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1.
K. A. Anderson 《Solar physics》1969,6(1):111-132
In 1966 and 1967 many long-lived streams of low-energy solar electrons and protons were observed near Earth. These streams were sometimes associated with bright flares which occurred many hours earlier and sometimes no individual flare could be found. In the latter case the particles are evidently to be associated in a general way with solar active centers as Fan
et al. (1968) have done. The long-lived solar events discussed here include energetic storm particles, delayed events and fluxes associated with solar active regions. It is suggested here that these are all probably the same basic phenomena viewed in somewhat different ways depending on the age of the region and its location on the solar disc. These events are usually associated with a depression in the sea-level neutron intensity and one or more sudden commencements or sudden impulses. Both electrons and protons are present in these events but in several cases electrons were not detected. The most unusual feature is that when both particle species are present, the electron flux is centered several hours before the proton flux. 相似文献
2.
G. M. Simnett 《Solar physics》1972,22(1):189-219
Data are presented from the IMP-4 satellite of 0.3–12 MeV electrons from the Sun between May 24, 1967 and May 2, 1969. Correlations with contemporary proton intensity increases at energies above 1 MeV are studied. Classical solar flare events such as those frequently observed from 30°W–60°W in solar longitude are not discussed. Categories of unusual events are defined and examples of each type are given. Discussion of these events centers around the emission and propagation of energetic particles from the point of origin on the Sun to the Earth. The results of this study are the following: (1) The differential electron energy spectrum (0.3–12 keV) from solar flares appears to be a constant of the flare process, with the spectral index = (-)3.0 ± 0.2. (2) Particle emission from solar flares contains a prompt component, which is injected into the interplanetary medium beyond the Sun and which is responsible for the diffusion characteristics of solar particle events, and a delayed component which is effectively contained in the lower solar atmosphere where it diffuses typically ± 100° in longitude and gradually escapes into interplanetary space. The delayed component gives rise to the corotating features commonly observed after the impulsive and diffusive onset from the prompt component. This is not the same as the two component model discussed by Lin (1970a) in which 40 keV electrons are often observed as a separate phenomenon and frequently precede higher energy particles observed at 1 AU. (3) Storage of electrons > 300 keV and protons > 1 MeV is essential to explain emission and propagation characteristics of solar particle events. In some rare cases the storage mechanism appears to be very efficient, culminating in a catastrophic decay of the trapping region. (4) The events with low proton/electron ratios all occur at least three weeks after the previous relativistic electron producing flare. 相似文献
3.
《Planetary and Space Science》1987,35(11):1359-1366
The Low Energy Charged Particle (LECP) experiment on the Voyager 2 spacecraft in the outer heliosphere ( > 10 a.u.) has observed several occasions when there was a peak in the interplanetary ion spectra for ions of energies ∼ 0.5–1.0 MeV. Such enhancements can last for several days, suggesting that at these times particles of these energies dominate the low energy cosmic population in this region of the heliosphere. Two specific cases are discussed. The enhancements seem to be associated with the passage of transient interplanetary shock events, with the ion anisotropies generally showing outflow. The most straight-forward explanation for the observations seems to involve only a propagation effect of ions from the inner to the outer solar system. This conclusion is supported by simple modeling of the propagation of an event observed at 1 a.u. to the spacecraft at ∼ 12 a.u. 相似文献
4.
The Sun is an effective particle accelerator that produces solar energetic particle (SEP) events, during which particles of up to several GeVs can be observed. These events, when they are observed at Earth with the neutron monitor network, are called ground-level enhancements (GLEs). Although these events with their high-energy component have been investigated for several decades, a clear relation between the spectral shape of the SEPs outside the Earth’s magnetosphere and the increase in neutron monitor count rate has yet to be established. Hence, an analysis of these events is of interest for the space weather and for the solar event community.In this article, SEP events with protons accelerated to above 500 MeV were identified using data obtained with the Electron Proton Helium Instrument (EPHIN) onboard the Solar and Heliospheric Observatory (SOHO) between 1995 and 2015. For a statistical analysis, onset times were determined for the events and the proton energy spectra were derived and fitted with a power law.As a result, we present a list of 42 SEP events with protons accelerated to above 500 MeV measured with the EPHIN instrument onboard SOHO. The statistical analysis based on the fitted spectral slopes and absolute intensities is discussed, with special emphasis on whether an event has been observed as a GLE. Furthermore, we are able to determine that the derived intensity at 500 MeV and the observed increase in neutron monitor count rate are correlated for a subset of events. 相似文献
5.
R. T. Stewart 《Astrophysics and Space Science》1986,118(1-2):115-125
Observations of the solar corona collected over the past decade are discussed from the point of view of short-term (<1 day) and long-term (>1 year) effects. Various phenomena are described, including coronal mass ejections, shock waves, and magnetic sector structures. It is argued that emerging magnetic flux is probably the prime cause of these phenomena, although the details of the interaction processes in the corona are not fully understood.Short-term changes are caused by the sudden release of energy in the lower corona or chromosphere. The prime cause is thought to be due to the build-up of highly sheared magnetic flux. Theoretical work of late has concentrated on attempting to explain the time-scales of flare events (<10 s) in terms of magnetic reconnection. Other work has concentrated on attempting to explain observed features of coronal mass ejections which last for periods of several hours. Long-term changes last for several years and are characterized by the slow evolution of coronal structures, especially magnetic sectors, which extend into interplanetary space out and beyond the Earth. Recent observations place new restraints on the solar dynamo which is thought to be responsible for the emerging magnetic flux involved in these long-term changes.Paper presented at the IAU Third Asian-Pacific Regional Meeting, held in Kyoto, Japan, between 30 September–6 October, 1984. 相似文献
6.
Following many solar flares, electrons with kinetic energy > 40 keV appear in interplanetary space. There are two classes of such electrons: prompt electrons which arrive within an hour of the flare and delayed electrons which arrive about a day following the flare. The promptly arriving electrons are found to be of two types: Simple (S) events are associated with solar flares which occur in the absence of large area Type I radio noise storm and the complex (C) events resulting from flares beneath these large radio noise regions. The propagation of energetic solar flare electrons to the earth is best described in terms of cones of propagation. In the S-events the cones have about 30° opening angle whereas in the C-type events the cones open to about 90° full angle. Outside the boundaries of these cones the electron flux is much reduced. Within the cones there is a net streaming of the electrons away from the sun. Solar flare electron fluxes do not show filamentary structure even at times when protons from the same flare do. This suggests that the electrons are injected into the interplanetary field from regions distinct from the proton injection region. The delayed solar electron events are accompanied by large fluxes of protons > 500 keV. These events are sometimes closely related to a sudden commencement. 相似文献
7.
Fifteen type II solar radio events have been identified in the 2 MHz to 30 kHz frequency range by the radio astronomy experiment on the ISEE-3 satellite over the period from September 1978 to December 1979. These data provide the most comprehensive sample of type II radio bursts hitherto observed at kilometer wavelengths. Dynamic spectra of a number of events are presented. Where possible, the 15 events have been associated with an initiating flare, ground-based radio data, the passage of a shock at the spacecraft and the sudden commencement of a geomagnetic storm. The general characteristics of kilometric type II bursts are discussed.Research Associate, University of Maryland, U.S.A. 相似文献
8.
The integral flux of low energy protons (> 10 MeV) observed by the University of New Hampshire cosmic ray detector aboard the Pioneer 9 spaceprobe has been compared with similar measurements of the near-Earth spacecraft Explorer 34 during the decay phase of the February 25–March 2, 1969 series of solar cosmic ray events. At this time the Pioneer 9 spaceprobe was 0.8 AU from the Sun and close to the Sun-Earth radial line. The ratio of integral fluxes as measured by the separated spacecraft can be calculated theoretically during the convective phase of the decay of these events and will depend on whether energy loss processes are operative. A comparison of the observed and theoretically calculated ratios suggests that the adiabatic energy loss process is operative. 相似文献
9.
We studied the cosmic ray intensity variation due to interplanetary magnetic clouds during an unusual class of low amplitude
anisotropic wave train events. The low amplitude anisotropic wave train events in cosmic ray intensity have been identified
using the data of ground based Deep River neutron monitor and studied during the period 1981–1994. Even though the occurrence
of low amplitude anisotropic wave trains does not depend on the onset of interplanetary magnetic clouds, but the possibility
of occurrence of these events cannot be overlooked during the periods of the interplanetary magnetic cloud events. It is observed
that the solar wind velocity remains higher (> 300) than normal and the interplanetary magnetic field B remains lower than normal on the onset of the interplanetary magnetic cloud during the passage of low amplitude wave trains.
It is also noted that the proton density remains significantly low during high solar wind velocity, which is expected. The
north south component of interplanetary magnetic field Bz turns southward to one day before the arrival of cloud and remains in the southward direction after the arrival of a cloud.
During these events the cosmic ray intensity is found to increase with increase of solar wind velocity. The superposed epoch
analysis of cosmic ray intensity for these events during the onset of interplanetary magnetic clouds reveals that the decrease
in cosmic ray intensity starts not at the onset of the cloud but after a few days. The cosmic ray intensity increases on arrival
of the magnetic cloud and decreases gradually after the passage of the magnetic cloud. 相似文献
10.
An extensive study of the IMP-6 and IMP-8 plasma and radio wave data has been performed to try to find electron plasma oscillations associated with type III radio noise bursts and low energy solar electrons. This study shows that electron plasma oscillations are seldom observed in association with solar electron events and type III radio bursts at 1.0 AU. In nearly four years of observations only one event was found in which electron plasma oscillations are clearly associated with solar electrons. Numerous cases were found in which no electron plasma oscillations with field strengths greater than 1 V/m could be detected even though electrons from the solar flare were clearly detected at the spacecraft.For the one case in which electron plasma oscillations are definitely produced by the electrons ejected by the solar flare, the electric field strength is very small, only about 100 V/m. This field strength is about a factor of ten smaller than the amplitude of electron plasma oscillations generated by electrons streaming into the solar wind from the bow shock. Electromagnetic radiation, believed to be similar to the type III radio emission, is also observed coming from the region of more intense electron plasma oscillations upstream of the bow shock. Quantitative calculations of the rate of conversion of the plasma oscillation energy to electromagnetic radiation are presented for plasma oscillations excited by both solar electrons and electrons from the bow shock. These calculations show that neither the type III radio emissions nor the radiation from upstream of the bow shock can be adequately explained by a current theory for the coupling of electron plasma oscillations to electromagnetic radiation. Possible ways of resolving these difficulties are discussed. 相似文献
11.
A number of meter wavelength solar radio bursts of spectral Type-III have been observed by means of a solar radio spectroscope (40–240 MHz) simultaneously with sudden enhancements of low frequency (164 KHz) field strength (SES's) of Radio Tashkent which are known to take place due to the enhancements of D-layer ionization caused by flare-time solar X-rays.The association between the solar X-ray flares as detected by the SES's and the Type-III meter-wave solar bursts is discussed. It is found that the association of SES's and meter wave solar bursts, which implies the ejection of flare-time electrons towards the photosphere as well as corona, is about 72%. 相似文献
12.
A discussion is presented on the half hour averaged low energy solar alpha to solar proton flux ratios observed following the three large solar flares of May 23, 1967. One of the large changes observed in the particle ratios (following a sudden commencement (SC) storm observed on the earth) is interpreted as due to a source effect. The second large change, again observed following an SC, is observed in the equal velocity and equal rigidity ratios and not in the equal energy/charge ratios. This observation suggests that electric fields in an interplanetary disturbance may be the cause of the modulations. 相似文献
13.
Energetic solar electrons in the interplanetary medium 总被引：3，自引：0，他引：3
R. P. Lin 《Solar physics》1985,100(1-2):537-561
ISEE-3 measurements extending down to 2 keV energy have provided a new perspective on energetic solar electrons in the interplanetary medium. Impulsive solar electron events are observed, on average, several times a day near solar maximum, with 40% detected only below 15 keV. The electron energy spectra have a nearly power-law shape extending smoothly down to 2 keV, indicating that the origin of these events is high in the corona. These coronal flare-like events often produced 3He-rich particle events.In large solar flares which accelerate electrons and ions to relativistic energies, the electron spectrum appears to be modified by a second acceleration which results in a double power-law shape above 10 keV with a break near 100 keV and flattening from 10–100 keV. Large flares result in long-lived (many days) streams of outflowing electrons which dominate the interplanetary fluxes at low energies. Even in the absence of solar activity, significant fluxes of low energy electrons flow out from the Sun.Solar type-III radio bursts are produced by the escaping 2–102 keV electrons through a beam-plasma instability. The detailed ISEE-3 measurements show that electron plasma waves are generated by the bump-on-tail distribution created by the faster electrons running ahead of the slower ones. These plasma waves appear to be converted into radio emission by nonlinear wave-wave interactions. 相似文献
14.
The height structure of a thick-target solar hard X-ray source is predicted for a beam injected vertically downward with a power-law spectrum and dominated by Coulomb collisional energy losses. This structure is characterised by the ratio of hard X-ray flux from an upper part of the source to that from the entire source, and is essentially a function only of the atmospheric column density ΔN (cm?2) in the upper region. These predictions are compared with the flux ratios at 150 keV and 350 keV observed by two spacecraft for five events in which the solar limb occults part of the source for one spacecraft. In three events the occulting levels h ranged from 0 to 2500 km. For these the theoretical and observed ratios are found to be comparable for values of ΔN in reasonable accord with those found at these altitudes by optical and UV spectroscopic modelling of flare chromospheres. In one event the occultation ratio was observed to rise after the burst peak and it is found that this rise is consistent with an increase in ΔN due to conductively driven chromospheric evaporation. However the energy dependence of the occultation ratio is not consistent with that predicted by the model and it is concluded that non-collisional losses must be significant in beam dynamics. In the other two events, the occultation level h was ? 25 000 km. For these the energy dependence of the occultation ratio is comparable with the model predictions. However the values of ΔN required demand extremely high coronal densities and/or acceleration altitudes. Furthermore, the one observed evolution of the occultation ratio is entirely inconsistent with the model. It is concluded that in these, bremsstrahlung emissions other than that from a beam must be important. 相似文献
15.
A recent model of solar energetic particle propagation suggests that large fluxes of protons may produce their own turbulence. To verify this theoretical prediction it becomes essential to find out whether these fluxes cause appreciable changes in the interplanetary magnetic field (IMF) fluctuation regime. It is also important to check if the suggested optimum conditions for wave production are consistent with observational evidence. In the present work we perform a study of directional power and magnetic helicity spectra of the IMF fluctuations from a few hours before to a few hours after the maximum flux of 4–13 MeV protons observed on board the two Helios spacecraft during eight solar events. The time evolution of the directional power and helicity spectra show increases which may be associated with the solar energetic proton (SEP) flux in two of the analysed events. In one event, we present a decrease of turbulence and helicity coincident with the maximum flux of SEP may also admit an interpretation in terms of self-generated waves. The existence of solar wind phenomena such as sector boundaries or interplanetary shocks obscure possible signatures of proton self-generated waves in two events. One event with a low level of turbulence previous to the arrival of particles shows no turbulence increase which might be associated with them. The remaining two events show no evidence of particle-generated turbulence, but the conditions on which these were observed do not fulfil some assumptions of the model. 相似文献
16.
Carlos Roberto A. Augusto Anderson C. Fauth Carlos E. Navia Hisatake Shigeouka Kin H. Tsui 《Experimental Astronomy》2011,31(2-3):177-197
An overview of the results of the search for small solar transient events, in association with muon enhancements (deficits) registered at ground-level by the Tupi muon telescopes, is presented. Among the events, there are three interplanetary shocks and two solar flares of small scale whose X-ray emission flux is much smaller than 10???5 W m?2 at 1 AU (GOES-Tupi connection). Two of the interplanetary shocks are cataloged as corotating interaction region and the third shock is due to the passage of a CME (coronal mass ejection) ejecta (ACE and SOHO-Tupi connection) in the Earth’s proximities. In most cases, the particles excess (deficit) coming from these events have only been observed with spacecraft instruments. However, the Tupi telescopes are located at sea level and within the South Atlantic Anomaly (SAA), a region where the shielding effect of the magnetosphere is not perfectly spherical and shows a ‘dip’. This fact enables the muon telescopes to achieve a low rigidity of response to primary and secondary charged particles (≥?0.1 GV). Muon excesses (deficits) with significances above 4σ have been found. These events observed at ground admit a temporal correlation with solar transient events observed by spacecrafts, which suggests strongly a real connection between them. Details of these observations are reported. 相似文献
17.
Measurements of the flux of helium nuclei in the 24 January, 1971, event and of helium and (C, N, O) nuclei in the 1 September, 1971, event are combined with previous measurements to obtain the relative abundances of helium, (C, N, O), and Fe-group nuclei in these events. These data are then summarized together with previously reported results to show that, even when the same detector system using a dE/dx plus range technique is used, differences in the He/(C, N, O) value in the same energy/nucleon interval are observed in solar cosmic ray events. Further, when the He/(C, N, O) value is lower the He/(Fe-group nuclei) value is also systematically lower in these large events. When solar particle acceleration theory is analyzed, it is seen that the results suggest that, for large events, Coulomb energy loss probably does not play a major role in determining solar particle composition at higher energies (> 10 MeV). The variations in multicharged nuclei composition are more likely due to partial ionization during the acceleration phase.NASA/NAS Senior Resident Research Associate, on leave from Tata Institute of Fundamental Research, Bombay. 相似文献
18.
We study 27 increases of the flux of 300–800 keV electrons on board HELIOS A or B, associated with intense type III radio bursts close to perihelion passages of the two spacecraft, during the solar minimum. Electrons can be detected inside cones with an angular width between 30° and 60°. Though only intense type III bursts are associated with recognizable electron events in space, such an association does not exist for all of them; this fact and great differences in fluxes of the individual events indicate that, apart from the intensity, also some other charactefistic of the type III burst acceleration or propagation process determines the resulting flux of electrons in space; the energy spectrum of the accelerated electrons is one of the likely candidates. A comparison of the electron flux in these events with the flux of 1.7–3.7 MeV nucl–1 helium reveals very large variations of the helium/electron flux ratio, by a factor of at least 15 and possibly much higher. We demonstrate that these variations are not caused by propagation effects in interplanetary space. Therefore, they must be due either to propagation effects in the solar corona or, more likely, to intrinsic variations in the relative production of electrons and nuclei in the type III burst process. An extrapolation of the observed fluxes to 1 AU shows that in only 7 of the 27 electron events studied might a marginal > 1.7 MeV helium flux be recognized ar the Earth distance. 相似文献
19.
We have deduced the power-law rigidity spectra, J(P)=AP
–, and the spectral evolution of the solar flare events that occurred in the present solar activity cycle on 6 November 1997, 14 July 2000, and 15 and 18 April 2001. The implications of these results for the acceleration of high-energy protons are discussed. The analysis is based on the ratios of the Mt. Washington to the Durham neutron monitor count-rate increases during the solar flare events. These two neutron monitors are located at different elevations (828 and 1030 g cm–2, respectively) but at approximately the same geographical latitude and longitude. The proton spectra from 1 to 10 GV determined from the ratios of the count rate increases of the two neutron monitors are found to agree with those deduced from the global neutron monitor network or selected neutron monitors in 10 solar flare events from 1960 to 1990 for which comparative results are available. Thus the ratio method is quick, easy and reliable for deducing the spectral shape of solar flare protons at neutron monitor rigidities and for obtaining the spectral evolution as a function of time. 相似文献
20.
In the present work an analysis has been made of the extreme events occurring during July 2005. Specifically, a rather intense
Forbush decrease was observed at different neutron monitors all over the world during 16 July 2005. An effort has been made
to study the effect of this unusual event on cosmic ray intensity as well as various solar and interplanetary plasma parameters.
It is noteworthy that during 11 to 18 July 2005 the solar activity ranged from low to very active. Especially low levels occurred
on 11, 15, and 17 July whereas high levels took place on 14 and 16 July 2005. The Sun is observed to be active during 11 to
18 July 2005, the interplanetary magnetic field intensity lies within 15 nT, and solar wind velocity was limited to ∼500 kms-1.
The geomagnetic activity during this period remains very quiet, the Kp index did not exceed 5, the disturbance storm time
Dst index remains ∼-70 nT and no sudden storm commencement has been detected during this period. It is noted that for the
majority of the hours, the north/south component of the interplanetary magnetic field, Bz, remains negative, and the cosmic
ray intensity increases and shows good/high correlation with Bz, as the polarity of Bz tends to shift from negative to positive
values, the intensity decreases and shows good/high anti-correlation with Bz. The cosmic ray intensity tends to decrease with
increase of interplanetary magnetic field strength (B) and shows anti-correlation for the majority of the days.
Published in Astrofizika, Vol. 51, No. 2, pp. 255–265 (May 2008). 相似文献