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1.
The propagation and modulation of electrons in the heliosphere play an important part in improving our understanding and assessment of the modulation processes. A full three-dimensional numerical model is used to study the modulation of galactic electrons, from Earth into the inner heliosheath, over an energy range from 10 MeV to 30 GeV. The modeling is compared with observations of 6–14 MeV electrons from Voyager 1 and observations at Earth from the PAMELA mission. Computed spectra are shown at different spatial positions. Based on comparison with Voyager 1 observations, a new local interstellar electron spectrum is calculated. We find that it consists of two power-laws: In terms of kinetic energy E, the results give E ?1.5 below ～500 MeV and E ?3.15 at higher energies. Radial intensity profiles are computed also for 12 MeV electrons, including a Jovian source, and compared to the 6–14 MeV observations from Voyager 1. Since the Jovian and galactic electrons can be separated in the model, we calculate the intensity of galactic electrons below 100 MeV at Earth. The highest possible differential flux of galactic electrons at Earth with E=12 MeV is found to have a value of 2.5×10?1 electrons m?2?s?1?sr?1?MeV?1 which is significantly lower (a factor of 3) than the Jovian electron flux at Earth. The model can also reproduce the extraordinary increase of electrons by a factor of 60 at 12 MeV in the inner heliosheath. A lower limit for the local interstellar spectrum at 12 MeV is estimated to have a value of (90±10) electrons m?2?s?1?sr?1?MeV?1.  相似文献   

2.
Flux ropes ejected from the Sun may change their geometrical orientation during their evolution, which directly affects their geoeffectiveness. Therefore, it is crucial to understand how solar flux ropes evolve in the heliosphere to improve our space-weather forecasting tools. We present a follow-up study of the concepts described by Isavnin, Vourlidas, and Kilpua (Solar Phys. 284, 203, 2013). We analyze 14 coronal mass ejections (CMEs), with clear flux-rope signatures, observed during the decay of Solar Cycle 23 and rise of Solar Cycle 24. First, we estimate initial orientations of the flux ropes at the origin using extreme-ultraviolet observations of post-eruption arcades and/or eruptive prominences. Then we reconstruct multi-viewpoint coronagraph observations of the CMEs from ≈?2 to 30 R⊙ with a three-dimensional geometric representation of a flux rope to determine their geometrical parameters. Finally, we propagate the flux ropes from ≈?30 R⊙ to 1 AU through MHD-simulated background solar wind while using in-situ measurements at 1 AU of the associated magnetic cloud as a constraint for the propagation technique. This methodology allows us to estimate the flux-rope orientation all the way from the Sun to 1 AU. We find that while the flux-ropes’ deflection occurs predominantly below 30 R⊙, a significant amount of deflection and rotation happens between 30 R⊙ and 1 AU. We compare the flux-rope orientation to the local orientation of the heliospheric current sheet (HCS). We find that slow flux ropes tend to align with the streams of slow solar wind in the inner heliosphere. During the solar-cycle minimum the slow solar-wind channel as well as the HCS usually occupy the area in the vicinity of the solar equatorial plane, which in the past led researchers to the hypothesis that flux ropes align with the HCS. Our results show that exceptions from this rule are explained by interaction with the Parker-spiraled background magnetic field, which dominates over the magnetic interaction with the HCS in the inner heliosphere at least during solar-minimum conditions.  相似文献   

3.
Using the STEERB (storm-time evolution of electron radiation belt) code, we simulate the evolution of radiation belt energetic electrons during geomagnetic storms in the case of low energy electron injection. The STEERB code is used to solve the three-dimensional Fokker–Planck diffusion equation which incorporates wave-particle interaction, Coulomb collisions and radial diffusion. Numerical simulations show that under the short time (～1 h) injection of low energy (0.1 MeV≤E k ≤0.2 MeV) fluxes of radiation belt energetic electrons can increase during the entire storm period. During the main and recovery phases, such injection efficiently enhances chorus-driven acceleration of radiation belt energetic electrons, allowing fluxes of energetic electrons by a factor of 1–2 orders higher than those in the absence of injection. The current results indicate that substorm-induced electron injection must be incorporated to investigate the evolution of radiation belt energetic electrons.  相似文献   

4.
Langmuir waves (LWs), which are believed to play a crucial role in the plasma emission of solar radio bursts, can be excited by streaming instability of energetic electron beams. However, solar hard X-ray observations imply that the energetic flare electrons usually have a power-law energy distribution with a lower energy cutoff. In this paper, we investigate LWs driven by the power-law electrons. The results show that power-law electrons with the steepness cutoff behavior can excite LWs effectively because of the population inversion distribution below the cutoff energy (E c ). The growth rate of LWs increases with the steepness index (δ) and decreases with the power-law index (α). The wave number of the fastest growing LWs (kλ D ), decreases with the characteristic velocity of the power-law electrons ( \(v_{c}=\sqrt{2E_{c}/m_{e}}\) ) and increases with the thermal velocity of ambient electrons (v T ). This can be helpful for us to understand better the physics of LWs and the dynamics of energetic electron beams in space and astrophysical plasmas.  相似文献   

5.
A full three-dimensional, numerical model is used to study the modulation of Jovian and Galactic electrons from 1 MeV to 50 GeV, and from the Earth into the heliosheath. For this purpose the very local interstellar spectrum and the Jovian electron source spectrum are revisited. It is possible to compute the former with confidence at kinetic energies \(E < 50~\mbox{MeV}\) since Voyager 1 crossed the heliopause in 2012 at \(\sim 122~\mbox{AU}\), measuring Galactic electrons at these energies. Modeling results are compared with Voyager 1 observations in the outer heliosphere, including the heliosheath, as well as observations at or near the Earth from the ISSE3 mission, and in particular the solar minimum spectrum from the PAMELA space mission for 2009, also including data from Ulysses for 1991 and 1992, and observations above 1 MeV from SOHO/EPHIN. Making use of the observations at or near the Earth and the two newly derived input functions for the Jovian and Galactic electrons respectively, the energy range over which the Jovian electrons dominate the Galactic electrons is determined so that the intensity of Galactic electrons at Earth below 100 MeV is calculated. The differential intensity for the Galactic electrons at Earth for \(E = 1~\mbox{MeV}\) is \(\sim 4\) electrons \(\mbox{m}^{-2}\,\mbox{s}^{-1}\,\mbox{sr}^{-1}\,\mbox{MeV}^{-1}\), whereas for Jovian electrons it is \(\sim 350\) electrons \(\mbox{m}^{-2}\,\mbox{s}^{-1}\,\mbox{sr}^{-1}\,\mbox{MeV}^{-1}\). At \(E = 30~\mbox{MeV}\) the two intensities are the same; above this energy the Jovian electron intensity quickly subsides so that the Galactic intensity completely dominates. At 6 MeV, in the equatorial plane the Jovian electrons dominate but beyond \(\sim 15~\mbox{AU}\) the Galactic intensity begins to exceed the Jovian intensity significantly.  相似文献   

6.
The 5 July 2012 solar flare SOL2012-07-05T11:44 (11:39?–?11:49 UT) with an increasing millimeter spectrum between 93 and 140 GHz is considered. We use space and ground-based observations in X-ray, extreme ultraviolet, microwave, and millimeter wave ranges obtained with the Reuven Ramaty High-Energy Solar Spectroscopic Imager, Solar Dynamics Observatory (SDO), Geostationary Operational Environmental Satellite, Radio Solar Telescope Network, and Bauman Moscow State Technical University millimeter radio telescope RT-7.5. The main parameters of thermal and accelerated electrons were determined through X-ray spectral fitting assuming the homogeneous thermal source and thick-target model. From the data of the Atmospheric Imaging Assembly/SDO and differential-emission-measure calculations it is shown that the thermal coronal plasma gives a negligible contribution to the millimeter flare emission. Model calculations suggest that the observed increase of millimeter spectral flux with frequency is determined by gyrosynchrotron emission of high-energy (\(\gtrsim 300\) keV) electrons in the chromosphere. The consequences of the results are discussed in the light of the flare-energy-release mechanisms.  相似文献   

7.
Multi-spacecraft observations are used to study the in-situ effects of a large coronal mass ejection (CME) erupting from the farside of the Sun on 3 November 2011, with particular emphasis on the associated solar energetic particle (SEP) event. At that time both Solar Terrestrial Relations Observatory (STEREO) spacecraft were located more than 90 degrees from Earth and could observe the CME eruption directly, with the CME visible on-disk from STEREO-B and off the limb from STEREO-A. Signatures of pressure variations in the corona such as deflected streamers were seen, indicating the presence of a coronal shock associated with this CME eruption. The evolution of the CME and an associated extreme-ultraviolet (EUV) wave were studied using EUV and coronagraph images. It was found that the lateral expansion of the CME low in the corona closely tracked the propagation of the EUV wave, with measured velocities of 240±19 km?s?1 and 221±15 km?s?1 for the CME and wave, respectively. Solar energetic particles were observed to arrive first at STEREO-A, followed by electrons at the Wind spacecraft at L1, then STEREO-B, and finally protons arrived simultaneously at Wind and STEREO-B. By carrying out a velocity-dispersion analysis on the particles arriving at each location, it was found that energetic particles arriving at STEREO-A were released first and that the release of particles arriving at STEREO-B was delayed by about 50 minutes. Analysis of the expansion of the CME to a wider longitude range indicates that this delay is a result of the time taken for the CME edge to reach the footpoints of the magnetic-field lines connected to STEREO-B. The CME expansion is not seen to reach the magnetic footpoint of Wind at the time of solar-particle release for the particles detected here, suggesting that these particles may not be associated with this CME.  相似文献   

8.
A three-dimensional (3D) tomographic reconstruction of the local differential emission measure (LDEM) of the global solar corona during the whole heliosphere interval (WHI, Carrington rotation CR 2068) is presented, based on STEREO/EUVI images. We determine the 3D distribution of the electron density, mean temperature, and temperature spread, in the range of heliocentric heights 1.03 to 1.23 R ??. The reconstruction is complemented with a potential-field source-surface (PFSS) magnetic-field model. The streamer-core, streamer-leg, and subpolar regions are analyzed and compared to a similar analysis previously performed for CR 2077, very near the absolute minimum of Solar Cycle 23. In each region, the typical values of density and temperature are similar in both periods. The WHI corona exhibits a streamer structure of relatively smaller volume and latitudinal extension than during CR 2077, with a global closed-to-open density contrast about 6% lower, and a somewhat more complex morphology. The average basal electron density is found to be about 2.23 and 1.08×108 cm?3, in the streamer core and subpolar regions, respectively. The electron temperature is quite uniform over the analyzed height range, with average values of about 1.13 and 0.93 MK, in the streamer core and subpolar regions, respectively. Within the streamer closed region, both periods show higher temperatures at mid-latitudes and lower temperatures near the Equator. Both periods show ??>1 in the streamer core and ??<1 in the surrounding open regions, with CR 2077 exhibiting a stronger contrast. Hydrostatic fits to the electron density are performed, and the scale height is compared to the LDEM mean electron temperature. Within the streamer core, the results are consistent with an isothermal hydrostatic plasma regime, with the temperatures of ions and electrons differing by up to about 10%. In the subpolar open regions, the results are consistent with departures from thermal equilibrium with T ions>T e (and values of T ions/T e up to about 1.5), and/or the presence of wave-pressure mechanisms linear in the density.  相似文献   

9.
Counterstreaming beams of electrons are ubiquitous in coronal mass ejections (CMEs) – although their existence is not unanimously accepted as a necessary and/or sufficient signature of these events. We continue the investigation of a high-latitude CME registered by the Ulysses spacecraft on 18?–?19 January 2002 (Dumitrache, Popescu, and Oncica, Solar Phys. 272, 137, 2011), by surveying the solar-wind electron distributions associated with this event. The temporal evolution of the pitch-angle distributions reveals populations of electrons that are distinguishable through their anisotropy, with clear signatures of i) electron strahls, ii) counter-streaming in the magnetic clouds and their precursors, and iii) unidirectionality in the fast wind preceding the CME. The analysis of the counter-streams inside the CME allows us to elucidate the complexity of the magnetic-cloud structures embedded in the CME and to refine the borders of the event. Identifying such strahls in CMEs, which preserve properties of the low β [<1] coronal plasma, gives more support to the hypothesis that these populations are remnants of the hot coronal electrons that escape from the electrostatic potential of the Sun into the heliosphere.  相似文献   

10.
The deposition of energetic electrons in Jupiter's upper atmosphere provides a means, via auroral observations, of monitoring electron and plasma wave activity within the magnetosphere. Not only does particle precipitation indicate a potential change in atmospheric chemistry, it allows for the study of episodic, pronounced flux enhancements in the energetic electron population. A study has been made of the effects of such electron injections into the jovian magnetosphere and of their ability to provide the source population for variations in diffuse auroral emissions. To identify the source region of precipitating auroral electrons, we have investigated the pitch-angle distributions of high-resolution Galileo Energetic Particle Detector (EPD) data that indicate strong flux levels near the loss cone. The equatorial source region of precipitating electrons has been determined from the locations of Galileo's in situ measurements by tracing magnetic field lines using the KK97 model. The primary source region for Jupiter's diffuse aurora appears to lie in the magnetic equator at 15-40 RJ, with the predominant contribution to precipitation flux (tens of ergs cm−2 s−1 sr−1) stemming from <30 RJ. Variability of flux for energetic electrons in this region is also important to the irradiation of surfaces and atmospheres for the Galilean moons: Europa, Ganymede, and Callisto. The average diffuse auroral precipitation flux has been shown to vary by as much as a factor of six at a given radial location. This variability appears to be associated with electron injection events that have been identified in high-resolution Galileo EPD data. These electron flux enhancements are also associated with increased whistler-mode wave activity and magnetic field perturbations, as detected by the Galileo Plasma Wave Subsystem (PWS) and Magnetometer (MAG), respectively. Resonant interactions with the whistler-mode waves cause electron pitch-angle scattering and lead to pitch-angle isotropization and precipitation.  相似文献   

11.
Based on data from the SONG and SPR-N multichannel hard electromagnetic radiation detectors onboard the CORONAS-F space observatory and the X-ray monitors onboard GOES satellites, we have distinguished the thermal and nonthermal components in the X-ray spectrum of an extreme solar flare on January 20, 2005. In the impulsive flare phase determined from the time of the most efficient electron and proton acceleration, we have obtained parameters of the spectra for both components and their variations in the time interval 06:43–06:54 UT. The spectral index in the energy range 0.2–2 MeV for a single-power-law spectrum of accelerated electrons is shown to have been close to 3.4 for most of the time interval under consideration. We have determined the time dependence of the lower energy cutoff in the energy spectrum of nonthermal photons E γ0(t) at which the spectral flux densities of the thermal and nonthermal components become equal. The power deposited by accelerated electrons into the flare volume has been estimated using the thick-target model under two assumptions about the boundary energy E 0 of the electron spectrum: (i) E 0 is determined by E γ0(t) and (ii) E 0 is determined by the characteristic heated plasma energy (≈5kT (t)). The reality of the first assumption is proven by the fact that plasma cooling sets in at a time when the radiative losses begin to prevail over the power deposited by electrons only in this case. Comparison of the total energy deposited by electrons with a boundary energy E γ0(t) with the thermal energy of the emitting plasma in the time interval under consideration has shown that the total energy deposited by accelerated electrons at the beginning of the impulsive flare phase before 06:47 UT exceeds the thermal plasma energy by a factor of 1.5–2; subsequently, these energies become approximately equal and are ～(4–5) × 1030 erg under the assumption that the filling factor is 0.5–0.6.  相似文献   

12.
The Solar Electron and Proton Telescope (SEPT) aboard the Solar Terrestrial Relations Observatory (STEREO) is designed to provide the three-dimensional distribution of energetic electrons and protons with good energy and time resolution. Each SEPT instrument consists of two double-ended magnet–foil particle telescopes which cleanly separate and measure electrons in the energy range from 30 keV to 400 keV and protons from 60 keV to 7000 keV. Anisotropy information on a non-spinning spacecraft is provided by two separate but identical instruments: SEPT-E aligned along the Parker spiral magnetic field in the ecliptic plane looking both towards and away from the Sun, and SEPT-NS aligned vertical to the ecliptic plane looking towards North and South. The dual set-up refers to two adjacent sensor apertures for each of the four viewing directions SUN, ANTISUN, NORTH, and SOUTH: one for protons, one for electrons. In this contribution a simulation of SEPT utilizing the GEANT4 toolkit has been set up with an extended instrument model in order to calculate improved response functions of the four different telescopes. Here we applied these response functions to quiet-time periods during the minimum between Solar Cycles 23 and 24 (SC-23 and SC-24) when the flux of ions above 10 MeV is dominated by galactic cosmic rays (GCRs). The corresponding spectra are determined by a force-field approximation and used as input for our calculation, leading to good agreement of the computed ion count rates with measurements of SEPT above 400 keV.  相似文献   

13.
The relationship between the X-ray flux and the radio flux from cosmic objects is investigated. We consider the emission from energetic electrons on the condition in which a plasma and a magnetic field exist. As energetic electrons under the circumstances emit both X-rays by the bremsstrahlung mechanism and radio waves by the gyrosynchrotron mechanism simultaneously, it is shown that the radio flux density is closely related to the X-ray flux density. Solving an integral equation describing the X-ray flux density at Earth, we obtain the energy spectrum of electrons in the emitting region. Inserting the result into equation of the radio flux density at Earth, we obtain the direct formula between the X-ray flux density and the radio flux density. The relation is independent of the distance between Earth and cosmic sources. Assuming a power-law X-ray spectrum, we evaluate the numerical relation between two flux densities.  相似文献   

14.
We report an observation of the radial profile of a Pc5 magnetic pulsation and the associated energetic electron flux oscillations from 10 to 18 Re, recorded by the IMP-5 satellite at 19.00 M.L.T. on 21 March 1970. The Pc5 pulsation was mainly compressional and occurred during extremely quiet geomagnetic conditions. Fluxes of energetic electrons detected above three energy thresholds (18, 45, and 80 keV) were found to oscillate out of phase with magnetic field intensity. One new result is that both the wave amplitude and the wave period increased with radial distance. Second, the electron flux oscillation amplitude was roughly proportional to magnetic field fluctuation amplitude and wave period. The wave event is found to be interpreted better as an ion drift wave because of lack of polarization reversal. The characteristics of energetic electron flux oscillations are shown to agree qualitatively with theoretical calculations of the kinetic perturbation of distribution functions by compressional waves.  相似文献   

15.
Simultaneous measurements of keV ions and electrons with the ESRO 1A satellite have shown the following ion characteristics among others. Ions of about 6 keV energy are strongly field-aligned on the flanks of the inverted V events (mainly through the disappearance of the ion flux near 90° pitch angle). Field-aligned electron fluxes are often found in the same regions of the inverted V events where the ions are field-aligned. At the centre of inverted V events isotropization occurs (except in some small events). The 1 keV ion flux at large pitch angles (80°) is generally not reduced very much when the 6 keV, 80° ion flux shows strongly decreased values. The ratio of the 1 to 6 keV ion flux has a maximum near the centre of an inverted V event where the electron spectrum is hardest and the 6 keV ions are isotropic (or nearly isotropic).The observations are interpreted in terms of a model with two oppositely directed field-aligned electrostatic potential drops: one upper accelerating electrons downward and one lower, produced by the electron influx, which accelerates ions downward. Ion scattering in turbulent wave fields is proposed to be responsible for the observation that the 1 keV ion flux at large pitch angles does not decrease strongly where the 6 keV ion flux does and as an explanation of the isotropization at the centre of the event. The source problem for the ions is eliminated by the precipitating electrons ionizing continuously the thin neutral atmosphere even at altitudes of a few thousand kilometers.  相似文献   

16.
Simnett  G.M. 《Solar physics》2003,213(2):387-412
In 2001 the Ulysses spacecraft crossed the ecliptic plane near perihelion. The heliographic longitude with respect to the Earth was within ±20° of the west solar limb while it was ±15° of the ecliptic plane, which meant that coronal mass ejections seen off the solar west limb were likely to pass over Ulysses. On 10 May the largest >38 keV electron intensity of the mission, since the Jovian encounter in 1992, was observed, which was accompanied by a fast perpendicular shock. This event was preceded by a fast coronal mass ejection some two and a half days earlier which is the probable source of the shock. However, both the ACE spacecraft and Ulysses observed, simultaneously, an intense, prompt electron event on 7 May from a solar flare associated with earlier coronal mass ejections also observed off the west limb; Ulysses was magnetically connected to a longitude well behind the west limb. ACE did not observe any (at the 0.1% level) energetic electrons which were associated with the 10 May event seen at Ulysses. We discuss in detail the energetic particles seen at the two spacecraft during 7–11 May, with the objective of understanding the origin of the intense electron event seen on 10 May and the manner in which particles escaping from the shock populate the inner heliosphere. The energy spectrum of the ions at both ACE and Ulysses exhibits a maximum at around 400 keV; this form of the spectrum was seen at the shock itself. It appears that the strong shock driven by the fast coronal mass ejection is able to populate a large fraction of the inner heliosphere with accelerated ions. The shock-accelerated electrons do not pervade the inner heliosphere in the same manner as the ions. We suggest that the electron acceleration was enhanced by the presence of multiple coronal mass ejections.  相似文献   

17.
The angular distribution of electrons accelerated in solar flares is a key parameter in the understanding of the acceleration and propagation mechanisms that occur there. However, the anisotropy of energetic electrons is still a poorly known quantity, with observational studies producing evidence for an isotropic distribution and theoretical models mainly considering the strongly beamed case. We use the effect of photospheric albedo to infer the pitch-angle distribution of X-ray emitting electrons using Hard X-ray data from RHESSI. A bi-directional approximation is applied and a regularised inversion is performed for eight large flare events to deduce the electron spectra in both downward (towards the photosphere) and upward (away from the photosphere) directions. The electron spectra and the electron anisotropy ratios are calculated for a broad energy range, from about ten up to ～?300 keV, near the peak of the flares. The variation of electron anisotropy over short periods of time lasting 4, 8 and 16 seconds near the impulsive peak has been examined. The results show little evidence for strong anisotropy and the mean electron flux spectra are consistent with the isotropic electron distribution. The 3σ level uncertainties, although energy and event dependent, are found to suggest that anisotropic distribution with anisotropy larger than ～?three are not consistent with the hard X-ray data. At energies above 150?–?200 keV, the uncertainties are larger and thus the possible electron anisotropies could be larger.  相似文献   

18.
Energetic solar electrons in the interplanetary medium   总被引：3，自引：0，他引：3  
R. P. Lin 《Solar physics》1985,100(1-2):537-561
ISEE-3 measurements extending down to 2 keV energy have provided a new perspective on energetic solar electrons in the interplanetary medium. Impulsive solar electron events are observed, on average, several times a day near solar maximum, with 40% detected only below 15 keV. The electron energy spectra have a nearly power-law shape extending smoothly down to 2 keV, indicating that the origin of these events is high in the corona. These coronal flare-like events often produced 3He-rich particle events.In large solar flares which accelerate electrons and ions to relativistic energies, the electron spectrum appears to be modified by a second acceleration which results in a double power-law shape above 10 keV with a break near 100 keV and flattening from 10–100 keV. Large flares result in long-lived (many days) streams of outflowing electrons which dominate the interplanetary fluxes at low energies. Even in the absence of solar activity, significant fluxes of low energy electrons flow out from the Sun.Solar type-III radio bursts are produced by the escaping 2–102 keV electrons through a beam-plasma instability. The detailed ISEE-3 measurements show that electron plasma waves are generated by the bump-on-tail distribution created by the faster electrons running ahead of the slower ones. These plasma waves appear to be converted into radio emission by nonlinear wave-wave interactions.  相似文献   

19.
B. Li  Iver H. Cairns 《Solar physics》2014,289(3):951-976
Detailed simulations based on quasi-linear theory are presented for fundamental ( $f_{\rm p}$ ) emission of type III bursts produced in non-Maxwellian, suprathermal, background coronal plasma by injection of energetic electrons during flares with a power-law or Maxwellian velocity distribution, where $f_{\rm p}$ is the electron plasma frequency. The background plasma is assumed to have a kappa (κ) distribution, as inferred from solar wind data and proposed by theories for the corona and solar wind. The predicted type III beam speeds, Langmuir wave levels, and the drift rate and flux of $f_{\rm p}$ emission are strongly sensitive to the presence of suprathermal background electrons in the corona. The simulations show the following results. i) Fast beams with speeds $v_{\rm b}>0.5c$ are produced for coronal background electrons with small κ (κ?5) by injected electrons with power-law spectra. ii) Moderately fast beams with $v_{\rm b} \approx0.3\,\mbox{--}\,0.5c$ are generated in coronal plasma with κ?8 by injections of power-law or Maxwellian electrons. iii) Slow beams with $v_{\rm b}<0.3c$ are produced for coronal background electrons with large κ (κ>8), including the asymptotic limit κ→∞ where the electrons are Maxwellian, for both power-law and Maxwellian injections. The observation of fast type III beams (with $v_{\rm b}>0.5c$ ) thus suggests that these beams are produced in coronal regions where the background electron distribution has small κ by injected electrons with power-law spectra, at least when such beams are observed. The simulations, from the viewpoint of type III bursts, thus support: i) the presence, at least sometimes, of suprathermal background electrons in the corona and the associated mechanisms for coronal heating and solar wind acceleration; ii) power-law spectra for injected energetic electrons, consistent with observations of such electrons in situ and of X-ray emission.  相似文献   

20.
We present the analysis of a large solar near-relativistic electron event observed by the Ulysses and the ACE spacecraft on 8 November 2000, when Ulysses was located at a heliocentric distance of 2.4 AU and at a heliographic latitude of ??80° S. We use a particle propagation model to infer the local interplanetary transport conditions and the injection histories of the near-relativistic electrons observed by both spacecraft. We find different local transport conditions for each set of observations. The inferred injection profiles for both spacecraft extend for several hours; but the injection at Ulysses was smaller and started later. The association with type II radio emission suggests that the heliospheric electrons were provided by coronal shock acceleration. An analysis of the in situ magnetic field and plasma measurements indicates that the global configuration of the heliosphere (disturbed by transient structures) could play a role in shaping the characteristics of solar energetic particle events observed from different locations.  相似文献   

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