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In late October and early November 2003, a series of space weather hazard events erupted in solar-terrestrial space. Aiming
at two intense storm (shock) events on 28 and 29 October, this paper presents a Two-Step method, which combines synoptic analysis
of space weather–`observing’ and quantitative prediction – ‘palpating’, and uses it to test predictions. In the first step,
‘observing’, on the basis of observations of the source surface magnetic field, interplanetary scintillation (IPS) and ACE
spacecraft, we find that the propagation of the shock waves is asymmetric and northward relative to the normal direction of
their solar sources due to the large-scale configuration of the coronal magnetic fields, and the Earth is located near the
direction of the fastest speed and greatest energy of the shocks. Being two fast ejection shock events, the fast explosion
of extremely high temperature and strong magnetic field, and background solar wind velocity as high as 600 and 1000 km s−1, are also helpful to their rapid propagation. According to the synoptic analysis, the shock travel times can be estimated
as 21 and 20 h, which are close to the observational results of 19.97 and 19.63 h, respectively. In the second step, ‘palpating’,
we adopt a new membership function of the fast shock events for the ISF method. The predicted results here show that for the
onset time of the geomagnetic disturbance, the relative errors between the observational and the predicted results are 1.8
and 6.7%, which are consistent with the estimated results of the first step; and for the magnetic disturbance magnitude, the
relative errors between the observational and the predicted results are 4.1 and 3.1%, respectively. Furthermore, the comparison
among the predicted results of our Two-Step method with those of five other prevailing methods shows that the Two-Step method
is advantageous in predicting such strong shock event. It can predict not only shock arrival time, but also the magnitude
of magnetic disturbance. The results of the present paper tell us that understanding the physical features of shock propagation
thoroughly is of great importance in improving the prediction efficiency. 相似文献
2.
In this paper, we reconstruct the finite energy force-free magnetic field of the active region NOAA 8100 on 4 November 1997
above the photosphere. In particular, the 3-D magnetic field structures before and after a 2B/X2 flare at 05:58 UT in this
region are analyzed. The magnetic field lines were extrapolated in close coincidence with the Yohkoh soft X-ray (SXR) loops accordingly. It is found that the active region is composed of an emerging flux loop, a complex loop
system with differential magnetic field shear, and large-scale, or open field lines. Similar magnetic connectivity has been
obtained for both instants but apparent changes of the twisting situations of the calculated magnetic field lines can be observed
that properly align with the corresponding SXR coronal loops. We conclude that this flare was triggered by the interaction
of an emerging flux loop and a large loop system with differential magnetic field shear, as well as large-scale, or open field
lines. The onset of the flare was at the common footpoints of several interacting magnetic loops and confined near the footpoints
of the emerging flux loop. The sheared configuration remained even after the energetic flare, as demonstrated by calculated
values of the twist for the loop system, which means that the active region was relaxed to a lower energy state but not completely
to the minimum energy state (two days later another X-class flare occurred in this region). 相似文献
3.
4.
Propagation of solar flare-associated interplanetary shock waves in the heliospheric meridional plane 总被引:4,自引:0,他引:4
We have analyzed 149 flare-associated shock wave events based on interplanetary scintillation (IPS) observational data. All of the flare-associated shock waves tend to propagate toward the low latitude region near the solar equator for flares that are located in both the solar northern and southern hemispheres. Also, the fastest propagation directions tend toward the heliospheric current sheet near 1 AU. We suggest that this tendency is caused by the dynamic action of near-Sun magnetic forces on the ejected coronal plasma that traverses the helmet-like magnetic topologies near the Sun outward to the classical topology that is essentially parallel to the heliospheric current sheet. 相似文献
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6.
In this paper, the Space–Time Conservation Element and Solution Element (CESE) method is applied to 2.5-dimensional resistive
magnetohydrodynamics (MHD) equations in Cartesian coordinates, with the purpose of modeling the magnetic reconnection study.
To show the validity and capacity of its application to MHD reconnection problem, spontaneous fast reconnection and magnetic
reconnection in multiple heliospheric current sheets are studied, which show good consistency with those obtained formerly
by other authors. In order to assess the ∇ ⋅ B = 0 constraint numerically, the contours and evolution of ∇ ⋅ B are analyzed. The numerical results tell us that the CESE numerical scheme not only has good numerical resolution but also
can keep the divergence-free condition for magnetic fields in the reconnection problems during the evolutionary process without
any special treatment. 相似文献
7.
In this paper, an operable solution approach is proposed to solve interplanetary hydrodynamic shock waves propagating in the interplanetary medium of solar wind background derived from Parker's hydrodynamic model. In our case the problem concerned is reduced to a set of ordinary differential equations (ODEs) involving the solar wind background parameters velocity v0(r), density 0(r), and pressure p0(r). The entire information for the shock can be obtained easily by obtaining the numerical solutions to the set of ODEs. 相似文献
8.
太阳等离子体和磁场输出的全球结构 总被引:1,自引:0,他引:1
太阳等离子体和磁场输出的全球结构魏奉思(中国科学院空间科学与应用研究中心北京100080)关键词太阳等离子体,太阳磁场,全球结构一个特定的太阳活动现象会有什么样的行星际表现,会引起什么样的地球空间环境变化发生?这是全世界日地物理学家们面临的重大科学问... 相似文献
9.
Using 180 interplanetary (IP) shock events associated with coronal mass ejections (CMEs) during 1997 – 2005, we investigate
the influence of the heliospheric current sheet (HCS) upon the propagation and geoeffectiveness of IP shocks. Our preliminary
results are: (1) The majority of CME-driving IP shocks occurred near the HCS. (2) The numbers of shock events and related
geomagnetic storms observed when the Earth and the solar source are located on the same side of the HCS, represented by f
SS and f
SG, respectively, are obviously higher than those when the Earth and the solar source are located on the opposite sides of the
HCS, denoted by f
OS and f
OG, with f
SS/f
OS=126/54, f
SG/f
OG = 91/36. (3) Parameter jumps across the shock fronts for the same-side events are also higher than those for the opposite-side
events, and the stronger shocks (Δ V ≥ 200 km s−1) are mainly attributed to be same-side events, with f
SSh/f
OSh = 28/15, where f
SSh and f
OSh are numbers of stronger shocks which belong to same-side events and opposite-side events, respectively. (4) The level of
the geomagnetic disturbances is higher for the same-side events than for the opposite-side events. The ratio of the number
of intense magnetic storms (Dst < −100) triggered by same-side events to those triggered by opposite-side events is 25/10.
(5) We propose an empirical model to predict the arrival time of the shock at the Earth, whose accuracy is comparable to that
of other prevailing models. These results show that the HCS is an important physical structure, which probably plays an important
role in the propagation of interplanetary shocks and their geoeffectiveness. 相似文献
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