共查询到20条相似文献，搜索用时 31 毫秒
1.
V. K. Verma 《Astrophysics and Space Science》2011,334(1):83-102
We present study of relationship of GSXR flares with Hα flares, hard X-ray (HXR) bursts, microwave (MW) bursts at 15.4 GHz, type II/IV radio bursts, coronal mass ejections (CMEs),
protons flares (>10 MeV) and ground level enhancement (GLE) events we find that about 85.7%, 93%, 97%, 69%, 60%, 11.1%, 79%,
46%, and 23%% GSXR flares are related/associated with observed Hα flares, HXR bursts, MW bursts at 15.4 GHz, type II radio bursts, type IV radio bursts, GLE events, CMEs, halo CMEs, and proton
flares (>10 MeV), respectively. In the paper we have studied the onset time delay of GSXR flares with Hα flares, HXR, and MW bursts which shows the during majority GSXR flares SXR emissions start before the Hα, HXR and MW emissions, respectively while during 15–20% of GSXR flares the SXR emissions start after the onset of Hα, HXT and MW emissions, respectively indicating two types of solar flares. The, onset time interval between SXR emissions
and type II radio bursts, type IV radio bursts, GLE events CMEs, halo CMEs, and protons flares are 1–15 min, 1–20 min, 21–30 min,
21–40 min, 21–40 min, and 1–4 hrs, respectively. Following the majority results we are of the view that the present investigations
support solar flares models which suggest flare triggering first in the corona and then move to chromospheres/ photosphere
to starts emissions in other wavelengths. The result of the present work is largely consistent with “big flare syndrome” proposed
by Kahler (1982). 相似文献
2.
“Elementary bursts” refer to fine time structures on scales of tens of milli-second to a few seconds in flare radiations.
In this paper, we investigate temporal and spatial properties of elementary bursts by exploiting high-cadence Hα (100 ms)
and hard X-ray (125 – 500 ms) observations of an impulsive flare on March 16, 2000. We find that the time scale of 2 – 3 s
is likely an upper limit of the elementary bursts in this event, at which hard X-ray emissions observed by different instruments
correlate, low energy (≤30 keV) hard X-rays and Hα flux correlate, and Hα emissions at conjugate flare kernels correlate.
From our methods, and also largely limited by instrument resolutions, there is a weak indication of existence of sub-second
structures. With the high-resolution Hα data, we also attempt to explore the spatial structure of “elementary bursts” by determining
the average spatial displacement of Hα peak emission between successive “elementary bursts” defined from hard X-ray light
curves. We find that, at the time scale of 3 s, the smallest spatial scale, as limited by the imaging resolution, is about
0.4″. We discuss these results with respect to mechanisms of fragmented magnetic energy release. 相似文献
3.
G.S. Suryanarayana 《New Astronomy》2012,17(2):117-129
We study solar radio type II bursts combining with Wind/WAVES type II bursts and coronal mass ejections (CMEs). The aim of the present work is to investigate the effectiveness of shocks to cause type II bursts in the solar corona and the interplanetary space. We consider the following findings. The distribution of the cessation heights of type II emission is confined to a rather narrow range of height than the distribution of the heights of start frequencies. This is suggestive of the presence of a gradient for the Alfvén speed from the heliocentric height of ∼1.4 solar radii. The range of the kinetic energy of CMEs associated with coronal type II emission taken together with the suggested computation method and the Alfvén speed gradient, indicates the limit to the height up to which type II emission could be expected. This height is ∼2 solar radii from the center of the Sun. Further, the large time gap between the cessation time and heights of coronal type II emission and the commencement time and heights of most of the IP type II bursts do not account for the difference between the two heights and the average shock speed. Also, there is clear difference in the magnitude of the kinetic energies and the distinct characteristics of the CMEs associated with coronal and IP type II bursts. Hence, we suggest that in most instances the coronal type II bursts and IP type II bursts occur due to distinct shocks. We also address the question of the origin of type II bursts and discuss the possible explanation of observed results. 相似文献
4.
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
5.
V. N. Melnik A. A. Konovalenko V. V. Dorovskyy H. O. Rucker E. P. Abranin V. N. Lisachenko A. Lecacheux 《Solar physics》2005,231(1-2):143-155
The results of observations of solar decametric drift pair bursts are presented. These observations were carried out during
a Type III burst storm on July 11–21, 2002, with the decameter radio telescope UTR-2, equipped with new back-end facilities.
High time and frequency resolution of the back-end allowed us to obtain new information about the structure and properties
of these bursts. The statistical analysis of more than 700 bursts observed on 13–15 July was performed separately for “forward”
and “reverse” drift pair bursts. Such an extensive amount of these kind of bursts has never been processed before. It should
be pointed out that “forward” and “reverse” drift pair bursts have a set of similar parameters, such as time delay between
the burst elements, duration of an element, and instant bandwidth of an element. Nevertheless some of their parameters are
different. So, the absolute average value of frequency drift rate for “forward” bursts is 0.8 MHz s−1, while for “reverse” ones it is 2 MHz s−1. The obtained functional dependencies “drift rate vs. frequency” and “flux density vs. frequency” were found to be different
from the current knowledge. We also report about the observation of unusual variants of drift pairs, in particular, of “hook”
bursts and bursts with fine time and frequency structure. A possible mechanism of drift pairs generation is proposed, according
to which this emission may originate from the interaction of Langmuir waves with the magnetosonic waves having equal phase
and group velocities. 相似文献
6.
We present a statistical analysis of the relationship between the kinematics of the leading edge and the eruptive prominence
in coronal mass ejections (CMEs). We study the acceleration phase of 18 CMEs in which kinematics was measured from the pre-eruption
stage up to the post-acceleration phase. In all CMEs, the three part structure (the leading edge, the cavity, and the prominence)
was clearly recognizable from early stages of the eruption. The data show a distinct correlation between the duration of the
leading edge (LE) acceleration and eruptive prominence (EP) acceleration. In the majority of events (78%) the acceleration
phase onset of the LE is very closely synchronized (within ± 20 min) with the acceleration of EP. However, in two events the
LE acceleration started significantly earlier than the EP acceleration (> 50 min), and in two events the EP acceleration started
earlier than the LE acceleration (> 40 min). The average peak acceleration of LEs (281 m s−2) is about two times larger than the average peak acceleration of EPs (136 m s−2). For the first time, our results quantitatively demonstrate the level of synchronization of the acceleration phase of LE
and EP in a rather large sample of events, i.e., we quantify how often the eruption develops in a “self-similar” manner. 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.
D. Horns F. Aharonian A. I. D. Hoffmann A. Santangelo 《Astrophysics and Space Science》2007,309(1-4):189-195
Observations of the inner radian of the Galactic disk at very high energy (VHE) gamma-rays have revealed at least 16 new sources.
Besides shell type super-nova remnants, pulsar wind nebulae (PWN) appear to be a dominant source population in the catalogue
of VHE gamma-ray sources. Except for the Crab nebula, the newly discovered PWN are resolved at VHE gamma-rays to be spatially
extended (5–20 pc). Currently, at least 3 middle aged (t>10 kyrs) PWN (Vela X, G18.0-0.7, and G313.3+0.6 in the “Kookaburra” region) and 1 young PWN MSH 15-52 (t=1.55 kyrs) have been identified to be VHE emitting PWN (sometimes called “TeV Plerions”). Two more candidate “TeV Plerions”
have been identified and have been reported at this conference (Carrigan, These proceedings, in preparation). In this contribution,
the gamma-ray emission from Vela X is explained by a nucleonic component in the pulsar wind. The measured broad band spectral
energy distribution is compared with the expected X-ray emission from primary and secondary electrons. The observed X-ray
emission and TeV emission from the three middle aged PWN are compared with each other. 相似文献
9.
During solar cycle 23, 82 interplanetary magnetic clouds (MCs) were identified by the Magnetic Field Investigation (MFI) team
using Wind (1995 – 2003) solar wind plasma and magnetic field data from solar minimum through the maximum of cycle 23. The average occurrence
rate is 9.5 MCs per year for the overall period. It is found that some of the anomalies in the frequency of occurrence were
during the early part of solar cycle 23: (i) only four MCs were observed in 1999, and (ii) an unusually large number of MCs
(17 events) were observed in 1997, just after solar minimum. We also discuss the relationship between MCs, coronal mass ejections
(CMEs), and geomagnetic storms. During the period 1996 – 2003, almost 8000 CMEs were observed by SOHO-LASCO. The occurrence
frequency of MCs appears to be related neither to the occurrence of CMEs as observed by SOHO LASCO nor to the sunspot number.
When we included “magnetic cloud-like structures” (MCLs, defined by Lepping, Wu, and Berdichevsky, 2005), we found that the
occurrence of the joint set (MCs + MCLs) is correlated with both sunspot number and the occurrence rate of CMEs. The average
duration of the MCL structures is ~40% shorter than that of the MCs. The MCs are typically more geoeffective than the MCLs,
because the average southward field component is generally stronger and longer lasting in MCs than in MCLs. In addition, most
severe storms caused by MCs/MCLs with Dst
min≤ −100 nT occurred in the active solar period. 相似文献
10.
We study the internal structure of coronal mass ejections (CMEs) using wavelet analysis. We derive wavelet spectra, spatially
integrated over regions of interest within LASCO C2 white-light coronographic images. These spectra show an inflection point,
which we use to characterize each spectrum. In a diagram of flux vs. spatial scale of the inflection point, we find that the analyzed structures fall into two, distinct groups: a low-flux,
small-spatial-scale group (which we call the “homogeneous” type), and a high-flux, larger-spatial-scale group (the “collimated”
type). Interestingly, if we study different regions of a given image, all of the structures fall into one of the two groups
described above. From a qualitative comparison with the images, it is clear that the two groups identified by the wavelet
analysis correspond to two types of morphologies, which are seen as either more-homogeneous or more-collimated structures. 相似文献
11.
“EIT waves” are a wavelike phenomenon propagating in the corona, which was initially observed in the extreme ultraviolet (EUV)
wavelength by the EUV Imaging Telescope (EIT). Their nature is still elusive, with the debate on-going between fast-mode wave
model and non-wave model. In order to distinguish between these models, we investigate the relation between the EIT wave velocity
and the local magnetic field in the corona. It is found that the two parameters show significant negative correlation in most
of the EIT wave fronts, i.e., the EIT wave propagates more slowly in the regions of stronger magnetic field. Such a result poses a big challenge to the
fast-mode wave model, which would predict a strong positive correlation between the two parameters. However, it is demonstrated
that such a result can be explained by the fieldline stretching model, i.e., that “EIT waves” are the propagation of apparent brightenings, which are generated by successive stretching of closed magnetic
field lines pushed by the erupting flux rope during coronal mass ejections (CMEs). 相似文献
12.
E. H. Nikogossian 《Astrophysics》2000,43(1):32-39
The hierarchical structure of the clusters of galaxies A 999, A 1016, and A 1142, which are part of one supercluster, is investigated.
The HTree method is used to determine that A 999 and A 1016 are a single, dynamically bound system consisting of two “cores”
and a common field of galaxies. The composition of the “cores” includes almost all the E and S0 galaxies, the luminosity function
of which is very nearly Gaussian. It is also established that the cluster A 1142 has a nonuniform structure, both in density
distribution and in radial velocity distribution. The location of the maxima in density and in the radial velocity distribution
correlates with the galaxies that are sources of radio and x-ray emission.
Translated from Astrofizika, Vol. 43, No. 1, pp. 45-54, January–March, 2000. 相似文献
13.
The Solar Electron Proton Telescope on board the twin STEREO spacecraft measures electrons and ions in the energy range from
30 to above 400 keV with an energy resolution better than 10%. On 22 February 2010 during a short interval of 100 minutes,
a sequence of impulsive energetic electron events in the range below 120 keV was observed with the STEREO-A/SEPT instrument.
Each of the four events was associated with a type III radio burst and a narrow EUV jet. All the events show nearly symmetric
“spike”-like time profiles with very short durations ≃ 5 min. The estimated electron injection time for each individual event
shows a small time delay between the electron spike and the corresponding type III radio emission and a close coincidence
with an EUV jet. These observations reveal the existence of spike-like electron events showing nearly “scatter-free” propagation
from the Sun to STEREO-A. From the time coincidence we infer that the mildly relativistic electrons are accelerated at the
same time and at the same location as the accompanying type III emitting electrons and coronal EUV jets. The characteristics
of the spikes reflect the injection and acceleration profiles in the corona rather than interplanetary propagation effects. 相似文献
14.
The Transition Region and Coronal Explorer (TRACE) instrument includes a “white light” imaging capability with novel characteristics.
Many flares with such white-light emission have been detected, and this paper provides an introductory overview of these data.
These observations have 0.5″ pixel size and use the full broad-band response of the CCD sensor; the images are not compromised
by ground-based seeing and have excellent pointing stability as well as high time resolution. The spectral response of the
TRACE white-light passband extends into the UV, so these data capture, for the first time in images, the main radiative energy
of a flare. This initial survey is based on a sample of flares observed at high time resolution for which the Reuven Ramaty
High-Energy Solar Spectroscopic Imager (RHESSI) had complete data coverage, a total of 11 events up to the end of 2004. We
characterize these events in terms of source morphology and contrast against the photosphere. We confirm the strong association
of the TRACE white-light emissions - which include UV as well as visual wavelengths – with hard X-ray sources observed by
RHESSI. The images show fine structure at the TRACE resolution limit, and often show this fine structure to be extended over
large areas rather than just in simple footpoint sources. The white-light emission shows strong intermittency both in space
and in time and commonly contains features unresolved at the TRACE resolution. We detect white-light continuum emission in
flares as weak as GOES C1.6. limited by photon statistics and background solar fluctuations, and support the conclusion of
Neidig (1989) that white-light continuum occurs in essentially all flares. 相似文献
15.
We study a time – latitudinal distribution of CMEs observed by the SOHO spacecraft, their projected speeds and associated
magnetic fields, as well as the north – south (N – S) asymmetry of solar surface magnetic fields, and the coronal green line
intensities. We have found that (a) there exists an intricate relation between the average projected velocity of CMEs and
the mean value of large-scale magnetic fields; (b) there exists a pronounced N – S asymmetry in both the distribution and
the number of CMEs; (c) this asymmetry is in favor of the northern hemisphere at the beginning of the cycle, and of the southern
hemisphere from 2001 onward, being, in fact, (d) closely related with the N – S asymmetry in the distribution of large-scale
magnetic fields and the coronal green line intensities. 相似文献
16.
Chin-Teh Yeh 《中国天文和天体物理学报》2005,5(2):193-197
Inspired by the finding that the large waiting time of solar flares presents a power-law distribution, we investigate the waiting time distribution (WTD) of coronal mass ejections (CMEs). SOHO/LASCO CME observations from 1996 to 2003 are used in this study. It is shown that the observed CMEs have a similar power-law behavior to the flares, with an almost identical power-law index. This strongly supports the viewpoint that solar flares and CMEs are different manifestations of the same physical process. We have also investigated separately the WTDs of fast-type and slow-type CMEs and found that their indices are identical, which imply that both types of CME may originate from the same physical mechanism. 相似文献
17.
Studies of the onset of Earth-directed coronal mass ejections (CMEs) rely on solar disk observations where CME structures
are difficult to disentangle because of the diversity and transient character of the phenomena involved. Dimmings and coronal
waves are among the best evidence of the large-scale reorganization of coronal magnetic fields associated with the onset of
CMEs. The physical mechanism behind EIT waves is still unclear: they are considered as MHD waves and/or as a consequence of
plasma compression on the extending border of a dimming. In this paper, we address the problem of automatically detecting
and analyzing EIT waves and dimmings in EUV images. This paper presents a “proof of principle” that automated detection of
EIT wave and dimmings is indeed possible. At the current stage of work, the method can unambiguously detect dimmings and EIT
waves when applied on a typical test-case event. Moreover, we propose a way to extract these events from the data, and determine
such parameters as life time, depth, area and volume of dimmings for future catalogs. For EIT waves we unambiguously define,
in near solar minimum conditions, the eruption center, the front of EIT wave and its propagation velocity. In addition, we
show that the presented methods yield new insights about the geometrical shape of dimmings and the connection with the EIT
wave front properties, and the apparent angular rotation of the EIT wave under study. 相似文献
18.
P. A. Tarakanov 《Astrophysics》2000,43(2):170-175
A possible mechanism of formation of interstellar clouds in the Galaxy by aggregation from gas “cloudlets” ejected by red
giants is considered. A numerical model of the motion of a “cloudlet” in the interstellar medium of the Galaxy is constructed.
The resulting clouds are fractal with a fractal dimensionality that coincides with the observed one. The characteristic time
of formation of a cloud agrees with observations.
Translated from Astrofizika, Vol. 43, No. 2, pp. 229–237, April–June, 2000. 相似文献
19.
A. E. Rosenbush 《Astrophysics》1999,42(2):140-148
The separation of novae into groups, proposed in Part 1 of this paper, is discussed: it is based on the criterion of the shape
of the light curve, plotted on “outburst amplitude-logarithm of shell radius ” scales. The observational characteristics of
novae belonging to certain groups are considered. Novae of the GQ Mus group may be characterized by x ray emission. The proposed
separation of novae into groups may be related to the structure of the shell ejected in the outburst. Novae with smooth light
curves have ellipsoidal shells without pronounced nonuniformities. Novae with temporary fading or with brightness fluctuations
in the transitional stage of the outburst have ellipsoidal shells with a nonuniform distribution of matter (equatorial and
tropical belts in novae of the DQ Her group, an equatorial belt for the RR Pic group, and a patchy structure for the CP Pup
group). Relationships among certain parameters of novae are considered: absolute stellar magnitude, outburst amplitude, shell
expansion velocity, etc. From the “depth of temporary fading in the transitional stage of the outburst-shell expansion velocity”
dependence it can be concluded that the kinetic energy of the shell may be a constant for novae of the DQ Her group.
Translated from Astrofizika, Vol. 42, No. 2, pp. 189–202, April–June, 1999. 相似文献
20.
The superconducting proton condensate in the “npe” phase of a neutron star is considered. It is shown to be a type II superconductor
in the outer layer of the “npe” phase and a type I superconductor in the inner layer. Relaxation times are found for elastic
scattering of normal relativistic electrons from the magnetic fields of proton vortex clusters in the case of a type II superconductor
and elastic scattering from the magnetic field at the center of a neutron vortex in the case of a superconductor of the first
kind. The dynamical relaxation times obtained for the angular velocity of the pulsar PSR 0833—45 vary, as a function of the
density of the layers taking part in the relaxation process, within a fairly wide range: from several hours to l09 years. This means that the characteristic times of variation of pulsar angular velocity may be observed to lie in the indicated
time range.
Translated from Astrofizika, Vol. 40, No. 4, op. 497–506, October–December, 1997. 相似文献