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1.
We revisit the flare that occurred on 13 January 1992, which is now universally termed the “Masuda flare”. The new analysis
is motivated not just by its uniqueness despite the increasing number of coronal observations in hard X-rays, but also by
the improvement of Yohkoh hard X-ray image processing, which was achieved after the intensive investigations on this celebrated event. Using an uncertainty
analysis, we show that the hard X-ray coronal source is located closer to the soft X-ray loop by about 5000 km (or 7 arcsec)
in the re-calibrated Hard X-ray Telescope (HXT) images than in the original ones. Specifically, the centroid of the M1-band
(23 – 33 keV) coronal source is above the maximum brightness of the Soft X-ray Telescope (SXT) loop by 5000±1000 km (9600
km in the original data) and above the apex of the SXT loop represented by the 30% brightness contour by 2000±1000 km (∼ 7000 km
in the original data). The change is obviously significant, because most coronal sources are above the thermal loop by less
than 6 arcsec. We suggest that this change may account for the discrepancy in the literature, i.e., the spectrum of the coronal emission was reported to be extremely hard below ∼ 20 keV in the pre-calibration investigations,
whereas it was reported to be considerably softer in the literature after the re-calibration done by Sato, Kosugi, and Makishima
(Pub. Astron. Soc. Japan
51, 127, 1999). Still, the coronal spectrum is flatter at lower energies than at higher energies, due to the lack of a similar, co-spatial
source in the L-band (14 – 23 keV), for which a convincing explanation is absent. 相似文献
2.
We discuss the implications of the recent X-ray and TeV γ-ray observations of the PSR B1259–63 system (a young rotation powered pulsar orbiting a Be star) for the theoretical models
of interaction of pulsar and stellar winds. We show that previously considered models have problems to account for the observed
behaviour of the system. We develop a model in which the broad band emission from the binary system is produced in result
of collisions of GeV–TeV energy protons accelerated by the pulsar wind and interacting with the stellar disk. In this model
the high energy γ-rays are produced in the decays of secondary neutral pions, while radio and X-ray emission are synchrotron and inverse Compton
emission produced by low-energy (≤100 MeV) electrons from the decays of secondary charged π
± mesons. This model can explain not only the observed energy spectra, but also the correlations between TeV, X-ray and radio
emission components.
相似文献
3.
Evidence that Synchrotron Emission from Nonthermal Electrons Produces the Increasing Submillimeter Spectral Component in Solar Flares 总被引：1，自引：0，他引：1
Adriana V. R. Silva G. H. Share R. J. Murphy J. E. R. Costa C. G. Giménez de Castro J.-P. Raulin P. Kaufmann 《Solar physics》2007,245(2):311-326
We investigate the origin of the increasing spectra observed at submillimeter wavelengths detected in the flare on 2 November
2003 starting at 17:17 UT. This flare, classified as an X8.3 and 2B event, was simultaneously detected by RHESSI and the Solar
Submillimeter Telescope (SST) at 212 and 405 GHz. Comparison of the time profiles at various wavelengths shows that the submillimeter
emission resembles that of the high-energy X rays observed by RHESSI whereas the microwaves observed by the Owens Valley Solar
Array (OVSA) resemble that of ∼50 keV X rays. Moreover, the centroid position of the submillimeter radiation is seen to originate
within the same flaring loops of the ultraviolet and X-ray sources. Nevertheless, the submillimeter spectra are distinct from
the usual microwave spectra, appearing to be a distinct spectral component with peak frequency in the THz range. Three possibilities
to explain this increasing radio spectra are discussed: (1) gyrosynchrotron radiation from accelerated electrons, (2) bremsstrahlung
from thermal electrons, and (3) gyrosynchrotron emission from the positrons produced by pion or radioactive decay after nuclear
interactions. The latter possibility is ruled out on the grounds that to explain the submillimeter observations requires 3000
to 2×105 more positrons than what is inferred from X-ray and γ-ray observations. It is possible to model the emission as thermal; however, such sources would produce too much flux in the
ultraviolet and soft X-ray wavelengths. Nevertheless we are able to explain both spectral components at microwave and submillimeter
wavelengths by gyrosynchrotron emission from the same population of accelerated electrons that emit hard X rays and γ rays. We find that the same 5×1035 electrons inferred from RHESSI observations are responsible for the compact submillimeter source (0.5 arcsec in radius) in
a region of 4500 G low in the atmosphere, and for the traditional microwave spectral component by a more extended source (50
arcsec) in a 480 G magnetic field located higher up in the loops. The extreme values in magnetic field and source size required
to account for the submillimeter emission can be relaxed if anisotropy and transport of the electrons are taken into account. 相似文献
4.
A simple model is presented to account for theYohkoh flare observations of Feldmanet al. (1994), and Masuda (1994). Electrons accelerated by the flare are assumed to encounter the dense, small regions observed by Feldmanet al. at the tops of impulsively flaring coronal magnetic loops. The values of electron density and volume inferred by Feldmanet al. imply that these dense regions present an intermediate thick-thin target to the energised electrons. Specifically, they present a thick (thin) target to electrons with energy much less (greater) thanE
c
, where 15 keV <E
c
< 40 keV. The electrons are either stopped at the loop top or precipitate down the field lines of the loop to the footpoints. Collisional losses of the electrons at the loop top produce the heating observed by Feldmanet al. and also some hard X-rays. It is argued that this is the mechanism for the loop-top hard X-ray sources observed in limb flares by Masuda. Adopting a simple model for the energy losses of electrons traversing the dense region and the ambient loop plasma, hard X-ray spectra are derived for the loop-top source, the footpoint sources and the region between the loop top and footpoints. These spectra are compared with the observations of Masuda. The model spectra are found to qualitatively agree with the data, and in particular account for the observed steepening of the loop-top and footpoint spectra between 14 and 53 keV and the relative brightnesses of the loop-top and footpoint sources. 相似文献
5.
On the basis of our multiwavelength observations made with the one-dimensional RATAN-600 radio telescope, we study the inversion
of the circular polarization in the solar microwave emission at different frequencies. The inversion is detected in the emission
of flare-producing active regions (FPARs) at various stages of their development, starting from the pre-flare stage. During
the latest 23rd solar cycle maximum, numerous FPARs revealed spectral inhomogeneities in their polarized microwave radiation
(Bogod and Tokhchukova, 2003, Astron. Lett.
29, 263). Here, we discuss a particular case of such inhomogeneities, the frequency-dependent double inversion of the sign of
circular polarization, which probably reflects some essential processes in FPARs. We consider several mechanisms for the double
inversion: linear interaction of waves in the region of a quasitransverse magnetic field, the propagation of waves through
a region of zero magnetic field, the scattering of radio waves on waves of high-frequency plasma turbulence, the influence
of the current fibrils on the propagation of the radio emission, and the magnetic “dips,” in which the direction of magnetic
field lines changes the sign relative to the observer. All of them have shortcomings, but the last mechanism explains the
observations the best. 相似文献
6.
Very-Large-Array (VLA) observations of the Sun at 20, 91 and 400 cm have been combined with data from the SOHO, TRACE and Wind solar missions to study the properties of long-lasting Type I noise storms and impulsive metric and decimetric bursts during solar flares and associated coronal mass ejections. These radio observations provide information about the acceleration and propagation of energetic electrons in the low and middle corona as well as their interactions with large-scale magnetic structures where energy release and transport takes place. For one flare and its associated CME, the VLA detected impulsive 20 and 91 cm bursts that were followed about ten minutes later by 400 cm burst emission that appeared to move outward into the corona. This event was also detected by the Waves experiment on Wind which showed intense, fast-drifting interplanetary Type III bursts following the metric and decimetric bursts detected by the VLA. For another event, impulsive 91 cm emission was detected about a few minutes prior to impulsive bursts at 20.7 cm, suggesting an inwardly propagating beam of electrons that excited burst emission at lower levels and shorter wavelengths. We also find evidence for significant changes in the intensity of Type I noise storms in the same or nearby active region during impulsive decimetric bursts and CMEs. These changes might be attributed to flare-initiated heating of the Type I radio source plasma by outwardly-propagating flare ejecta or to the disruption of ambient magnetic fields by the passage of a CME. 相似文献
7.
We have applied detailed theories of gyro-synchrotron emission and absorption in a magnetoactive plasma, X-ray production by the bremsstrahlung of non-thermal electrons on ambient hydrogen, and electron relaxation in a partially ionized and magnetized gas to the solar flare burst phenomenon. The hard X-ray and microwave bursts are shown to be consistent with a single source of non-thermal electrons, where both emissions arise from electrons with energies < mc
2. Further-more, the experimental X-ray and microwave data allow us to deduce the properties of the electron distribution, and the values of the ambient magnetic field, the hydrogen density, and the size of the emitting region. The proposed model, although derived mostly from observations of the 7 July 1966 flare, is shown to be representative of this type of event.NAS-NRC Resident Research Associate. 相似文献
8.
N. J. Lehtinen S. Pohjolainen K. Huttunen-Heikinmaa R. Vainio E. Valtonen A. E. Hillaris 《Solar physics》2008,247(1):151-169
A high-speed, halo-type coronal mass ejection (CME), associated with a GOES M4.6 soft X-ray flare in NOAA AR 0180 at S12W29
and an EIT wave and dimming, occurred on 9 November 2002. A complex radio event was observed during the same period. It included
narrow-band fluctuations and frequency-drifting features in the metric wavelength range, type III burst groups at metric – hectometric
wavelengths, and an interplanetary type II radio burst, which was visible in the dynamic radio spectrum below 14 MHz. To study
the association of the recorded solar energetic particle (SEP) populations with the propagating CME and flaring, we perform
a multi-wavelength analysis using radio spectral and imaging observations combined with white-light, EUV, hard X-ray, and
magnetogram data. Velocity dispersion analysis of the particle distributions (SOHO and Wind
in situ observations) provides estimates for the release times of electrons and protons. Our analysis indicates that proton acceleration
was delayed compared to the electrons. The dynamics of the interplanetary type II burst identify the burst source as a bow
shock created by the fast CME. The type III burst groups, with start times close to the estimated electron-release times,
trace electron beams travelling along open field lines into the interplanetary space. The type III bursts seem to encounter
a steep density gradient as they overtake the type II shock front, resulting in an abrupt change in the frequency drift rate
of the type III burst emission. Our study presents evidence in support of a scenario in which electrons are accelerated low
in the corona behind the CME shock front, while protons are accelerated later, possibly at the CME bow shock high in the corona. 相似文献
9.
We investigate the temporal correlation function and the mean intensity of monochromatic radio emission in the neighborhood
of a regular caustic produced by radio sounding of near-solar plasma. Using asymptotic analysis and numerical simulation,
we determine conditions under which the temporal correlation function is related to the temporal structure function by a relation
similar to that used for the solar wind diagnostics (Coles and Harmon, Astrophys. J.
337, 1023, 1989) in the case of weak refraction of radio waves. Information on the correlation function and on the mean intensity in the
caustic shadow region can be used to determine the parameters of the electron density fluctuation spectrum at small heliocentric
distances. 相似文献
10.
Second and sub-second structures were simultaneously detected in optical, radio and hard X-ray (HXR) band, respectively by
the GanYu Station of Purple Mountain Observatory, Nobeyama Radio Observatory, and RHESSI satellite in the November 1, 2004 flare (Ji et al., in Astrophys. J. 636:L173, 2006), which may be contributed to the energy transport of the continuous heat flux from the hot corona or chromosphere evaporation
and of the accelerated electrons. The linear correlations between the amplitudes of these fluctuations and their flare emissions,
and those between the cross-correlation coefficients of the fluctuations at two H
α
kernels, or two radio frequencies, or two X-ray energies and their flare emissions may support the causal relationship of
the flare and these time structures. While, the cross-correlations of the fluctuations at three different bands suggest that
the fluctuations are caused by the common thermal or nonthermal processes in the flare. Moreover, some new features of the
fluctuations are reported in the flare: (1) The sub-second fluctuations in radio and HXR bands have a same timescale, which
is evidently larger than that in H-alpha band. The difference may be explained by the downward movements of nonthermal electrons
or the upward motion of chromosphere evaporation. (2) The power-law distributions of the amplitudes of the second and the
sub-second structures are obtained at optical, radio and HXR bands with different indices. (3) The peak-to-peak correspondence
of Stokes I and V components in the sub-second structures at radio band suggests that they may be resulted from a periodical
particle acceleration and particle injection in this event. However, the second structures may be caused by the modulations
of Alfvén waves with an upward speed of 103 km/s. 相似文献
11.
Two small radio flares following the great gamma-ray burst on 11 June 1991 are studied. We analyse the different association of emission features at microwaves, decimeter waves, and soft and hard X-rays for the events. The first flare has well-defined emission features in microwaves and soft and hard X-rays, and a faint decimetric signature well after the hard X-ray burst. It is not certain if the decimetric event is connected to the burst features. The second event is characterized by an almost simultaneous appearance of hard X-ray burst maxima and decimetric narrowband drift bursts, but soft X-ray emission is missing from the event. With the exception of the possibility that the soft X-ray emission is absorbed along the way, the following models can explain the reported differences in the second event: (1) Microwave emission in the second event is produced by 150 keV electrons spiraling in the magnetic field relatively low in the corona, while the hard X-ray emission is produced at the beginning of the burst near the loop top as thick-target emission. If the bulk of electrons entered the loop, the low-energy electrons would not be effectively mirrored and would eventually hit the footpoints and cause soft X-ray emission by evaporation, which was not observed. The collisions at the loop top would not produce observable plasma heating. The observed decimetric type III bursts could be created by plasma oscillations caused by electron beams traveling along the magnetic field lines at low coronal heights. (2) Microwave emission is caused by electrons with MeV energies trapped in the large magnetic loops, and the electrons are effectively mirrored from the loop footpoints. The hard X-ray emission can come both from the loop top and the loop footpoints as the accelerated lower energy electrons are not mirrored. The low-energy electrons are not, however, sufficient to create observable soft X-ray emission. The type III emission in this case could be formed either at low coronal heights or in local thick regions in the large loops, high in the corona. 相似文献
12.
We develop a diagnostic tool for determination of the electron densities in solar prominences using eclipse data. The method
is based on analysis of the hydrogen Balmer-line intensities (namely Hα and Hβ) and the white-light emission due to Thomson
scattering on the prominence electrons. Our approach represents a generalization of the ratio method already used by Koutchmy,
Lebecq, and Stellmacher (Astron. Astrophys.
119, 261, 1983). In this paper we use an extended grid of non-LTE prominence models of Gouttebroze, Heinzel, and Vial (Astron. Astrophys. Suppl. Ser.
99, 513, 1993) and derive various useful relations between prominence radiation properties and electron densities. Simultaneously, an effective
geometrical thickness of the prominence can also be obtained. As an example we apply our general technique to original eclipse
data of Koutchmy, Lebecq, and Stellmacher (Astron. Astrophys.
119, 261, 1983). Finally, we use our results to determine the color of prominences as it should be seen during total eclipses. 相似文献
13.
This work investigates the spatial relation between coronal X-ray sources and coherent radio emissions, both generally thought to be signatures of particle acceleration. Two limb events were selected during which the radio emission was well correlated in time with hard X-rays. The radio emissions were of the type of decimetric pulsations as determined from the spectrogram observed by Phoenix-2 of ETH Zurich. The radio positions were measured from observations with the Nançay Radioheliograph between 236 and 432 MHz and compared to the position of the coronal X-ray source imaged with RHESSI. The radio pulsations originated at least 30?–?240 Mm above the coronal hard X-ray source. The altitude of the radio emission increases generally with lower frequency. The average positions at different frequencies are on a line pointing approximately to the coronal hard X-ray source. Thus, the pulsations cannot be caused by electrons trapped in the flare loops, but are consistent with emission from a current sheet above the coronal source. 相似文献
14.
We analyze hard and soft X-ray, microwave and meter wave radio, interplanetary particle, and optical data for the complex energetic solar event of 22 July 1972. The flare responsible for the observed phenomena most likely occurred 20° beyond the NW limb of the Sun, corresponding to an occultation height of 45 000 km. A group of type III radio bursts at meter wavelengths appeared to mark the impulsive phase of the flare, but no impulsive hard X-ray or microwave burst was observed. These impulsive-phase phenomena were apparently occulted by the solar disk as was the soft X-ray source that invariably accompanies an H flare. Nevertheless essentially all of the characteristic phenomena associated with second-stage acceleration in flares - type II radio burst, gradual second stage hard X-ray burst, meter wave flare continuum (FC II), extended microwave continuum, energetic electrons and ions in the interplanetary medium - were observed. The spectrum of the escaping electrons observed near Earth was approximately the same as that of the solar population and extended to well above 1 MeV.Our analysis of the data leads to the following results: (1) All characteristics are consistent with a hard X-ray source density n
i
108 cm–3 and magnetic field strength 10 G. (2) The second-stage acceleration was a physically distinct phenomenon which occurred for tens of minutes following the impulsive phase. (3) The acceleration occurred continuously throughout the event and was spatially widespread. (4) The accelerating agent was very likely the shock wave associated with the type II burst. (5) The emission mechanism for the meter-wave flare continuum source may have been plasma-wave conversion, rather than gyrosynchrotron emission. 相似文献
15.
The sunspot-associated sources at the frequency of 17 GHz give information on plasma parameters in the regions of magnetic
field about B=2000 G at the level of the chromosphere-corona transition region. The observations of short period (from one to ten minutes)
oscillations in sunspots reflect propagation of magnetohydrodynamic (MHD) waves in the magnetic flux tubes of the sunspots.
We investigate the oscillation parameters in active regions in connection with their flare activity. We confirm the existence
of a link between the oscillation spectrum and flare activity. We find differences in the oscillations between pre-flare and
post-flare phases. In particular, we demonstrate a case of powerful three-minute oscillations that start just before the burst.
This event is similar to the cases of the precursors investigated by Sych et al. (Astron. Astrophys.
505, 791, 2009). We also found well-defined eight-minute oscillations of microwave emission from sunspot. We interpret our observations
in terms of a relationship between MHD waves propagating from sunspots and flare processes. 相似文献
16.
P. Goldoni M. Ribó T. Di Salvo J. M. Paredes V. Bosch-Ramon M. Rupen 《Astrophysics and Space Science》2007,309(1-4):293-297
LS 5039 is the only X-ray binary persistently detected at TeV energies by the Cherenkov HESS telescope. It is moreover a γ-ray emitter in the GeV and possibly MeV energy ranges. To understand important aspects of jet physics, like the magnetic
field content or particle acceleration, and emission processes, such as synchrotron and inverse Compton (IC), a complete modeling
of the multiwavelength data is necessary. LS 5039 has been detected along almost all the electromagnetic spectrum thanks to
several radio, infrared, optical and soft X-ray detections. However, hard X-ray detections above 20 keV have been so far elusive
and/or doubtful, partly due to source confusion for the poor spatial resolution of hard X-ray instruments. We report here
on deep (∼300 ks) serendipitous INTEGRAL hard X-ray observations of LS 5039, coupled with simultaneous VLA radio observations. We obtain a 20–40 keV flux of 1.1±0.3 mCrab
(5.9 (±1.6) ×10−12 erg cm−2 s−1), a 40–100 keV upper limit of 1.5 mCrab (9.5×10−12 erg cm−2 s−1), and typical radio flux densities of ∼25 mJy at 5 GHz. These hard X-ray fluxes are significantly lower than previous estimates
obtained with BATSE in the same energy range but, in the lower interval, agree with extrapolation of previous RXTE measurements. The INTEGRAL observations also hint to a break in the spectral behavior at hard X-rays. A more sensitive characterization of the hard
X-ray spectrum of LS 5039 from 20 to 100 keV could therefore constrain key aspects of the jet physics, like the relativistic
particle spectrum and the magnetic field strength. Future multiwavelength observations would allow to establish whether such
hard X-ray synchrotron emission is produced by the same population of relativistic electrons as those presumably producing
TeV emission through IC. 相似文献
17.
G. A. Dulk 《Solar physics》1990,130(1-2):139-150
The purpose of this paper is to review the observations of particle beams of the kind that are frequently observed in the interplanetary medium, usually but not always accompanying a solar flare. Most frequent are beams of electrons. They are generally associated with radio bursts of type III and only sometimes with flares and X-ray bursts. The properties of these electron beams have been well studied using quasi-linear and nonlinear theory, in situ observations of electrons and of plasma waves, and remote observations of radio waves Thanks to the interaction between theory and observation, the decade of the 1980s has been one of great progress in understanding the main features of these beams and their associated plasma waves and radio bursts. However, uncertainties remain in terms of (1) whether fine scale features, filamentary structures or wave condensations, occur together with the beams, (2) whether quasi-linear or nonlinear wave emission is the dominant process, and (3) if wave condensations are important, what is the mechanism of conversion of some Langmuir wave energy into radio emission.Other particle beams are composed of protons, of neutrons, of helium ions (sometimes with a large excess of 3He), and of heavy ions with varying concentrations. Sometimes the observations seem to require the fractionation of certain ions, followed by resonant acceleration of certain species.Objects other than the Sun that are the source of interplanetary particle beams include comets and planets, especially the Earth and Jupiter. 相似文献
18.
We present the observation and interpretation of a solar radio burst whose evolution of the source position at 48 GHz has been correlated with microwave spectral observations from 3.1 to 19.6 GHz and H imaging spectrograms. The event of November 19, 1990 showed 4 impulsive peaks in microwaves and 2 H kernels. There exists strong evidence that the impulsive emission has originated from nonthermal electrons including an electron beam during the rising phase of the third microwave peak. The complex evolution of the source position at 48 GHz is attributed to two inhomogeneous and spatially separated sources with changing relative brightness. 相似文献
19.
Michael Nowak 《Astrophysics and Space Science》2005,300(1-3):159-166
Previous work by Motch et al. [1985, Space Sci. Rev. 40, 219] suggested that in the low/hard state of GX, the soft X-ray power-law extrapolated backward in energy agrees with the
IR flux level. Corbel and Fender [2002, ApJ 573, L35–L39] later showed that the typical hard state radio power-law extrapolated forward in energy meets the backward extrapolated
X-ray power-law at an IR spectral break, which was explicitly observed twice in GX. This has been cited as further evidence
that jet synchrotron radiation might make a significant contribution to the observed X-rays in the hard state. We explore
this hypothesis with a series of simultaneous radio/X-ray hard state observations of GX. We fit these spectra with a simple,
but remarkably successful, doubly broken power-law model that indeed requires a spectral break in the IR. For most of these
observations, the break position as a function of X-ray flux agrees with the jet model predictions. We then examine the radio
flux/X-ray flux correlation in CYG through the use of 15 GHz radio data, obtained with the Ryle radio telescope, and Rossi X-ray Timing Explorer data, from the All Sky Monitor and pointed observations. We find evidence of ‘parallel tracks’ in the radio/X-ray correlation which are associated with
‘failed transitions’ to, or the beginning of a transition to, the soft state. We also find that for CYG the radio flux is
more fundamentally correlated with the hard, rather than the soft, X-ray flux. 相似文献
20.
Andrea Merloni Sebastian Heinz Tiziana Di Matteo 《Astrophysics and Space Science》2005,300(1-3):45-53
We examine the disc-jet connection in stellar mass and supermassive black holes by investigating the properties of their compact
emission in the hard X-ray and radio bands. We compile a sample of ∼100 active galactic nuclei with measured mass, 5 GHz core
emission, and 2–10 keV luminosity, together with eight galactic black holes with a total of ∼50 simultaneous observations
in the radio and X-ray bands. Using this sample, we study the correlations between the radio (LR) and the X-ray (LX) luminosity and the black hole mass (M). We find that the radio luminosity is correlated with both M and LX, at a highly significant level. We show how this result can be used to extend the standard unification by orientation scheme
to encompass unification by mass and accretion rate. 相似文献