177-193
Energetic particle observations of the ERNE instrument on board SOHO enable measurements of 3He and 4He fluxes beyond 15 MeV nucleon–1 with good statistical resolution. We report results of a survey of the ERNE observations covering the period from 8 February 1999 to 6 December 2000. We find 10 and 5 days during which the 3He-to-4He ratio exceeds the levels of 20% and 50%, respectively. Those periods include, in particular, four 3He-rich events that are sufficiently strong for a reasonably accurate estimate of the time-intensity profiles. We analyze the history of solar and interplanetary phenomena associated with these high-energy 3He-rich events. Basic properties of such events and significant solar and interplanetary factors are formulated. The significant factors comprise, in particular, a strong, impulsive flare, typically observed about
day before the 3He onset, and an interplanetary shock wave or magnetic field enhancement arriving at 1 AU about frac43 day after the 3He onset. The high-energy 3He-rich events make up a new kind of hybrid events, possessing the impulsive-type composition and the gradual-type time-profiles. We emphasize a dependence of the resultant particle event on the history of the particular solar eruption comprising coronal mass ejection (CME) and the flare associated with the CME. 相似文献
14.
We have analyzed five solar energetic particle (SEP) events observed aboard the SOHO spacecraft during 1996–1997. All events
were associated with impulsive soft X-ray flares, Type II radio bursts and coronal mass ejections (CMEs). Most attention is
concentrated on the SEP acceleration during the first 100 minutes after the flare impulsive phase, post-impulsive-phase acceleration,
being observed in eruptions centered at different solar longitudes. As a representative pattern of a (nearly) well-connected
event, we consider the west flare and CME of 9 July 1996 (S10 W30). Similarities and dissimilarities of the post-impulsive-phase
acceleration at large heliocentric-angle distance from the eruption center are illustrated with the 24 September 1997 event
(S31 E19). We conclude that the proton acceleration at intermediate scales, between flare acceleration and interplanetary
CME-driven shock acceleration, significantly contributes to the production of ≳10 MeV protons. This post-impulsive-phase acceleration
seems to be caused by the CME lift-off. 相似文献
15.
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
16.
We consider the prolonged injection of the high-energy (> 10 MeV) protons during the three successive events observed by GOES in October 1989. We apply a solar-rotation-stereoscopy approach to study the injection of the accelerated particles from the CME-driven interplanetary shock waves in order to find out how the effectiveness of the particle acceleration and/or escape depends on the angular distance from the shock axis. We use an empirical model for the proton injection at the shock and a standard model of the interplanetary transport. The model can reproduce rather well the observed intensity-time profiles of the October 1989 events. The deduced proton injection rate is highest at the nose of the shock; the injection spectrum is always harder near the Sun. The results seem to be consistent with the scheme that the CME-driven interplanetary shock waves accelerate a seed particle population of coronal origin. 相似文献
17.
Solar particle events with helium-over-hydrogen enhancement in the energy range up to 100 MeV nucl−1
J. Torsti L. Kocharov J. Laivola S. Pohjolainen S.P. Plunkett B.J. Thompson M.L. Kaiser M.J. Reiner 《Solar physics》2002,205(1):123-147
Flux measurements of solar energetic particles (SEPs) in the ERNE instrument onboard SOHO indicate that the abundance of 4He-nuclei compared to protons in the energy range up to 100 MeV nucl–1 was exceptionally high during the particle events on 27 May 1998 and 28 December 1999. The 4He/p ratio stayed between 0.15–0.50 for more than ten hours. There was also a prolonged enhancement in helium-3, 3He/4H 1%. Observations of EIT and LASCO on board SOHO confirm that the originators of both SEP events were western eruptions, flares and coronal mass ejections (CMEs). The onset of the SEP release took place close to the maximum of flares which were probably triggered by the rising CMEs. The observations suggest that the SEP events were started with the flare-(pre)accelerated particles, but impact of the CME-associated shocks might explain the continuation and modification of the helium and proton fluxes well after the flare production. These observations support the idea that the helium enhancements in the CME-associated events reflect the availability of seed particles that originate previously in flares. 相似文献
18.
We summarize ERNE/SOHO observations of solar energetic particle events associated with impulsive soft X-ray flares and LASCO coronal mass ejections (CMEs). The new observational data support an idea that the >10 MeV proton acceleration may be initiated at different coronal sources, operating in the flaring active region and on the global coronal scale, in concert with CME development. However, the particle acceleration continues beyond the coronal scales and may culminate at the interplanetary CME well after the flare. We emphasize the importance of CME liftoff/aftermath processes in the solar corona and the possible role of seed particle re-acceleration, which may explain the existence of hybrid solar energetic particle events. 相似文献
19.
We analysed the solar particle event following the 9 July 1996 solar flare. High-energy protons were detected by the ERNE
instrument on board SOHO. Anisotropy of arriving protons revealed very peculiar non-monotonic development. A short period
of almost isotropic distribution was imbedded into the prolonged period of beam-like distribution of 14–17 MeV protons. This
implies the existence of a narrow magnetic channel with a much smaller mean free path than in the surrounding quiet solar
wind plasma.
We used Monte Carlo simulations of interplanetary transport to fit the observed anisotropies and intensity–time profiles.
Proton injection and transport parameters are estimated. The injection scenario is found to be very close to the scenario
of the 24 May 1990 event, but the intensity and the interplanetary transport parameters are different. The extreme anisotropy
observed implies prolonged injection of high-energy protons at the Sun and at the interplanetary shock front, and either a
very large mean free path (≥ 5 AU) outside the slow transport channel, or alternatively, a somewhat smaller mean free path
(≈2 AU) and enhanced focusing between the Sun and the Earth. 相似文献
20.
J. Torsti T. Laitinen R. Vainio L. Kocharov A. Anttila E. Valtonen 《Solar physics》1997,175(2):771-784
A solar energetic particle event was observed on 9 July 1996, by the ERNE sensors LED and HED on board the SOHO spacecraft.
The arrival of the first protons in the energy range >20 MeV took place at 09:55 UT, 43 min after the maximum in the X-ray
and Hα radiation of a flare located at S10 W30. The rise phase of the particle intensities at all energies was exceptionally
rapid. At 12:50 UT, the intensities dropped in all energy channels. Simultaneously, the magnetic field instrument MFI on board
WIND, not far from SOHO, detected a sharp and large change in the magnetic field direction. The analysis of the directional
measurements of ERNE in the energy range 14–17 MeV shows the presence of a strong flux anisotropy during the whole period
10:10–12:50 UT. From 12:50 UT until about 16:00 UT, the directional analysis of the proton fluxes gives only a weak anisotropy
at the limit of the sensor resolution. Later on, the flux anisotropy was found to recur, indicating a continuous injection
of particles into the flux tubes connected to the SOHO spacecraft. These experimental results lead to strict limits on particle
injection and transport models. The first period of the anisotropy and its recurrent phase cover 24 hours. This suggests an
extended injection of particles. The strength and stability of the anisotropy indicate that, during these periods, SOHO was
in an interplanetary sector where the particle transport was almost scatter-free. On the other hand, during the intermediate
3-hr period, we observed particles which traveled in a sector of diffusive transport or which were retarded by magnetic field
disturbances not far from the observation site. 相似文献