Mean occurrence frequency and temporal risk analysis of solar particle events

The protection of astronauts from space radiation is required on future exploratory class and long-duration missions. For the accurate projections of radiation doses, a solar cycle statistical model, which quantifies the progression level within the cycle, has been developed. The resultant future cycle projection is then applied to estimate the mean frequency of solar particle events (SPEs) in the near future using a power law function of sunspot number. Detailed temporal behaviors of the recent large event and two historically large events of the August 1972 SPE and the November 1960 SPE are analyzed for dose-rate and cumulative dose equivalent at sensitive organs. Polyethylene shielded “storm shelters” inside spacecraft are studied to limit astronauts’ total exposure at a sensitive site within 10 cSv from a large event as a potential goal that fulfills the ALARA (as low as reasonably achievable) requirement.     

The solar particle enhancement of April 14–17, 1994 observed without flare signature

We present the results of measurements of the solar energetic particle (SEP) flows in the Earth polar caps obtained from KORONAS-I on April 14, 1994. The maximum energy of protons was 12 MeV and the maximum energy of electrons was 1.3 MeV. The asymmetry of the North-South flows was observed several hours after their peak intensity. We determined the propagation characteristics of SEP in the isotropic diffusion model. Although the SEP enhancement has not been related to the solar flaring event, the genetic relationship of this effect with one of the largest-scale dynamical events on the Sun measured from YOHKOH is obvious. The possible sources of particle acceleration are discussed.     

Solar particle event dose and dose-rate distributions: parameterization of dose-time profiles, with subsequent dose-rate analysis.

Calculations of total dose and equivalent dose as functions of time, as well as dose-rate and equivalent dose rate since event start are presented for fifteen of the larger solar particle events that occurred during the period between November 1987 and August 1991. The doses, dose-equivalents, and rates presented are for exposures to the skin, ocular lens, and bone marrow behind a thickness of aluminum shielding which provides protection comparable to that of a thin spacecraft. The calculated dose vs time profiles are parameterized using a Weibull cumulative distribution as the fitting function. Parameters are determined using least-squares techniques. Fitted curves are then differentiated to produce smoothed dose-rate curves for each of the events. These results provide a useful starting point for the development of methods to predict the cumulative doses and times to reach various dose limits from a limited number of dosimeter measurements early in the evolution of a solar particle event.     

Comparison of the SPE model with proton and heavy ion data.

Proton data from the GOES 6 and 7 satellites and heavy ion data from the IMP-8 satellite have been compared to the expected results of Nymmik's new model for solar particle event fluences. This model calculates the energy spectra of ions for protons through nickel for solar particle events, based upon the observed proton integral fluence above 30 MeV. Based upon 27 observed proton events of solar cycle 22, and three large historical events, with integral fluences above 30 MeV of greater than 10(6) particles/cm2, a reasonable agreement with model predictions is seen for more than half of the events. However, several events show a marked departure from the model predictions, leading to the conclusion that there may exist more than a single class of event, or that it may be necessary to include additional parameters within the model, such as solar disk position of the source flare, or height of disturbance in the solar corona. Data for heavy ions, (oxygen and iron), were limited to a total of six solar particle events, of which only two occurred in solar cycle 22. The agreement between data and the model predictions appeared to be quite good, however this agreement was sensitively dependent upon the value taken for the proton fluence above 30 MeV.     

Evaluation of the energy spectrum of solar protons according to the balloon measurement data and Monte Carlo simulation

The method for evaluating the energy spectra of solar protons at the boundary of the Earth’s atmosphere according to the data of balloon measurements carried out at the Lebedev Institute of Physics, Russian Academy of Sciences, and the results of Monte Carlo simulation of the processes of proton interaction in the Earth’s atmosphere has been developed. The balloon measurements during solar proton events make it possible to determine the absorption spectra of solar cosmic rays in the atmosphere. Comparison of the experimental data with the results of the simulation of propagation of solar protons (E _p = 10 MeV-10 GeV) in the atmosphere, based on GEANT-4, allows determination of the energy spectra of solar protons at the atmospheric boundary. The results of the determination of the energy spectra of solar protons in a number of solar proton events in the current (23th) solar activity cycle are reported.     

“Hot” bands of CO and the effect of vibration-rotation interaction on the solar CO spectrum

For the first overtone bands of CO, theoretical Herman-Wallis factors and experimental values show some inconsistencies for high excitation transitions. To resolve this problem, the relative band intensities, as well as the relative line intensities, are examined with CO lines in the solar infrared spectrum. The relative rotationless dipole-moment matrix elements and the Herman-Wallis factors for 2-0, 3-1, 4-2, 5-3 and 6-4 bands obtained from the solar CO spectrum are reasonably consistent with the theoretical predictions based on the dipole-moment function but disagree with results obtained in high-temperature emission measurements. It is shown that a reinterpretation of the high-temperature emission measurements is possible; the resulting Herman-Wallis factors become compatible with theoretical predictions as well as with the solar analysis.     

Analysis of proton events from long-lived active regions accompanied by hectometric radio bursts

Proton events accompanied by hectometric radio bursts have been analyzed on the basis of the PROGNOZ-8 satellite measurements. Proton fluxes with energies E>100 MeV andE > 500 MeV were recorded in April and May 1981 from the powerful flares developed in large sunspot groups which existed on the Sun during two solar revolutions.     

Comment on the use of GOES solar proton data and spectra in solar proton dose calculations.

There is a need to understand the calibration and response of the GOES solar particle detectors since the GOES data are being used to evaluate high energy solar particle events. We share some of our experience in utilizing these data in the analysis of solar particle ground-level events (GLEs). For the 29 September 1989 event, we have evaluated the solar proton and alpha particle spectral characteristics throughout the event. The results show that the solar cosmic ray spectrum is extremely hard at low energies with the magnitude of the slope increasing with increasing energy and with time.     

Absorbed dose from galactic cosmic rays and solar protons as derived from stratospheric measurements

Regular measurements of charged-particle fluxes in the Earth’s atmosphere, performed at the Lebedev Institute of Physics, Russian Academy of Sciences since 1957 up to date, are used to determine the absorbed dose rate in the atmosphere from galactic cosmic rays in the period of minimum solar activity and from solar protons during solar proton events. The values of the absorbed dose rate estimated from the measurement data for some intense solar proton events are reported.     

Spectral peculiarities of high energy X-ray radiation,gamma radiation,and Submillimeter radio emission in the impulsive phase of a solar flare

We analyze experimental data on the temporal behavior of fluxes and energy spectra of hard solar X-ray and gamma radiation in the energy range of 0.015 to 300 MeV, obtained onboard the CORONAS-F satellite during a solar flare on August 25, 2001. These data are compared with measurements of the radio emission fluxes over the wide frequency range of 1–405 GHz. For our analysis, we use data obtained onboard the YOHKOH, TRACE and GOES satellites, along with ground-based observations of this solar event using the Solar Submillimeter Telescope (SST; Argentina). For the first time, we find nearly simultaneous changes in the energy spectra of gamma radiation over the range 10–150 MeV and the frequency spectrum of radio emission at the beginning and during a impulsive phase of this event (whose duration did not exceed three minutes).     

Radiation measurements on the Mir Orbital Station

Radiation measurements made onboard the MIR Orbital Station have spanned nearly a decade and covered two solar cycles, including one of the largest solar particle events, one of the largest magnetic storms, and a mean solar radio flux level reaching 250 x 10(4) Jansky that has been observed in the last 40 years. The cosmonaut absorbed dose rates varied from about 450 microGy day-1 during solar minimum to approximately half this value during the last solar maximum. There is a factor of about two in dose rate within a given module, and a similar variation from module to module. The average radiation quality factor during solar minimum, using the ICRP-26 definition, was about 2.4. The drift of the South Atlantic Anomaly was measured to be 6.0 +/- 0.5 degrees W, and 1.6 +/- 0.5 degrees N. These measurements are of direct applicability to the International Space Station. This paper represents a comprehensive review of Mir Space Station radiation data available from a variety of sources.     

Detection of cosmic ray events by LEP experiments

Accelerator experiments located at LEP collider have been used also to detect cosmic ray events. Various results obtained by Cosmo-ALEPH, DELPHI and L3+C collaborations are described). Emphasis is put on comparisons of various measurements with Monte-Carlo simulations based on current models of primary hadron-hadron interactions. Analysis of muon momentum spectrum by Cosmo-ALEPH is presented and the link of these measurements to various tests of hadron-hadron interactions models is explained using L3+C data. Cosmo-ALEPH studies of coincident events between distant scintillator stations is briey described. The analyses of multi-muon bundles are explained in more details for all three experiments Cosmo-ALEPH, DELPHI and L3+C. Other topics like source searches by L3+C, ALEPH and DELPHI, L3+C results on anti-proton/proton flux, solar are study, etc. demonstrate large variety of cosmic ray studies at LEP.     

Identification of major proton fluence events from nitrates in polar ice cores.

Large transient concentrations of nitrates in polar ice cores have been identified as the signature of some major solar proton fluence events between 1940 and 1991. We review this solar proton proxy identification technique using nitrate concentration measurements in ice cores from the Arctic and Antarctic. Using this identification technique we go back in time in an attempt to identify major solar proton events during the past several centuries. There is a very large nitrate increase corresponding to the Carrington flare of 1859 evident in the Arctic ice core. Other significant nitrate increases may indicate that major solar proton events occurred toward the end of the last century. The problems associated with this new technique of using nitrates as proxies to identify solar proton events are discussed.     

QCD studies with {\rm e^+e^-} annihilation data at 172-189 GeV

We have studied hadronic events from annihilation data at centre-of-mass energies of 172, 183 and 189 GeV. The total integrated luminosity of the three samples, measured with the OPAL detector, corresponds to 250 pb. We present distributions of event shape variables, charged particle multiplicity and momentum, measured separately in the three data samples. From these we extract measurements of the strong coupling , the mean charged particle multiplicity and the peak position in the distribution. In general the data are described well by analytic QCD calculations and Monte Carlo models. Our measured values of , and are consistent with previous determinations at . Received: 17 December 1999 / Published online: 18 May 2000     

Analysis of ground level enhancement on January 6, 2014

Variations in the rigidity spectrum and anisotropy of cosmic rays during ground level enhancement (GLE) on January 6, 2014, is investigated using ground-based observations of cosmic rays (CRs) from the worldwide network of stations and spacecraft measurements obtained via a spectrographic global survey. The CR rigidity spectrum and relative variations in the intensity of CRs with rigidity of 4 GV are presented in the solar–ecliptic geocentric coordinate system in certain periods of the investigated event. It is shown that protons were accelerated during this GLE up to a particle rigidity of R ~ 2.4 GV. In the ~0.3 to ~2.4 GV range of rigidity, the CR differential rigidity spectra during the considered event were described by neither a power function nor an exponential function of particle rigidity. At the time of GLE, the Earth was in a loop-like IMF structure.     

Ionization states of cosmic rays:Anuradha (IONS) experiment in Spacelab-3

The measurements of the ionization states, composition, energy spectra and spatial distribution of heavy ions of helium to iron of energies 10–100 MeV/amu in the anomalous cosmic rays are of major importance in understanding their origin which is unknown at present.Anuradha (IONS) cosmic ray experiment in Spacelab-3 was designed to determine the above properties in near earth space and this had a highly successful flight and operations aboard the shuttle Challenger at an orbital altitude of 352 km during 29 April to 6 May 1985. The instrument employs solid state nuclear track detectors (CR-39) of high sensitivity and large collecting area of about 800 cm² and determines the arrival time information of particles with active elements. Experimental methods, flight operations and preliminary results are briefly described. Initial results indicate that relatively high fluxes of low energy cosmic ray α-particles, oxygen group and heavier ions were obtained. The flight period corresponded to that of quiet Sun and the level of solar activity was close to solar minimum. It is estimated that about 10,000 events of low energy cosmic ray alpha particles with time annotation are recorded in the detector together with similar number of events of oxygen and heavier ions of low energy cosmic rays. The authors felicitate Prof. D S Kothari on his eightieth birthday and dedicate this paper to him on this occasion.     

The space environment monitor aboard FY-2 satellite

The space environment monitor (SEM) aboard FY-2 satellite consists of the high energy particle detector (HEPD) and the solar X-ray flux detector (SXFD). The SEM can provide real-time monitoring of flare and solar proton event for its operation at geostationary orbit and is also the first Chinese space system for monitoring and alerting solar proton event. During the 23rd solar maximum cycle, almost all the solar proton events that took place in this period are monitored and some of them are predicted successfully by analyzing the characteristics of X-ray flare monitored by the SEM. Some basic variation characteristics of particle at geostationary orbit are found such as day-night periodic variation of particle flux, the electron flux with energy >1.4 MeV in the scope from 10 to 200/cm2 s sr and the proton flux with energy >1.1 MeV in the scope from 600 to 8000/cm·s·sr during the time with no magnetic storm and solar eruption.     

干旱破纪录事件预估理论研究

对中国614个常规观测站1960—2007年的月温度、降水等要素计算出的干旱指数资料进行统计分析,揭示了48年来中国干旱破纪录事件的强度特征.根据破纪录事件的相关概率理论,提出了适用于任意分布下的计算破纪录事件发生强度和时间的方法,并推导了在高斯分布情况下的破纪录事件强度和时间的理论值计算公式.利用历史资料验证了干旱指数服从高斯分布,并将历史资料中已知的干旱破纪录事件作为初始条件,经理论推导得到下一次干旱破纪录事件的期望值,并与实测数据进行了对比,结果符合观测事实,预估效果较好.在此基础上对中国未来可能发 关键词： 破纪录事件 极端气候事件 干旱指数 预估     

Numerical Simulation of the 12 May 1997 CME Event

Our newly developed CESE MHD model is used to simulate sun-earth connection event with the well-studied 12 May 1997 CME event as an example. The main features and approximations of our numerical model are as follows： （1） The modifed conservation element and solution element （CESE） numerical scheme in spherical geometry is implemented in our code. （2） The background solar wind is derived from a 3D time-dependent numerical MHD model by input measured photospheric magnetic fields. （3） Transient disturbances are derived from solar surface by introducing a mass flow of hot plasma. The numerical simulation has enabled us to predict the arrival of the interplanetary shock and provided us with a relatively satisfactory comparison with the WIND spacecraft observations.