共查询到20条相似文献,搜索用时 15 毫秒
1.
Evangelos Paouris 《Solar physics》2013,284(2):589-597
Monthly coronal mass ejection (CME) counts, – for all CMEs and CMEs with widths >?30°, – and monthly averaged speeds for the events in these two groups were compared with both the monthly averaged cosmic ray intensity and the monthly sunspot number. The monthly P i-index, which is a linear combination of monthly CME count rate and average speed, was also compared with the cosmic ray intensity and sunspot number. The main finding is that narrow CMEs, which were numerous during 2007?–?2009, are ineffective for modulation. A cross-correlation analysis, calculating both the Pearson (r) product–moment correlation coefficient and the Spearman (ρ) rank correlation coefficient, has been used. Between all CMEs and cosmic ray intensity we found correlation coefficients r=??0.49 and ρ=??0.46, while between CMEs with widths >?30° and cosmic ray intensity we found r=??0.75 and ρ=??0.77, which implies a significant increase. Finally, the best expression for the P i-index for the examined period was analyzed. The highly anticorrelated behavior among this CME index, the cosmic ray intensity (r=??0.84 and ρ=??0.83), and the sunspot number (r=+?0.82 and ρ=+?0.89) suggests that the first one is a very useful solar–heliospheric parameter for heliospheric and space weather models in general. 相似文献
2.
3.
The diurnal variation of the galactic cosmic ray (GCR) count rates measured by a ground-based neutron monitor (NM) station represents an anisotropic flow of GCR at 1 AU. The variation of the local time of GCR maximum intensity (we call the phase) is thought in general to have a period of two sunspot cycles (22 years). However, other interpretations are also possible. In order to determine the cyclic behavior of GCR anisotropic variation more precisely, we have carried out a statistical study on the diurnal variation of the phase. We examined 54-year data of Huancayo (Haleakala), 40-year data from Rome, and 43-year data from Oulu NM stations using the ‘pile-up’ method and the F-test. We found that the phase variation has two components: of 22-year and 11-year cycles. All NM stations show mainly the 22-year phase variation controlled by the drift effect due to solar polar magnetic field reversal, regardless of their latitudinal location (cut-off rigidity). However, the lower the NM station latitude is (the higher the cut-off rigidity is), the higher is the contribution from the 11-year phase variation controlled by the diffusion effect due to the change in strength of the interplanetary magnetic fields associated with the sunspot cycle. 相似文献
4.
A feasibility study has been carried out to assess the potentialof an Artificial Neural Network (ANN) for determiningthe direction of incidence of an Atmospheric Cerenkov Event(ACE) from the arrival-time information registered by aspaced-array of wide-angle Cerenkov detectors. Theresults obtained so far, using both, simulated and experimental data, indicate that a properly-trained net can yield a degree of accuracy which is comparable with what is achieved through the conventional 2-minimization, wavefront-fitting procedure. 相似文献
5.
R. P. Kane 《Solar physics》2006,236(1):207-226
After increasing almost monotonically from sunspot minimum, sunspot activity near maximum falters and remains in a narrow
grove for several tens of months. During the 2–3 years of turmoil near sunspot maximum, sunspots depict several peaks (Gnevyshev
peaks). The spaces between successive peaks are termed as Gnevyshev Gaps (GG). An examination showed that the depths of the troughs varied considerably from one GG to the next in the same cycle, with magnitudes varying in a wide range (<1%
to ∼20%). In any cycle, the sunspot patterns were dissimilar to those of other solar parameters, qualitatively as well as
quantitatively, indicating a general turbulence, affecting different solar parameters differently. The solar polar magnetic
field reversal does not occur at the beginning of the general turmoil; it occurs much later. For cosmic ray (CR) modulation
which occurs deep in the heliosphere, one would have thought that the solar open magnetic field flux would play a crucial
role, but observations show that the sunspot GGs are not reflected well in the solar open magnetic flux, where sometimes only
one peak occurred (hence no GG at all), not matching with any sunspot peak and with different peaks in the northern and southern
hemispheres (north – south asymmetry). Gaps are seen in interplanetary parameters but these do not match exactly with sunspot
GGs. For CR data available only for five cycles (19 – 23), there are CR gaps in some cycles, but the CR gaps do not match
perfectly with gaps in the solar open magnetic field flux or in interplanetary parameters or with sunspot GGs. Durations are
different and/or there are variable delays, and magnitudes of the sunspot GGs and CR gaps are not proportional. Solar polar
magnetic field reversal intervals do not coincide with either sunspot GGs or CR gaps, and some CR gaps start before magnetic field reversals, which should not happen if the magnetic field reversals are the cause of the CR gaps. 相似文献
6.
C. Grimani 《Astrophysics and Space Science》1999,268(4):475-481
Quest for antimatter in cosmic rays has revealed no compelling evidence of primary, extragalactic antiparticles up to the
present time. Recent positron and antiproton observations have been found to be consistent with a pure galactic origin up
to energies of 50 GeV and 20 GeV respectively. In this paper it is discussed which role might be played by Ultra High Energy
(UHE) extragalactic particles and antiparticles in cosmic-ray observations near Earth.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
7.
R.E.Ugwoke A.A.Ubachukwu J.O.Urama O.Okike J.A.Alhassan A.E.Chukwude 《天文和天体物理学研究(英文版)》2023,(3):157-171
We applied principal component analysis(PCA) to the study of five ground level enhancements(GLEs) of cosmic ray(CR) events. The nature of the multivariate data involved makes PCA a useful tool for this study. A subroutine program written and implemented in the R software environment generated interesting principal components.Analysis of the results shows that the method can distinguish between neutron monitors(NMs) that observed Forbush decreases from those that observed GLEs at the same time. T... 相似文献
8.
无先验基准方法在SLR资料处理中的应用 总被引:1,自引:0,他引:1
SLR(satellite Laser Ranging)资料处理一般来说总是由各SLR测站构成的从标框架里进行。为了克服在SLR资料处理过程中对坐标框架的重复定义,利用全球1999年1月到12月的LAGEOS-1的SLR资料以无先验基准方法解算EOP(Earth Orientation Parameters)和所有SLR站的坐标的试验。在SLR资料处理中用无先验基准方法与GPS(Glaobal Positioning System)的不太一样,由于SLR的资料不能把SLR观测站连结成非常牢固的空间多面体(GPS的资料在每一瞬间可以拟测站联成一完整的空间多面体),因此需要加一些约束,以避免法方程出现秩亏。解得的测站从标用7参数转换到ITRF97坐标系,rms为1.3cm。EOP与IERS的eopc04序列相比,Xp、Yp、的rms分别为0.37mas、0.30mas,LOD(Length Of Day)的rmas为0.019ms。 相似文献
9.
10.
One dimensional numerical results of the non-linear interaction between cosmic rays and a magnetic field are presented. These
show that cosmic ray streaming drives large amplitude Alfvénic waves. The cosmic ray streaming energy is very efficiently
transfered to the perturbed magnetic field of the Alfvén waves. Thus a magnetic field of interstellar values, assumed in models
of supernova remnant blast wave acceleration, would not be appropriate in the region of the shock. The increased magnetic
field reduces the acceleration time and so increases the maximum cosmic ray energy, which may provide a simple and elegant
resolution to the highest energy galactic cosmic ray problem were the cosmic rays themselves provide the fields necessary
for their acceleration.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
11.
E. Samara A. Smponias I. Lytrosyngounis D. Lingri H. Mavromichalaki C. Sgouropoulos 《Solar physics》2018,293(4):67
Although the current Solar Cycle 24 is characterized by low solar activity, an intense geomagnetic storm (G4) was recorded in June 2015. It was a complex phenomenon that began on 22 June 2015 as the result of intense solar activity, accompanied by several flares and coronal mass ejections that interacted with the Earth’s magnetic field. A Forbush decrease was also recorded at the neutron monitors of the worldwide network, with an amplitude of 8.4%, and in its recovery phase, a second Forbush decrease followed, with an amplitude of 4.0% for cosmic rays of 10 GV obtained with the global survey method. The Dst index reached a minimum value of ?204 nT that was detected on 23 June 2015 at 05:00?–?06:00 UT, while the Kp index reached the value eight. For our analysis, we used hourly cosmic-ray intensity data recorded by polar, mid-, and high-latitude neutron monitor stations obtained from the High Resolution Neutron Monitor Database. The cosmic-ray anisotropy variation at the ecliptic plane was also estimated and was found to be highly complex. We study and discuss the unusual and complex cosmic-ray and geomagnetic response to these solar events. 相似文献
12.
We present a combined method to classify stellar spectra of the seventh data release (DR7) of the SDSS via an Artificial Neural Network (ANN), derive radial velocities and to estimate distances from an isochrone fitting technique. In total, we used 29 182 spectra of stars falling in the effective temperature range between 10000 and 5500 K, including white dwarfs. The targets were selected on the basis of SDSS colours. We compare our results not only with the SEGUE Stellar Parameter Pipeline output, but also with already published values and find excellent agreement. With new and extensive data sets from all‐sky ground based as well as satellite missions, our approach will become very important and efficient to analyse these information (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
13.
A new method is proposed to predict cosmic ray intensity and solar modulation parameters. The method is coupled with the McNish
and Lincoln method, which predicts first smoothed sunspot numbers. The error achieved is estimated and compared with the same
chain of predictions using two other methods developed for US and Russian space applications. The three methods give satisfactory
results when applied, for example, to prediction of the dose received on-board commercial aeroplane flights. 相似文献
14.
Bo-Yang Wang Qian Ye Li Fu Guo-Xiang Meng Jin-Qing Wang Qing-Hui Liu Zhi-Qiang Shen 《天文和天体物理学研究(英文版)》2022,(3):194-204
Recent investigations have derived the relation between the near-field plane amplitude and the surface deformation of reflector antenna,namely deformation-ampli... 相似文献
15.
The unusually low amplitude anisotropic wave train events (LAWEs) in cosmic ray intensity using the ground based Deep River neutron monitor data has been studied during the period 1991–1994. It has been observed that the amplitude of the diurnal anisotropy for LAWE events significantly remains quite low and statistically constant as compared to the quiet day annual average amplitude for majority of the events. The time of maximum of the diurnal anisotropy of LAWE significantly shifts towards earlier hours as compared to the co-rotational direction and remains in the direction of quiet day annual average anisotropy for majority of the events. On the other hand, the amplitude of the semi/tri-diurnal anisotropy remains statistically the same and high whereas, phase shift towards later hours as compared to the quiet day annual average values for majority of the LAWEs. The diurnal anisotropy vectors are found to shifts towards earlier hours for 50% of the events; whereas they are found to shifts towards later hours for rest of the events (50%) relative to the average vector for the entire period. It is also noted that the amplitude of these vectors are found to increase significantly with the shift of the diurnal anisotropy vectors towards later hours. The high-speed solar wind streams do not play a significant role in causing the LAWE events on short-term basis, however it may be responsible in causing these events on long-term basis (Mishra and Mishra 2007). Occurrence of LAWE is dominant, when the polarity of Bx and Bz remains positive and polarity of By remains negative, which is never been reported earlier. The amplitude of first harmonic shows good anti-correlation and direction of first and third harmonic shows nearly good anti-correlation with solar wind velocity, whereas the direction of second harmonic shows nearly good anti-correlation with interplanetary magnetic field strength. 相似文献
16.
R. P. Kane 《Solar physics》2006,234(2):353-362
During the Forbush decrease of April 11, 2001, the Ooty (11.4∘N, 76.7∘E, 2200 m altitude, South India) high energy muon detectors showed considerable anisotropies. Some anisotropies and asymmetries
indicated that the Earth did not pass the middle of the interplanetary structure (blob), and passed its northern part. Some
anisotropies which occurred when the Earth was outside the blob (notably before the Forbush decrease) could be the precursory
increases due to reflection from the shock fronts, but some others could not be understood as these appeared in a direction
away from the blob. 相似文献
17.
Identifying the precursors (pre-increases or pre-decreases) of a geomagnetic storm or a Forbush decrease is of great importance since they can forecast and warn of oncoming space weather effects. A wide investigation using 93 events which occurred in the period from 1967 to 2006 with an anisotropy A xy >1.2% has been conducted. Twenty-seven of the events revealed clear signs of precursors and were classified into three categories. Here we present one of the aforementioned groups, including five Forbush decreases (24 June 1980, 28 October 2000, 17 August 2001, 23 April 2002, and 10 May 2002). Apart from hourly cosmic ray intensity data, provided by the worldwide network of neutron monitor stations, data on solar flares, solar wind speed, geomagnetic indices (Kp and Dst), and interplanetary magnetic field were used for the analysis of the examined cosmic ray intensity decreases. The asymptotic longitudinal cosmic ray distribution diagrams were plotted using the “ring of stations” method. Results reveal a long pre-decrease up to 24 hours before the shock arrival in a narrow longitudinal zone from 90° to 180°. 相似文献
18.
19.
The pressure-corrected hourly counting rate data of four neutron monitor stations have been employed to study the variation
of cosmic ray diurnal anisotropy for a period of about 50 years (1955–2003). These neutron monitors, at Oulu (
R
c = 0.78 GV), Deep River (
R
c = 1.07 GV), Climax (
R
c = 2.99 GV), and Huancayo (
R
c = 12.91 GV) are well distributed on the earth over different latitudes and their data have been analyzed. The amplitude of
the diurnal anisotropy varies with a period of one solar cycle (∼11 years), while the phase varies with a period of two solar
cycles (∼22 years). In addition to its variation on year-to-year basis, the average diurnal amplitude and phase has also been
calculated by grouping the days for each solar cycle, viz. 19, 20, 21, 22, and 23. As a result of these groupings over solar
cycles, no significant change in the diurnal vectors (amplitude as well as phase) from one cycle to other has been observed.
Data were analyzed by arranging them into groups on the basis of the polarity of the solar polar magnetic field and consequently
on the basis of polarity states of the heliosphere (
A > 0 and
A < 0). Difference in time of maximum of diurnal anisotropy (shift to earlier hours) is observed during
A < 0 (1970s, 1990s) polarity states as compared to anisotropy observed during
A > 0 (1960s, 1980s). This shift in phase of diurnal anisotropy appears to be related to change in preferential entry of cosmic
ray particles (via the helioequatorial plane or via solar poles) into the heliosphere due to switch of the heliosphere from
one physical/magnetic state to another following the solar polar field reversal. 相似文献
20.
Power spectral density (PSD) of cosmic rays has been calculated from hourly averaged counts observed by underground muon telescopes
located at Mawson over the low-frequency range 2.7×10−7 – 1.4×10−4 Hz. The first two harmonics of the solar daily variation are well defined for even cycles (20 and 22) whereas only the first
harmonic is defined in cycle 21. The amplitude of the diurnal variation is lower for even cycles than for the odd cycle. The
spectral power of the odd cycle exceeds those of the even cycles. The spectra are flatter and have lower power when the interplanetary
magnetic field (IMF) is directed away from the Sun above the current sheet (A>0) than when the IMF is directed toward the Sun above the current sheet (A<0). The spectra imply that heliospheric magnetic turbulence may be more variable on time scales of several years than previously
suspected. 相似文献