共查询到20条相似文献,搜索用时 31 毫秒
1.
Werner M. Neupert 《Solar physics》2011,272(2):319-335
The two-band soft X-ray observations of solar flares made by the Naval Research Laboratory’s (NRL) SOLar RADiation (SOLRAD)
satellites and by the Geostationary Orbiting Environmental Satellites (GOES) operated by the National Oceanic and Atmospheric Administration’s (NOAA) Space Weather Prediction Center have produced
a nearly continuous record of solar flare observations over a period of more than forty years (1969 – 2011). However, early
GOES observations (i.e., GOES-2) and later (GOES-8 and subsequent missions) are not directly comparable due to changes in the conversion of measured
currents to integrated fluxes in the two spectral bands that were adopted: 0.05 – 0.3 (or 0.4) nm, which we refer to as XS
and 0.1 – 0.8 nm (XL). Furthermore, additional flux adjustments, using overlapping data sets, were imposed to provide consistency
of flare-flux levels from mission to mission. This article evaluates the results of these changes and compares experimental
GOES-8/GOES-2 results with changes predicted from modeled flare spectra. The factors by which recent GOES observations can
be matched to GOES-2 are then optimized by adapting a technique first used to extrapolate GOES X-ray fluxes above saturation
using ionospheric VLF radio phase enhancements. A nearly 20% increase in published GOES-8 XL data would be required to match
to GOES-2 XL fluxes, which were based on observed flare spectra. On the other hand, a factor of 1.07 would match GOES-8 and
later flat-spectrum 0.1 – 0.8 nm fluxes to GOES-2 XL if the latter data were converted to a flat-spectrum basis. Finally,
GOES-8 observations are compared to solar soft X-ray estimates made concurrently with other techniques. Published GOES-8 0.1 – 0.8 nm
fluxes are found to be 0.59 of the mean of these other determinations. Rescaling GOES to a realistic flare spectrum and removing
a 30% downward adjustment applied to the GOES-8 measurements during initial data processing would place GOES-8 and later GOES
XL fluxes at 0.94 of this XL mean. GOES-2 on the same scale would lie at about 0.70 of this mean. Significant uncertainties
in the absolute levels of broad band soft X-ray fluxes still remain, however. 相似文献
2.
We report very high temporal and spectral resolution interferometric observations of some unusual solar radio bursts near
1420 MHz. These bursts were observed on 13 September 2005, 22 minutes after the peak of a GOES class X flare from the NOAA
region 10808. Our observations show 11 episodes of narrow-band intermittent emission within a span of ≈ 8 s. Each episode
shows a heavily frequency-modulated band of emission with a spectral slope of about −245.5 MHz s−1, comprising up to 8 individual blobs of emission and lasts for 10 – 15 ms. The blobs themselves have a spectral slope of
≈ 0 MHz s−1, are ≈ 200 – 250 kHz wide, appear every ≈ 400 kHz and last for ≈ 4 – 5 ms. These bursts show brightness temperatures in the
range 1012 K, which suggests a coherent emission mechanism. We believe these are the first high temporal and spectral resolution interferometric
observations of such rapid and narrow-bandwidth solar bursts close to 1420 MHz and present an analysis of their temporal and
spectral characteristics. 相似文献
3.
Some 15% of solar flares having a soft X-ray flux above GOES class C5 are reported to lack coherent radio emission in the
100 – 4000 MHz range (type I – V and decimetric emissions). A detailed study of 29 such events reveals that 22 (76%) of them
occurred at a radial distance of more than 800″ from the disk center, indicating that radio waves from the limb may be completely
absorbed in some flares. The remaining seven events have statistically significant trends to be weak in GOES class and to
have a softer non-thermal X-ray spectrum. All of the non-limb flares that were radio-quiet above 100 MHz were accompanied
by metric type III emission below 100 MHz. Out of 201 hard X-ray flares, there was no flare except near the limb (R>800″) without coherent radio emission in the entire meter and decimeter range. We suggest that flares above GOES class C5
generally emit coherent radio waves when observed radially above the source. 相似文献
4.
This contribution is a follow-up to the recent paper of Kuznetsov et al. (Contrib. Astron. Obs. Skalnaté Pleso
36, 85, 2006) on the ground level enhancement (GLE) on 20 January 2005. We focused on a study of Forbush decrease (FD) of 17 – 18 and
21 – 22 January 2005, respectively. The data from the neutron monitor at Lomnicky Štít (1 min counts) and from the Geomagnetic
Observatory in Hurbanovo, both in Slovakia, were used as the basis for our investigation. The data on magnetic field and solar
wind from GOES 10 and 12, SOHO-CELIAS, ACE and WIND satellites were used for better understanding of the global evolution
of the event. The magnetic field is transformed to the RTN (Radial – Tangential – Normal) system where only the disturbed
part of the field is compared, i.e., daily variations and a constant part are subtracted. The field reduction method is described. Our results are temporal vector
diagrams of variation of all parameters at all positions from where we used the data. The amplitudes of |B| exceed 100 nT and variations during the arrival of the wavefront of CME take place simultaneously at the ground-based station
and at GOES satellites. The character of the variations is as if there would be regions with the dominant electric charge
of opposite signs, or electric currents with different orientations in the CME. On the basis of the values v
p and n
p and using certain assumptions we determined the mass of CME on 17 January and 21 January, respectively, of 1012 kg. A decrease of the cosmic ray level runs suddenly (during 10 minutes), starting, however, about two hours after a sudden
change of the magnetic field. 相似文献
5.
Based on the analysis of the microwave observations at the frequency range of 2.60 – 3.80 GHz in the solar X1.3 flare event
observed at the Solar Broadband RadioSpectrometer in Huairou (SBRS/Huairou) on 30 July 2005, an interesting reversed drifting quasi-periodic pulsating structure (R-DPS) is
confirmed. The R-DPS is mainly composed of two drifting pulsating components: one is a relatively slow very short-period pulsation
(VSP) with a period of about 130 – 170 ms, the other is a relatively fast VSP with a period of about 70 – 80 ms. The R-DPS
has a weak left-handed circular polarization. Based on the synthetic investigations of Reuven Ramaty High Energy Solar Spectroscopic Imaging (RHESSI) hard X-ray, Geostationary Operational Environmental Satellite (GOES) soft X-ray observations, and magnetic field extrapolation, we suggest that the R-DPS possibly reflects flaring dynamic
processes of the emission source regions. 相似文献
6.
We have used the daily values of the equatorial rotation rate determined from the Mt. Wilson daily Doppler-velocity measurements
during the period 3 December 1985 – 5 March 2007 to search for periodicities in the solar equatorial rotation rate on time
scales shorter than 11 years. After the daily values have been binned into 61-day intervals, a cosine fit with a period of
one year was applied to the sequence to remove any seasonal trend. The spectral properties of this sequence were then investigated
by using standard Fourier analysis, maximum-entropy methods, and a Morlet-wavelet analysis. From the analysis of the Fourier
power spectrum we detected peaks with periodicities around 7.6, 2.8, and 1.47 years and 245, 182, and 158 days, but none of
them were at a statistically significant level. In the Morlet-wavelet analysis the ≈1.47-year periodicity is detected only
for 1990 (i.e., near the maximum of cycle 22) and near the end of cycle 22 in 1995. From the same wavelet analysis we found some evidence
for the existence of a 2.8-year periodicity and a 245-day periodicity in the equatorial rotation rate around the years 1990
and 1992, respectively. In the data taken during the period 1996 – 2007, when the Mt. Wilson spectrograph instrumentation
was more stable, we were unable to detect any signal from the wavelet analysis. Thus, the detected periodicities during the
period before 1996 could be artifacts of frequent changes in the Mt. Wilson spectrograph instrumentation. However, the temporal
behavior of most of the activity phenomena during cycles 22 (1986 – 1996) and 23 (after 1997) is considerably different. Therefore,
the presence of the aforementioned short-term periodicities during the last cycle and absence of them in the current cycle
may, in principle, be real temporal behavior of the solar rotation during these cycles. 相似文献
7.
Pierre Kaufmann Gérard Trottet C. Guillermo Giménez de Castro Jean-Pierre Raulin Säm Krucker Albert Y. Shih Hugo Levato 《Solar physics》2009,255(1):131-142
The presence of a solar burst spectral component with flux density increasing with frequency in the sub-terahertz range, spectrally
separated from the well-known microwave spectral component, bring new possibilities to explore the flaring physical processes,
both observational and theoretical. The solar event of 6 December 2006, starting at about 18:30 UT, exhibited a particularly
well-defined double spectral structure, with the sub-THz spectral component detected at 212 and 405 GHz by the Solar Submilimeter
Telescope (SST) and microwaves (1 – 18 GHz) observed by the Owens Valley Solar Array (OVSA). Emissions obtained by instruments
onboard satellites are discussed with emphasis to ultra-violet (UV) obtained by the Transition Region And Coronal Explorer
(TRACE), soft X-rays from the Geostationary Operational Environmental Satellites (GOES) and X- and γ-rays from the Ramaty High Energy Solar Spectroscopic Imager (RHESSI). The sub-THz impulsive component had its closer temporal
counterparts only in the higher energy X- and γ-rays ranges. The spatial positions of the centers of emission at 212 GHz for the first flux enhancement were clearly displaced
by more than one arc-minute from positions at the following phases. The observed sub-THz fluxes and burst source plasma parameters
were difficult to be reconciled with a purely thermal emission component. We discuss possible mechanisms to explain the double
spectral components at microwaves and in the THz ranges. 相似文献
8.
As part of a program to estimate the solar spectrum back to the early twentieth century, we have generated fits to UV spectral
irradiance measurements from 1 – 410 nm. The longer wavelength spectra (150 – 410 nm) were fit as a function of two solar
activity proxies, the Mg ii core-to-wing ratio, or Mg ii index, and the total Ca ii K disk activity derived from ground based observations. Irradiance spectra at shorter wavelengths (1 – 150 nm) where used
to generate fits to the Mg ii core-to-wing ratio alone. Two sets of spectra were used in these fitting procedures. The fits at longer wavelengths (150
to 410 nm) were derived from the high-resolution spectra taken by the Solar Ultraviolet Spectral Irradiance Monitor (SUSIM)
on the Upper Atmospheric Research Satellite (UARS). Spectra measured by the Solar EUV Experiment (SEE) instrument on the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) satellite were used for the fits at wavelengths from 1 to 150 nm. To generate fits between solar irradiance and solar
proxies, this study uses the above irradiance data, the NOAA composite Mg ii index, and daily Ca ii K disk activity determined from images measured by Big Bear Solar Observatory (BBSO). In addition to the fitting coefficients
between irradiance and solar proxies, other results from this study include an estimated relationship between the fraction
of the disk with enhanced Ca ii K activity and the Mg ii index, an upper bound of the average solar UV spectral irradiance during periods where the solar disk contains only regions
of the quiet Sun, as was believed to be present during the Maunder Minimum, as well as results indicating that slightly more
than 60% of the total solar irradiance (TSI) variability occurs between 150 and 400 nm. 相似文献
9.
In an effort to examine the relationship between flare flux and corresponding CME mass, we temporally and spatially correlate
all X-ray flares and CMEs in the LASCO and GOES archives from 1996 to 2006. We cross-reference 6733 CMEs having well-measured
masses against 12 050 X-ray flares having position information as determined from their optical counterparts. For a given
flare, we search in time for CMEs which occur 10 – 80 minutes afterward, and we further require the flare and CME to occur
within ± 45° in position angle on the solar disk. There are 826 CME/flare pairs which fit these criteria. Comparing the flare
fluxes with CME masses of these paired events, we find CME mass increases with flare flux, following an approximately log-linear,
broken relationship: in the limit of lower flare fluxes, log (CME mass)∝0.68×log (flare flux), and in the limit of higher
flare fluxes, log (CME mass)∝0.33×log (flare flux). We show that this broken power-law, and in particular the flatter slope
at higher flare fluxes, may be due to an observational bias against CMEs associated with the most energetic flares: halo CMEs.
Correcting for this bias yields a single power-law relationship of the form log (CME mass)∝0.70×log (flare flux). This function
describes the relationship between CME mass and flare flux over at least 3 dex in flare flux, from ≈ 10−7 – 10−4 W m−2. 相似文献
10.
D. B. Jess M. Mathioudakis D. J. Christian F. P. Keenan R. S. I. Ryans P. J. Crockett 《Solar physics》2010,261(2):363-373
The Rapid Oscillations in the Solar Atmosphere (ROSA) instrument is a synchronized, six-camera high-cadence solar imaging
instrument developed by Queen’s University Belfast. The system is available on the Dunn Solar Telescope at the National Solar
Observatory in Sunspot, New Mexico, USA, as a common-user instrument. Consisting of six 1k × 1k Peltier-cooled frame-transfer
CCD cameras with very low noise (0.02 – 15 e s−1 pixel−1), each ROSA camera is capable of full-chip readout speeds in excess of 30 Hz, or 200 Hz when the CCD is windowed. Combining
multiple cameras and fast readout rates, ROSA will accumulate approximately 12 TB of data per 8 hours observing. Following
successful commissioning during August 2008, ROSA will allow for multi-wavelength studies of the solar atmosphere at a high
temporal resolution. 相似文献
11.
V. N. Melnik A. A. Konovalenko H. O. Rucker V. V. Dorovskyy E. P. Abranin A. Lecacheux A. S. Lonskaya 《Solar physics》2010,264(1):103-117
Solar S-bursts observed by the radio telescope UTR-2 in the period 2001 – 2002 are studied. The bursts chosen for a detailed
analysis occurred in the periods 23 – 26 May 2001, 13 – 16 and 27 – 39 July 2002 during three solar radio storms. More than
800 S-bursts were registered in these days. Properties of S-bursts are studied in the frequency band 10 – 30 MHz. All bursts
were always observed against a background of other solar radio activity such as type III and IIIb bursts, type III-like bursts,
drift pairs and spikes. Moreover, S-bursts were observed during days when the active region was situated near the central
meridian. Characteristic durations of S-bursts were about 0.35 and 0.4 – 0.6 s for the May and July storms, respectively.
For the first time, we found that the instantaneous frequency width of S-bursts increased with frequency linearly. The dependence
of drift rates on frequency followed the McConnell dependence derived for higher frequencies. We propose a model of S-bursts
based on the assumption that these bursts are generated due to the confluence of Langmuir waves with fast magnetosonic waves,
whose phase and group velocities are equal. 相似文献
12.
We applied special data-processing algorithms to the study of long-period oscillations of the magnetic-field strength and
the line-of-sight velocity in sunspots. The oscillations were investigated with two independent groups of data. First, we
used an eight-hour-long series of solar spectrograms, obtained with the solar telescope at the Pulkovo Observatory. We simultaneously
measured Doppler shifts of six spectral lines, formed at different heights in the atmosphere. Second, we had a long time series
of full-disk magnetograms (10 – 34 hour) from SOHO/MDI for the line-of-sight magnetic-field component. Both ground- and space-based
observations revealed long-period modes of oscillations (40 – 45, 60 – 80, and 160 – 180 minutes) in the power spectrum of
the sunspots and surrounding magnetic structures. With the SOHO/MDI data, one can study the longer periodicities. We obtained
two new significant periods (> 3σ) in the power spectra of sunspots: around 250 and 480 minutes. The power of the oscillations in the lower frequencies is
always higher than in the higher ones. The amplitude of the long-period magnetic-field modes shows magnitudes of about 200 – 250 G.
The amplitude of the line-of-sight velocity periodicities is about 60 – 110 m s−1. The absence of low-frequency oscillations in the telluric line proves their solar nature. Moreover, the absence of low-frequency
oscillations of the line-of-sight velocity in the quiet photosphere (free of magnetic elements) proves their direct connection
to magnetic structures. Long-period modes of oscillation observed in magnetic elements surrounding the sunspot are spread
over the meso-granulation scales (10″ – 12″), while the sunspot itself oscillates as a whole. The amplitude of the long-period
mode of the line-of-sight velocity in a sunspot decreases rapidly with height: these oscillations are clearly visible in the
spectral lines originating at heights of approximately 200 km and fade away in lines originating at 500 km. We found a new
interesting property: the low-frequency oscillations of a sunspot are strongly reduced when there is a steady temporal trend
(strengthening or weakening) of the sunspot’s magnetic field. Another important result is that the frequency of long-period
oscillations evidently depends on the sunspot’s magnetic-field strength. 相似文献
13.
The evolution of the 27-day recurrence in the series of two solar indices (Wolf number WN and 10.7 cm radio flux F) and two geomagnetic indices (Dst and ζ, variance of the geomagnetic field recorded at a magnetic observatory) have been studied over the 1957 – 2007 time
span. Spectral energies contained in two period domains (25 – 27.3 and 27.3 – 31 days), designated as E
1 and E
2, have been computed. Whereas the evolution of E
1 is the same for the four indices, that of E
2 is essentially different for WN and F on the one hand, Dst and ζ on the other hand. Some general conclusions on the dynamics of the solar outer layers are inferred from these results.
First the solar activity, as measured by WN, and when averaged over a few years, evolves in the same way whatever the latitude.
Second, two families of coronal holes (CHs) are identified; the rapidly and the slowly rotating CHs evolve quite differently. 相似文献
14.
The frequency dependence of the quasi-quantized energy release is reported for the first time in 14 bursts with pulsations
of seconds at 1.0, 2.0, 3.75, 9.4, 17, and 35 GHz, observed by the Nobeyama Radio Polarimeters (NoRP). There is a linear correlation
between the repetition rate of pulsations and the radio flux during the burst, the so-called R – S relation, at each burst frequency. The slope in the linear fitting, which is equivalent to the energy release in an individual
pulse, becomes maximum at a particular frequency around 10 GHz, which can be explained by electrons accelerated in solar flares
with maximum energy density around this frequency or coronal height. 相似文献
15.
T. Shimizu S. Nagata S. Tsuneta T. Tarbell C. Edwards R. Shine C. Hoffmann E. Thomas S. Sour R. Rehse O. Ito Y. Kashiwagi M. Tabata K. Kodeki M. Nagase K. Matsuzaki K. Kobayashi K. Ichimoto Y. Suematsu 《Solar physics》2008,249(2):221-232
The Hinode Solar Optical Telescope (SOT) is the first space-borne visible-light telescope that enables us to observe magnetic-field
dynamics in the solar lower atmosphere with 0.2 – 0.3 arcsec spatial resolution under extremely stable (seeing-free) conditions.
To achieve precise measurements of the polarization with diffraction-limited images, stable pointing of the telescope (<0.09 arcsec,
3σ) is required for solar images exposed on the focal plane CCD detectors. SOT has an image stabilization system that uses image
displacements calculated from correlation tracking of solar granules to control a piezo-driven tip-tilt mirror. The system
minimizes the motions of images for frequencies lower than 14 Hz while the satellite and telescope structural design damps
microvibration in higher frequency ranges. It has been confirmed from the data taken on orbit that the remaining jitter is
less than 0.03 arcsec (3σ) on the Sun. This excellent performance makes a major contribution to successful precise polarimetric measurements with 0.2 – 0.3 arcsec
resolution.
K. Kobayashi now at NASA/Marshall Space Flight Center, Huntsville, AL 35812, USA. 相似文献
16.
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
17.
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
18.
Navin Chandra Joshi Neeraj Singh Bankoti Seema Pande Bimal Pande Kavita Pandey 《Solar physics》2009,260(2):451-463
In this article we present the results of a study of the spatial distribution and asymmetry of solar active prominences (SAP)
for the period 1996 through 2007 (solar cycle 23). For more meaningful statistical analysis we analyzed the distribution and
asymmetry of SAP in two subdivisions viz. Group1 (ADF, APR, DSF, CRN, CAP) and Group2 (AFS, ASR, BSD, BSL, DSD, SPY, LPS). The North – South (N – S) latitudinal distribution
shows that the SAP events are most prolific in the 21° to 30° slice in the Northern and Southern Hemispheres; the East – West
(E – W) longitudinal distribution study shows that the SAP events are most prolific (best observable) in the 81° to 90° slice
in the Eastern and Western Hemispheres. It was found that the SAP activity during this cycle is low compared to previous solar
cycles. The present study indicates that during the rising phase of the cycle the number of SAP events are roughly equal in
the Northern and Southern Hemispheres. However, activity in the Southern Hemisphere has been dominant since 1999. Our statistical
study shows that the N – S asymmetry is more significant then the E – W asymmetry. 相似文献
19.
Forecasting space weather more accurately from solar observations requires an understanding of the variations in physical
properties of interplanetary (IP) shocks as solar activity changes. We examined the characteristics (occurrence rate, physical
parameters, and types of shock driver) of IP shocks. During the period of 1995 – 2001, a total of 249 forward IP shocks were
observed. In calculating the shock parameters, we used the solar wind data from Wind at the solar minimum period (1995 – 1997) and from ACE since 1998 including the solar maximum period (1999 – 2001). Most
of IP shocks (68%) are concentrated in the solar maximum period. The values of physical quantities of IP shocks, such as the
shock speed, the sonic Mach number, and the ratio of plasma density compression, are larger at solar maximum than at solar
minimum. However, the ratio of IMF compression is larger at solar minimum. The IP shock drivers are classified into four groups:
magnetic clouds (MCs), ejecta, high speed streams (HSSs), and unidentified drivers. The MC is the most dominant and strong
shock driver and 150 out of total 249 IP shocks are driven by MCs. The MC is a principal and very effective shock driver not
only at solar maximum but also at solar minimum, in contrast to results from previous studies, where the HSS is considered
as the dominant IP shock driver. 相似文献
20.
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