共查询到20条相似文献,搜索用时 10 毫秒
1.
The paper presents a new method of the estimation of spatial variations of the magnetic field and superthermal electron distribution
in solar cm-radio burst sources. The method is based on minimization of the difference between the theoretical and observed
radio fluxes and on the analysis of several burst spectra recorded in different moments of time. Several solar cm-radio bursts
are analyzed by this method. It is found that the measure of the spatial variations of the superthermal electron distribution
in the radio source is always larger than that for the magnetic field. 相似文献
2.
The spatial and spectral behaviors of two solar flares observed by the Nobeyama Radioheliograph (NoRH) on 24 August 2002 and
22 August 2005 are explored. They were observed with a single loop-top source and double footpoint sources at the beginning,
then with looplike structures for the rest of the event. NoRH has high spatial and temporal resolution at the two frequencies
of 17 and 34 GHz where a nonthermal radio source is often optically thin. Such capabilities give us an opportunity to study
the spatial and spectral behaviors of different microwave sources. The 24 August 2002 flare displayed a soft – hard – soft
(SHS) spectral pattern in the rising – peak – decay phases at 34 GHz, which was also observed for the spectral behavior of
both loop-top and footpoint sources. In contrast, the 22 August 2005 flare showed a soft – hard – harder (SHH) spectral pattern
for its both loop-top and footpoint sources. It is interesting that this event showed a harder spectrum in the early rising
phase. We found a positive correlation between the spectral index and microwave flux in both the loop-top source and the footpoint
sources in both events. The conclusions drawn from the flux index could apply to the electron index as well, because of their
simple linear relationship under the assumption of nonthermal gyrosynchrotron mechanism. Such a property of spatial and spectral
behaviors of microwave sources gives an observational constraint on the electron acceleration mechanism and electron propagation. 相似文献
3.
In this paper, we revisited the relationship between the spectral index and the core-dominance parameter using a larger sample of blazars. Conclusively, we explain that the spectral index is associated with the core-dominance parameter using the two-component relativistic beaming model. 相似文献
4.
We study the spatial distribution of solar energetic particles (SEPs) throughout the inner heliosphere during six large SEP events from the period 1977 through 1979, as deduced from observations on the Helios 1 and 2, IMP 7 and 8, ISEE 3, and Voyager 1 and 2 spacecraft. Evidence of intensity maxima associated with the expanding shock wave is commonly seen along its central and western flanks, although the region of peak acceleration or “nose” of the shock is sometimes highly localized in longitude. In one event (1 January 1978) a sharp peak in 20?–?30 MeV proton intensities is seen more strongly by Voyager at ~?2 AU than it is by spacecraft at nearby longitudes at ~?1 AU. Large spatial regions, or “reservoirs,” often exist behind the shocks with spatially uniform SEP intensities and invariant spectra that decrease adiabatically with time as their containment volume expands. Reservoirs are seen to sweep past 0.3 AU and can extend out many AU. Boundaries of the reservoirs can vary with time and with particle velocity, rather than rigidity. In one case, a second shock wave from the Sun reaccelerates protons that retain the same hard spectrum as protons in the reservoir from the preceding SEP event. Thus reservoirs can provide not only seed particles but also a “seed spectrum” with a spectral shape that is unchanged by a weaker second shock. 相似文献
5.
We present new statistical results on the spectral index-flux density relation for large samples of radio sources using archival data of the most sensitive surveys, such as 6C, Miyun, WENSS, B3, NVSS, GB87. Instrumental selection effects and the completeness of the catalogs are discussed. Based on the spectral indices calculated for about 200 000 sources from the WENSS (327 MHz) and NVSS (1.4 GHz) catalogs, we obtained (1) The median spectral index increases from amed --0.9 toαmed --0.8 (Svαvα), while S327 flux densities decrease from 0.1 Jy down to 25mJy. The median spectral indices nearly show no variation within the error bars when the flux density is larger than 0.1 Jy. (2) A dependence of the fraction of ultra-steep spectrum sources (USS, -1.5 <α<-1.0), steep spectrum sources (SSS, -1.0 <α< -0.5) and flat spectrum sources (FSS, -0.5≤α≤0.0) is partly responsible for the spectral flattening. Another contribution to the spectral flattening comes from the variation of αmed of steep spectrum so 相似文献
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Zhan-Le Du Hua-Ning Wang Xiang-Tao He National Astronomical Observatories Chinese Academy of Sciences Beijing Department of Astronomy Beijing Normal University Beijing 《中国天文和天体物理学报》2006,6(4):489-494
The maximum amplitudes of solar activity cycles are found to be well anti-correlated (r = -0.72) with the newly defined solar cycle lengths three cycles before (at lag -3) in 13-month running mean sunspot numbers during the past 190 years. This result could be used for predicting the maximum sunspot numbers. The amplitudes of Cycles 24 and 25 are estimated to be 149.5±27.6 and 144.3±27.6, respectively. 相似文献
9.
Donald V. Reames 《Solar physics》2017,292(8):113
We have studied the spatial and temporal distribution of abundances of chemical elements in large “gradual” solar energetic-particle (SEP) events, and especially the source plasma temperatures, derived from those abundances, using measurements from the Wind and Solar TErrestrial RElations Observatory (STEREO) spacecraft, widely separated in solar longitude. A power-law relationship between abundance enhancements and mass-to-charge ratios [\(A/Q\)] of the ions can be used to determine \(Q\)-values and source plasma temperatures at remote spacecraft with instruments that were not designed for charge-state measurements. We search for possible source variations along the accelerating shock wave, finding one clear case where the accelerating shock wave appears to dispatch ions from \(3.2\pm 0.8~\mbox{MK}\) plasma toward one spacecraft and those from \(1.6\pm 0.2~\mbox{MK}\) plasma toward another, 116° away. The difference persists for three days and then fades away. Three other SEP events show less-extreme variation in source temperatures at different spacecraft, in one case observed over 222° in longitude. This initial study shows how the power-law relation between abundance enhancements and ion \(A/Q\)-values provides a new technique to determine \(Q\) and plasma temperatures in the seed population of SEP ions over a broad region of space using remote spacecraft with instruments that were not originally designed for measurements of ionization states. 相似文献
10.
From the monthly data of cosmic ray intensity (CRI), sunspot numbers (SSN) and solar flare index (SFI), an attempt has been
made to study the relationship between CRI and solar activity (SA) parameters SSN and SFI. The correlation between SA parameters
and CRI for different neutron monitoring stations having low, middle and high cut-off rigidity has been investigated. The
anti-correlation between SA and CRI is found to exist with some time lag. Based on the method of minimizing correlation coefficient
and time-delayed component method, the observed time-lag between SA parameters (SSN and SFI) and CRI has been found to be
large for odd solar cycles in comparison to even solar cycles. The results of time-lag analysis between CRI and SSN and between
CRI-SFI have also been compared. The findings of correlative study between CRI and SSN are in agreement with earlier results,
while the CRI-SFI relationship provides new insights to understand the solar modulation of cosmic rays. 相似文献
11.
In the relativistic case, the dispersion equation of longitudinal oscillations in unmagnetized, collisionless and isotropic plasmas of fast electron distribution is derived from the longitudinal dielectric constant of plasma. The equation is analytically solved, and the long-wavelength and short-wavelength dispersion relations are obtained. Because of the discontinuity of the analytical dispersion curve, the dimensionless dispersion equation of longitudinal oscillations is numerically calculated to obtain the full dispersion curve of longitudinal oscillations in relativistic plasmas of fast electron distribution. Further more, by fitting the numerical solution, a simple functional expression of the dispersion curve is given in favor of applications. Finally, in the extremely relativistic case, the dispersion relation of fast electron distribution is compared with that of Maxwell distribution. It is shown that the two kinds of dispersion relations have similar properties in a certain range of wave numbers. 相似文献
12.
文章研究了162个射电源,其中包括了47个BL Lacs ,21个galaxies ,94个平谱射电类星体( FSRQs ) ,这些源是通过Michigan大学的26m的射电望远镜观测的。大多数源都包含了3个波段的观测数据:4 .8GHz ,8GHz和14 .5GHz。文中计算了3个子类的平均的流量密度,并且得到了相应的谱指数(αwei) ,αBL=0 .08±0 .28 ,αGAL=-0 .91±0 .32 ,αFSRQ=-0 .14±0 .4。同时也讨论了这些源的射电性质,其中包含了谱指数,流量密度和红移之间的关系,流量密度和谱指数之间的关系。 相似文献
13.
Oran R. White Giuliana De Toma Gary J. Rottman Thomas N. Woods Barry G. Knapp 《Solar physics》1998,177(1-2):89-103
The solar Mgii core-to-wing ratio is a useful index of UV variability throughout the solar cycle because it has been measured since 1978 in a series of successive satellite missions: Nimbus 7, Solar Mesosphere Explorer (SME), the NOAA 9–14 series, Upper Atmosphere Research Satellite (UARS), and ERS-2. Eventual construction of a single time series from 1978 to the present by combining these measurements will give a long record of almost daily UV variability to serve as a surrogate for estimating both UV and EUV solar radiation. Here we address the effect of spectral resolution on determination of both long-term and short-term solar variability from this index. We use UARS/SOLSTICE measurements of the Mgii line from October 1991 to December 1996 to study the effect of two spectral resolution regimes characteristic of existing measurements, 0.20 to 0.25 nm and 1.10 to 1.15 nm, on determination of the amplitude of 27-day rotational modulation and the more gradual change in chromospheric radiation in the declining phase of solar cycle 22. The two Mgii indices give solar variations that differ by a scaling factor of 2× for both the solar cycle change from 1992 to 1997 and the amplitude of 27-day modulation over the same period. Both types of measurements appear to yield solar signal equally well except at solar minimum when the solar changes become quite small. 相似文献
14.
The photometrical flattening index of the solar corona a+b is defined according to Ludendorff. In this paper we have investigated how the flattening index varies with respect to the
phase of solar activity and the sunspot number. We have compiled 170 values of the flattening index using the data on 60 total
solar eclipses from 1851 to 2010. We have found that the flattening index takes values from 0 to 0.4, and is anticorrelated
with solar activity. The value of the flattening index at the beginning of solar cycle 24 was used as a precursor to forecast
the amplitude of the cycle. It was found that the amplitude of solar cycle 24 will be about 95 in terms of the smoothed monthly
sunspot numbers. 相似文献
15.
We present calculations, made for the first time, of the gyrosynchrotron emission by mildly relativistic electrons with anisotropic
pitch-angle distribution using a realistic magnetic loop model in three dimensions. We investigated the intensity, spectral
index of the optically thin region of the spectrum, the spatial morphology and the dependency on the source position on the
solar disk. The method to describe a three-dimensional source and the procedure to perform the calculations are presented.
We have modified the Ramaty’s gyrosynchrotron code to allow the evaluation of anisotropic pitch-angle electron distributions,
as described in the complete formalism. We found that anisotropic electron distributions affect the intensity of the radiation,
spatial morphology and spectrum of spatially resolved sources. However, the spatially integrated spectrum of the emission
seems to be insensitive to the electron pitch-angle distribution, as the magnetic field inhomogeneity smooths out the effects
of the anisotropic distribution in the produced radiation, in contrast to homogeneous sources. 相似文献
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17.
电子是太阳风粒子中最为重要的组分之一,它可以通过多种机制对太阳风产生影响.太阳风中的电子通常具有温度各向异性和束流两种非热平衡分布特征,这些偏离热平衡分布的特征可以通过波粒相互作用激发电子不稳定性和等离子体波动,激发的等离子体波动又可以通过波粒相互作用调制太阳风粒子的分布,从而加热太阳风中的背景粒子.因此电子动力学不稳定性在太阳风的演化过程中扮演了极为重要的角色.详细介绍了太阳风中常见的电子动力学不稳定性,并基于等离子体动力论,详细介绍太阳风传播过程中所出现的各种不稳定性,尤其是在近日球层和太阳大气区域所出现的电子声热流不稳定性以及低混杂热流不稳定性,并分析其波粒相互作用机制,以便更加深入地研究太阳风传播过程中的电子分布函数演化. 相似文献
18.
在相对论性情况下,从等离子体纵介电常数出发,推导出无磁化、无碰撞、各向同性的快电子分布等离子体纵振荡的色散方程.对纵振荡的色散方程进行解析分析,得到长波支和短波支的色散关系.由于解析色散曲线的不连续性,直接对无量纲化的纵振荡色散方程进行数值计算,得到相对论性快电子分布等离子体纵振荡完整的色散曲线.对数值结果进行拟合,得到简单的色散函数表述以便于应用.并在极端相对论条件下,将这种分布与经典Maxwell分布的色散关系进行比较,得出两种分布情况下纵振荡的色散关系在一定的波数范围内有类似的性质. 相似文献
19.
Elena Dzifčáková 《Solar physics》2000,196(1):113-127
The influence of electron non-Maxwellian distributions (power and -distribution) on the electron excitation rate in the solar corona is demonstrated. It is shown that the deviations in electron excitation rate are sufficient to affect intensities of spectral lines. As an example the diagnostics of a power-law distribution are demonstrated for a simplified calculation of the resonance lines of Fexxiv, Fexxv and Fexxvi. The results can be used in diagnosing solar flare plasmas, where the deviations of the electron distribution from a Maxwellian distribution can be large. 相似文献
20.
Experiments based on multi-source radio occultation measurements of the circumsolar plasma at R∼4.0−70R
S were carried out during 1997 – 2008 to locate the inner boundary of the solar-wind transonic transition region, R
in. The data obtained were used to correlate the solar-wind stream structure and magnetic fields on the source surface (R=2.5R
S) in the solar corona. The method of the investigation is based on the analysis of the dependence R
in=F(|B
R|) in the correlation diagrams, where R
in is the inner boundary of the solar-wind transition region and |B
R| is the intensity of the magnetic field at the source surface. On such diagrams, the solar wind is resolved into discrete
branches, streams of different types. The analysis of the stream types using a continuous series of data from 1997 to 2008
allowed us to propose a physical criterion for delimiting the epochs in the current activity cycle. 相似文献