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1.
Energetic Particle Fluxes during the Bastille Day Solar Eruption 总被引：2，自引：0，他引：2
We report on our observations of solar energetic particle fluxes of p, He, C, O, Ne, Mg, Si, and Fe ions measured by the Energetic and Relativistic Nucleon and Electron (ERNE) experiment associated
with the Bastille Day solar flare and coronal mass ejection (CME) on 14 July 2000. We observed two clear maxima of the Fe/O
ratio at the energies 8.5–15 MeV nucl−1. The first Fe/O maximum occurred ∼ 3 hours after the beginning of the particle event, and the second maximum ∼ 22 hours after
the first one at the arrival of the shock associated with the Bastille Day eruption. We also observed a change in the energy
spectrum of oxygen concurrent with a change in the direction of the interplanetary magnetic field at the start of the second
enhancement of the Fe/O ratio. We propose an interpretation of the particle event where observed interplanetary particle fluxes
are associated with two different particle sources near the Sun and in interplanetary space. We suggest that heavy ions observed
during the first period of the Fe/O enhancement were released when a coronal shock reached a magnetic foot point connected
to 1 AU. The second maximum of Fe/O occurred when spacecraft encountered Fe-rich material stored in magnetic field flux tubes
early in the event and was possibly reaccelerated by the interplanetary shock. 相似文献
2.
Salvatore Mancuso 《Solar physics》2011,273(2):511-523
We report results from the combined analysis of UV and radio observations of a CME-driven shock observed on 7 May 2004 above
the southeast limb of the Sun at 1.86 R
⊙ with the Ultraviolet Coronagraph Spectrometer (UVCS) on board the Solar and Heliospheric Observatory (SOHO). The coronal mass ejection (CME) was first detected in white-light by the SOHO’s Large Angle and Spectrometric Coronagraph
(LASCO) C2 telescope and shock-associated type II metric emission was recorded simultaneously by ground-based radio spectrographs.
The shock speed (∼ 690 km s−1), as deduced from the analysis of the type II emission drift in the radio spectra and the pre-shock local electron density
estimated with the diagnostics provided by UVCS observations of the O vi
λλ 1031.9, 1037.6 doublet line intensities, is just a factor ∼ 0.1 higher than the CME speed inferred by means of the white-light
(and EUV) data in the middle corona. The local magnetosonic speed, computed from a standard magnetic field model, was estimated
as high as ∼ 600 km s−1, implying that the CME speed was probably just sufficient to drive a weak fast-mode MHD shock ahead of the front. Simultaneously
with the type II radio emission, significant changes in the O vi doublet line intensities and profiles were recorded in the UVCS spectra and found compatible with abrupt post-shock plasma
acceleration and modest ion heating. This work provides further evidence for the CME-driven origin of the shocks observed
in the middle corona. 相似文献
3.
P. K. Manoharan 《Solar physics》2006,235(1-2):345-368
Knowledge of the radial evolution of the coronal mass ejection (CME) is important for the understanding of its arrival at
the near-Earth space and of its interaction with the disturbed/ambient solar wind in the course of its travel to 1 AU and
further. In this paper, the radial evolution of 30 large CMEs (angular width > 150∘, i.e., halo and partial halo CMEs) has been investigated between the Sun and the Earth using (i) the white-light images of
the near-Sun region from the Large Angle Spectroscopic Coronagraph (LASCO) onboard SOHO mission and (ii) the interplanetary scintillation (IPS) images of the inner heliosphere obtained from the Ooty Radio Telescope (ORT). In the LASCO field of view at heliocentric
distances R≤30 solar radii (R⊙), these CMEs cover an order of magnitude range of initial speeds, VCME≈260–2600 km s−1. Following results have been obtained from the speed evolution of these CMEs in the Sun–Earth distance range: (1) the speed
profile of the CME shows dependence on its initial speed; (2) the propagation of the CME goes through continuous changes,
which depend on the interaction of the CME with the surrounding solar wind encountered on the way; (3) the radial-speed profiles
obtained by combining the LASCO and IPS images yield the factual view of the propagation of CMEs in the inner heliosphere
and transit times and speeds at 1 AU computed from these profiles are in good agreement with the actual measurements; (4)
the mean travel time curve for different initial speeds and the shape of the radial-speed profiles suggest that up to a distance
of ∼80 R⊙, the internal energy of the CME (or the expansion of the CME) dominates and however, at larger distances, the CME's interaction
with the solar wind controls the propagation; (5) most of the CMEs tend to attain the speed of the ambient flow at 1 AU or
further out of the Earth's orbit. The results of this study are useful to quantify the drag force imposed on a CME by the
interaction with the ambient solar wind and it is essential in modeling the CME propagation. This study also has a great importance
in understanding the prediction of CME-associated space weather at the near-Earth environment. 相似文献
4.
Near 1 AU the solar wind structure associated with the solar flare of 14 July 2000 (Bastille Day) consisted of a large high-speed
stream of 15 July and five nearby small streams during a 10-day period. At the leading edge of the large high-speed stream,
in less than 6 hours, the flow speed increased from 600 km s−1 to 1100 km s−1, the magnetic field intensity increased from 10 nT to 60 nT, and an interaction region was identified. The interaction region
was bounded between the pair of a forward shock F and a reverse shock R. Additional forward shocks were also identified at the leading edge of each of the five smaller streams. This paper presents
a magnetohydrodynamics (MHD) simulation using ACE plasma and magnetic field data near 1 AU as input to study the radial evolution
of the Bastille Day solar wind event. The two shocks, F and R, propagated in opposite directions away from each other in the solar wind frame and interacted with neighboring shocks and
streams; the spatial and temporal extent of the interaction region continued to increase with the heliocentric distance. The
solar wind was restructured from a series of streams at 1 AU to a huge merged interaction region (MIR) extending over a period
of 12 days at 5.5 AU. Throughout the interior of the MIR bounded by the shock pair F and R the magnetic field intensity was a few times stronger than that outside the MIR. The simulation shows how merging of shocks,
collision of shocks, and formation of new shocks contributed to the evolution process. 相似文献
5.
A transient flow system containing several streams and shocks associated with the Bastille Day 2000 solar event was observed
by the WIND and ACE spacecraft at 1 AU. Voyager 2 (V2) at 63 AU observed this flow system after it moved through the interplanetary medium and into the distant heliosphere,
where the interstellar pickup protons strongly influence the MHD structures and flow dynamics. We discuss the Voyager 2 magnetic and plasma observations of this event. Increases in the magnetic field strength B, density N, temperature T and
speed V were observed at the front of a stream at V2, consistent with presence of a shock related to the Bastille Day shock
at 1 AU. However, the jumps occurred in a 16.9-hour data gap, so that the shock was not observed directly, and the properties
of the candidate shock cannot be determined precisely. The candidate shock was followed by a merged interaction region (MIR)
that moved past V2 for at least 10 days. The first part of this MIR contains a structure that might be a magnetic cloud. Just
ahead of the shock there was an abrupt increase in density associated with a decrease in temperature such that the solar wind
thermal pressure was constant across it. Just behind the shock there was an abrupt decrease in density associated with a net
increase in magnetic field strength. This appears to be a pressure balanced structure in which the interstellar pickup protons
make a significant contribution. 相似文献
6.
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
7.
We describe the radio signatures that led up to and concluded the solar eruptive event of 14 July 2000 (Bastille Day Event).
These radio signatures provide a means of remotely sensing the associated solar activity and transient phenomena. For many
days prior to the Bastille Day Event kilometric Type III radio storm emissions were observed that were presumably associated
with the active region NOAA 9077. These storm emissions continued until the X5.7 flare at ∼ 10 UT on 14 July 2000 that characterized
the Bastille Day Event, then ceased abruptly. The Bastille Day Event itself produced very intense, complex, long-duration
Type III-like radio emissions, which appear to have been associated with electrons generated (accelerated) deep in the solar
corona. The coronal mass ejection (CME) associated with the Bastille Day Event generated decametric to kilometric Type II
radio emissions as the CME propagated through the solar corona and interplanetary medium. The frequency drift of these Type II
radio emissions are related to the dynamics of the propagating CME and indicate that the CME experienced significant deceleration
as it propagated from the high corona into the interplanetary medium. 相似文献
8.
Smith C.W. Ness N.F. Burlaga L.F. Skoug R.M. McComas D.J. Zurbuchen T.H. Gloeckler G. Haggerty D.K. Gold R.E. Desai M.I. Mason G.M. Mazur J.E. Dwyer J.R. Popecki M.A. Möbius E. Cohen C.M.S. Leske R.A. 《Solar physics》2001,204(1-2):227-252
We present ACE observations for the six-day period encompassing the Bastille Day 2000 solar activity. A high level of transient
activity at 1 AU, including ICME-driven shocks, magnetic clouds, shock-accelerated energetic particle populations, and solar
energetic ions and electrons, are described. We present thermal ion composition signatures for ICMEs and magnetic clouds from
which we derive electron temperatures at the source of the disturbances and we describe additional enhancements in some ion
species that are clearly related to the transient source. We describe shock acceleration of 0.3–2.0 MeV nucl−1 protons and minor ions and the relative inability of some of the shocks to accelerate significant energetic ion populations
near 1 AU. We report the characteristics of < 20 MeV nucl−1 solar energetic ions and < 0.32 MeV electrons and attempt to relate the release of energetic electrons to particular source
regions. 相似文献
9.
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
10.
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
11.
We analyze five events of the interaction of coronal mass ejections (CMEs) with the remote coronal rays located up to 90°
away from the CME as observed by the SOHO/LASCO C2 coronagraph. Using sequences of SOHO/LASCO C2 images, we estimate the kink
propagation in the coronal rays during their interaction with the corresponding CMEs ranging from 180 to 920 km s−1 within the interval of radial distances from 3 R
⊙ to 6 R
⊙. We conclude that all studied events do not correspond to the expected pattern of shock wave propagation in the corona. Coronal
ray deflection can be interpreted as the influence of the magnetic field of a moving flux rope within the CME. The motion
of a large-scale flux rope away from the Sun creates changes in the structure of surrounding field lines, which are similar
to the kink propagation along coronal rays. The retardation of the potential should be taken into account since the flux rope
moves at a high speed, comparable with the Alfvén speed. 相似文献
12.
A detailed analysis of characteristics of coronal mass ejections and flares associated with deca-hectometer wavelength type-II radio bursts (DH-CMEs and DH-flares) observed in the period 1997–2008 is presented. A sample of 62 limb events is divided into two populations known as after-flare CMEs (AF-CMEs) and before-flare CMEs (BF-CMEs) based on the relative timing of the flare and CME onsets. On average, AF-CMEs (1589 km s−1) have more speed than the BF-CMEs (1226 km s−1) and the difference between mean values are highly significant (P∼2%). The average CME nose height at the time of type-II start is at larger distance for AF-CMEs than the BF-CMEs (4.89 and 3.84 R o, respectively). We found a good anti-correlation for accelerating (R a=−0.89) and decelerating (R d=−0.78) AF-CMEs. In the case of decelerating BF-CMEs, the correlation seems to be similar to that for decelerating AF-CMEs (R d=−0.83). The number of decelerating AF-CMEs is 51% only; where as, the number of decelerating BF-CMEs is 83%. The flares associated with BF-CMEs have shorter rise and decay times than flares related to AF-CMEs. We found statistically significant differences between the two sets of associated DH-type-II bursts characteristics: starting frequency (P∼4%), drift rate (P∼1%), and ending frequency (P∼6%). The delay time analysis of DH-type-II start and flare onset times shows that the time lags are longer in AF-CME events than in BF-CME events (P≪1%). From the above results, the AF-CMEs which are associated with DH-type-II bursts are found to be more energetic, associated with long duration flares and DH-type-IIs of lower ending frequencies. 相似文献
13.
This is an account of Allan Sandage’s work on (1) The character of the expansion field. For many years he has been the strongest defender of an expanding Universe. He later explained the CMB dipole by a local velocity of 220±50 km s−1 toward the Virgo cluster and by a bulk motion of the Local supercluster (extending out to ∼3500 km s−1) of 450–500 km s−1 toward an apex at l=275, b=12. Allowing for these streaming velocities he found linear expansion to hold down to local scales (∼300 km s−1). (2) The calibration of the Hubble constant. Probing different methods he finally adopted—from Cepheid-calibrated SNe Ia and from independent RR Lyr-calibrated TRGBs—H 0=62.3±1.3±5.0 km s−1 Mpc−1. 相似文献
14.
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
15.
One of the large Sun–Earth connection events in solar cycle 23 occurred between 14 and 16 July 2000. Anomalies occurring on
several satellites were reported in association with this event. Statistical study of extreme events is important not only
for a view of space weather but for seeking ways to predict such kinds of large events. The Bastille Day event was characterized
by a large flux (24 000 p.f.u. at its maximum) of solar energetic protons and a fast average transit speed of approximately
1500 km s−1 of the interplanetary disturbance. A geomagnetic Kp index of more than 9 was observed after an interval of approximately eleven years since 1989. We found that return periods
of extreme space weather (e.g., large flares, solar energetic proton events, and large geomagnetic storms) satisfied the Weibull
distribution. 相似文献
16.
Michael A. Dopita Michiel Reuland Wil van Breugel Wim de Vries S. A. Stanford Huub Röttgering George Miley Bram Venemans Hy Spinrad Steve Dawson Arjun Dey Mark Lacy Daniel Stern Andrew Bunker 《Astrophysics and Space Science》2007,311(1-3):305-309
We present results from a Keck optical and near IR spectroscopic study of the giant emission line halos of the z>3 High Redshift Radio Galaxies (HiZRGs) 4C 41.17, 4C 60.07 and B2 0902+34. The outer regions of these halos show quiet kinematics
with typical velocity dispersions of a few hundred km s−1 and velocity shears consistent with rotation. The inner regions contain shocked, clumpy cocoons of gas closely associated
with the radio lobes with disturbed kinematics and expansion velocities and/or velocity dispersions >1000 km s−1. We also find evidence for the ejection of chemically enriched material in 4C 41.17 up to a distance of ∼60 kpc along the
radio-axis. We infer that these HiZRGs are undergoing a final jet-induced phase of star formation with the ejection of most
of their interstellar medium before evolving to become “red and dead” Elliptical galaxies. 相似文献
17.
Starting with a large number (N=100) of Wind magnetic clouds (MCs) and applying necessary restrictions, we find a proper set of N=29 to investigate the average ecliptic plane projection of the upstream magnetosheath thickness as a function of the longitude
of the solar source of the MCs, for those cases of MCs having upstream shock waves. A few of the obvious restrictions on the
full set of MCs are the need for there to exist a driven upstream shock wave, knowledge of the MC’s solar source, and restriction
to only MCs of low axial latitudes. The analysis required splitting this set into two subsets according to average magnetosheath
speed: slow/average (300 – 500 km s−1) and fast (500 – 1100 km s−1) speeds. Only the fast set gives plausible results, where the estimated magnetosheath thickness (ΔS) goes from 0.042 to 0.079 AU (at 1 AU) over the longitude sector of 0° (adjusted source-center longitude of the average magnetic
cloud) to 40° off center (East or West), based on N=11 appropriate cases. These estimates are well determined with a sigma (σ) for the fit of 0.0055 AU, where σ is effectively the same as
(chi-squared) for the appropriate quadratic fit. The associated linear correlation coefficient for ΔS versus |Longitude| was very good (c.c.=0.93) for the fast range, and ΔS at 60° longitude is extrapolated to be 2.7 times the value at 0°. For the slower speeds we obtain the surprising result that
ΔS is typically more-or-less constant at 0.040±0.013 AU at all longitudes, indicating that the MC as a driver, when moving close
to the normal solar wind speed, has little influence on magnetosheath thickness. In some cases, the correct choice between
two candidate solar-source longitudes for a fast MC might be made by noting the value of the observed ΔS just upstream of the MC. Also, we point out that, for the 29 events, the average sheath speed was well correlated with the
quantity ΔV[=(〈V
MC〉−〈V
UPSTREAM〉)], and also with both 〈V
MC〉 and 〈V
MC,T〉, where 〈V
MC〉 is the first one-hour average of the MC speed, 〈V
MC,T〉 is the average MC speed across the full MC, and 〈V
UPSTREAM〉 is a five-hour average of the solar wind speed just upstream of the shock. 相似文献
18.
K. S. Dwarakanath Siddharth Malu Ruta Kale 《Journal of Astrophysics and Astronomy》2011,32(4):529-532
We have discovered a giant radio halo in the massive merging cluster MACSJ0417.5-1154. This cluster, at a redshift of 0.443,
is one of the most X-ray luminous galaxy cluster in the MAssive Cluster Survey (MACS) with an X-ray luminosity in the 0.1–2.4
keV band of 2.9×1045 erg s − 1. Recent observations from GMRT at 230 and 610 MHz have revealed a radio halo of ∼ 1.2 × 0.3 Mpc2 in extent. This halo is elongated along the North-West, similar to the morphology of the X-ray emission from Chandra. The
1400 MHz radio luminosity (L
r) of the halo is ∼2 × 1025 W Hz − 1, in good agreement with the value expected from the L
x − L
r correlation for cluster halos. 相似文献
19.
We studied the characteristics of Coronal Mass Ejections (CMEs) associated with solar flares and Deca-Hectometric (DH) type
II radio bursts, based on source position during 23rd solar cycle (1997–2007). We classified these CME events into three groups
using solar flare locations as, (i) disk events (0–30∘); (ii) intermediate events (31–60∘) and (iii) limb events (61–90∘). Main results from this studies are, (i) the number of CMEs associated with solar flares and DH-type IIs decreases as the
source position approaches from disk to limb, (ii) most of the DH CMEs are halo (72%) in disk events and the number of occurrence
of halo CMEs decreases from disk to limb, (iii) the average width and speed of limb events (164∘ and 1447 km s−1) are higher than those of disk events (134∘ and 1035 km s−1) and intermediate events (146∘ and 1170 km s−1) and (iv) the average accelerations for disk, intermediate and limb events are −8.2 m s−2, −10.3 m s−2 and −4.5 m s−2 respectively. These analysis of CMEs properties show more dependency on longitude and it gives strong evidence for projection
effect. 相似文献
20.
A new orbital period analysis for U Geminorum is made by means of the standard O–C technique based on 187 times of light minima
including the three newest CCD data from our observation. Although there are large scatter near 70,000 cycles in its O–C diagram,
there is strong evidence (>99.9% confidence level) to show the secular increase of orbital period with a rate
s−1. Using the physical parameters recently derived by Echevarría et al. (Astron. J. 134:262, 2007), the range of mass transfer rate for U Geminorum is estimated as from −3.5(5)×10−9 M
⊙ yr−1 to −1.30(6)×10−8 M
⊙ yr−1. Moreover, the data before 60,000 cycles shows the obvious quasi-period variations. The least square estimation of a ∼17.4 yr
quasi-periodic variation superimposed on secular orbital period increase is derived. Considering the possibility that solar-type
magnetic activity cycles in the secondary star of U Geminorum may produce the quasi-period variations of the orbital period,
Applegate’s mechanism is discussed and the results indicate such mechanism has difficulty explaining the quasi-period variation
for U Geminorum. Hence, we attempted to apply the light-travel time effect to interpret the quasi-period variation and found
the perturbation of ∼17.4 yr quasi-period may result from a brown dwarf. If the orbital inclination is assumed as i∼15°, corresponding to the upper limit of mass of a brown dwarf, then its orbital radii is ∼7.7 AU. 相似文献