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1.
On July 5, 1980 the Hard X-Ray Imaging Spectrometer on board the Solar Maximum Mission observed a complex flare event starting at 22 : 32 UT from AR 2559 (Hale 16955), then at N 28 W 29, which developed finally into a 2-ribbon flare. In this paper we compare the X-ray images with Hα photographs taken at the Big Bear Solar Observatory and identify the site of the most energetic flare phenomena. During the early phases of the event the hard X-rays (>16 keV) came from a compact source located near one of the two bright Hα kernels; we believe the latter are at the footpoints of a compact magnetic loop. The kernel identified with the X-ray source is immediately adjacent to one of the principal sunspots and in fact appears to ‘rotate’ around the sunspot over 90° in the early phase of the flare. Two intense X-ray bursts occur at the site of the rotating kernel, and following each burst the loop fills with hot, X-ray emitting plasma. If the first burst is interpreted as bremsstrahlung from a beam of electrons impinging on a collisionally dominated medium, the energy in such electrons, >16 keV, is ～ 5 × 1030 erg. The altitude of the looptop is 7–10 × 103 km. The temperature structure of the flare is extremely non-homogeneous, and the highest temperatures are found in the top of the loop. A few minutes after the hard X-ray bursts the configuration of the region changes; some of the flare energy is transferred along a system of larger loops that now become the defining structure for a 2-ribbon flare, which is how the flare develops as seen in Hα. In the late, cooling phase of the flare 15 min after maximum, we find a significant component of the plasma at temperatures between 25 and 30 × 106 K. 相似文献
2.
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:
- The ～10–102 keV electrons accelerated during the flash phase constitute the bulk of the total flare energy.
- 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.
- 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.
- 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.
- 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.
- 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.
3.
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:
- The bright hard X-ray patches coincide with the footpoints of loops.
- The hard X-ray emission from the footpoints is most likely thick target emission from fast electrons moving downward into the dense chromosphere.
- 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.
- 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.
4.
In this paper we discuss the initial phase of chromospheric evaporation during a solar flare observed with instruments on the Solar Maximum Mission on May 21, 1980 at 20:53 UT. Images of the flaring region taken with the Hard X-Ray Imaging Spectrometer in the energy bands from 3.5 to 8 keV and from 16 to 30 keV show that early in the event both the soft and hard X-ray emissions are localized near the footpoints, while they are weaker from the rest of the flaring loop system. This implies that there is no evidence for heating taking place at the top of the loops, but energy is deposited mainly at their base. The spectral analysis of the soft X-ray emission detected with the Bent Crystal Spectrometer evidences an initial phase of the flare, before the impulsive increase in hard X-ray emission, during which most of the thermal plasma at 107 K was moving toward the observer with a mean velocity of about 80 km s-1. At this time the plasma was highly turbulent. In a second phase, in coincidence with the impulsive rise in hard X-ray emission during the major burst, high-velocity (370 km s-1) upward motions were observed. At this time, soft X-rays were still predominantly emitted near the loop footpoints. The energy deposition in the chromosphere by electrons accelerated in the flare region to energies above 25 keV, at the onset of the high-velocity upflows, was of the order of 4 × 1010 erg s-1 cm-2. These observations provide further support for interpreting the plasma upflows as the mechanism responsible for the formation of the soft X-ray flare, identified with chromospheric evaporation. Early in the flare soft X-rays are mainly from evaporating material close to the footpoints, while the magnetically confined coronal region is at lower density. The site where upflows originate is identified with the base of the loop system. Moreover, we can conclude that evaporation occurred in two regimes: an initial slow evaporation, observed as a motion of most of the thermal plasma, followed by a high-speed evaporation lasting as long as the soft X-ray emission of the flare was increasing, that is as long as plasma accumulation was observed in corona. 相似文献
5.
André Duijveman 《Solar physics》1983,84(1-2):189-203
Shortly after the occurrence of the impulsive spikes of the two-ribbon flare of May 21, 1980, a temperature analysis of the X-ray emitting flare plasma showed the presence of a low-temperature component [n = 15 × 1010 cm#X2212;3; T = 20 × 106 K] and a high-temperature component [n = 2 × 1010 cm#X2212;3; T = 40 × 106 K]. The mean free path of an electron in the hot component is comparable to the size of the source (≈ 104 km). Heat losses from the hot source can therefore not be described with classical formulae. Theoretical arguments show that most likely the electron to ion temperature ratio T e/Ti in the hot plasma is close to unity. This implies the presence of a hot ion component (T i ≈ 40 × 106 K) as well. Under these conditions (T e ≈ T i) heat flux limitation by electrostatic turbulence is ineffective. However, reduction of the heat flux is still possible due to the breakdown of classical theory. It is demonstrated that only non-classical current dissipation processes can sustain a hot source against cooling by a saturated heat flux. Investigation of the collisionality as a function of position along a magnetic loop shows that the breakdown of classical theory should be expected to occur first near the base of the loop. We conclude that the newly discovered hot source is important for the energy budget of the flare, even if the heat losses are considerably reduced. It is estimated that for the May 21, 1980 flare a total of about 1031 ergs were necessary to maintain the hot source against heat losses over the time period that it was observed (≈ 10 min). 相似文献
6.
Hard X-ray lightcurves, spectrograms, images, and spectra of three medium-sized flares observed by the Reuven Ramaty High-Energy
Solar Spectroscopic Imager (RHESSI) are presented. Imaging spectroscopy of the 20 February 2002, 11:06 UT flare at 10′′ spatial
resolution, comparable to the best previous hard X-ray imaging from Yohkoh, shows two footpoints with an ∼ 8 s delay of peak emission between footpoints. Subsequent imaging at le4′′ shows three sources consistent with two separate loops and simultaneous brightening in connected footpoints. Imaging for
the simple two footpoint flare of 2 June 2002 also shows simultaneous footpoint brightening. The more complex 17 March 2002
flare shows at least four different sources during the main peak of the event, and it is difficult to clearly demonstrate
simultaneous brightening of connected footpoints. Non-thermal power laws are observed down to ∼ 12–13 keV without flattening
in all these events, indicating the energy content in energetic electrons may be significantly greater than previously estimated
from assumed 25 keV low energy cutoff. Simultaneously brightening footpoints show similar spectra, at least in the three flares
investigated. Double-power-law spectra with a relatively sharp break are often observed.
Supplementary material to this paper is available in electronic form at http://dx.doi.org/10.1023/A:1022469902940 相似文献
7.
An analysis, with a representative (canonical) example of solar-flare-generated equatorial disturbances, is presented for the temporal and spatial changes in the solar wind plasma and magnetic field environment between the Sun and one astronomical unit (AU). Our objective is to search for first order global consequences rather than to make a parametric study. The analysis - an extension of earlier planar studies - considers all three plasma velocity and magnetic field components (V r, Vφ, V0, and B r, B0, Bφ) in any convenient heliospheric plane of symmetry such as the ecliptic plane, the solar equatorial plane, or the heliospheric equatorial plane chosen for its ability (in a tilted coordinate system) to order northern and southern hemispheric magnetic topology and latitudinal solar wind flows. Latitudinal velocity and magnetic field gradients in and near the plane of symmetry are considered to provide higher-order corrections of a specialized nature and, accordingly, are neglected, as is dissipation, except at shock waves. The representative disturbance is examined for the canonical case in which one describes the temporal and spatial changes in a homogeneous solar wind caused by a solar-flare-generated shock wave. The ‘canonical’ solar flare is assumed to produce a shock wave that has a velocity of 1000 km s#X2212;1 at 0.08 AU. We have examined all plasma and field parameters at three radial locations: central meridian and 33° W and 90° W of the flare's central meridian. A higher shock velocity (3000 km s#X2212;1) was also used to demonstrate the model's ability to simulate a strongly-kinked interplanetary field. Among the global (first-order) results are the following: (i) incorporation of a small meridional magnetic field in the ambient magnetic spiral field has negligible effect on the results; (ii) the magnetic field demonstrates strong kinking within the interplanetary shocked flow, even reversed polarity that - coupled with low temperature and low density - suggests a viable explanation for observed ‘magnetic clouds’ with accompanying double-streaming of electrons at directions ～ 90° to the heliocentric radius. 相似文献
8.
A. V. Bogomolov A. P. Ignat’ev K. Kudela S. N. Kuznetsov Yu. I. Logachev O. V. Morozov I. N. Myagkova S. N. Oparin A. A. Pertsov S. I. Svertilov B. Yu. Yushkov 《Astronomy Letters》2003,29(3):199-204
We consider temporal, spectral, and polarization parameters of the hard X-ray and gamma-ray radiation observed during the solar flare of May 20, 2002, in the course of experiments with the SONG and SPR-N instruments onboard the Coronas-F spacecraft. This flare is one of the most intense gamma-ray events among all of the bursts of solar hard electromagnetic radiation detected since the beginning of the Coronas-F operation (since July 31, 2001) and one of the few gamma-ray events observed during solar cycle 23. A simultaneous analysis of the Coronas-F and GOES data on solar thermal X-ray radiation suggests that, apart from heating due to currents of matter in the the flare region, impulsive heating due to the injection of energetic electrons took place during the near-limb flare S21E65 of May 20, 2002. These electrons produced intense hard X-ray and gamma-ray radiation. The spectrum of this radiation extends up to energies ≥7 MeV. Intense gamma-ray lines are virtually unobservable against the background of the nonthermal continuum. The polarization of the hard X-ray (20–100 keV) radiation was estimated to be ≤15–20%. No significant increase in the flux of energetic protons from the flare under consideration was found. At the same time, according to ACE data, the fluxes of energetic electrons in interplanetary space increased shortly (～25 min) after the flare. 相似文献
9.
In this paper, we reconstruct the finite energy force-free magnetic field of the active region NOAA 8100 on 4 November 1997
above the photosphere. In particular, the 3-D magnetic field structures before and after a 2B/X2 flare at 05:58 UT in this
region are analyzed. The magnetic field lines were extrapolated in close coincidence with the Yohkoh soft X-ray (SXR) loops accordingly. It is found that the active region is composed of an emerging flux loop, a complex loop
system with differential magnetic field shear, and large-scale, or open field lines. Similar magnetic connectivity has been
obtained for both instants but apparent changes of the twisting situations of the calculated magnetic field lines can be observed
that properly align with the corresponding SXR coronal loops. We conclude that this flare was triggered by the interaction
of an emerging flux loop and a large loop system with differential magnetic field shear, as well as large-scale, or open field
lines. The onset of the flare was at the common footpoints of several interacting magnetic loops and confined near the footpoints
of the emerging flux loop. The sheared configuration remained even after the energetic flare, as demonstrated by calculated
values of the twist for the loop system, which means that the active region was relaxed to a lower energy state but not completely
to the minimum energy state (two days later another X-class flare occurred in this region). 相似文献
10.
We analyzed the monochromatic Hα and spectral (within a range of 6549–6579 Å) observational data for the 2B/X6.9 flare of August 9, 2011, that produced emission in the optical continuum. The morphology and evolution of the Hα flare and the position, time evolution, spectrum, and energetics of the white-light flare (WLF) kernels were studied. The following results were obtained: the flare erupted in the region of collision of a new and rapidly growing and propagating magnetic flux and a preexisting one. This collision led to a merger of two active bipolar regions. The white-light flare had a complex structure: no less than five kernels of continuum emission were detected prior to and in the course of the impulsive flare phase. Preimpulsive and impulsive white-light emission kernels belonged to different types (types II and I, respectively) of white-light flares. A close temporal agreement between the white-light emission maxima and the microwave emission peak was observed for the impulsive white-light emission kernels. The maximum flux, luminosity, and total energy emitted by the brightest impulsive WLF kernel equaled 1.4 × 1010 ergs cm?2 s?1, 1.5 × 1027 ergs/s, and 5 × 1029 ergs, respectively. The Hα profiles within the impulsive WLF kernels had broad wings (with a total extent of up to 26 Å and a half-width of up to 9 Å) and self-reversed cores. The profiles were symmetrical, but were shifted towards the red side of the spectrum. This is indicative of a downward motion of the entire emitting volume with a radial velocity of several tens of km/s. The intensity pattern in the wings did not correspond to the Stark one. The profiles were broadened by nonthermal turbulent motions with velocities of 150–300 km/s. The observed Hα profiles were analyzed and compared in their features to the profiles calculated for an intense heating of the chromosphere by nonthermal electrons accompanied by the development of a chromospheric condensation propagating downward. We came to the conclusion that the analyzed flare exhibited spectral features that may not be readily explained within the framework of chromosphere heating by a beam of nonthermal electrons. 相似文献
11.
We consider the plasma mechanism of sub-terahertz emission from solar flares and determine the conditions for its realization in the solar atmosphere. The source is assumed to be localized at the chromospheric footpoints of coronal magnetic loops, where the electron density should reach n ≈ 1015 cm?3. This requires chromospheric heating at heights h ? 500 km to coronal temperatures, which provides a high degree of ionization needed for Langmuir frequencies ν p ≈ 200–400 GHz and reduces the bremsstrahlung absorption of the sub-THz emission as it escapes from the source. The plasma wave excitation threshold for electron-ion collisions imposes a constraint on the lower density limit for energetic electrons in the source, n 1 > 4 × 109 cm?3. The generation of emission at the plasma frequency harmonic ν ≈ 2ν p rather than the fundamental tone turns out to be preferred. We show that the electron acceleration and plasma heating in the sub-THz emission source can be realized when the ballooning mode of the flute instability develops at the chromospheric footpoints of a flare loop. The flute instability leads to the penetration of external chromospheric plasma into the loop and causes the generation of an inductive electric field that efficiently accelerates the electrons and heats the chromosphere in situ. We show that the ultraviolet radiation from the heated chromosphere emerging in this case does not exceed the level observed during flares. 相似文献
12.
We study sudden brightenings of coronal loops that interconnect active regions. Such brightenings often occur within one or two days after the birth of a new interconnecting loop, as well as in some old interconnections. The brightenings of young loops are obviously associated with the emergence of new magnetic flux near their footpoints, whereas some enhancements of old loops may be triggered by slowly moving disturbances propagating from other centers of activity. A few loop brightenings are associated with flares, but the loop does not brighten in consequence of energy supply from the flare. Both the flare and the loop brightening are independent consequences of one common agent, presumably newly emerging flux.Temperatures in brightened loops are between 3 and 4 × 106 K and densities are < 2 × 109 cm–3, probably < 5 × 108 cm–3 in some old loops. The top part of a loop is the site of the most intense brightening in the initial phase of a loop enhancement. The most frequent lifetime of these brightenings is 6 to 7 hr.Hale Observatories are operated jointly by the Carnegie Institution of Washington and the California Institute of Technology. 相似文献
13.
A review is given of observations and theories relevant to the solar flare of 21 May, 1980, 20 ∶ 50 UT, the best studied flare on record. For more than 30 hr before the flare there was filament activation and plasma heating to above 10 MK. A flare precursor was present ≥6 min before the flare onset. The flare started with filament activation (20 ∶ 50 UT), followed by thick-target heating of two footpoints and subsequent ablation and convective evaporation involving energies of 1 to 2 × 1031 erg. Coronal explosions occurred at 20 ∶ 57 UT (possibly associated with a type-II burst) and at 21 ∶ 04 UT (associated with an Hα spray?). Post-flare loops were first seen at 20 ∶ 57 UT, and their upward motion is interpreted as a manifestation of successive field-line reconnections. A type-IV radio burst which later changed into a type-I noise storm was related to a giant coronal arch located just below the radio noise storm region. Some implications and difficulties these observations present to current flare theories are mentioned. 相似文献
14.
We have investigated numerically how a temperature difference between electrons and protons is produced in a flaring loop by adopting a one-fluid, two-temperature model instead of a single-temperature model. We have treated a case in which flare energy is released in the form of heating of electrons located in the top part of the loop.In this case, a large temperature difference (T
e/T
p 10) appears in the corona in the energy-input phase of the flare. When the material evaporated from the chromosphere fills the corona, the temperature difference in the loop begins to shrink rapidly from below. Eventually, in the loop apex, the proton temperature exceeds the electron temperature mainly due to cooling of the electrons by conduction down the loop and heating of the protons by compression of the ascending material. In the late phase of the flare (t 15 min from the flare onset), the temperature difference becomes less than 2% of the mean temperature of electrons and protons at every point in the loop. 相似文献
15.
(1) Highly flare-productive new emerging active regions are characterized by numerous small low-lying loops which frequently show a chaotic pattern. (2) Flare activity in such a region subsides as the chaotic loop structures relax and expand into a bipolar configuration. (3) The transition zone in such an active region is highly unstable as shown by broadened and shifted non-thermal line profiles of medium ionized elements like Si iii, Si iv, C iv, etc. (4) These transition zone instabilities which occur as isolated events in active regions of low flare productivity are often observed prior to flares. (5) Transition zone instabilities can be traced to the footpoints of active loops, and seem to be accompanied by heating of the loop. (6) The loops vary in size and show differing degrees of activity, with the brightest and most compact ones seemingly being in a pre-flare state which results in the catastrophic energy release along the loop during a flare. 相似文献
16.
We present an analysis of spacecraft observations of non-thermal X-rays and escaping electrons for 5 selected small solar flares in 1967. OSO-3 multi-channel energetic X-ray measurements during the non-thermal component of the solar flare X-ray bursts are used to derive the parent electron spectrum and emission measure. IMP-4 and Explorer-35 observations of > 22 keV and > 45 keV electrons in the interplanetary medium after the flares provide a measure of the total number and spectrum of the escaping particles. The ratio of electron energy loss due to collisions with the ambient solar flare gas to the energy loss due to bremsstrahlung is derived. The total energy loss due to collisions is then computed from the integrated bremsstrahlung energy loss during the non-thermal X-ray burst. For > 22 keV flare electrons the total energy loss due to collisions is found to be 104 times greater than the bremsstrahlung energy loss and 102 times greater than the energy loss due to escaping electrons. Therefore the escape of electrons into the interplanetary medium is a negligible energetic electron loss mechanism and cannot be a substantial factor in the observed decay of the non-thermal X-ray burst for these solar flares.We present a picture of electron acceleration, energy loss and escape consistent with previous observations of an inverse relationship between rise and decay times of the non-thermal X-ray burst and X-ray energy. In this picture the acceleration of electrons occurs throughout the 10–100 sec duration of the non-thermal X-ray burst and determines the time profile of the burst. The average energy of the accelerated electrons first rises and then falls through the burst. Collisions with the ambient gas provide the dominant energetic electron loss mechanism with a loss time of 1 sec. This picture is consistent with the ratio of the total number of energetic electrons accelerated in the flare to the maximum instantaneous number of electrons in the flare region. Typical values for the parameters derived from the X-ray and electron observations are: total energy in > 22 keV electrons total energy lost by collisions = 1028–29 erg, total number of electrons accelerated above 22 keV = 1036, total energy lost by non-thermal bremsstrahlung = 1024erg, total energy lost in escaping > 22 keV electrons = 1026erg, total number of > 22 keV electrons escaping = 1033–34.The total energy in electrons accelerated above 22 keV is comparable to the energy in the optical or quasi-thermal flare, implying a flare mechanism with particle acceleration as one of the dominant modes of energy dissipation.The overall efficiency for electron escape into the interplanetary medium is 0.1–1% for these flares, and the spectrum of escaping electrons is found to be substantially harder than the X-ray producing electrons.Currently at Tokyo Astronomical Observatory, Mitaka, Tokyo, Japan. 相似文献
17.
The M7.7 solar flare of July 19, 2012, at 05:58 UT was observed with high spatial, temporal, and spectral resolutions in the hard X-ray and optical ranges. The flare occurred at the solar limb, which allowed us to see the relative positions of the coronal and chromospheric X-ray sources and to determine their spectra. To explain the observations of the coronal source and the chromospheric one unocculted by the solar limb, we apply an accurate analytical model for the kinetic behavior of accelerated electrons in a flare. We interpret the chromospheric hard X-ray source in the thick-target approximation with a reverse current and the coronal one in the thin-target approximation. Our estimates of the slopes of the hard X-ray spectra for both sources are consistent with the observations. However, the calculated intensity of the coronal source is lower than the observed one by several times. Allowance for the acceleration of fast electrons in a collapsing magnetic trap has enabled us to remove this contradiction. As a result of our modeling, we have estimated the flux density of the energy transferred by electrons with energies above 15 keV to be ～5 × 1010 erg cm?2 s?1, which exceeds the values typical of the thick-target model without a reverse current by a factor of ～5. To independently test the model, we have calculated the microwave spectrum in the range 1–50 GHz that corresponds to the available radio observations. 相似文献
18.
The problem of hydrodynamic response of the solar chromosphere on impulsive heating by energetic electrons is discussed. All basic physical processes are considered in a one-dimensional approximation, due to presence of a strong magnetic field. The calculations are performed for the heating of the chromosphere by electrons having a power-law energetic spectrum. In the upper chromosphere the electron temperature rises rapidly to values of order 107 K. The ion temperature is more than the order of magnitude less than the temperature of electrons. The heated high-temperature chromospheric plasma expands into corona with a velocity up to 1500 km s–1. In more dense layers, the fast re-emission of supplied energy takes place. This process gives rise to short-lived EUV flash. Just below the flare transition layer the thermal instability produces cold plasma condensation which moves downward at a velocity exceeding the sonic one in the quiet chromosphere. 相似文献
19.
《New Astronomy》2020
In this study, investigated 14,786 coronal mass ejection (CME) events and 5092 Gamma-ray Burst Monitor (GBM) solar flare events (called γ-ray burst solar flare) recorded during 2008–2017, by using temporal and spatial conditions criteria, we found 845 (about 16%) CME events associated with γ-ray burst solar flare events only (hereafter, CME–γ-preflare). All the 845 events are associated with solar flares that are detected in both GBM and RHESSI simultaneously. Investigating the characteristics of these events, we found that the best time interval is 0–2 h before the flare's start time. The mean time interval for these CME–γ-preflare associated events is 61 min, with the flare's duration mean value of 12 min, which is greater than non-associated γ-ray solar flare's duration. CME width of CME-γ-preflare associated events 64° is slightly wider and slightly faster (remain lower than solar wind's speed) than non-associated CME 53°. 相似文献
20.
It is proposed that the solar flare phenomenon can be understood as a manifestation of the electrodynamic coupling process of the photosphere-chromosphere-corona system as a whole. The system is coupled by electric currents, flowing along (both upward and downward) and across the magnetic field lines, powered by the dynamo process driven by the neutral wind in the photosphere and the lower chromosphere. A self-consistent formulation of the proposed coupling system is given. It is shown in particular that the coupling system can generate and dissipate the power of 1029 erg s#X2212;1 and the total energy of 1032 erg during a typical life time (103 s) of solar flares. The energy consumptions include Joule heat production, acceleration of current-carrying particles along field lines, magnetic energy storage and kinetic energy of plasma convection. The particle acceleration arises from the development of field-aligned potential drops of 10–150 kV due to the loss-cone constriction effect along the upward field-aligned currents, causing optical, X-ray and radio emissions. The total number of precipitating electrons during a flare is shown to be of order 1037–1038. 相似文献