共查询到20条相似文献，搜索用时 171 毫秒
1.
Richard A. Harrison Christopher J. Davis Christopher J. Eyles Danielle Bewsher Steve R. Crothers Jackie A. Davies Russell A. Howard Daniel J. Moses Dennis G. Socker Jeffrey S. Newmark Jean-Philippe Halain Jean-Marc Defise Emmanuel Mazy Pierre Rochus David F. Webb George M. Simnett 《Solar physics》2008,247(1):171-193
We show for the first time images of solar coronal mass ejections (CMEs) viewed using the Heliospheric Imager (HI) instrument
aboard the NASA STEREO spacecraft. The HI instruments are wide-angle imaging systems designed to detect CMEs in the heliosphere,
in particular, for the first time, observing the propagation of such events along the Sun – Earth line, that is, those directed
towards Earth. At the time of writing the STEREO spacecraft are still close to the Earth and the full advantage of the HI
dual-imaging has yet to be realised. However, even these early results show that despite severe technical challenges in their
design and implementation, the HI instruments can successfully detect CMEs in the heliosphere, and this is an extremely important
milestone for CME research. For the principal event being analysed here we demonstrate an ability to track a CME from the
corona to over 40 degrees. The time – altitude history shows a constant speed of ascent over at least the first 50 solar radii
and some evidence for deceleration at distances of over 20 degrees. Comparisons of associated coronagraph data and the HI
images show that the basic structure of the CME remains clearly intact as it propagates from the corona into the heliosphere.
Extracting the CME signal requires a consideration of the F-coronal intensity distribution, which can be identified from the
HI data. Thus we present the preliminary results on this measured F-coronal intensity and compare these to the modelled F-corona
of Koutchmy and Lamy (IAU Colloq.
85, 63, 1985). This analysis demonstrates that CME material some two orders of magnitude weaker than the F-corona can be detected; a specific
example at 40 solar radii revealed CME intensities as low as 1.7×10−14 of the solar brightness. These observations herald a new era in CME research as we extend our capability for tracking, in
particular, Earth-directed CMEs into the heliosphere. 相似文献
2.
B. V. Jackson J. A. Boyer P. P. Hick A. Buffington M. M. Bisi D. H. Crider 《Solar physics》2007,241(2):385-396
Interplanetary Scintillation (IPS) allows observation of the inner heliospheric response to corotating solar structures and
coronal mass ejections (CMEs) in scintillation level and velocity. With colleagues at STELab, Nagoya University, Japan, we
have developed near-real-time access of STELab IPS data for use in space-weather forecasting. We use a 3D reconstruction technique
that produces perspective views from solar corotating plasma and outward-flowing solar wind as observed from Earth by iteratively
fitting a kinematic solar wind model to IPS observations. This 3D modeling technique permits reconstruction of the density
and velocity structure of CMEs and other interplanetary transients at a relatively coarse resolution: a solar rotational cadence
and 10° latitudinal and longitudinal resolution for the corotational model and a one-day cadence and 20° latitudinal and longitudinal
heliographic resolution for the time-dependent model. This technique is used to determine solar-wind pressure (“ram” pressure)
at Mars. Results are compared with ram-pressure observations derived from Mars Global Surveyor magnetometer data (Crider et al.
2003, J. Geophys. Res.
108(A12), 1461) for the years 1999 through 2004. We identified 47 independent in situ pressure-pulse events above 3.5 nPa in the Mars Global Surveyor data in this time period where sufficient IPS data were available. We detail the large pressure pulse observed at Mars in
association with a CME that erupted from the Sun on 27 May 2003, which was a halo CME as viewed from Earth. We also detail
the response of a series of West-limb CME events and compare their response observed at Mars about 160° west of the Sun – Earth
line by the Mars Global Surveyor with the response derived from the IPS 3D reconstructions. 相似文献
3.
N. Lugaz P. Kintner C. M?stl L. K. Jian C. J. Davis C. J. Farrugia 《Solar physics》2012,279(2):497-515
We present a study of coronal mass ejections (CMEs) which impacted one of the STEREO spacecraft between January 2008 and early 2010. We focus our study on 20 CMEs which were observed remotely by the Heliospheric Imagers (HIs) onboard the other STEREO spacecraft up to large heliocentric distances. We compare the predictions of the Fixed-?? and Harmonic Mean (HM) fitting methods, which only differ by the assumed geometry of the CME. It is possible to use these techniques to determine from remote-sensing observations the CME direction of propagation, arrival time and final speed which are compared to in-situ measurements. We find evidence that for large viewing angles, the HM fitting method predicts the CME direction better. However, this may be due to the fact that only wide CMEs can be successfully observed when the CME propagates more than 100° from the observing spacecraft. Overall eight CMEs, originating from behind the limb as seen by one of the STEREO spacecraft can be tracked and their arrival time at the other STEREO spacecraft can be successfully predicted. This includes CMEs, such as the events on 4 December 2009 and 9 April 2010, which were viewed 130° away from their direction of propagation. Therefore, we predict that some Earth-directed CMEs will be observed by the HIs until early 2013, when the separation between Earth and one of the STEREO spacecraft will be similar to the separation of the two STEREO spacecraft in 2009??C?2010. 相似文献
4.
R. P. Kane 《Solar physics》2008,249(2):369-380
The sunspot number series at the peak of sunspot activity often has two or three peaks (Gnevyshev peaks; Gnevyshev, Solar Phys.
1, 107, 1967; Solar Phys.
51, 175, 1977). The sunspot group number (SGN) data were examined for 1997 – 2003 (part of cycle 23) and compared with data for coronal
mass ejection (CME) events. It was noticed that they exhibited mostly two Gnevyshev peaks in each of the four latitude belts
0° – 10°, 10° – 20°, 20 ° – 30°, and > 30°, in both N (northern) and S (southern) solar hemispheres. The SGN were confined
to within latitudes ± 50° around the Equator, mostly around ± 35°, and seemed to occur later in lower latitudes, indicating
possible latitudinal migration as in the Maunder butterfly diagrams. In CMEs, less energetic CMEs (of widths < 71°) showed
prominent Gnevyshev peaks during sunspot maximum years in almost all latitude belts, including near the poles. The CME activity
lasted longer than the SGN activity. However, the CME peaks did not match the SGN peaks and were almost simultaneous at different
latitudes, indicating no latitudinal migration. In energetic CMEs including halo CMEs, the Gnevyshev peaks were obscure and
ill-defined. The solar polar magnetic fields show polarity reversal during sunspot maximum years, first at the North Pole
and, a few months later, at the South Pole. However, the CME peaks and gaps did not match with the magnetic field reversal
times, preceding them by several months, rendering any cause – effect relationship doubtful. 相似文献
5.
We performed a detailed analysis of 27 slow coronal mass ejections (CMEs) whose heights were measured in at least 30 coronagraphic
images and were characterized by a high quality index (≥4). Our primary aim was to study the radial evolution of these CMEs
and their properties in the range 2 – 30 solar radii. The instantaneous speeds of CMEs were calculated by using successive
height – time data pairs. The obtained speed – distance profiles [v(R)] are fitted by a power law v = a(R−b)
c
. The power-law indices are found to be in the ranges a=30 – 386, b=1.95 – 3.92, and c=0.03 – 0.79. The power-law exponent c is found to be larger for slower and narrower CMEs. With the exception of two events that had approximately constant velocity,
all events were accelerating. The majority of accelerating events shows a v(R) profile very similar to the solar-wind profile deduced by Sheeley et al. (Astrophys. J.
484, 472, 1997). This indicates that the dynamics of most slow CMEs are dominated by the solar wind drag. 相似文献
6.
The geometric localization technique (Pizzo and Biesecker, Geophys. Res. Lett. 31, 21802, 2004) can readily be used with Solar Terrestrial Relations Observatory (STEREO) Space Weather Beacon data to observe coronal mass ejection (CME) propagation within three-dimensional space in near-real time. This technique is based upon simple triangulation concepts and utilizes a series of lines of sight from two space-based observatories to determine gross characteristics of CMEs, such as location and velocity. Since this work is aimed at space weather applications, the emphasis is on use of COR2 coronagraph data, which has a field of view from 2.5R ⊙ to 15R ⊙; this spatial coverage allows us to observe the early temporal development of a CME, and hence to calculate its velocity, even for very fast CMEs. We apply this technique to highly-compressed COR2 beacon images for several CMEs at various spacecraft separation angles: 21 August 2007, when the separation angle between the two spacecraft was 26°; 31 December 2007 and 2 January 2008, when the separation angle was 44°; and 17 October 2008, when the spacecraft separation was 79°. We present results on the speed and direction of propagation for these events and discuss the error associated with this technique. We also compare our results to the two-dimensional plane-of-sky speeds calculated from STEREO and SOHO. 相似文献
7.
This paper is a qualitative study of 42 events of solar filament/prominence sudden disappearances (“disparitions brusques”;
henceforth DBs) around two solar minima, 1985 – 1986 and 1994. The studied events were classified as 17 thermal and 25 dynamic
disappearances. Associated events, i.e. coronal mass ejections (CMEs), type II bursts, evolution of nearby coronal holes, as well as solar wind speed, and geomagnetic
disturbances are discussed. We have found that about 50% of the thermal DBs with adjacent (within 15° from the DB) coronal
holes were associated with CMEs within a selected time window. All the studied thermal disappearances with adjacent coronal
holes or accompanied by dynamic disappearances were associated with weak and medium geomagnetic storms. Also, nearly 64% of
dynamic DBs were associated with CMEs. Ten (40%) dynamic disappearances were associated with intense geomagnetic storms, even
when no CMEs was reported, six (24%) dynamic disappearances corresponded to extreme storms, and five (20%) corresponded to
medium geomagnetic storms. The extreme geomagnetic storms appeared to be related to combined events, involving dynamic disappearances
with adjacent coronal holes or including thermal disappearances. Furthermore, the geomagnetic activity (Dst index) increased
if the source was close to the central meridian (±30°). The highest interplanetary magnetic field (B), longest duration, lowest southward direction B
z
component, and lowest Dst were highly correlated for all studied events. The Sun – Earth transit time computed from the starting
time of the sudden disappearance and the time its effect was measured at Earth was about 4.3 days and was mainly well correlated
with the solar wind speed measured in situ (daily value). 相似文献
8.
We study the kinematical characteristics and 3D geometry of a large-scale coronal wave that occurred in association with the
26 April 2008 flare-CME event. The wave was observed with the EUVI instruments aboard both STEREO spacecraft (STEREO-A and
STEREO-B) with a mean speed of ∼ 240 km s−1. The wave is more pronounced in the eastern propagation direction, and is thus, better observable in STEREO-B images. From
STEREO-B observations we derive two separate initiation centers for the wave, and their locations fit with the coronal dimming
regions. Assuming a simple geometry of the wave we reconstruct its 3D nature from combined STEREO-A and STEREO-B observations.
We find that the wave structure is asymmetric with an inclination toward East. The associated CME has a deprojected speed
of ∼ 750±50 km s−1, and it shows a non-radial outward motion toward the East with respect to the underlying source region location. Applying
the forward fitting model developed by Thernisien, Howard, and Vourlidas (Astrophys. J. 652, 763, 2006), we derive the CME flux rope position on the solar surface to be close to the dimming regions. We conclude that the expanding
flanks of the CME most likely drive and shape the coronal wave. 相似文献
9.
The twin Solar Terrestrial Relations Observatory (STEREO) spacecraft reached a separation angle of 180° on 6 February 2011. This provided a unique opportunity to test the
intercalibration between the Sun–Earth Connection Coronal and Heliospheric Investigation (SECCHI) telescopes on both spacecraft
for areas above the limb. So long as the corona is optically thin, at 180° separation each spacecraft sees the same corona
from opposite directions. Thus, the data should appear as mirror images of each other. We report here on the results of the
comparison of the images taken by the inner coronagraph (COR1) on the STEREO-Ahead and -Behind spacecraft in the hours when the separation was close to 180°. We find that the intensity values seen by the two telescopes
agree with each other to a high degree of accuracy. This validates both the radiometric intercalibration between the COR1
telescopes, and the method used to remove instrumental background from the images. The relative error between COR1-A and COR1-B
is found to be less than 10−9
B/B
⊙ over most of the field-of-view, growing to a few ×10−9
B/B
⊙ for the brighter pixels near the edge of the occulter. The primary source of error is the background determination. We also
report on the analysis of star observations which show that the absolute radiometric calibration of either COR1 telescope
has not changed significantly since launch. 相似文献
10.
11.
We studied the kinematic evolution of the 8 October 2007 CME in the corona based on observations from Sun – Earth Connection Coronal and Heliospheric Investigation (SECCHI) onboard satellite B of Solar TErrestrial RElations Observatory (STEREO). The observational results show that this CME obviously deflected to a lower latitude region of about 30° at the
beginning. After this, the CME propagated radially. We also analyze the influence of the background magnetic field on the
deflection of this CME. We find that the deflection of this CME at an early stage may be caused by a nonuniform distribution
of the background magnetic-field energy density and that the CME tended to propagate to the region with lower magnetic-energy
density. In addition, we found that the velocity profile of this gradual CME shows multiphased evolution during its propagation
in the COR1-B FOV. The CME velocity first remained constant: 23.1 km s−1. Then it accelerated continuously with a positive acceleration of ≈7.6 m s−2. 相似文献
12.
R. P. Kane 《Solar physics》2008,249(2):355-367
The 12-month running means of the conventional sunspot number Rz, the sunspot group numbers (SGN) and the frequency of occurrence of Coronal Mass Ejections (CMEs) were examined for cycle
23 (1996 – 2006). For the whole disc, the SGN and Rz plots were almost identical. Hence, SGN could be used as a proxy for Rz, for which latitude data are not available. SGN values were used for 5° latitude belts 0° – 5°, 5° – 10°, 10° – 15°, 15° – 20°,
20° – 25°, 25° – 30° and > 30°, separately in each hemisphere north and south. Roughly, from latitudes 25° – 30° N to 20° – 25°
N, the peaks seem to have occurred later for lower latitudes, from latitudes 20° – 25° N to 15° – 20° N, the peaks are stagnant or occur slightly earlier, and then from latitudes 15° – 20° N to 0° – 5° N, the peaks seem to have occurred again later for lower latitudes. Thus, some latitudinal migration is suggested, clearly in the northern hemisphere, not very clearly
in the southern hemisphere, first to the equator in 1998, stagnant or slightly poleward in 1999, and then to the equator again
from 2000 onwards, the latter reminiscent of the Maunder butterfly diagrams. Similar plots for CME occurrence frequency also
showed multiple peaks (two or three) in almost all latitude belts, but the peaks were almost simultaneous at all latitudes,
indicating no latitudinal migration. For similar latitude belts, SGN and CME plots were dissimilar in almost all latitude
belts except 10° – 20° S. The CME plots had in general more peaks than the SGN plots, and the peaks of SGN often did not match
with those of CME. In the CME data, it was noticed that whereas the values declined from 2002 to 2003, there was no further
decline during 2003 – 2006 as one would have expected to occur during the declining phase of sunspots, where 2007 is almost
a year of sunspot minimum. An inquiry at GSFC-NASA revealed that the person who creates the preliminary list was changed in
2004 and the new person picks out more weak CMEs. Thus a subjectivity (overestimates after 2002) seems to be involved and
hence, values obtained before and during 2002 are not directly comparable to values recorded after 2002, except for CMEs with
widths exceeding 60°. 相似文献
13.
Yu Liu 《Solar physics》2008,249(1):75-84
Liu et al. (Astrophys. J.
628, 1056, 2005a) described one surge – coronal mass ejection (CME) event showing a close relationship between solar chromospheric surge ejection
and CME that had not been noted before. In this work, large Hα surges (>72 Mm, or 100 arcsec) are studied. Eight of these
were associated with CMEs. According to their distinct morphological features, Hα surges can be classified into three types:
jetlike, diffuse, and closed loop. It was found that all of the jetlike surges were associated with jetlike CMEs (with angular
widths ≤30 degrees); the diffuse surges were all associated with wide-angle CMEs (e.g., halo); the closed-loop surges were not associated with CMEs. The exclusive relation between Hα surges and CMEs indicates
difference in magnetic field configurations. The jetlike surges and related narrow CMEs propagate along coronal fields that
are originally open. The unusual transverse mass motions in the diffuse surges are suggested to be due to magnetic reconnections
in the corona that produce wide-angle CMEs. For the closed-loop surges, their paths are just outlining stable closed loops
close to the solar surface. Thus no CMEs are associated with them. 相似文献
14.
Using nine years of solar wind plasma and magnetic field data from the Wind mission, we investigated the characteristics of both magnetic clouds (MCs) and magnetic cloud-like structures (MCLs) during
1995 – 2003. A MCL structure is an event that is identified by an automatic scheme (Lepping, Wu, and Berdichevsky, Ann. Geophys.
23, 2687, 2005) with the same criteria as for a MC, but it is not usually identifiable as a flux rope by using the MC (Burlaga et al., J. Geophys. Res.
86, 6673, 1981) fitting model developed by Lepping, Jones, and Burlaga (Geophys. Res. Lett.
95(11), 957, 1990). The average occurrence rate is 9.5 for MCs and 13.6 for MCLs per year for the overall period of interest, and there were
82 MCs and 122 MCLs identified during this period. The characteristics of MCs and MCL structures are as follows: (1) The average
duration, Δt, of MCs is 21.1 h, which is 40% longer than that for MCLs (Δt=15 h); (2) the average
(minimum B
z
found in MC/MCL measured in geocentric solar ecliptic coordinates) is −10.2 nT for MCs and −6 nT for MCLs; (3) the average
Dstmin (minimum Dst caused by MCs/MCLs) is −82 nT for MCs and −37 nT for MCLs; (4) the average solar wind velocity is 453 km s−1 for MCs and 413 km s−1 for MCLs; (5) the average thermal speed is 24.6 km s−1 for MCs and 27.7 km s−1 for MCLs; (6) the average magnetic field intensity is 12.7 nT for MCs and 9.8 nT for MCLs; (7) the average solar wind density
is 9.4 cm−3 for MCs and 6.3 cm−3 for MCLs; and (8) a MC is one of the most important interplanetary structures capable of causing severe geomagnetic storms.
The longer duration, more intense magnetic field and higher solar wind speed of MCs, compared to those properties of the MCLs,
are very likely the major reasons for MCs generally causing more severe geomagnetic storms than MCLs. But the fact that a
MC is an important interplanetary structure with respect to geomagnetic storms is not new (e.g., Zhang and Burlaga, J. Geophys. Res.
93, 2511, 1988; Bothmer, ESA SP-535, 419, 2003). 相似文献
15.
G. Michalek 《Solar physics》2010,261(1):107-114
A set of 106 limb CMEs which are wide and could be possible halo events, when directed towards Earth, are used to check the
accuracy of the asymmetric cone model. For this purpose characteristics of CMEs (widths and radial speeds) measured for the
possible halo CMEs are compared with these obtained for halo CMEs using the asymmetric cone model (Michalek, Solar Phys.
237, 101, 2006). It was shown that the width and speed distributions for both datasets are very similar and with a probability of p>0.93 (using the Kolmogorov – Smirnov test) were drawn from the same distribution of events. We also determined the accurate
relationship between radial (V
rad) and expansion (V
exp) speeds of halo CMEs. This relation for the halo CMEs is simply V
rad=V
exp and could be very useful for space weather application. 相似文献
16.
Mutual quasi-periodicities near the solar-rotation period appear in time series based on the Earth’s magnetic field, the interplanetary
magnetic field, and signed solar-magnetic fields. Dominant among these is one at 27.03±0.02 days that has been highlighted
by Neugebauer et al. (J. Geophys. Res.
105, 2315, 2000). Extension of their study in time and to different data reveals decadal epochs during which the ≈ 27.0 days, or a ≈ 28.3 days,
or other quasi-periods dominate the signal. Space-time eigenvalue analyses of time series in 30 solar latitude bands, based
on synoptic maps of unsigned photospheric fields, lead to two maximally independent modes that account for almost 30% of the
data variance. One mode spans 45° of latitude in the northern hemisphere and the other one in the southern. The modes rotate
around the Sun rigidly, not differentially, suggesting connection with the subsurface dynamo. Spectral analyses yield familiar
dominant quasi-periods 27.04±0.03 days in the North and at 28.24±0.03 days in the South. These are replaced during cycle 23
by one at 26.45±0.03 days in the North. The modes show no tendency for preferred longitudes separated by ≈ 180°. 相似文献
17.
R. P. Kane 《Solar physics》2007,246(2):471-485
Many methods of predictions of sunspot maximum number use data before or at the preceding sunspot minimum to correlate with
the following sunspot maximum of the same cycle, which occurs a few years later. Kane and Trivedi (Solar Phys. 68, 135, 1980) found that correlations of R
z(max) (the maximum in the 12-month running means of sunspot number R
z) with R
z(min) (the minimum in the 12-month running means of sunspot number R
z) in the solar latitude belt 20° – 40°, particularly in the southern hemisphere, exceeded 0.6 and was still higher (0.86)
for the narrower belt > 30° S. Recently, Javaraiah (Mon. Not. Roy. Astron. Soc.
377, L34, 2007) studied the relationship of sunspot areas at different solar latitudes and reported correlations 0.95 – 0.97 between minima and maxima of sunspot areas at low latitudes
and sunspot maxima of the next cycle, and predictions could be made with an antecedence of more than 11 years. For the present
study, we selected another parameter, namely, SGN, the sunspot group number (irrespective of their areas) and found that SGN(min) during a sunspot minimum year at latitudes > 30° S had a correlation
+0.78±0.11 with the sunspot number R
z(max) of the same cycle. Also, the SGN during a sunspot minimum year in the latitude belt (10° – 30° N) had a correlation +0.87±0.07 with the
sunspot number R
z(max) of the next cycle. We obtain an appropriate regression equation, from which our prediction for the coming cycle 24 is R
z(max )=129.7±16.3. 相似文献
18.
J. Javaraiah 《Solar physics》2008,252(2):419-439
Recently, using Greenwich and Solar Optical Observing Network sunspot group data during the period 1874 – 2006, Javaraiah
(Mon. Not. Roy. Astron. Soc.
377, L34, 2007: Paper I), has found that: (1) the sum of the areas of the sunspot groups in 0° – 10° latitude interval of the Sun’s northern
hemisphere and in the time-interval of −1.35 year to +2.15 year from the time of the preceding minimum of a solar cycle n correlates well (corr. coeff. r=0.947) with the amplitude (maximum of the smoothed monthly sunspot number) of the next cycle n+1. (2) The sum of the areas of the spot groups in 0° – 10° latitude interval of the southern hemisphere and in the time-interval
of 1.0 year to 1.75 year just after the time of the maximum of the cycle n correlates very well (r=0.966) with the amplitude of cycle n+1. Using these relations, (1) and (2), the values 112±13 and 74±10, respectively, were predicted in Paper I for the amplitude
of the upcoming cycle 24. Here we found that the north – south asymmetries in the aforementioned area sums have a strong ≈44-year
periodicity and from this we can infer that the upcoming cycle 24 will be weaker than cycle 23. In case of (1), the north – south
asymmetry in the area sum of a cycle n also has a relationship, say (3), with the amplitude of cycle n+1, which is similar to (1) but more statistically significant (r=0.968) like (2). By using (3) it is possible to predict the amplitude of a cycle with a better accuracy by about 13 years
in advance, and we get 103±10 for the amplitude of the upcoming cycle 24. However, we found a similar but a more statistically
significant (r=0.983) relationship, say (4), by using the sum of the area sum used in (2) and the north – south difference used in (3).
By using (4) it is possible to predict the amplitude of a cycle by about 9 years in advance with a high accuracy and we get
87±7 for the amplitude of cycle 24, which is about 28% less than the amplitude of cycle 23. Our results also indicate that
cycle 25 will be stronger than cycle 24. The variations in the mean meridional motions of the spot groups during odd and even
numbered cycles suggest that the solar meridional flows may transport magnetic flux across the solar equator and potentially
responsible for all the above relationships.
The author did a major part of this work at the Department of Physics and Astronomy, UCLA, 430 Portola Plaza, Los Angeles,
CA 90095-1547, USA. 相似文献
19.
The solar wind quasi-invariant (QI) has been defined by Osherovich, Fainberg, and Stone (Geophys. Res. Lett.
26, 2597, 1999) as the ratio of magnetic energy density and the energy density of the solar wind flow. In the regular solar wind QI is a
rather small number, since the energy of the flow is almost two orders of magnitude greater than the magnetic energy. However,
in magnetic clouds, QI is the order of unity (less than 1) and thus magnetic clouds can be viewed as a great anomaly in comparison
with its value in the background solar wind. We study the duration, extent, and amplitude of this anomaly for two groups of
isolated magnetic clouds: slow clouds (360<v<450 km s−1) and fast clouds (450≤v<720 km s−1). By applying the technique of superposition of epochs to 12 slow and 12 fast clouds from the catalog of Richardson and Cane
(Solar Phys. 264, 189, 2010), we create an average slow cloud and an average fast cloud observed at 1 AU. From our analysis of these average clouds,
we obtain cloud boundaries in both time and space as well as differences in QI amplitude and other parameters characterizing
the solar wind state. Interplanetary magnetic clouds are known to cause major magnetic storms at the Earth, especially those
clouds which travel from the sun to the Earth at high speeds. Characterizing each magnetic cloud by its QI value and extent
may help in understanding the role of those disturbances in producing geomagnetic activity. 相似文献
20.
The behavior of solar energetic particles (SEPs) in a shock – magnetic cloud interacting complex structure observed by the
Advanced Composition Explorer (ACE) spacecraft on 5 November 2001 is analyzed. A strong shock causing magnetic field strength and solar wind speed increases
of about 41 nT and 300 km s−1, respectively, propagated within a preceding magnetic cloud (MC). It is found that an extraordinary SEP enhancement appeared
at the high-energy (≥10 MeV) proton intensities and extended over and only over the entire period of the shock – MC structure
passing through the spacecraft. Such SEP behavior is much different from the usual picture that the SEPs are depressed in
MCs. The comparison of this event with other top SEP events of solar cycle 23 (2000 Bastille Day and 2003 Halloween events)
shows that such an enhancement resulted from the effects of the shock – MC complex structure leading to the highest ≥10 MeV
proton intensity of solar cycle 23. Our analysis suggests that the relatively isolated magnetic field configuration of MCs
combined with an embedded strong shock could significantly enhance the SEP intensity; SEPs are accelerated by the shock and
confined into the MC. Further, we find that the SEP enhancement at lower energies happened not only within the shock – MC
structure but also after it, probably owing to the presence of a following MC-like structure. This is consistent with the
picture that SEP fluxes could be enhanced in the magnetic topology between two MCs, which was proposed based on numerical
simulations by Kallenrode and Cliver (Proc. 27th ICRC
8, 3318, 2001b). 相似文献