Hard X-rays and associated weak decimetric bursts     

H. S. Sawant  C. J. B. Lattari  A. O. Benz 《Solar physics》1990,130(1-2):57-73

In previous attempts to show one-to-one correlation between type III bursts and X-ray spikes, there have been ambiguities as to which of several X-ray spikes are correlated with any given type III burst. Here, we present observations that show clear associations of X-ray bursts with RS type III bursts between 16:46 UT and 16:52 UT on July 9, 1985. The hard X-ray observations were made at energies above 25 keV with HXRBS on SMM and the radio observations were made at 1.63 GHz using the 13.7m Itapetinga antenna in R and L polarization with a time resolution of 3 ms. Detailed comparison between the hard X-ray and radio observations shows:

1. In at least 13 cases we can identify the associated hard X-ray and decimetric RS bursts.
2. On average, the X-ray peaks were delayed from the peak of the RS bursts at 1.6 GHz by ～ 400 ms although a delay as long as 1 s was observed in one case.

One possible explanation of the long delays between the RS bursts and the associated X-ray bursts is that the RS burst is produced at the leading edge of the electron beam, whereas the X-ray burst peaks at the time of arrival of the bulk of the electrons at the high density region at the lower corona and upper chromosphere. Thus, the time comparison must be made between the peak of the radio pulse and the start of the X-ray burst. In that case the delays are consistent with an electron travel time with velocity ～ 0.3 c from the 800 MHz plasma level to the lower corona assuming that the radio emission is at the second harmonic.  相似文献   

Evidence of large scale diverging paths in the solar corona for type III bursts exciters     

C. Mercier 《Solar physics》1976,46(2):499-500

On 1 July 1971, about ten groups of type III bursts were observed with high time resolution (10^?1 sec) with the 169 MHz Nançay radioheliograph. Each group consists of two or several bursts, appearing successively from E to W in all cases, with very short delays. The analysis of successive E-W profiles allowed us to show that, for each event:

1. the delay between maximum times of the sources was in the range 0.3–0.8 s and that their time profiles were very similar.
2. the mutual distance between sources was ～1.5 × 10⁵ km.

Explanations by simultaneous emission at the fundamental and harmonic of the local plasma frequency, or by reflexion of electromagnetic radiations at boundary at a dense region are shown to be inconsistent with the observations. We suggest that distinct exciters are simultaneously accelerated at low levels in very close regions and propagate upward along very widely diverging magnetic field lines. This divergence could be related to the existence of large scale magnetic connexions in the corona as revealed by XUV observations. We stress the point that this kind of structure in type III bursts groups, visible only with high time resolution, may have led in the past to erroneous conclusions concerning diameter and decay time of type III bursts because of both spatial and temporal overlapping.  相似文献   

Observation of the impulsive phase of a simple flare     

E. Tandberg-Hanssen  P. Kaufmann  E. J. Reichmann  D. L. Teuber  R. L. Moore  L. E. Orwig  H. Zirin 《Solar physics》1984,90(1):41-62

We present a broad range of complementary observations of the onset and impulsive phase of a fairly large (1B, M1.2) but simple two-ribbon flare. The observations consist of hard X-ray flux measured by the SMM HXRBS, high-sensitivity measurements of microwave flux at 22 GHz from Itapetinga Radio Observatory, sequences of spectroheliograms in UV emission lines from Ov (T ≈ 2 × 10⁵ K) and Fexxi (T ≈ 1 × 10⁷ K) from the SMM UVSP, Hα and Hei D₃ cine-filtergrams from Big Bear Solar Observatory, and a magnetogram of the flare region from the MSFC Solar Observatory. From these data we conclude:

1. The overall magnetic field configuration in which the flare occurred was a fairly simple, closed arch containing nonpotential substructure.
2. The flare occurred spontaneously within the arch; it was not triggered by emerging magnetic flux.
3. The impulsive energy release occurred in two major spikes. The second spike took place within the flare arch heated in the first spike, but was concentrated on a different subset of field lines. The ratio of Ov emission to hard X-ray emission decreased by at least a factor of 2 from the first spike to the second, probably because the plasma density in the flare arch had increased by chromospheric evaporation.
4. The impulsive energy release most likely occurred in the upper part of the arch; it had three immediate products:

1. An increase in the plasma pressure throughout the flare arch of at least a factor of 10. This is required because the Fexxi emission was confined to the feet of the flare arch for at least the first minute of the impulsive phase.
2. Nonthermal energetic (～ 25 keV) electrons which impacted the feet of the arch to produce the hard X-ray burst and impulsive brightening in Ov and D₃. The evidence for this is the simultaneity, within ± 2 s, of the peak Ov and hard X-ray emissions.
3. Another population of high-energy (～100keV) electrons (decoupled from the population that produced the hard X-rays) that produced the impulsive microwave emission at 22 GHz. This conclusion is drawn because the microwave peak was 6 ± 3 s later than the hard X-ray peak.

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The Alfvén-wave theory of solar flares     

J. H. Piddington 《Solar physics》1974,38(2):465-481

Evidence is discussed showing that a representative solar flare event comprises three or more separate but related phenomena requiring separate mechanisms. In particular it is possible to separate the most energetic effect (the interplanetary blast) from the thermal flare and from the rapid acceleration of particles to high energies. The phenomena are related through the magnetic structure characteristic of a composite flare event, being a bipolar surface field with most of its field lines ‘closed’. Of primary importance are helical twists on all scales, starting with the ‘flux rope’ of the spot pair which was fully twisted before it emerged. Subsequent untwisting by the upward propagation of an Alfvén twist wave provides the main flare energy.

1. The interplanetary blast model is based on subsurface, helically twisted flux ropes which erupt to form spots and then transfer their twists and energy by Alfvén-twist waves into the atmospheric magnetic fields. The blast is triggered by the prior-commencing flash phase or by a coronal wave.
2. The thermal flare is explained in terms of Alfvén waves travelling up numerous ‘flux strands’ (Figure 3) which have frayed away from the two flux ropes. The waves originate in interaction (collisions, bending, twisting, rubbing) between subsurface flux strands; the sudden flash is caused by a collision. The classical twin-ribbon flare results from the collision of a flux rope with a tight bunch of S-shaped flux strands.
3. The impulsive acceleration of electrons (hard X-ray, EUV, Hα and radio bursts) is tentatively attributed to magnetic reconnection between fields in two parallel, helically twisted flux strands in the low corona.
4. Flare (Moreton) waves in the corona have the same origin as the interplanetary blast. Sympathetic flares represent only the start of enhanced activity in a flare event already in the slow phase. Filament activation also occurs during the slow phase as twist Alfvén waves store their energy in the atmosphere.
5. Flare ejecta are caused by Alfvén waves moving up flux strands. Surges are attributed to packets of twist Alfvén waves released into bundles of flux strands; the waves become non-linear and drive plasma upwards. Spray-type prominences result from accumulations of Alfvén wave energy in dome-shaped fields; excessive energy density eventually explodes the field.

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Observations of limb flares with a soft X-ray telescope     

Edward G. Gibson 《Solar physics》1977,53(1):123-138

The structure and evolution of 26 limb flares have been observed with a soft X-ray telescope flown on Skylab. The results are:

1. One or more well defined loops were the only structures of flare intensity observed during the rise phase and near flare maximum, except for knots which were close to the resolution of the telescope in size (≈2 arc seconds) and whose structure can therefore not be determined.
2. The flare core features were always sharply defined during the rise phase.
3. For the twenty events which contain loops, the geometry of the structure near maximum was that of a loop in ten cases, a loop with a spike at the top in four cases, a cusp or triangle in four cases, and a cusp combined with a spike in another two cases.
4. Of the fifteen cases in which sufficient data were available to allow us to follow a flare's evolution, five showed no significant geometrical deviation from a loop structure, one displayed little change except for a small scale short-lived perturbation on one side of the loop 10 seconds before a type III radio burst was observed, eight underwent a large scale deformation of the loop or loops on a time scale comparable to that of the flare itself and one double loop event changed in a complex and undetermined manner, with reconnection being one possibility.

Based on observation of the original film, it is suggested that the eight flares which underwent large scale deformations had become unstable to MHD kinks. This implies that these flares occurred in magnetic flux tubes through which significant currents were flowing. It is suggested that the high energy electrons responsible for type III bursts accompanying these flares could have been accelerated by the V x B electric field induced by a small scale short-lived perturbation of parts of a flaring flux tube, similar to the one perturbation which was observed having these characteristics.  相似文献   

Chromospheric inhomogeneities in sunspot umbrae     

Jacques M. Beckers  Paul E. Tallant 《Solar physics》1969,7(3):351-365

The properties of rapidly changing inhomogeneities visible in the H and K lines above sunspot umbrae are described. We find as properties for these ‘Umbral Flashes’:

1. A lifetime of 50 sec. The light curve is asymmetrical, the increase is faster than the decrease in brightness.
2. A diameter ranging from the resolution limit up to 2000 km.
3. A tendency to repeat every 145 sec.
4. A ‘proper motion’ of 40 km/sec generally directed towards the penumbra.
5. A Doppler shift of 6 km/sec.
6. A magnetic field of 2100 G.
7. A decrease in this field of 12 G/sec. This decrease is probably related to the flash motion.
8. At any instant an average of 3–5 flashes in a medium-sized umbra. A weak feature often persists in the umbra after the flash. This post-flash structure initially shows a blue shift, but 100–120 sec after the flash, it shows a rapid red shift just before the flash repeats.

  相似文献   

Science with ASKAP     

S. Johnston  R. Taylor  M. Bailes  N. Bartel  C. Baugh  M. Bietenholz  C. Blake  R. Braun  J. Brown  S. Chatterjee  J. Darling  A. Deller  R. Dodson  P. Edwards  R. Ekers  S. Ellingsen  I. Feain  B. Gaensler  M. Haverkorn  G. Hobbs  A. Hopkins  C. Jackson  C. James  G. Joncas  V. Kaspi  V. Kilborn  B. Koribalski  R. Kothes  T. Landecker  A. Lenc  J. Lovell  J.-P. Macquart  R. Manchester  D. Matthews  N. McClure-Griffiths  R. Norris  U.-L. Pen  C. Phillips  C. Power  R. Protheroe  E. Sadler  B. Schmidt  I. Stairs  L. Staveley-Smith  J. Stil  S. Tingay  A. Tzioumis  M. Walker  J. Wall  M. Wolleben 《Experimental Astronomy》2008,22(3):151-273

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Flare fragmentation and type III productivity in the 1980 June 27 flare     

M. J. Aschwanden  A. O. Benz  R. A. Schwartz  R. P. Lin  R. M. Pelling  W. Stehling 《Solar physics》1990,130(1-2):39-55

We present observations of the solar flare on 1980 June 27, 16:14–16:33 UT, which was observed by a balloon-borne 300 cm² phoswich hard X-ray detector and by the IKARUS radio spectrometer. This flare shows intense hard X-ray (HXR) emission and an extreme productivity of (at least 754) type III bursts at 200–400 MHz. A linear correlation was found between the type III burst rate and the HXR fluence, with a coefficient of 7.6 × 10²⁷ photons keV^–1 per type III burst at 20 keV. The occurrence of 10 type III bursts per second, and also the even higher rate of millisecond spikes, suggests a high degree of fragmentation in the acceleration region. This high quantization of injected beams, assuming the thick-target model, shows up in a linear relationship between hard X-ray fluence and the type III rate, but not as fine structures in the HXR time profile.The generation of a superhot isothermal HXR component in the decay phase of the flare coincides with the fade-out of type III production.Universities Space Research Associates.ST Systems Corporation.  相似文献   

Decimetric type III radio bursts and associated hard X-ray spikes     

B. R. Dennis  A. O. Benz  M. Ranieri  G. M. Simnett 《Solar physics》1984,90(2):383-399

A detailed comparison is made between hard X-ray spikes and decimetric type III radio bursts for a relatively weak solar flare on 1981 August 6 at 10: 32 UT. The hard X-ray observations were made at energies above 30 keV with the Hard X-Ray Burst Spectrometer on the Solar Maximum Mission and with a balloon-born coarse-imaging spectrometer from Frascati, Italy. The radio data were obtained in the frequency range from 100 to 1000 MHz with the analog and digital instruments from Zürich, Switzerland. All the data sets have a time resolution of 0.1 s or better. The dynamic radio spectrum shows many fast drift type III radio bursts with both normal and reverse slope, while the X-ray time profile contains many well resolved short spikes with durations of 1 s. Some of the X-ray spikes appear to be associated in time with reverse-slop bursts suggesting either that the electron beams producing the radio bursts contain two or three orders of magnitude more fast electrons than has previously been assumed or that the electron beams can trigger or occur in coincidence with the acceleration of additional electrons. One case is presented in which a normal slope radio burst at 600 MHz occurs in coincidence with the peak of an X-ray spike to within 0.1 s. If the coincidence is not merely accidental and if it is meaningful to compare peak times, then the short delay would indicate that the radio signal was at the harmonic and that the electrons producing the radio burst were accelerated at an altitude of 4 × 10⁹ cm. Such a short delay is inconsistent with models invoking cross-field drifts to produce the electron beams that generate type III bursts but it supports the model incorporating a MASER proposed by Sprangle and Vlahos (1983).  相似文献   

Solar flare physics enlivened by TRACE and RHESSI     

Markus J. Aschwanden 《Journal of Astrophysics and Astronomy》2008,29(1-2):115-124

The Transition Region and Coronal Explorer (TRACE) gave us the highest EUV spatial resolution and the Ramaty High Energy Solar Spectrometric Imager (RHESSI) gave us the highest hard X-ray and gammaray spectral resolution to study solar flares. We review a number of recent highlights obtained from both missions that either enhance or challenge our physical understanding of solar flares, such as:

1. Multi-thermal Diagnostic of 6.7 and 8.0 keV Fe and Ni lines
2. Multi-thermal Conduction Cooling Delays
3. Chromospheric Altitude of Hard X-Ray Emission
4. Evidence for Dipolar Reconnection Current Sheets
5. Footpoint Motion and Reconnection Rate
6. Evidence for Tripolar Magnetic Reconnection
7. Displaced Electron and Ion Acceleration Sources.

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X-ray imaging of three flares during the impulsive phase     

André Duijveman  Peter Hoyng  Marcos E. Machado 《Solar physics》1982,81(1):137-157

The impulsive phases of three flares that occurred on April 10, May 21, and November 5, 1980 are discussed. Observations were obtained with the Hard X-ray Imaging Spectrometer (HXIS) and other instruments aboard SMM, and have been supplemented with Hα data and magnetograms. The flares show hard X-ray brightenings (16–30 keV) at widely separated locations that spatially coincide with bright Hα patches. The bulk of the soft X-ray emission (3.5–5.5 keV) originates from in between the hard X-ray brightenings. The latter are located at different sides of the neutral line and start to brighten simultaneously to within the time resolution of HXIS. Concluded is that:

1. The bright hard X-ray patches coincide with the footpoints of loops.
2. The hard X-ray emission from the footpoints is most likely thick target emission from fast electrons moving downward into the dense chromosphere.
3. The density of the loops along which the beam electrons propagate to the footpoints is restricted to a narrow range (10⁹ < n < 2 × 10¹⁰ cm^-3), determined by the instability threshold of the return current and the condition that the mean free path of the fast electrons should be larger than the length of the loop.
4. For the November 5 flare it seems likely that the acceleration source is located at the merging point of two loops near one of the footpoints.

It is found that the total flare energy is always larger than the total energy residing in the beam electrons. However, it is also estimated that at the time of the peak of the impulsive hard X-ray emission a large fraction (at least 20%) of the dissipated flare power has to go into electron acceleration. The explanation of such a high acceleration efficiency remains a major theoretical problem.  相似文献   

Non-thermal processes in large solar flares     

R. P. Lin  H. S. Hudson 《Solar physics》1976,50(1):153-178

We analyze particle acceleration processes in large solar flares, using observations of the August, 1972, series of large events. The energetic particle populations are estimated from the hard X-ray and γ-ray emission, and from direct interplanetary particle observations. The collisional energy losses of these particles are computed as a function of height, assuming that the particles are accelerated high in the solar atmosphere and then precipitate down into denser layers. We compare the computed energy input with the flare energy output in radiation, heating, and mass ejection, and find for large proton event flares that:

1. The ～10–10² keV electrons accelerated during the flash phase constitute the bulk of the total flare energy.
2. The flare can be divided into two regions depending on whether the electron energy input goes into radiation or explosive heating. The computed energy input to the radiative quasi-equilibrium region agrees with the observed flare energy output in optical, UV, and EUV radiation.
3. The electron energy input to the explosive heating region can produce evaporation of the upper chromosphere needed to form the soft X-ray flare plasma.
4. Very intense energetic electron fluxes can provide the energy and mass for interplanetary shock wave by heating the atmospheric gas to energies sufficient to escape the solar gravitational and magnetic fields. The threshold for shock formation appears to be ～10³¹ ergs total energy in >20 keV electrons, and all of the shock energy can be supplied by electrons if their spectrum extends down to 5–10 keV.
5. High energy protons are accelerated later than the 10–10² keV electrons and most of them escape to the interplanetary medium. The energetic protons are not a significant contributor to the energization of flare phenomena. The observations are consistent with shock-wave acceleration of the protons and other nuclei, and also of electrons to relativistic energies.
6. The flare white-light continuum emission is consistent with a model of free-bound transitions in a plasma with strong non-thermal ionization produced in the lower solar chromosphere by energetic electrons. The white-light continuum is inconsistent with models of photospheric heating by the energetic particles. A threshold energy of ～5×10³⁰ ergs in >20 keV electrons is required for detectable white-light emission.

The highly efficient electron energization required in these flares suggests that the flare mechanism consists of rapid dissipation of chromospheric and coronal field-aligned or sheet currents, due to the onset of current-driven Buneman anomalous resistivity. Large proton flares then result when the energy input from accelerated electrons is sufficient to form a shock wave.  相似文献   

Correlation and spectral analysis of daily solar radio flux     

Mohamed El-Raey  Phillip Scherrer 《Solar physics》1973,30(1):149-158

Correlation and spectral analysis of solar radio flux density and sunspot number near the maximum of the sunspot cycle has indicated the existence of

1. long period amplitude modulation of the slowly varying component (SVC) of radio emission
2. coronal storage over a period of the order of three solar rotations
3. fast decay (one solar rotation period or less) of gyromagnetic emissions from radio sources
4. shift in location of chromospheric sources compared to those of either the upper corona or the photosphere.

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Coherent mechanisms of radio emission and magnetic models of pulsars     

V. L. Ginzburg  V. V. Zheleznyakov  V. V. Zaitsev 《Astrophysics and Space Science》1969,4(4):464-504

This paper is primarily concerned with the questions of models and the mechanisms of radio emission for pulsars, the polarization of this radiation and related topic. For convenience and to provide a more complete picture of the problems involved, a short summary of the data on pulsars is also given. Besides the introduction, the paper contains the following sections:

1. Some Facts about Pulsars.
2. The Astrophysical Nature of Pulsars.
3. Coherent Mechanisms of Radio Emission from Pulsars.
4. Models of Pulsars: Magnetic, Pulsating White Dwarfs and Neutron Stars.
5. The Polarization of the Radio Emission from Pulsars.
6. A Synthesized Model of Pulsars — Magnetic, Pulsating and Rotating Neutron Stars.
7. Concluding Remarks.

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On the coronal source regions of U bursts     

S. Suzuki 《Solar physics》1978,57(2):415-422

The projected source positions at 43, 80, and 160 MHz and the sense and degree of circular polarization in the range 24 to 220 MHz, as observed with the Culgoora radioheliograph and spectropolarimeter respectively, are used:

1. To substantiate the hypothesis that metric U bursts originate in high coronal, magnetic loops.
2. To strengthen the hypothesis that U-burst radiation is in the ordinary magneto-ionic mode.

The occasional observation of different senses of circular polarization on either side of the turning point of a U burst suggests that U-burst radiation in these cases reaches its limiting polarization at or near the source. This observation raises the same difficulties as those discussed by Melrose (1973) in connection with the bi-polar nature of type-I storm sources.  相似文献   

Unstable chromospheric dark features and type-III bursts association     

F. Chiuderi-Drago  N. Mein  M. Pick 《Solar physics》1986,103(2):235-247

The temporal association between the kinematic parameters of chromospheric dark features (DF) and the production of radio type-III bursts is investigated during a period of five months. The Doppler shifts inside six different DF are measured by means of the Meudon Multichannel Subtracting Double Pass Spectrograph (MSDP) during periods of some minutes around 24 type-III bursts. The position of the radio bursts has been checked to be associated with the same active region observed by MSDP, by using the Nançay Radioheliograph. It appears that 23 out of 24 bursts take place when the DF is totally or predominantly blue-shifted. In 18 out of 21 cases, a maximum of the outward velocity is observed in the optical image closest in time to the radio burst. The following peculiarities are also shown by the analyzed DF:

1. All of them present a lengthened shape, in most cases pointing toward a sunspot: a bright region coinciding with a parasitic polarity is observed in between.
2. Horizontal velocities along the DF major axis are often observed, always in a direction opposite to the sunspots.

This association is interpreted by assuming that a shock wave, generated by the moving chromospheric material, is able to accelerate coronal electrons (according to a mechanism proposed by Leroy and Mangeney, 1984) thus producing type-III bursts.  相似文献   

Evidence for a common origin of the electrons responsible for the impulsive X-ray and type III radio bursts     

S. R. Kane 《Solar physics》1972,27(1):174-181

Observations of impulsive solar flare X-rays 10 keV made with the OGO-5 satellite are compared with ground based measurements of type III solar radio bursts in 10–580 MHz range. It is shown that the times of maxima of these two emissions, when detectable, agree within 18 s. This maximum time difference is comparable to that between the maxima of the impulsive X-ray and impulsive microwave bursts. In view of the various observational uncertainties, it is argued that the observations are consistent with the impulsive X-ray, impulsive microwave, and type III radio bursts being essentially simultaneous. The observations are also consistent with 10–100 keV electron streams being responsible for the type III emission. It is estimated that the total number of electrons 22 keV required to produce a type III burst is 10³⁴. The observations indicate that the non-thermal electron groups responsible for the impulsive X-ray, impulsive microwave, and type III radio bursts are accelerated simultaneously in essentially the same region of the solar atmosphere.  相似文献   

On the distribution of magnitudes of solar microwave events     

A. D. Fokker 《Solar physics》1980,67(1):101-108

A microwave magnitude is defined as a logarithmic measure of the energy content of a microwave event. The distributions of microwave magnitudes are derived for collections of bursts that:

1. Occurred during two periods in solar cycle 20, one relatively early and the other relatively late;
2. Occurred in association with optical flares in particular centres of activity.

No dependence on the phase in the solar cycle has been found. One centre of activity was found that produced a distribution different from normal. The distribution of microwave magnitudes can be satisfactorily represented by the expression n(m) = const (m/α)e ^{?(m/α) 2}. A phenomenological model for the flare build-up process is indicated which leads to a distribution of this very shape.  相似文献   

3C 120 and the surrounding region of sky     

Halton Arp 《Journal of Astrophysics and Astronomy》1987,8(3):231-239

Image processing performed on a series of photographs of the superluminal Seyfert galaxy, 3C 120, shows the outer optical disc to consist of fragmented segments generally pointing toward the centre. One long arm of peculiar, separated knots comes off to the W and SW. A peculiar companion is seen along the line of the NW radio jet. In the interior, optical jets are detected which are aligned along the direction of the outer radio jets. A region of the sky 45 ×; 25 degrees around 3C120 is investigated. It is found that:

1. A nebulous filament about 3/4 degree in length points to 3C 120.
2. Hydrogen clouds of redshiftz = ?130 and ?210 km s^?1 are situated at 3 and 1 degrees on either side of 3C 120.
3. Eleven low-surface-brightness galaxies with 4500 <z < 5300 km s^?1 fall within a radius of 8 degrees.
4. Seven quasars withz ? 1.35 and radio fluxesS _b ? 0.3 fall within a radius of 10 degrees.

It is concluded that the concentration of these objects in the vicinity of this unique, active galaxy has a negligible chance of being accidental and that all those objects of diverse redshift are at the same nearby distance. This smaller distance reduces the supposed superluminal motions in 3C 120 to quite precedented ejection velocities.  相似文献   

Observations of moving magnetic features near sunspots     

K. Harvey  J. Harvey 《Solar physics》1973,28(1):61-71

The properties of small (< 2″) moving magnetic features near certain sunspots are studied with several time series of longitudinal magnetograms and Hα filtergrams. We find that the moving magnetic features:

1. Are associated only with decaying sunspots surrounded entirely or in part by a zone without a permanent vertical magnetic field.
2. Appear first at or slightly beyond the outer edge of the parent sunspot regardless of the presence or absence of a penumbra.
3. Move approximately radially outward from sunspots at about 1 km s^?1 until they vanish or reach the network.
4. Appear with both magnetic polarities from sunspots of single polarities but appear with a net flux of the same sign as the parent sunspot.
5. Transport net flux away from the parent sunspots at the same rates as the flux decay of the sunspots.
6. Tend to appear in opposite polarity pairs.
7. Appear to carry a total flux away from sunspots several times larger than the total flux of the sunspots.
8. Produce only a very faint emmission in the core of Hα.

A model to help understand the observations is proposed.  相似文献