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1.
The flare plasma temperature calculated from GOES-11 (1.5–12.4 and 3.1–24.8 keV) data is compared with the solar nonthermal
fluxes in various energy ranges in the December 6, 2006 event. Particle acceleration and plasma heating episodes took place
in the pre-flare and impulsive phases; a hard (ACS SPI > 150 keV) X-ray emission was observed 5 min before the onset of the GOES X-ray flare and was not accompanied by a temperature
rise. A close correlation has been found between the flare plasma temperature and the hard X-ray intensity. The temperature
delayed by 0.4 min turned out to be directly proportional to the logarithm of the ACS SPI count rate within the first 3 min
of the impulsive phase. This shows that the accelerated electrons responsible for the X-ray emission were the main plasma
heating source in the pre-flare and impulsive phases. The correlation between the temperature and the hard X-ray intensity
disappears after the observation of a resonance peak at a frequency of 245 MHz. Significant electron fluxes may no longer
be able to effectively heat the expanding plasma when its density in the interaction region reaches ∼109 cm−3. The observations of the July 23, 2002 and December 5, 2006 events confirm the trends found. 相似文献
2.
Marta M. Cassiano Pierre Kaufmann Rogério Marcon Amauri S. Kudaka Adolfo Marun Rodolfo Godoy Pablo Pereyra Arline M. Melo Hugo Levato 《Solar physics》2010,264(1):71-79
Solar observations in the mid-infrared 8 – 14 μm band continuum were carried out with cadence of 5 frames per second, in December 2007.
Rapid small heated sources, with a typical duration of the order of seconds, were found on the bright plage-like areas around
sunspots, in association with relatively weak GOES soft X-ray bursts. This work presents the analysis of fast mid-infrared
flashes detected during a GOES B2.0-class event on 10 December 2007, beginning at about 10:40 UT. Rapid brightness temperature
enhancements of 0.5 to 2.0 K were detected at the Earth by a microbolometer array, using a telescope with 10.5 cm diameter
aperture producing a diffraction-limited photometric beam of 25 arc sec. The minimum detectable temperature change was of
0.1 K. The corresponding fluxes are 30 – 130 solar flux units. At the solar surface the estimated rapid brightenings represented
a temperature enhancement of 50 – 150 K. 相似文献
3.
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
4.
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
5.
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
6.
Ulysses was launched in October 1990, and its Solar X-ray/Cosmic Gamma-Ray Burst Experiment (GRB) has provided more than 13 years
of uninterrupted observations of solar X-ray flare activity. Due to the large variation of the relative solar latitude and
longitude of the spacecraft orbit with respect to the Earth, the perspective of the GRB instrument often differed significantly
from that of X-ray instruments on Earth-orbiting satellites. During extended periods the GRB experiment made direct observations
of flares on the hidden face of the Sun, providing a unique record of events not visible to other instruments. The small detector
area of GRB and its optimization for very high counting rates minimized the effects of pulse pile-up. We interpret the spectra,
time histories, and occurrence distribution patterns of GRB data in terms of “thermal feed-through”, the confusion of thermal
soft X-rays and non-thermal hard X-rays. This effect is a systematic problem for scintillation-counter spectrometers observing
the solar hard X-ray spectrum. This paper provides a definitive catalog of the Ulysses X-ray flare observations and discusses various features of this unique database. For the equivalent GOES range X2 – X25,
we find a power-law fit for the (differential) occurrence frequency at >25 keV with slope −1.61±0.04, with no evidence for
a downturn at the highest event magnitudes (for the relatively small sample of such events available in this study). If the
nine most intense events are excluded because of concerns about the effects of pulse pile-up, the slope steepens to −1.75±0.08. 相似文献
7.
8.
The solar soft X-ray (XUV) radiation is important for upper atmosphere studies as it is one of the primary energy inputs and
is highly variable. The XUV Photometer System (XPS) aboard the Solar Radiation and Climate Experiment (SORCE) has been measuring
the solar XUV irradiance since March 2003 with a time cadence of 10 s and with about 70% duty cycle. The XPS measurements
are between 0.1 and 34 nm and additionally the bright hydrogen emission at 121.6 nm. The XUV radiation varies by a factor
of ∼2 with a period of ∼27 days that is due to the modulation of the active regions on the rotating Sun. The SORCE mission
has observed over 20 solar rotations during the declining phase of solar cycle 23. The solar XUV irradiance also varies by
more than a factor of 10 during the large X-class flares observed during the May–June 2003, October–November 2003, and July
2004 solar storm periods. There were 7 large X-class flares during the May–June 2003 storm period, 11 X-class flares during
the October–November 2003 storm period, and 6 X-class flares during the July 2004 storm period. The X28 flare on 4 November
2003 is the largest flare since GOES began its solar X-ray measurements in 1976. The XUV variations during the X-class flares
are as large as the expected solar cycle variations. 相似文献
9.
The Naval Research Laboratory flew solar X-ray ionization chamber detectors on a series of Solar Radiation (SOLRAD) satellites from 1960 through 1979. The flare responses of the SOLRAD 11 detectors are compared with those of the similar NOAA SMS/GOES detectors during two periods of common observations. The nominal GOES fluxes exceed those of SOLRAD 11 by a factor of 1.5–2 in the 0.5–4 Å band, but fall below those of SOLRAD by a factor of 2–4 in the 1–8 Å band. Significant passband differences account for these relationships between the detector responses. Since the X-ray detectors are standardized among the various SOLRAD satellites, and all detectors are closely matched among the various SMS/GOES satellites, these conversion factors allow the SOLRAD flare observations to serve as proxies for GOES X-ray observations prior to the GOES era. We summarize the detector characteristics and data sources of the 0.5–3 Å and 1–8 Å detectors for the SOLRAD series. 相似文献
10.
We analyze the high-frequency drift radio structures observed by the spectrometer at Purple Mountain Observatory (PMO) over
the frequency range of 4.5 – 7.5 GHz during the 18 March 2003 solar flare. The drifting structures take place before the soft
X-ray maximum, almost at the maximum of hard X-ray flux at 25 – 50 keV. For the first time, the positive drift in this kind
of radio structures is detected in such a high frequency range. Their global drifting rate is roughly estimated as 3.6 GHz s−1. They appear in four groups, lasting in total for less than 6 s, and have a broad bandwidth of more than 2 GHz but a smaller
ratio of the bandwidth of the drifting structures to mean frequency than that of the lower frequency range. The lifetime of
each individual burst in this event can be derived by using the high temporal resolution of the spectrometer at PMO and has
an average value of 36.3 ms. Since the negative drifting structures observed in the 0.6 – 4.5 GHz frequency range were interpreted
to be a radio signature of a plasmoid ejected upward (moving out of the Sun), the present observation may imply that it is
possible for a plasmoid to move downward during a solar flare. However, for a confirmation of this suggestion direct radio
imaging observation would be needed. 相似文献
11.
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
12.
The fluxes of extreme ultraviolet (EUV) and soft X-ray emission are key parameters for modelling the ionosphere and upper atmosphere. A new aspect is considered in using these fluxes for diagnostics and short-term prediction of proton radiation danger from the flare. The EUV (λ < 105 nm) and soft X-ray (0.1–0.8 nm) fluxes were compared for two types of solar flares. The first type is followed by a strong enhancement in solar energetic (E >10 MeV) proton flux, the second is not followed by any enhancement in proton flux. It was discovered that the flare UV flux was considerably higher for flares with protons than for those without protons. Soft X-ray fluxes were approximately equal in both cases. An excess of EUV emission in proton flares grows with increasing proton flux. An analytic expression was found for the growth in proton flux as a function of the excess of EUV radiation at a given X-ray flux. These results can be used in predicting flare radiation danger. 相似文献
13.
14.
Zongjun Ning 《Solar physics》2008,248(1):99-111
Previous observations show that in many solar flares there is a causal correlation between the hard X-ray flux and the derivative
of the soft X-ray flux. This so-called Neupert effect is indicative of a strong link between the primary energy release to
accelerate particles and plasma heating. It suggests a flare model in which the hard X-rays are electron – ion bremsstrahlung
produced by energetic electrons as they lose their energy in the lower corona and chromosphere and the soft X-rays are thermal
bremsstrahlung from the “chromospheric evaporation” plasma heated by those same electrons. Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) observes in a broad energy band and its high spectral resolution and coverage of the low-energy range allow us to
separate the thermal continuum from the nonthermal component, which gives us an opportunity to investigate the Neupert effect.
In this paper, we use the parameters derived from RHESSI observations to trace the primary energy release and the plasma response:
The hard X-ray flux or spectral hardness is compared with the derivative of plasma thermal energy in three impulsive flares
on 10 November 2002 and on 3 and 25 August 2005. High correlations show that the Neupert effect does hold for the two hard
X-ray peaks of the 10 November 2002 flare, for the first peaks of the 3 August 2005 flare, and for the beginning period of
the 25 August 2005 flare. 相似文献
15.
A database combining information about solar proton enhancements (SPEs) near the Earth and soft X-ray flares (GOES measurements)
has been used for the study of different correlations through the period from 1975 to May 2006. The emphasis of this work
is on the treatment of peak-size distributions of SXR flares and SPEs. The frequency of SXR flares and solar proton events
(>10 and >100 MeV, respectively) for the past three solar cycles has been found to follow mainly a power-law distribution
over three to five orders of magnitude of fluxes, which is physically correct beyond the “sensitivity” problem with the smallest
peak values. The absence of significant spectral steepening in the domain of the highest peak values demonstrates that during
the period considered, lasting 30 years, the limit of the highest flare’s energy release has not yet been achieved. The power-law
exponents were found to be −2.19±0.04, −1.34±0.02, and −1.46±0.04, for the total SXR flare distribution and the total SPE
distributions (for both E
P>10 MeV and E
P>100 MeV), respectively. For SPEs associated with flares located to the West of 20° W, the exponents are −1.22±0.05 (E
P>10 MeV) and −1.26±0.03 (E
P>100 MeV). The size distribution for corresponding flares follows a power law with a slope of −1.29±0.12. Thus, X-ray and
proton fluxes produced in the same solar events have very similar distribution shapes. Moreover, the derived slopes are not
incompatible with a linear dependence between X-ray flare power and proton fluxes near the Earth. A similar statistical relation
is obtained independently from the direct comparison of the X-ray and proton fluxes. These all argue for a statistically significant
relationship between X-ray and proton emissions. 相似文献
16.
Rates of flaring in individual active regions on the Sun during the period 1981–1999 are examined using United States Air Force/Mount Wilson (USAF/MWL) active-region observations together with the Geostationary Operational Environmental Satellite (GOES) soft X-ray flare catalog. Of the flares in the catalog above C1 class, 61.5% are identified with an active region. Evidence is presented for obscuration, i.e. that the increase in soft X-ray flux during a large flare decreases the likelihood of detection of soft X-ray events immediately following the large flare. This effect means that many events are missing from the GOES catalog. It is estimated that in the absence of obscuration the number of flares above C1 class would be higher by (75±23)%. A second observational selection effect – an increased tendency for larger flares to be identified with an active region – is also identified. The distributions of numbers of flares produced by individual active regions and of mean flaring rate among active regions are shown to be approximately exponential, although there are excess numbers of active regions with low flare numbers and low flaring rates. A Bayesian procedure is used to analyze the time history of the flaring rate in the individual active regions. A substantial number of active regions appear to exhibit variation in flaring rate during their transit of the solar disk. Examples are shown of regions with and without rate variation, illustrating the different distributions of times between events (waiting-time distributions) that are observed. A piecewise constant Poisson process is found to provide a good model for the observed waiting-time distributions. Finally, applications of analysis of the rate of flaring to understanding the flare mechanism and to flare prediction are discussed. 相似文献
17.
Based on the solar X-ray data in the band of 0.1??C?0.8?nm observed by Geostationary Operational Environmental Satellites (GOES), the XUV and EUV data in the bands of 26??C?34?nm and 0.1??C?50?nm observed by the Solar EUV Monitor (SEM) onboard the Solar and Heliospheric Observatory (SOHO), a statistical analysis on the excess peak flux (the pre-flare flux is subtracted) in two SEM bands during M- and X-class flares from 1998 to 2007 is given. The average ratio of the excess peak flux to the pre-flare flux for the M-class flares is 5.5?%±3.7?% and that for the X-class flares is 16?%±11?%. The excess peak fluxes in two SEM bands are positively correlated with the X-ray flare class; with the increase in the X-ray flare class, the excess peak flux in two SEM bands increases. However, a large dispersion in the excess peak flux in the SEM bands and their ratio is found for the same X-ray flare class. The relationship between the excess peak fluxes of the two SEM bands also shows large dispersion. It is considered that the diversity we found in the flare spectral irradiance is caused by many variable factors related to the structure and evolution of solar flares. 相似文献
18.
Proton Enhancements and Their Relation to the X-Ray Flares During the Three Last Solar Cycles 总被引：1，自引：0，他引：1
Energetic proton measurements obtained from the GOES and IMP-8 satellites as well as from ground-based neutron monitors are
compared with the GOES soft X-ray measurements of the associated solar flares for the period 1975–2003. The present study
investigates a broad range of phenomenology relating proton events to flares (with some references to related interplanetary
disturbances), including correlations of occurrence, intensities, durations and timing of both the particle event and the
flare as well as the role of the heliographic location of the designated active region. 1144 proton events of > 10 MeV energy
were selected from this 28-year period. Owing primarily to the low particle flux threshold employed more than half of this
number was found to be reliably connected with an X-ray flare. The statistical analysis indicates that the probability and
magnitude of the near-Earth proton enhancement depends critically on the flare's importance and its heliolongitude. In this
study all flares of X-ray importance > X5 and located in the most propitious heliolongitude range, 15∘W to 75∘W, were succeeded by a detectable proton enhancement. It was also found that the heliolongitude frequently determines the
character of the proton event time profile. In addition to intensity, duration and timing, proton events were found to be
related to the other flare properties such as lower temperatures and longer loop lengths. 相似文献
19.
Yūki Kubo 《Solar physics》2008,248(1):85-98
This article discusses statistical models for the solar flare interval distribution in individual active regions. We analyzed
solar flare data in 55 active regions that are listed in the Geosynchronous Operational Environmental Satellite (GOES) soft X-ray flare catalog for the years from 1981 to 2005. We discuss some problems with a conventional procedure to
derive probability density functions from any data set and propose a new procedure, which uses the maximum likelihood method
and Akaike Information Criterion (AIC) to objectively compare some competing probability density functions. Previous studies
of the solar flare interval distribution in individual active regions only dealt with constant or time-dependent Poisson process
models, and no other models were discussed. We examine three models – exponential, lognormal, and inverse Gaussian – as competing
models for probability density functions in this study. We found that lognormal and inverse Gaussian models are more likely
models than the exponential model for the solar flare interval distribution in individual active regions. The possible solar
flare mechanisms for the distribution models are briefly mentioned. We also briefly investigated the time dependence of probability
density functions of the solar flare interval distribution and found that some active regions show time dependence for lognormal
and inverse Gaussian distribution functions. The results suggest that solar flares do not occur randomly in time; rather,
solar flare intervals appear to be regulated by solar flare mechanisms. Determining a solar flare interval distribution is
an essential step in probabilistic solar flare forecasting methods in space weather research. We briefly mention a probabilistic
solar flare forecasting method as an application of a solar flare interval distribution analysis. The application of our distribution
analysis to a probabilistic solar flare forecasting method is one of the main objectives of this study. 相似文献
20.
Dryer M. Andrews M. D. Aurass H. DeForest C. Galvin A. B. Garcia H. Ipavich F. M. Karlický M. Kiplinger A. Klassen A. Meisner R. Paswaters S. E. Smith Z. Tappin S. J. Thompson B. J. Watari S. I. Michels D. J. Brueckner G. E. Howard R. A. Koomen M. J. Lamy P. Mann G. Arzner K. Schwenn R. 《Solar physics》1998,181(1):159-183
The first X-class flare in four years occurred on 9 July 1996. This X2.6/1B flare reached its maximum at 09:11 UT and was located in active region 7978 (S10° W30°) which was an old-cycle sunspot polarity group. We report the SOHO LASCO/EIT/MDI and SOONSPOT observations before and after this event together with Yohkoh SXT images of the flare, radio observations of the type II shock, and GOES disk-integrated soft X-ray flux during an extended period that included energy build-up in this active region.The LASCO coronagraphs measured a significant coronal mass ejection (CME) on the solar west limb beginning on 8 July at about 09:53 UT. The GOES 8 soft X-ray flux (0.1–0.8 nm) had started to increase on the previous day from below the A-level background (10-8 W m-2). At the start time of the CME, it was at the mid-B level and continued to climb. This CME is similar to many events which have been seen by LASCO and which are being interpreted as disruption of existing streamers by emerging flux ropes.LASCO and EIT were not collecting data at the time of the X-flare due to a temporary software outage. A larger CME was in progress when the first LASCO images were taken after the flare. Since the first image of the 'big' CME was obtained after the flare's start time, we cannot clearly demonstrate the physical connection of the CME to the flare. However, the LASCO CME data are consistent with an association of the flare and the CME. No eruptive filaments were observed during this event.We used the flare evidence noted above to employ in real time a simplified Shock-Time-of-Arrival (STOA) algorithm to estimate the arrival of a weak shock at the WIND spacecraft. We compare this prediction with the plasma and IMF data from WIND and plasma data from the SOHO/CELIAS instrument and suggest that the flare - and possibly the interplanetary consequences of the 'big' CME - was the progenitor of the mild, high-latitude, geomagnetic storm (daily sum of Kp=16+, Ap=8) on 12 July 1996. We speculate that the shock was attenuated enroute to Earth as a result of interaction with the heliospheric current/plasma sheet.presently at High Altitude Observatory, Boulder, CO80309, U.S.A.presently at Naval Research Laboratory, Washington DC, 20375, U.S.A. 相似文献