共查询到20条相似文献,搜索用时 15 毫秒
1.
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
2.
A. Papaioannou A. Anastasiadis A. Kouloumvakos M. Paassilta R. Vainio E. Valtonen A. Belov E. Eroshenko M. Abunina A. Abunin 《Solar physics》2018,293(7):100
We perform a principal component analysis (PCA) on a set of six solar variables (i.e. width/size (\(s\)) and velocity (\(u\)) of a coronal mass ejection, logarithm of the solar flare (SF) magnitude (\(\log\mathit{SXRs}\)), SF longitude (\(\mathit{lon}\)), duration (\(\mathit{DT}\)), and rise time (\(\mathit{RT}\))). We classify the solar energetic particle (SEP) event radiation impact (in terms of the National Oceanic and Atmospheric Administration scales) with respect to the characteristics of their parent solar events. We further attempt to infer the possible prediction of SEP events. In our analysis, we use 126 SEP events with complete solar information, from 1997 to 2013. Each SEP event is a vector in six dimensions (corresponding to the six solar variables used in this work). The PCA transforms the input vectors into a set of orthogonal components. By mapping the characteristics of the parent solar events, a new base defined by these components led to the classification of the SEP events. We furthermore applied logistic regression analysis with single, as well as multiple explanatory variables, in order to develop a new index (\(I\)) for the nowcasting (short-term forecasting) of SEP events. We tested several different schemes for \(I\) and validated our findings with the implementation of categorical scores (probability of detection (POD) and false-alarm rate (FAR)). We present and interpret the obtained scores, and discuss the strengths and weaknesses of the different implementations. We show that \(I\) holds prognosis potential for SEP events. The maximum POD achieved is 77.78% and the relative FAR is 40.96%. 相似文献
3.
We compare the initial behavior of Fe/O and He/H abundance ratios and their relationship to the evolution of the proton energy spectra in "small" and "large" gradual solar energetic particle (SEP) events. The results are qualitatively consistent with the behavior predicted by the theory of Ng et al. published in 1999. He/H ratios that initially rise with time are a signature of scattering by non-Kolmogorov Alfvén wave spectra generated by intense beams of shock-accelerated protons streaming outward in large gradual SEP events. 相似文献
4.
Particle Acceleration and Propagation in Strong Flares without Major Solar Energetic Particle Events
Solar energetic particles (SEPs) detected in space are statistically associated with flares and coronal mass ejections (CMEs).
But it is not clear how these processes actually contribute to the acceleration and transport of the particles. The present
work addresses the question why flares accompanied by intense soft X-ray bursts may not produce SEPs detected by observations
with the GOES spacecraft. We consider all X-class X-ray bursts between 1996 and 2006 from the western solar hemisphere. 21
out of 69 have no signature in GOES proton intensities above 10 MeV, despite being significant accelerators of electrons,
as shown by their radio emission at cm wavelengths. The majority (11/20) has no type III radio bursts from electron beams
escaping towards interplanetary space during the impulsive flare phase. Together with other radio properties, this indicates
that the electrons accelerated during the impulsive flare phase remain confined in the low corona. This occurs in flares with
and without a CME. Although GOES saw no protons above 10 MeV at geosynchronous orbit, energetic particles were detected in
some (4/11) confined events at Lagrangian point L1 aboard ACE or SoHO. These events have, besides the confined microwave emission,
dm-m wave type II and type IV bursts indicating an independent accelerator in the corona. Three of them are accompanied by
CMEs. We conclude that the principal reason why major solar flares in the western hemisphere are not associated with SEPs
is the confinement of particles accelerated in the impulsive phase. A coronal shock wave or the restructuring of the magnetically
stressed corona, indicated by the type II and IV bursts, can explain the detection of SEPs when flare-accelerated particles
do not reach open magnetic field lines. But the mere presence of these radio signatures, especially of a metric type II burst,
is not a sufficient condition for a major SEP event. 相似文献
5.
A. Anastasiadis A. Papaioannou I. Sandberg M. Georgoulis K. Tziotziou A. Kouloumvakos P. Jiggens 《Solar physics》2017,292(9):134
A novel integrated prediction system for solar flares (SFs) and solar energetic particle (SEP) events is presented here. The tool called forecasting solar particle events and flares (FORSPEF) provides forecasts of solar eruptive events, such as SFs with a projection to occurrence and velocity of coronal mass ejections (CMEs), and the likelihood of occurrence of an SEP event. In addition, the tool provides nowcasting of SEP events based on actual SF and CME near real-time data, as well as the SEP characteristics (e.g. peak flux, fluence, rise time, and duration) per parent solar event. The prediction of SFs relies on the effective connected magnetic field strength (\(B_{\mathrm{eff}}\)) metric, which is based on an assessment of potentially flaring active-region (AR) magnetic configurations, and it uses a sophisticated statistical analysis of a large number of AR magnetograms. For the prediction of SEP events, new statistical methods have been developed for the likelihood of the SEP occurrence and the expected SEP characteristics. The prediction window in the forecasting scheme is 24 hours with a refresh rate of 3 hours, while the respective prediction time for the nowcasting scheme depends on the availability of the near real-time data and ranges between 15?–?20 minutes for solar flares and 6 hours for CMEs. We present the modules of the FORSPEF system, their interconnection, and the operational setup. Finally, we demonstrate the validation of the modules of the FORSPEF tool using categorical scores constructed on archived data, and we also discuss independent case studies. 相似文献
6.
7.
It has been argued that the highest intensities measured near 1 AU during large solar energetic particle events occur in association
with the passage of interplanetary shocks driven by coronal mass ejections, whereas the intensities measured early in the
events (known as the prompt component) are bounded by a maximum intensity plateau known as the streaming limit. A few events
in Solar Cycle 23 showed prompt components with intensities above the previously determined streaming limit. One of the scenarios
proposed to explain intensities that exceed this limit in these events invokes the existence of transient plasma structures
beyond 1 AU able to confine and/or mirror energetic particles. We study whether other particle events with prompt-component
intensities close to the previously determined streaming limit are similarly affected by the presence of interplanetary structures.
Whereas such structures were observed in four out of the nine events studied here, we conclude that only the events on 22 October
1989, 29 October 2003, and 17 January 2005 show interplanetary structures that can have modified the transport conditions
in a way similar to those events with prompt components exceeding the previously determined streaming limit. The other six
events with prompt components close to the previously determined streaming limit were characterized by either a low level
of pre-event solar activity and/or the absence of transient interplanetary structures able to modify the transport of energetic
particles. 相似文献
8.
9.
S. W. Feng Y. Chen B. Li H. Q. Song X. L. Kong L. D. Xia X. S. Feng 《Solar physics》2011,272(1):119-136
In this paper we conduct a data survey searching for well-defined streamer wave events observed by the Large Angle and Spectrometric
Coronagraph (LASCO) on-board the Solar and Heliospheric Observatory (SOHO) throughout Solar Cycle 23. As a result, eight candidate events are found and presented here. We compare different
events and find that in most of them the driving CMEs’ ejecta are characterized by a high speed and a wide angular span, and
the CME–streamer interactions occur generally along the flank of the streamer structure at an altitude no higher than the
bottom of the field of view of LASCO C2. In addition, all front-side CMEs have accompanying flares. These common observational
features shed light on the excitation conditions of streamer wave events. 相似文献
10.
We revisited assessments of the occurrence probability distribution of large events in solar energetic particles (SEP), based on measurements of cosmogenic radionuclides in lunar rocks. We present a combined cumulative occurrence probability distribution of SEP events based on three timescales: directly measured SEP fluences for the past 60 years; estimates based on the terrestrial cosmogenic radionuclides 10Be and 14C for the multi-millennial (Holocene) timescale; and cosmogenic radionuclides measured in lunar rocks on a timescale of up to 1 Myr. These three timescales yield a consistent distribution. The data suggest a strong roll-over of the occurrence probability, so that SEP events with a proton fluence with energy >?30 MeV greater than 1011 (protons cm?2?yr?1) are not expected on a Myr timescale. 相似文献
11.
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
12.
von Rosenvinge T. T. Richardson I. G. Reames D. V. Cohen C. M. S. Cummings A. C. Leske R. A. Mewaldt R. A. Stone E. C. Wiedenbeck M. E. 《Solar physics》2009,256(1-2):443-462
Solar Physics - The solar energetic particle event on 14 December 2006 was observed by several near-Earth spacecraft including the Advanced Composition Explorer (ACE), STEREO A and B, SOHO and... 相似文献
13.
14.
Recently we (Kahler and Ling, Solar Phys.292, 59, 2017: KL) have shown that time–intensity profiles [\(I(t)\)] of 14 large solar energetic particle (SEP) events can be fitted with a simple two-parameter fit, the modified Weibull function, which is characterized by shape and scaling parameters [\(\alpha\) and \(\beta\)]. We now look for a simple correlation between an event peak energy intensity [\(I_{\mathrm{p}}\)] and the time integral of \(I(t)\) over the event duration: the fluence [\(F\)]. We first ask how the ratio of \(F/I_{\mathrm{p}}\) varies for the fits of the 14 KL events and then examine that ratio for three separate published statistical studies of SEP events in which both \(F\) and \(I_{\mathrm{p}}\) were measured for comparisons of those parameters with various solar-flare and coronal mass ejection (CME) parameters. The three studies included SEP energies from a 4?–?13 MeV band to \(E > 100~\mbox{MeV}\). Within each group of SEP events, we find a very robust correlation (\(\mathrm{CC} > 0.90\)) in log–log plots of \(F\)versus\(I_{\mathrm{p}}\) over four decades of \(I_{\mathrm{p}}\). The ratio increases from western to eastern longitudes. From the value of \(I_{\mathrm{p}}\) for a given event, \(F\) can be estimated to within a standard deviation of a factor of \({\leq}\,2\). Log–log plots of two studies are consistent with slopes of unity, but the third study shows plot slopes of \({<}\,1\) and decreasing with increasing energy for their four energy ranges from \(E > 10~\mbox{MeV}\) to \({>}\,100~\mbox{MeV}\). This difference is not explained. 相似文献
15.
Energetic Particle Fluxes during the Bastille Day Solar Eruption 总被引:2,自引:0,他引:2
We report on our observations of solar energetic particle fluxes of p, He, C, O, Ne, Mg, Si, and Fe ions measured by the Energetic and Relativistic Nucleon and Electron (ERNE) experiment associated
with the Bastille Day solar flare and coronal mass ejection (CME) on 14 July 2000. We observed two clear maxima of the Fe/O
ratio at the energies 8.5–15 MeV nucl−1. The first Fe/O maximum occurred ∼ 3 hours after the beginning of the particle event, and the second maximum ∼ 22 hours after
the first one at the arrival of the shock associated with the Bastille Day eruption. We also observed a change in the energy
spectrum of oxygen concurrent with a change in the direction of the interplanetary magnetic field at the start of the second
enhancement of the Fe/O ratio. We propose an interpretation of the particle event where observed interplanetary particle fluxes
are associated with two different particle sources near the Sun and in interplanetary space. We suggest that heavy ions observed
during the first period of the Fe/O enhancement were released when a coronal shock reached a magnetic foot point connected
to 1 AU. The second maximum of Fe/O occurred when spacecraft encountered Fe-rich material stored in magnetic field flux tubes
early in the event and was possibly reaccelerated by the interplanetary shock. 相似文献
16.
We study the influence of the large-scale interplanetary magnetic field configuration on the solar energetic particles (SEPs) as detected at different satellites near Earth and on the correlation of their peak intensities with the parent solar activity. We selected SEP events associated with X- and M-class flares at western longitudes, in order to ensure good magnetic connection to Earth. These events were classified into two categories according to the global interplanetary magnetic field (IMF) configuration present during the SEP propagation to 1 AU: standard solar wind or interplanetary coronal mass ejections (ICMEs). Our analysis shows that around 20 % of all particle events are detected when the spacecraft is immersed in an ICME. The correlation of the peak particle intensity with the projected speed of the SEP-associated coronal mass ejection is similar in the two IMF categories of proton and electron events, ≈?0.6. The SEP events within ICMEs show stronger correlation between the peak proton intensity and the soft X-ray flux of the associated solar flare, with correlation coefficient r=0.67±0.13, compared to the SEP events propagating in the standard solar wind, r=0.36±0.13. The difference is more pronounced for near-relativistic electrons. The main reason for the different correlation behavior seems to be the larger spread of the flare longitude in the SEP sample detected in the solar wind as compared to SEP events within ICMEs. We discuss to what extent observational bias, different physical processes (particle injection, transport, etc.), and the IMF configuration can influence the relationship between SEPs and coronal activity. 相似文献
17.
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
18.
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
19.
20.
G. A. Kovaltsov I. G. Usoskin E. W. Cliver W. F. Dietrich A. J. Tylka 《Solar physics》2014,289(12):4691-4700
While data on the cosmogenic isotopes 14C and 10Be made it possible to evaluate extreme solar proton events (SPEs) in the past, their relation to standard parameters quantifying the SPE strengths, viz. the integrated fluence of protons with energy above 30 MeV, F 30, is ambiguous and strongly depends on the assumed shape of the energy spectrum. Here we propose a new index, the integral fluence of an SPE above 200 MeV, F 200, which is related to the production of the cosmogenic isotopes 14C and 10Be in the Earth atmosphere, independently of the assumptions on the energy spectrum of the event. The F 200 fluence is reconstructed from past cosmogenic isotope data, which provides an assessment of the occurrence probability density function for extreme SPEs. In particular, we evaluate that extreme SPEs with F 200>1010 cm?2 occur no more frequently than once per 10?–?15 kyr. 相似文献