共查询到19条相似文献,搜索用时 31 毫秒
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分析了22太阳活动周(1986.1—1995.6;CR1771—CR1898)冕洞对地磁扰动的长期效应和短期效应。作为长期效应,赤道冕洞数和面积指数随太阳活动周的演化与同期的地磁Ap指数的长期变化基本一致,二者在α=0.01的信度水平上密切相关,表明赤道冕洞不仅对低年的磁扰有贡献,而且对峰年期间地磁扰动的贡献也是不可忽视的。对冕洞的短期地磁效应的研究表明,不论哪种类型的冕洞,在它们过中经后的1—4天,地磁Ap指数都有不同程度的增长;大冕洞比小冕洞引起的地磁效应较强烈;跨越赤道的冕洞比未跨越赤道的同级冕洞引起的地磁效应较强烈 相似文献
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本文用1970-1995年的冕洞资料,分析了冕洞的分布规律,磁场极性的演化特征和冕洞的地磁效应,以及它们与太阳黑子周期的演化关系,得到了一些有意义的结论。特别指出赤道冕洞和极区冕洞具有相反的演化规律和不同的特征。 相似文献
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冕洞的研究在近二十多年里取得了丰硕的成果。本文回顾了冕洞的发现及观测历史,系统阐述了冕洞的结构特征、形成及演化规律,讨论了冕洞对日地空间产生的影响,冕洞与超级活动区的关系以及冕洞在太阳活动预报中所起的作用,在此基础上利用1970—1995年的冕洞资料对冕洞的时空分布和磁极性演化规律与太阳活动周的关系,以及冕洞与太阳风速度、地磁扰动等方面进行分析研究,得出以下结论:(1)冕洞在南北半球的分布在形态上基本是对称的,但在冕洞数量上北半球稍占优势;(2)冕洞的盛衰演化呈周期性,表现为赤道冕洞周期与黑子周期是完全一致的,极冕洞周期与黑子周期相位相差180°;(3)赤道冕洞的纬度分布随太阳活动周上升而上升,当太阳活动周达到极大值时,它也达到极大,然后再随太阳活动周下降而下降,极冕洞的纬度延伸方向演化与赤道冕洞相反;(4)极冕洞的极场呈11年周期性,并且极场反转出现在太阳活动峰年期间;(5)太阳风和地磁扰动与冕洞的演化有着密切的关系 相似文献
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简要介绍了在1988-1995年期间冕洞观测研究的主要进展。文中共分五个方面:1.冕洞磁场观测研究的新进展;2.冕洞在太阳活动周不同位相时的规律性;3.冕洞区高速太阳风观测的新结果;4.冕洞加热问题;5.存在问题。 相似文献
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主要论述宁静日冕洞,以及日冕加热问题的研究现状。讨论了宁静日冕的理论模型、观测模型和混合模型,以及冕洞区大气模型和太阳风加热问题。最后对计划中的日冕空间探测作了简要介绍。 相似文献
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冕洞的研究在近二十多年里取得了丰硕的成果。本文回顾了冕洞的发现及观测历史,系统阐述了冕洞的结果特征,形成及演化规律,讨论了冕洞对日地空间产生的影响,冕洞与超级活动区的关系以及冕洞在太阳活动预报中所起的作用,在此基础上利用1970-1995年的晚洞资料听时空分 布和磁极性演化规律与太阳活动区的关系以及冕洞的时空分布和磁极性演化 规律与太阳活性周的得出以下结论:(1)冕洞在南北半球的分布在形态上基本是 相似文献
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本文对22太阳活动周以来的中低纬冕洞和地磁指数Ap进行了统计。对以月,年及22周以来不同时段冕洞和地磁指数的时段合成图进行了分析。 相似文献
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New X-ray observations of the north polar region taken from the X-ray Telescope (XRT) of the Hinode spacecraft are used to analyze several time sequences showing small loop brightenings with a long ray above. We focus on
the formation of the jet and discuss scenarios to explain the main features of the events: the relationship with the expected
surface magnetism, the rapid and sudden radial motion, and possibly the heating, based on the assumption that the jet occurs
above a null point of the coronal magnetic field. We conclude that 2-D reconnection models should be complemented in order
to explain the observational details of these events and suggest that alternative scenarios may exist. 相似文献
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Periodic Appearance of Coronal Holes and the Related Variation of Solar Wind Parameters 总被引:1,自引:0,他引:1
We compared the variability of coronal hole (CH) areas (determined from daily GOES/SXI images) with solar wind (daily ACE
data) and geomagnetic parameters for the time span 25 January 2005 until 11 September 2005 (late declining phase of solar
cycle 23). Applying wavelet spectral analysis, a clear 9-day period is found in the CH time series. The GOES/SXI image sequence
suggests that this periodic variation is caused by a mutual triangular distribution of CHs ∼120° apart in longitude. From
solar wind parameters a 9-day periodicity was obtained as well, simultaneously with the 9-day period in the CH area time series.
These findings provide strong evidence that the 9-day period in solar wind parameters, showing up as higher harmonic of the
solar rotation frequency, is caused by the “periodic” longitudinal distribution of CHs on the Sun recurring for several solar
rotations. The shape of the wavelet spectrum from the Dst index matches only weakly with that from the CH areas and is more similar to the wavelet spectrum of the solar wind magnetic
field magnitude. The distinct 9-day period does not show up in sunspot group areas which gives further evidence that the solar
wind modulation is strongly related to CH areas but not to active region complexes. The wavelet power spectra for the whole
ACE data range (∼1998 – 2006) suggest that the 9-day period is not a singular phenomenon occurring only during a specific
time range close to solar minimum but is occasionally also present during the maximum and decay phase of solar cycle 23. The
main periods correspond to the solar rotation (27d) as well as to the second (13.5d) and third (9d) harmonic.
Electronic Supplementary Material The online version of this article () contains supplementary material, which is available to authorized users. 相似文献
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Using Fe ix/x 17.1 nm observations from the Extreme-Ultraviolet Imaging Telescope (EIT) on the Solar and Heliospheric Observatory (SOHO), we have identified many coronal plumes inside low-latitude coronal holes as they transited the solar limb during the late
declining phase of cycle 23. These diffuse, linear features appear to be completely analogous to the familiar polar plumes.
By tracking them as they rotate from the limb onto the disk (or vice versa), we confirm that EUV plumes seen against the disk appear as faint, diffuse blobs of emission surrounding a brighter core.
When the EIT images are compared with near-simultaneous magnetograms from the SOHO Michelson Doppler Imager (MDI), the low-latitude, on-disk plumes are found to overlie regions of mixed polarity, where small
bipoles are in contact with unipolar flux concentrations inside the coronal hole. The birth and decay of the plumes are shown
to be closely related to the emergence of ephemeral regions, their dispersal in the supergranular flow field, and the cancellation
of the minority-polarity flux against the dominant-polarity network elements. In addition to the faint polar and nonpolar
plumes associated with ephemeral regions, we note the existence of two topologically similar coronal structures: the giant
plume-like features that occur above active regions inside coronal holes, and the even larger scale “pseudostreamers” that
separate coronal holes of the same polarity. In all three cases, the basic structure consists of open field lines of a given
polarity overlying a photospheric region of the opposite polarity; ongoing interchange reconnection at the X-point separating
the open field domains from the underlying double-arcade system appears to result in the steady evaporation of material from
the closed into the open region. 相似文献
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Yunhee Choi Y.-J. Moon Seonghwan Choi Ji-Hye Baek Sungsoo S. Kim K.-S. Cho G. S. Choe 《Solar physics》2009,254(2):311-323
We have examined the relationships among coronal holes (CHs), corotating interaction regions (CIRs), and geomagnetic storms in the period 1996?–?2003. We have identified 123 CIRs with forward and reverse shock or wave features in ACE and Wind data and have linked them to coronal holes shown in National Solar Observatory/Kitt Peak (NSO/KP) daily He i 10?830 Å maps considering the Sun?–?Earth transit time of the solar wind with the observed wind speed. A sample of 107 CH?–?CIR pairs is thus identified. We have examined the magnetic polarity, location, and area of the CHs as well as their association with geomagnetic storms (Dst≤?50 nT). For all pairs, the magnetic polarity of the CHs is found to be consistent with the sunward (or earthward) direction of the interplanetary magnetic fields (IMFs), which confirms the linkage between the CHs and the CIRs in the sample. Our statistical analysis shows that (1) the mean longitude of the center of CHs is about 8°E, (2) 74% of the CHs are located between 30°S and 30°N (i.e., mostly in the equatorial regions), (3) 46% of the CIRs are associated with geomagnetic storms, (4) the area of geoeffective coronal holes is found to be larger than 0.12% of the solar hemisphere area, and (5) the maximum convective electric field E y in the solar wind is much more highly correlated with the Dst index than any other solar or interplanetary parameter. In addition, we found that there is also a semiannual variation of CIR-associated geomagnetic storms and discovered new tendencies as follows: For negative-polarity coronal holes, the percentage (59%; 16 out of 27 events) of CIRs associated with geomagnetic storms in the first half of the year is much larger than that (25%; 6 out of 24 events) in the second half of the year and the occurrence percentage (63%; 15 out of 24 events) of CIR-associated storms in the southern hemisphere is significantly larger than that (26%; 7 out of 27 events) in the northern hemisphere. Positive-polarity coronal holes exhibit an opposite tendency. 相似文献
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With the use of coronal mass ejections (CMEs) observed by the Large Angle and Spectrometric Coronagraph (LASCO) onboard the
Solar and Heliospheric Observatory (SOHO) from January 1996 through December 2005, it is found that, for the cyclical activity of CMEs, there is surprisingly
no equatorward drift at low latitudes (thus, no “butterfly diagram”) and no poleward drift at high latitudes, and no antiphase
relationship between CME activity at low and high latitudes. The cyclical behaviors of CMEs differ in a significant way from
that of the small-scale solar photospherical and chromospherical phenomena. Thus, our analysis leads to results that are inconsistent
with a close, physical relationship with small-scale aspects of solar activity, and it is suggested that there is possibly
a single so-called large-scale activity cycle in CMEs. 相似文献
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Bojan Vršnak Darije Maričić Andrew L. Stanger Astrid M. Veronig Manuela Temmer Dragan Roša 《Solar physics》2007,241(1):85-98
We study kinematics of 22 coronal mass ejections (CMEs) whose motion was traced from the gradual pre-acceleration phase up
to the post-acceleration stage. The peak accelerations in the studied sample range from 40, up to 7000 m s−2, and are inversely proportional to the acceleration phase duration and the height range involved. Accelerations and velocities
are, on average, larger in CMEs launched from a compact source region. The acceleration phase duration is proportional to
the source region dimensions; i.e., compact CMEs are accelerated more impulsively. Such behavior is interpreted as a consequence of stronger Lorentz force and
shorter Alfvén time scales involved in compact CMEs (with stronger magnetic field and larger Alfvén speed being involved at
lower heights). CMEs with larger accelerations and velocities are on average wider, whereas the widths are not related to
the source region dimensions. Such behavior is explained in terms of the field pile-up ahead of the erupting structure, which
is more effective in the case of a strongly accelerated structure. 相似文献
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We present a procedure to extract bright loop features from solar EUV images. In terms of image intensities, these features
are elongated ridge-like intensity maxima. To discriminate the maxima, we need information about the spatial derivatives of
the image intensity. Commonly, the derivative estimates are strongly affected by image noise. We therefore use a regularized
estimation of the derivative, which is then used to interpolate a discrete vector field of ridge points; these “ridgels” are
positioned on the ridge center and have the intrinsic orientation of the local ridge direction. A scheme is proposed to connect
ridgels to smooth, spline-represented curves that fit the observed loops. Finally, a half-automated user interface allows
one to merge or split curves or eliminate or select loop fits obtained from this procedure. In this paper we apply our tool
to one of the first EUV images observed by the SECCHI instrument onboard the recently launched STEREO spacecraft. We compare
the extracted loops with projected field lines computed from near-simultaneous magnetograms measured by the SOHO/MDI Doppler
imager. The field lines were calculated by using a linear force-free field model. This comparison allows one to verify faint
and spurious loop connections produced by our segmentation tool and it also helps to prove the quality of the magnetic-field
model where well-identified loop structures comply with field-line projections. We also discuss further potential applications
of our tool such as loop oscillations and stereoscopy. 相似文献
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Previous attempts to produce three-dimensional (3-D) reconstructions of coronal mass ejections (CMEs) have required either
modeling efforts or comparisons with secondary associated eruptions near the solar surface. This is because coronagraphs are
only able to produce sky-plane-projected images of CMEs and it has hence been impossible to overcome projection effects by
using coronagraphs alone. The SECCHI suite aboard the twin STEREO spacecraft allows us to provide the means for 3-D reconstruction
of CMEs directly from coronagraph measurements alone for the first time. We present these measurements from two CMEs observed
in November 2007. By identifying common features observed simultaneously with the LASCO coronagraphs aboard SOHO and the COR
coronagraphs aboard STEREO we have triangulated the source region of both CMEs. We present the geometrical analysis required
for this triangulation and identify the location of the CME in solar-meridional, ecliptic, and Carrington coordinates. None
of the two events were associated with an easily detectable solar surface eruption, so this triangulation technique is the
only means by which the source location of these CMEs could be identified. We present evidence that both CMEs originated from
the same magnetic structure on the Sun, but from a different magnetic field configuration. Our results reveal some insight
into the evolution of the high corona magnetic field, including its behavior over time scales of a few days and its reconfiguration
after a major eruption. 相似文献