Interplanetary acceleration of low-energy protons as observed during the 25 september 1978 shock event

ISEE-3 observations of a long-lasting low-energy proton intensity increase during the 25 September 1978 shock event are presented as an example for interplanetary particle acceleration in association with shock waves. The observations are discussed in the light of current models for particle acceleration. The particular shape of the time intensity behaviour of the particle intensity increase, the existence of a shock spike and the observed particle distributions indicate that the particles are accelerated at the shock by the induced electric field $\text{E}\text{= ?}\text{1}\text{c}\text{V}\text{×}\text{B}$.     

Low-energy proton interaction with interplanetary magnetohydrodynamic discontinuities

Low energy proton measurements associated with interplanetary MHD discontinuities were detected by the DFH instrument on ISEE-3 spacecraft during the solar maximum period, September 1978–March 1980. The observations were made by three detectors, within eight sectors 45°wide each around the spacecraft, in eight energy channels extended from 35–1600Kev. They confirm that local magnetohydrodynamic conditions, especially discontinuities, significantly affect the propagation of low energy particles in the interplanetary medium.     

Enhancement in low-energy region ofa proton flux associated with interplanetary shock waves

We study time evolution of an energy spectrum of a proton flux in the range of 47 – 4750 keV for the energeticparticle event occurred on 255 DOY in 1999, which we consider as one of typical diffusive acceleration events associated with interplanetary shocks and irrespective of large X-ray solar flares. Fast enhancement during evolution is found in the range of less than about 0.5 MeV. Our previous numerical simulations using Stochastic Differential Equation method could not show this behavior, although we obtained results showing a power law energy spectrum, which suggesting that energetic particles are accelerated diffusively by shock waves, the first-order Fermi acceleration. We consider that less than 0.5 MeV protons need to exist to explain behavior of the observational energy spectrum and perform numerical simulations in order to investigate proper injection models for this event.     

亚暴偶极化中近地磁尾质子的非绝热加速

亚暴偶极化过程中离子加速是亚暴粒子注入的重要产生机制. 通过试验粒子的方法模拟研究了亚暴偶极化期间磁尾等离子体片-8R_e～-5R_e处超低频电磁波对质子的加速过程. 研究表明, 质子在大尺度偶极化电磁场的作用下向内磁层注入, 与质子回旋频率相近的超低频电磁波能够引起低能质子发生非绝热加速. 质子在偶极化前后的能量变化与质子的初始能量密切相关, 初始能量远小于截止能量的质子, 末能量要比初始能量显著增加, 其值与扰动波频率相关, 且量级与偶极化造成的低能氧离子能量增加量级基本相当; 初始能量在截止能量以上的质子受超低频电磁波影响不大, 注入过程能量基本保持不变.      

Comparing proton fluxes of central meridian SEP events with those predicted by SOLPENCO

We have developed an operational code, SOLPENCO, that can be used for space weather prediction schemes of solar energetic particle (SEP) events. SOLPENCO provides proton differential flux and cumulated fluence profiles from the onset of the event up to the arrival of the associated traveling interplanetary shock at the observer’s position (either 1.0 or 0.4 AU). SOLPENCO considers a variety of interplanetary scenarios where the SEP events develop. These scenarios include solar longitudes of the parent solar event ranging from E75 to W90, transit speeds of the associated shock ranging from 400 to 1700 km s⁻¹, proton energies ranging from 0.125 to 64 MeV, and interplanetary conditions for the energetic particle transport characterized by specific mean free paths. We compare the results of SOLPENCO with flux measurements of a set of SEP events observed at 1 AU that fulfill the following four conditions: (1) the association between the interplanetary shock observed at 1 AU and the parent solar event is well established; (2) the heliolongitude of the active region site is within 30° of the Sun–Earth line; (3) the event shows a significant proton flux increase at energies below 96 MeV; (4) the pre-event intensity background is low. The results are discussed in terms of the transit velocity of the shock and the proton energy. We draw conclusions about both the use of SOLPENCO as a prediction tool and the required improvements to make it useful for space weather purposes.     

A statistical analysis of substorm associated tail activity

Substorm onset timing is a critical issue in magnetotail dynamics research. Solar wind energy is accumulated in the magnetosphere and the configuration of the magnetosphere evolves toward an unstable state during the growth phase. At some point, the expansion phase begins and the stored energy is released through a variety of processes that return the magnetosphere to a lower energy state. In recovery the various processes die away. Unfortunately, the ground and magnetospheric signatures of onset, i.e. energy release, can be seen both in the growth phase prior to onset and in the expansion phase after onset. Some investigators refer to each of these events as a substorm. Tail observations suggest that most substorms have one event that differentiates the behavior of the tail field and plasma. We refer to this time as the “main substorm onset”. Each substorm associated phenomenon is timed independently and then compared with main substorm onsets. ISEE-2 tail observations are used to examine the tail lobe magnetic conditions associated with substorms because ISEE-2 orbit has a high inclination and frequently observes lobe field. Approximately 70 ∼ 75% of tail lobe B_t and B_z change are associated with the main substorm onset. If the satellite is more than 3 Re above (below) the neutral sheet, 86% (57%) of plasma pressure dropouts are associated with substorms. We interpret our results as evidence that the effect of the growth phase is to drive the magnetosphere towards instability. As it approaches global instability local regions become temporarily unstable but are rapidly quenched. Eventually one of these events develops into the global instability that releases most of the stored energy and returns the magnetosphere to a more stable configuration.     

Response of the low latitude geomagnetic field to the major proton event of November 2001

A major solar flare eruption occurred at 16:20 UT on 4 November 2001, followed by strong solar radiation storm and proton event recorded by the SOHO and other interplanetary satellites. Coronal mass ejection associated with the flare event triggered an interplanetary shock, which impacted the geomagnetic field after about 33 h. The shock impact was quite intense to produce a SSC magnitude of 80 nT in the low latitude ground magnetic records followed by sharp and deep main phase (Dst −300 nT) in the first stage, following the density (N_p) enhancement. High time resolution digital magnetic field data from the equatorial and low latitude stations in India are analyzed to study the influence of various IP parameters on the intensity and duration of the magnetic storm. A double step storm was found to be in progress caused by the multiple injections. During the period of recovery, after a period of 8 h, a third stage of depression in the ground magnetic field was set in, which corresponded to the southward directed Bz. The energy transfer processes associated with the event is presented.     

First-order Fermi shock acceleration in solar flares

First order Fermi shock acceleration of electrons, protons and alpha particles is compared to observations of energetic particle events. For each event, a unique shock compression ratio produces spectra in good agreement with observation. The simple model predicts that the acceleration time to a given energy will be approximately equal for electrons and protons and, for reasonable solar parameters, can be less than 1 second to ～ 100 MeV.     

Propagation of upstream protons in the near-earth solar wind

The propagation of energetic protons (35–1600 keV) from the Earth's magnetosphere to the ISEE-3 spacecraft located about 240 earth radii (R_E) upstream in the solar wind is used as a tool to study the interaction between these protons and the solar wind. In this preliminary study we present proton pitch angle distributions seen at different times during the development of upstream events that occur in relatively quiet interplanetary conditions. In general a highly anisotropic sunward flow is seen at the beginning of the events. During the course of the events pitch angle distributions may vary between streaming along the field lines (peaked around 0° pitch angle), a uniform intensity between 0° and 90°, and a peaked distribution around a preferred pitch angle that is often near 90°.     

Counterstreaming hydrogen and oxygen ions observed in the magnetosphere on ISEE-1

Counterstreaming ions or ions travelling simultaneously both parallel and antiparallel to the magnetic field direction have been briefly noted in the literature but have not been studied previously in depth. We have studied over 60 counterstreaming ion (CSI) events observed on the ISEE-1 satellite. They were found to occur at altitudes of about 2 to 8 Earth radii on L shells of about 5 to 12 in the evening-to-morning sector from about 1700 - 0900 LT. Often both oxygen and hydrogen ions at a number of energy levels are counterstreaming but some events show only either oxygen or hydrogen ions involved. One particularly interesting event shows only counterstreaming oxygen ions with 417 eV energy; oxygen ions of lower energy (215 eV) and above (630–17000 eV) and all the hydrogen ions between 215–17000 eV energy have lower fluxes and/or nearly isotropic pitch angle distributions. This event correlates well with wave activity in the 17–100 Hz band and is also accompanied by 200 eV downgoing and 400 eV upgoing electrons. Details of this event and the other counterstreaming events are presented.     

利用质子强度变化对太阳质子事件进行短期预报方法初步研究

采用GOSE-10卫星4～9 MeV(P2),9～15 MeV(P3),15～40 MeV(P4),40～80 MeV(P5)能段上的质子通量数据,结合质子能谱,对太阳质子事件发生前各能谱参数的变化特征进行分析,详细介绍利用能谱参数的变化特征及能量E>10 MeV的质子通量数据对太阳质子事件进行预报的新方法,并运用这种方法对2002-2006年期间太阳质子事件进行了预报.预报结果显示,预报提前量最多达到100 h以上,对质子事件的报准率达97.5%,预报方法具备一定的有效性和实用性.      

On compositional variations of heavy ions during solar particle events

Intensity-time profiles of protons, alpha particles, and heavy ions (C, O, Fe) in the MeV/nucleon energy range have been analyzed for one solar particle event following the solar flare on September 23, 1978. The data have been obtained with the wide angle double dE/dx-E sensor of the Max-Planck-Institut/University of Maryland experiment onboard ISEE-3. We found time variations in the iron to helium ratio of up to 2 orders of magnitude and a significant variation of the O/He ratio during this event, whereas the C/O-ratio at the same energy/nucleon appears to be time independent. We investigated the influence of a rigidity dependent mean free path in interplanetary space and of rigidity dependent coronal propagation on heavy ion ratios during solar particle events. We found that both the magnitude and time scale of the ratio changes during the September 23 event cannot be explained by rigidity dependent interplanetary or coronal propagation alone. These ratio changes are probably caused by multiple injection at the sun.     

Origin of coronal and interplanetary shock and particle acceleration of a flare/CME event

By using radio data from ground-based telescopes (from 270 MHz to 25 MHz), and from the Radio and Plasma Wave experiment (WAVES) on board the WIND spacecraft (1–14 MHz and several kHz-11 MHz), as well as FY -2 satellite data, the origin of coronal and interplanetary shock and particle acceleration of the 14 July 2000 flare/CME event (the Bastille day event) have been studied. Main conclusions are as follows: (1) We investigate the causal relationship between metric type 11 bursts observed by the digital IZMIRAN radio spectrograph and type II radio emissions in the frequency range from 1–14 MHz and several kHz-11 MHz observed by the WAVES/WIND. The analysis indicate that the fast CME is the origin of both coronal and interplanetary shocks. (2)According to the time profiles of Hard X-ray, and energetic particles (include proton, ³He, and ⁴He) from FY-2 satellite, it is obvious that the Bastille day event is the event, in which both impulsive and gradual phenomena occur. The energetic particles accelerated not only in flare but also in CME.     

Relativistic solar protons in the ground level event of 23 February 1956: New study

In this study we applied again to the outstanding solar particle event of 23 February 1956, the largest one in the entire history of observations of solar cosmic rays. Due to significant improvement of the analysis/modeling techniques and new understanding of physical processes in the solar atmosphere and interplanetary space, a possibility arises to interpret the old data in the light of modern concept of multiple particle acceleration at/near the Sun. In our new analysis the data of available then neutron monitors and muon telescopes are used. The technique of the analysis includes: (a) calculation of asymptotic cones of ground-based detectors; (b) modeling of cosmic ray detector responses at variable parameters of the flux of solar relativistic protons; (c) determination of primary solar proton parameters outside magnetosphere by comparison of computed responses with observations. Certain evidence was obtained that the flux of relativistic solar protons consisted of two distinct components: prompt and delayed ones. The prompt component with exponential energy spectrum caused a giant impulse-like increase at a number of European cosmic ray stations. The delayed component had a power-law spectrum and was a cause of gradual increase at cosmic ray stations in the North American region. A numerical simulation of the proton acceleration in the vicinity of the magnetic reconnection region brings to the proton spectrum with exponential dependence on energy. This agrees with observational data for the prompt component. It is also shown that the huge increase in ∼5000% on neutron monitors was due to the prompt component only with the exponential proton spectrum. The power-law spectrum of comparable intensity gave considerably smaller effect.     

Particle acceleration and transport at an oblique CME-driven shock

In gradual solar energetic particle (SEP) events, protons and heavy ions are often accelerated to >100 MeV/nucleon at a CME-driven shock. In this work, we study particle acceleration at an oblique shock by extending our earlier particle acceleration and transport in heliosphere (PATH) code to include shocks with arbitrary θ_BN, where θ_BN is the angle between the upstream magnetic field and the shock normal. Instantaneous particle spectra at the shock front are obtained by solving the transport equation using the total diffusion coefficient κ, which is a function of the parallel diffusion coefficient κ_∥ and the perpendicular diffusion coefficient κ_⊥. In computing κ_∥ and κ_⊥, we use analytic expressions derived previously. The particle maximum energy at the shock front as a function of time, the time intensity profiles and particle spectra at 1 AU for five θ_BN’s are calculated for an example shock.     

The dose rate observed on 19-21 October 1989 and its modulation by geophysical effects.

The Liulin dosimeter-radiometer on the MIR space station detected the 19 October 1989 high energy solar proton event. These results show that the main particle increase contains protons with energies up to about 9 GeV. After the main particle onset the Liulin dosimeter observed a typical geomagnetic cutoff modulation of the dose rate from the solar particles as the MIR space station traversed magnetic latitudes. When the interplanetary shock and associated solar plasma enveloped the earth on 20 October between 14 and 17 UT the radiation exposure increased significantly due to the lowering of the geomagnetic cutoff. The analysis of this event shows how various geophysical phenomena can significantly modulate the dose rate encountered by earth-orbiting spacecraft.     

The influence of interplanetary shocks on solar protons measured in the stratosphere.

Since the beginning of the 22nd solar cycle twenty solar proton events were observed by the regular balloon measurements of cosmic rays. Temporal changes of intensities and energy spectra of solar protons with energy 100-500 MeV were obtained. The strong influence of interplanetary shock waves on the proton flux characteristics near the Earth was observed. Possible effects of solar proton transport in the vicinity of shock fronts are discussed to explain the observational data.     

三种类型的质子耀斑

根据SMM卫星观测资料,分析了GRL,PE和GRL/PE三种类型质子耀斑在硬X射线辐射特征上的差异。结果表明,存在的差异与粒子加速区(或作用区)分别处于不同的日面高度有关。      

太阳质子事件与大气臭氧扰动

本文利用统计分析方法分析了1960至1982年间1级以上的太阳质子事件与四个不同地理纬度大气臭氧含量的相互关系.分析结果表明,对于中、低纬度地区,1、2级太阳质子事件基本上不影响大气臭氧含量,只有3、4级的大事件才对臭氧含量产生扰动,而且具有明显的纬度效应;对于极区,1级以上的太阳质子事件就能对臭氧含量产生影响,随着质子事件级别的增高,对臭氧含量的扰动也加大.通常,太阳质子事件发生的当天,臭氧含量开始下降,在第4天下降达最小值,整个扰动持续数日.由太阳质子事件扰动大气臭氧明显的纬度效应证明了太阳质子事件的确是使大气臭氧含量变化的重要因素.此外,分析结果表明,冬天出现的太阳质子事件对臭氧的扰动要大于夏天质子事件对臭氧的扰动.这些结果给出了太阳质子事件影响大气臭氧的一个总轮廓,而且从理论上得到了较好的解释.      

Effects of orbit progression on the radiation exposures from solar proton fluxes in low Earth orbit under geomagnetic storm conditions.

The present study examines the effects of orbit progression on the exposures within a Space Station Freedom module in a 51.6-degree inclined orbit at 450 km. The storm evolution is modeled after the November 1960 event, and the solar proton flux evolution is taken from the August 1972 solar proton event. The effects of a strong magnetic shock, such as was observed during the October 1989 event, is also modeled. The statistics on hourly average storm fields for the last forty years reveal that the largest geomagnetic storms approach a Dst value of -500 nanotesla at the storm peak. Similarly, one of the largest satellite-measured proton flux (> 10 MeV) for space exposures is the event of August 1972. The effects of orbit progression (advance of the line of nodes) is examined for the above conditions to study the variation of exposures under differing times of occurrence of the solar proton peak intensity, attainment of geomagnetic storm maximum, and the location of the line of nodes of the last geomagnetically protected orbit. The impact of the inherent inhomogeneity of the space station module is examined as a limiting factor on exposure with regard to the need of additional parasitic shielding.