Solar particle events as seen on CRRES.

High energy proton detectors on the Combined Release and Radiation Effects Satellite (CRRES) were used to measure near-Earth solar protons in an 18 degrees inclination orbit between 350 km and 36000 km from July 1990 to October 1991. CRRES data from the major solar particle event on 23-25 March 1991 show conclusively that MeV solar protons can penetrate deep inside the magnetosphere (to an L-shell of 2.5 RE) when a large shock-induced Sudden Storm Commencement (SSC) occurs and significant solar particle populations are present at geosynchronous altitudes. The penetration of solar particles well inside boundaries predicted by Stormer theory occurred during every large solar event of the CRRES mission, as well as many of the smaller ones. Often the deep penetrations occurred simultaneously with the formation of new trapped radiation populations which peak at L-values between 2.3 and 4 RE (depending on particle energy) and which last from days to months.     

Low altitude dose measurements from APEX, CRRES and DMSP

Dosimeter data taken on the APEX (1994–1996), CRRES (1990–1991) and DMSP (1984–1987) satellites have been used to study the low altitude (down to 350 km) radiation environment. Of special concern has been the inner edge of the inner radiation belt due to its steep gradient. We have constructed dose models of the inner edge of the belt from all three spacecraft and put them into a personal computer utility, called APEXRAD, that calculates dose for user-selected orbits. The variation of dose for low altitude, circular orbits is given as a function of altitude, inclination and particle type. Dose-depth curves show that shielding greater than 1/4 in Al is largely ineffectual for low altitude orbits. The contribution of outer zone electrons to low altitude dose is shown to be important only for thin shields and to have significant variation with magnetic activity and solar cycle.     

Direct comparison of transient radiation belt topology and dynamics in 1991 based on measurements onboard Mir space station and NOAA satellite.

In March 1991 the CRRES spacecraft measured a new transient radiation belt resulting from a solar proton event and subsequent geomagnetic disturbance. The presence of this belt was also noted by dosimeter-radiometers aboard the Mir space station (approx. 400 km, 51 degrees orbit) and by particle telescopes on the NOAA-10 spacecraft (850 km, 98 degrees). This event provides a unique opportunity to compare particle flux and dose measurements made by different instruments in different orbits under changing conditions. We present here a comparison of the measurements made by the different detectors. We discuss the topology and dynamics of the transient radiation belt over a period of more than one year.     

Microelectronics effects as seen on CRRES.

A MicroElectronics Test Package (MEP) measured total dose degradation and single event upsets (SEUs) on 60 device types on the Combined Release and Radiation Effects Satellite (CRRES) in an 18 degrees inclination orbit between 350 km and 36000 km from July 1990 to October 1991. Simultaneous measurements of the high energy particle environment were used to make a direct cause and effect comparison of the energetic particle backgrounds and microelectronic performance characteristics. The galactic cosmic ray background for the period of the CRRES mission was at a minimum. The SEUs experienced from the cosmic ray background were correspondingly few in number, but surprisingly produced an equal probability of upset over an L-shell range of 8.5 Earth radii (RE) down to less than 3.0 RE. Cosmic ray induced upset frequencies in proton sensitive chips were over 2 orders of magnitude lower than those produced by protons in the heart of the inner proton radiation belts. Multiple upsets, those produced when a single particle upsets more than one memory location, were just as common from protons as from cosmic rays.     

辐射带AP9模式在南大西洋异常区的系统性量化评估

针对目前辐射带AP9模式量化评估不够系统的问题，基于F_10.7指数确定高、中、低太阳活动水平，以三种太阳活动水平条件下NOAA-15观测的140~500MeV的全向质子通量为参考数据，以南大西洋异常区为对比区域，定义边界吻合度和大小量级差为评估指标，将辐射带AP9模式分别与AP8模式和参考数据进行对比，对AP9模式进行系统性量化评估.结果表明，AP8和AP9模式均能重构出南大西洋异常区，但AP8模式重构的南大西洋异常区轮廓与观测结果更为吻合.平均而言，AP8和AP9模拟结果均比观测值高，AP8比AP9更接近观测值.太阳活动水平越低，AP9与观测之间的差距越小.      

Inner radiation belt source of helium and heavy hydrogen isotopes

Nuclear interactions between inner zone protons and atoms in the upper atmosphere provide the main source of energetic H and He isotopes nuclei in the radiation belt. This paper reports on the specified calculations of these isotope intensities using various inner zone proton intensity models (AP-8 and SAMPEX/PET PSB97), the atmosphere drift-averaged composition and density model MSIS-90, and cross-sections of the interaction processes from the GNASH nuclear model code. To calculate drift-averaged densities and energy losses of secondaries, the particles were tracked in the geomagnetic field (modelled through IGRF-95) by integrating numerically the equation of the motion. The calculations take into account the kinematics of nuclear interactions along the whole trajectory of trapped proton. The comparison with new data obtained from the experiments on board RESURS-04 and MITA satellites and with data from SAMPEX and CRRES satellites taken during different phases of solar activity shows that the upper atmosphere is a sufficient source for inner zone helium and heavy hydrogen isotopes. The calculation results are energy spectra and angular distributions of light nuclear isotopes in the inner radiation belt that may be used to develop helium inner radiation belt model and to evaluate their contribution to SEU (single event upset) rates.     

地磁长期变化引起的低高度卫星轨道辐射带粒子环境的变化

利用IGRF2000模式计算了几个典型轨道辐射带粒子环境并与IGRF1970模式计算的结果进行了比较。计算结果表明，在辐射带的低部，对应某些倾角的能量大于0．1MeV质子的轨道积分通量变化达到2个量级，而通量大10MeV的辐射带质子的轨道积分通量变化达到1个量级；轨道积分通量的最大值变化为1个量级。能量大于0．04MeV辐射带电子的轨道积分通量变化在某些倾角达到3个量级，但轨道积分最大值的变化低于1个量级。1000km以上高度辐射带粒子环境的变化很小。     

Creation of model of quasi-trapped proton fluxes below Earth’s radiation belt

The object of investigation is the phenomenon of proton (from tens keV to several MeV) flux enhancement in near-equatorial region (L < 1.15) at altitude up to ∼1300 km (the storm-time equatorial belt). These fluxes are quite small but the problem of their origin is more interesting than the possible damage they can produce. The well known sources of these protons are radiation belt and ring current. The mechanism of transport is the charge-exchange on neutral hydrogen of exosphere and the charge-exchange on oxygen of upper atmosphere. Therefore this belt is something like the ring current projection to low altitudes. Using the large set of satellites data we obtain the average energy spectrum, the approximation of spectrum using kappa-function, the flux dependence on L, B geomagnetic parameters. On the basis of more than 30 years of experimental observations we made the empiric model that extends model of proton fluxes below 100 keV in the region of small L-values (L < 1.15). The model was realized as the package of programs integrated into COSRAD system available via Internet. The model can be used for revision of estimation of dose that low-orbital space devices obtain.     

Trapped proton fluxes measured on board LEO satellites in comparison with models

The proton fluxes from the low-Earth orbital satellites databases (NPOES-17 and CORONAS-F) were analyzed for the quiet geomagnetic period in April 2005. The satisfactory consent was found between the experimental and the AP8 model fluxes of the trapped protons with energy more than ∼10 MeV. At the same time, trapped proton fluxes with energy less than 10 MeV measured by LEO satellites were higher than the ones predicted by the AP8 model in the region of the SAA (drift shell L < 1.5).     

Measurements of trapped protons and cosmic rays from recent Shuttle flights.

We have flown two new charged particle detectors in five recent Shuttle flights. In this paper we report on the dose rate, equivalent dose rate, and radiation quality factor for trapped protons and cosmic radiation separately. A comparison of the integral linear energy transfer (LET) spectra with recent transport code calculations show significant disagreement. Using the calculated dose rate from the omni-directional AP8MAX model with IGRF reference magnetic field epoch 1970, and observed dose rate as a function of (averaged over all geographic latitude) and longitude, we have determined the westward drift of the South Atlantic anomaly. We have also studied the east-west effect, and observed a 'second' radiation belt. A comparison of the galactic cosmic radiation lineal energy transfer spectra with model calculations shows disagreement comparable to those of the trapped protons.     

Decay rate of the second radiation belt.

Variations in the Earth's trapped (Van Allen) belts produced by solar flare particle events are not well understood. Few observations of increases in particle populations have been reported. This is particularly true for effects in low Earth orbit, where manned spaceflights are conducted. This paper reports the existence of a second proton belt and it's subsequent decay as measured by a tissue-equivalent proportional counter and a particle spectrometer on five Space Shuttle flights covering an eighteen-month period. The creation of this second belt is attributed to the injection of particles from a solar particle event which occurred at 2246 UT, March 22, 1991. Comparisons with observations onboard the Russian Mir space station and other unmanned satellites are made. Shuttle measurements and data from other spacecraft are used to determine that the e-folding time of the peak of the second proton belt. It was ten months. Proton populations in the second belt returned to values of quiescent times within eighteen months. The increase in absorbed dose attributed to protons in the second belt was approximately 20%. Passive dosimeter measurements were in good agreement with this value.     

MONITORING OF ENERGETIC PARTICLE ENVIRONMENT INSIDE THE CHINA-BRAZIL EARTH RESOURCE SATELLITE

On 14 October 1999, the Chinese-Brazil earth resource satellite (CBERS-1) was launched in China. On board of the satellite there was an instrument designed at Peking University to detect the energetic particle radiation inside the satellite so the radiation fluxes of energetic particles in the cabin can be monitored continuously. Inside a satellite cabin, radiation environment consists of ether penetrated energetic particles or secondary radiation from satellite materials due to the interactions with primary cosmic rays.Purpose of the detectors are twofold, to monitor the particle radiation in the cabin and also to study the space radiation environment The data can be used to study the radiation environment and their effects on the electronics inside the satelhte cabin. On the other hand, the data are useful in study of geo-space energetic particle events such as solar proton events, particle precipitation and variations of the radiation belt since there should be some correlation between the radiation situation inside and outside the satellite.The instrument consists of two semi-conductor detectors for protons and electrons respectively. Each detector has two channels of energy ranges. They are 0.5-2MeV and ≥2MeV for electrons and 5-30MeV and 30-60MeV for protons. Counting rate for all channels are up to 104/(cm2@s)and power consumption is about 2.5 W. There are also the additional functions of CMOS TID (total integrated dose) effect and direct SEU monitoring. The data of CBMC was first sent back on Oct. 17 1999 and it's almost three years from then on. The detector has been working normally and the quality of data is good.The preliminary results of data analysis of CBMC not only reveal the effects of polar particle precipitation and radiation belt on radiation environment inside a satellite, but also show some important features of the geo-space energetic particle radiation.As one of the most important parameters of space weather, the energetic charged particles have great influences on space activities and ground tech nology. CBMC is perhaps the first long-term on-board special equipment to monitor the energetic particle radiation environment inside the satellite and the data it accnmulated are very useful in both satellite designing and space research.     

Using cross-correlation techniques to assess the validity of AP8 at low altitude

Background effects, such as single event upsets, are used as proxy data sets to evaluate AP8 at low altitude. The approach is to use a 2-D (longitude and latitude) cross-correlation between the background data set and the current-epoch AP8 predicted fluxes. The technique can be used to determine the energy of the particle that is producing a particular effect. This cross-correlation technique shows that using AP8 with a present-epoch magnetic field model accurately predicts the present location of the South Atlantic Anomaly proton flux enhancement and that a dual-peaked intensity structure above 100 MeV in the model is an artifact of AP8 and its interpolation routines.     

Pitch angle diffusion as seen by CRRES

Lifetimes and pitch angle distributions of radiation belt electrons injected into the slot region are determined from CRRES/MEA particle flux measurements. The dominant loss mechanism is presumed to be pitch angle scattering due to whistler waves, for which a theoretical formulation is available. The empirical lifetimes are compared to those from recent calculations, which rely on model whistler wave parameters. CRRES measurements of cyclotron-frequency electric fields are also presented and compared to the wave model.     

太阳周期活动对低高度内辐射带高能质子的影响

利用NOAA-15卫星1998年到2011年近13年的高能质子全向通量观测资料, 分析了一个太阳活动周内, 低高度内辐射带高能质子通量的分布变化特性及其物理原因, 比较了观测结果与AP8模型的不同. 研究表明, 低高度内辐射带高能质子通量与太阳活动水平的反相关关系与磁壳参数L值及磁场B值有关; L值越低, B值越大的空间点, 其高能质子通量与太阳活动水平的反向相关性越明显. 高能质子通量随太阳活动水平的变化存在明显滞后现象, L值越高、 B值越小的空间点, 滞后现象就越明显, 滞后严重时可以达到一年左右的时间; 这种滞后现象反映出低高度内辐射带高能质子的源与损失达到平衡是一个中长期过程. 通过与AP8模型计算结果的比较分析可以看出, 利用AP8模型时, 仅考虑地磁场长期变化对质子通量的影响可能会夸大低高度内辐射带局部高能质子通量的增强.      

低高度内辐射带高能质子空间分布位形的研究

利用国际地磁参考场模式(IGRF模式)分析了1970-2000年低高度南大西洋负磁异常区位形的漂移与变化，给出了几个高度异常区中心位置磁场强度的变化和位置的变化。利用带电粒子的运动学方程，简要分析了低高度辐射带高能粒子的运动，得出在低高度，磁场是决定辐射带高能粒子空间强度与分布的决定性因素．低高度辐射带空间分布位形的变化特征应该与低高度南大西洋负磁异常区的变化特征基本一致．低高度南大西洋负磁异常区的特征可以作为低高度辐射带空间分布位形的一个初步判据。     

质子辐射带辐射中心区域模型

利用AP-8和CRRESPRO质子辐射带模式数据库, 比较了二者在磁赤道面上计算结果 的差异并给出其差异原因. 利用AP-8模式数据库数据, 建立起质子辐射带函数形式的辐射中心区域模式, 包括各能道全向微分通量峰值所对应的L值(L_c) 随能量E的变化模式以及各能道全向微分通量峰值J_max随能量E的变化模式. 利用RBSP A卫星REPT望远镜在磁赤道面上的高能质子观测数据, 分别与 AP-8模式、CRRESPRO模式及本文所得辐射中心区域模式计算结果进行比较, 发现在78.9, 102.6和208MeV三个能道上, RBSP A卫星观测所得各能道全向微分 通量明显偏大, 而L_c与AP-8或本文辐射中心模式所得结果基本一致; RBSP A卫星也观测到CRRESPRO Quiet模式所得的隐性第二质子辐射带结构.      

Long-term observations of the trapped high-energy proton population (L < 4) by the NOAA Polar Orbiting Environmental Satellites (POES)

The Space Environment Monitor (SEM) onboard the NOAA POES satellites has been measuring the near-Earth charged particle environment since 1978, providing an extensive database that can be used for studying the long-term behavior of this population of trapped particles. POES stands for Polar Orbiting Environmental Satellite. These satellites orbit at ∼840 km altitude and at an inclination of 98°. The SEM-1 instrument was flown on the POES satellites beginning in 1978 with TIROS-N and NOAA-6 in 1979 and continuing to NOAA-14 launched in 1995 with the exception of NOAA-9 and NOAA-11 (NOAA-13 failed shortly after launch). Its replacement, SEM-2, has flown on the POES NOAA-15, -16, and -17 satellites (from 1998). Here we present the results of a study on the statistical variations of the high-energy trapped proton environment. Among the detectors in SEM, the four SEM-2 omni-directional proton detectors for energies >16 MeV, >36 MeV, >70 MeV, and >140 MeV provide the data most relevant to this study.     

FY-3A卫星与NOOA系列卫星高能带电粒子实测结果的比较

FY-3A卫星是运行于830 km高度的太阳同步轨道气象卫星,其搭载的空间环境监测器可观测3～300 MeV的高能质子和0.15～5.70 MeV的高能电子.FY-3A卫星在轨工作期间,太阳活动处于由谷年向峰年过渡期,空间环境非常平静,探测结果显示3～300 MeV的高能质子分布主要集中在南大西洋辐射带异常区,0.15～5.70 MeV的高能电子分布区域除南大西洋异常区外,还分布在南北两极高纬区域.FY-3A与NOAA卫星测量结果反映出带电粒子强度及分布区域随投掷角变化的空间各向异性特征.本文在充分考虑了带电粒子时间、空间分布差异以及比对探测器之间自身设计差异的前提下,经过归一化处理后,首次对两颗卫星同期探测结果进行相关性分析,验证了两颗卫星相同时空条件下高能带电粒子通量分布的一致性;说明FY-3A空间环境监测器不仅具备空间带电粒子辐射监测能力,且探测结果有效可靠,可用作辐射带环境数据源的组成部分,为发展新的模型,深入研究辐射带高能粒子的分布、起源和传输等提供新的观测依据.     

Energy spectrum of proton flux near geomagnetic equator at low altitudes

The results of proton energy (tens keV – several MeV) spectrum measurements near geomagnetic equator (L < 1.15) at low altitudes (<1000 km) are presented. We used data of experiments onboard ACTIVE, SAMPEX, NOAA TIROS-N satellites and SPRUT-VI (MIR station) and cover a time range of about 30 years (including previous measurements). It was found that the kappa-distribution function fits the experimental spectrum with the best correlation coefficient. A comparison of energy spectra of near-equatorial protons and ring-current protons was made. Using the estimation of the life time of near-equatorial protons we explain the difference in spectral indices of radiation belt and near-equatorial proton formation. We conclude that the ring current is the main source of the near-equatorial protons.