Direction-finding measurements of type III radio bursts out of the ecliptic plane     

Mark M. Baumback  William S. Kurth  Donald A. Gurnett 《Solar physics》1976,48(2):361-380

Direction-finding measurements with the plasma wave experiments on the HAWKEYE 1 and IMP 8 satellites are used to find the source locations of type III solar radio bursts in heliocentric latitude and longitude in a frequency range from 31.1 kHz to 500 kHz. IMP 8 has its spin axis perpendicular to the ecliptic plane; hence, by analyzing the spin modulation of the received signals the location of the type III burst projected into the ecliptic plane can be found. HAWKEYE 1 has its spin axis nearly parallel to the ecliptic plane; hence, the location of the source out of the ecliptic plane may also be determined. Using an empirical model for the emission frequency as a function of radial distance from the sun the three-dimensional trajectory of the type III radio source can be determined from direction-finding measurements at different frequencies. Since the electrons which produce these radio emissions follow the magnetic field lines from the Sun these measurements provide information on the three-dimensional structure of the magnetic field in the solar wind. The source locations projected into the ecliptic plane follow an Archimedean spiral. Perpendicular to the ecliptic plane the source locations usually follow a constant heliocentric latitude. When the best fit magnetic field line through the source locations is extrapolated back to the Sun this field line usually originates within a few degrees from the solar flare which produced the radio burst. With direction-finding measurements of this type it is also possible to determine the source size from the modulation factor of the received signals. For a type III event on June 8, 1974, the half angle source size was measured to be 60° at 500 kHz and 40° at 56.2 kHz as viewed from the Sun.Presented at Workshop on Mechanisms for Solar Type III Radio Bursts, Berkeley, California, May 8–9, 1975; see Solar Phys. 46, 433.  相似文献   

Radio observations of interplanetary magnetic field structures out of the ecliptic     

R. J. Fitzenreiter  J. Fainberg  R. R. Weber  H. Alvarez  F. T. Haddock  W. H. Potter 《Solar physics》1977,52(2):477-484

New observations of the out-of-the ecliptic trajectories of type III solar radio bursts have been obtained from simultaneous direction finding measurements on two independent satellite experiments, IMP-6 with spin plane in the ecliptic, and RAE-2 with spin plane normal to the ecliptic. Burst exciter trajectories were observed which originated at the active region and then crossed the ecliptic plane at about 0.8 AU. We find a considerable large scale north-south component of the interplanetary magnetic field followed by the exciters. The apparent north-south and east-west angular source sizes observed by the two spacecraft are approximately equal, and range from 25° at 600 kHz to 110° at 80 kHz.  相似文献   

Correlation of solar wind velocity with λ 5303 coronal intensity     

P. N. Pathak 《Solar physics》1971,20(2):462-473

Using solar wind velocity data obtained by Mariner-2 and IMP-1 spacecrafts, an attempt has been made to study its correlation with 5303 coronal intensity. It is shown that the long-lasting regions of enhanced 5303 intensity in the solar corona are well correlated with recurrent streams of solar wind having high velocity. The time-lag between the central meridian passage (CMP) of the coronal features and the detection of the solar wind streams at the spacecraft is found to be smaller than that implied by a radial solar wind. Significant positive correlations for Mariner-2 data are obtained for coronal intensity at heliolatitudes 5°S–10°N with a time-lag of + 2 days while for IMP-1 data, high positive correlations are obtained for the southern heliolatitudes (10°–25°S) without any time-lag. It should be noted that the average heliographic latitudes for Mariner-2 and IMP-1 were 4°N and 4°S respectively during the periods covered by the present analysis. The implications of the results are discussed.Presented at IUCSTP Symposium on Solar-Terrestrial Physics, Leningrad, May 1970.  相似文献   

In situ acceleration and gradients of charged particles in the outer solar system observed by the voyager spacecraft     

S. M. Krimigis  D. Venkatesan 《Astrophysics and Space Science》1988,144(1-2):463-486

The probable connection between cosmic rays and the electromagnetic state of the interplanetary medium was recognized by Hannes Alfvén as early as 1949 (Alfvén, 1949, 1950); he pointed out that the properties of cosmic rays necessitate a mechanism, external to Earth but within the solar system, capable of accelerating particles to extremely high energies. In advocating the view of local origin for part of the cosmic-ray spectrum, Alfvén and his colleagues developed a very general type of acceleration mechanism called magnetic pumping. The unique data set of the two Voyagers extends over an entire decade (1977–1987) and is most suitable to explore the problem of acceleration of charged particles in the heliosphere. The energy coverage of the Low Energy Charged Particle (LECP) experiment covers the range 30 keV to several hundred MeV for ions and 22 keV to several MeV for electrons. Selected observations of interplanetary acceleration events from 1 to 25 AU are presented and reviewed. These show frequent acceleration of ions to several tens of MeV in association with shocks; highest energies (220 MeV oxygen) were measured in the near-perpendicular ( _Bn 87.5°) shock of January 5, 1978 at 1.9 AU, where electron acceleration was also observed. Examples of ion acceleration in association with corotating interaction regions are presented and discussed. It is shown that shock structures have profound effects on high-energy (70 MeV) cosmic rays, especially during solar minimum, when a negative latitudinal gradient was observed after early 1985 at all energies from 70 MeV down to 30 keV. By early 1987, most shock acceleration activity in the outer heliosphere (25 to 30 AU) had ceased both in the ecliptic (Voyager-2) and at higher (30°) ecliptic latitudes (Voyager-1). The totality of observations demonstrate that local acceleration to a few hundred MeV, and as high as a few GeV is continually present throughout the heliosphere. It should be noted that in 1954 when Alfvén suggested local acceleration and containment of cosmic rays within the solar system, no one treated his suggestion seriously, at any energy. The observations reviewed in this paper illustrate once more Alfvén's remarkable prescience and demonstrate how unwise it is to dismiss his ideas.Paper dedicated to Professor Hannes Alfvén on the occasion of his 80th birthday, 30 May 1988.  相似文献   

Comet Hyakutake (C/1996 B2): Spectacular disconnection event and the latitudinal structure of the solar wind     

M Snow  J.C Brandt  C.C Petersen  H Mikuz 《Planetary and Space Science》2004,52(4):313-323

Images of comet Hyakutake (C/1996 B2) are analyzed in conjunction with solar wind data from spacecraft to determine the relationship between solar wind conditions and plasma tail morphology. The disconnection event (DE) on March 25, 1996 is analyzed with the aid of data from the IMP-8 and WIND Earth-orbiting spacecraft and the DE is found to be correlated with a crossing of the heliospheric current sheet. The comet was within of Earth at the time of the DE and data from IMP-8 and WIND show no high-speed streams, significant density enhancements or shocks.The latitudinal variation in the appearance and orientation of the plasma tail are interpreted based on results from the Ulysses spacecraft. In the polar solar wind region, the comet has a relatively undisturbed appearance, no DEs were observed, and the orientation of the plasma tail was consistent with a higher solar wind speed. In the equatorial solar wind region, the comet's plasma tail had a disturbed appearance, a major DE was observed, and the orientation of the plasma tail was consistent with a lower solar wind speed. The boundary between the equatorial and polar regions crossed by comet Hyakutake in April 1996 was near 30°N (ecliptic) or 24°N (solar) latitude.  相似文献   

10–100 keV electron acceleration and emission from solar flares     

R. P. Lin  H. S. Hudson 《Solar physics》1971,17(2):412-435

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 = 10^28–29 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 = 10^33–34.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   

Three-dimensional structure of the solar wind: Variation of density with the solar cycle     

P. K. Manoharan 《Solar physics》1993,148(1):153-167

Interplanetary Scintillation (IPS) measurements obtained from a large number of compact radio sources (nearly 150 sources) distributed over the heliocentric distance range 15–175 solar radii (R() and heliographic latitude 75° N-75° S have been used to study the global three-dimensional density distribution of the solar wind plasma. Contours of constant electron-density fluctuations (N _e) in the heliospheric plasma obtained for both the solar minimum and maximum show a strong solar latitude dependence. During low solar activity, the equatorial density-fluctuation value decreases away from the equator towards higher latitudes and is reduced by 2.5 times at the poles; the level of turbulence is reduced by a factor of 7; the solar-wind mass flux density at the poles is 25% lower than the equatorial value. However, during high solar activity, the average distribution of density fluctuations becomes spherically symmetric. In the ecliptic, the variation of N _e with the heliocentric distance follows a power law of the formR ^–2.2 and it does not show any change with solar activity.  相似文献   

Second-stage acceleration in a limb-occulted flare     

H. S. Hudson  R. P. Lin  R. T. Stewart 《Solar physics》1982,75(1-2):245-261

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   

Evidence for thin-target X-ray emission in a small solar flare on 26 February 1972     

D. W. Datlowe  R. P. Lin 《Solar physics》1973,32(2):459-468

We compare solar X-ray observations from the UCSD experiment aboard OSO-7 with high resolution energetic electron observations from the UCAL experiment on IMP-6 for a small solar flare on 26 February 1972. A proportional counter and NaI scintillator covered the X-ray energy range 5–300 keV, while a semiconductor detector telescope covered electrons from 18 to 400 keV. A series of four non-thermal X-ray spikes were observed from 1805 to 1814 UT with average spectrum dJ/d (hv) (hv)^–4.0 over the 14–64 keV range. The energetic electrons were observed at 1 AU beginning 1840 UT with a spectrum dJ/dE E ^–3.1. If the electrons which produce the X-ray emission and those observed at 1 AU are assumed to originate in a common source, then these observations are consistent with thin target X-ray production at the Sun and inconsistent with thick target production. Under a model consistent with the observed soft X-ray emission, we obtain quantitative estimates of the total energy, total number, escape efficiency, and energy lost in collisions for the energetic electrons.  相似文献   

Optical observations of geostationary spin-stabilised satellites     

A. B. Giles  K. M. Hill 《Astrophysics and Space Science》1988,147(2):359-379

The first two AUSSAT communication satellites have been located and their optical variability studied. We have found that the objects are exceptionally bright for the few days each year when an ideal solar mirror reflection occurs for our ground latitude. At this time their 1.1 s spin periods are detectable in real time and FFT analyses show a range of much faster periodic features. The frequencies of these components have been identified with the arragement of the solar cells on the outer surface of the AUSSAT spacecraft. Possible applications for these objects are mentioned and a list is given of other suitable spinning spacecraft.  相似文献   

Tracking of kilometric-wave type III solar bursts in elevation and elongation and apparent source sizes     

Paul J. Kellogg 《Solar physics》1976,46(2):449-458

With our experiment on the satellite IMP-6 (Explorer 43) we are able to track the position of type III solar bursts in elevation as well as elongation. We do this by measuring the correlations between signals on an electric dipole antenna which is approximately normal to the plane of the ecliptic, and either of two antennas rotating in the ecliptic plane. The result is that the sources are generally close to the ecliptic plane, close enough that their elevation above the ecliptic cannot account for the large apparent width which we and others observe, and that this width must therefore be real.  相似文献   

Direct observations of low-energy solar electrons associated with a type III solar radio burst     

L. A. Frank  D. A. Gurnett 《Solar physics》1972,27(2):446-465

A highly anisotropic packet of solar electron intensities was observed on 6 April 1971 with a sensitive electrostatic analyzer array on the Earth-orbiting satellite IMP-6. The anisotropies of intensities at electron energies of several keV were factors 10 favoring the expected direction of the interplanetary magnetic lines of force from the Sun. The directional, differential intensities of solar electrons were determined over the energy range 1–40 keV and peak intensities were 10² cm^–2 s^–1 sr^–1 eV^–1 at 2–6 keV. This anisotropic packet of solar electrons was detected at the sattelite for a period of 4200 s and was soon followed by isotropic intensities for a relatively prolonged period. This impulsive emission was associated with the onsets of an optical flare, soft X-ray emission and a radio noise storm at centimeter wavelengths on the western limb of the Sun. Simultaneous measurements of a type III radio noise burst at kilometric wavelengths with a plasma wave instrument on the same satellite showed that the onsets for detectable noise levels ranged from 500 s at 178 kHz to 2700 s at 31.1 kHz. The corresponding drift rate requires a speed of 0.15c for the exciting particles if the emission is at the electron plasma frequency. The corresponding electron energy of 6 keV is in excellent agreement with the above direct observations of the anisotropic electron packet. Further supporting evidence that several-keV solar electrons in the anisotropic packet are associated with the emission of type III radio noise beyond 50R is provided by their time-of-arrival at Earth and the relative durations of the radio noise and the solar electron packet. Electron intensities at E 45 keV and the isotropic intensities of lower-energy solar electrons are relatively uncorrelated with the measurements of type III radio noise at these low frequencies. The implications of these observations relative to those at higher frequencies, and heliocentric radial distances 50R , include apparent deceleration of the exciting electron beam with increasing heliocentric radial distance.Research supported in part by the National Aeronautics and Space Administration under contracts NAS5-11039 and NAS5-11074 and grant NGL16-001-002 and by the Office of Naval Research under contract N000-14-68-A-0196-0003.  相似文献   

Radio evidence for a delayed acceleration process in solar flares     

K. Kai  H. Nakajima  T. Kosugi  R. T. Stewart  G. J. Nelson  S. R. Kane 《Solar physics》1986,105(2):383-398

Evidence for a delayed acceleration process in solar flares is presented in the form of an analysis of simultaneous observations in microwaves, decimetre and metrewaves, and hard X-rays of six delayed gradual bursts which appear 0.5–1 hr after the strong main bursts have faded. The observed characteristics of the delayed bursts are: (a) similarity of flux time profiles at all the wavelengths, (b) low turn-over frequency (4 GHz) of the microwave spectrum, (c) moderately strong circular polarization (30–40%) and low altitude of the microwave source (which is displaced toward the disk centre by a projected distance of 10–20 from that of the preceding main burst), and (d) low spectral index of the energy spectrum of hard X-rays.From these observations it is suggested that (i) electrons are accelerated up to MeV even some tens of minutes after the impulsive phase acceleration has almost ceased, (ii) the delayed acceleration occurs in a large magnetic structure extending to a height of at least 2 × 10⁵ km, and (iii) the radio source has columnar structure with the microwave source predominantly near a leg or legs and the metrewave source near the top of the magnetic structure. The present observations of the delayed bursts do not seem to be consistent with the classical second-phase acceleration mechanism proposed in the past for normal hard X-ray gradual (extended) bursts.Minamimaki-mura, Minamisaku-gun, Nagano-ken 384-13, Japan.Greenbelt, MD 20771, U.S.A., NASA/NRC Research Associate, on leave from Tokyo Astronomical Observatory.P.O. Box 76, Epping, N.S.W. 2121, Australia.Berkeley, CA 94720, U.S.A.  相似文献   

Location of the electron acceleration region in solar flares     

S. R. Kane  R. P. Lin 《Solar physics》1972,23(2):457-466

Observations of impulsive solar flare X-rays 10 keV by the OGO-5 satellite and the measurements of energetic solar electrons made with the Explorer-35 and Explorer-41 (IMP-5) satellites during the period March 1968–September 1969 have been analyzed in order to determine the ion density in the X-ray source region as well as the location of the electron acceleration region in the solar atmosphere. If we assume that the efficiency of escape of the accelerated electrons into interplanetary space is 10^–3, the observations are found to be consistent with the following interpretation: (i) the ion density in the X-ray source region varies from event to event and lies between 10⁹ and 10¹¹ ions cm^–3 for those events in which the impulsive X-ray emission could be detected; (ii) for those events in which no impulsive emission was detected above threshold, the ion density in the X-ray source was < 10⁹ ions cm^–3; (iii) at least in some small solar flares the region where the electrons are accelerated during the flash phase is located in the lower corona.  相似文献   

Radio mapping of the heliospheric current sheet     

R. T. Stewart 《Solar physics》1971,109(1):139-147

Synoptic plots of solar radio noise storms in the interval 1973 to 1984 are described. The dividing line between opposite noise storm polarities appears to be a good representation of the heliospheric current sheet out to displacements in latitude of ± 50° from the solar equator. This result is surprising, because noise storms are closely associated with closed magnetic field regions near sunspots. The possibility that noise storm polarity is determined by mode coupling high in the corona, where field lines are open, can be ruled out by the available evidence. This leads us to conclude that it is the clustering in longitude of active region complexes which determines the sector structure of the interplanetary magnetic field.  相似文献   

Simulation of shell structures of comet Hale-Bopp     

J Tao  B.C Qian 《Planetary and Space Science》2003,51(1):19-29

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Prompt injection of relativistic protons from the September 1, 1971 solar flare   总被引：2，自引：0，他引：2  

Edward W. Cliver 《Solar physics》1982,75(1-2):341-345

The September 1, 1971 flare in McMath region 11482 was projected to have occurred 30° behind the west limb. An anisotropic Ground Level Effect (GLE) began <30 min after the inferred explosive phase of the flare. We attribute the rapid injection of relativistic protons onto the earth spiral field line to a shock wave associated with an observed type II burst.  相似文献   

Preliminary results on the apparent size of the sources of type III bursts observed at low frequencies     

Hector Alvarez 《Solar physics》1976,46(2):483-491

We present preliminary results on the apparent angular size of the sources of four type III bursts observed between 3500 and 50 kHz from the IMP-6 spacecraft. The observations were made with a dipole rotating in the plane of the ecliptic where the sources are assumed to be. The apparent angular sizes obtained are unexpectedly large. We discuss different explanations for the results. It seems that the scattering of radio waves by electron density inhomogeneities is the most likely cause.We report a temporal increase of the apparent angular size of the source during the burst lifetime for some bursts. From its characteristics it apears to be a real effect.  相似文献   

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   

Pulsations at the Onset of the Great Solar Burst of 22 October 1989     

Makhmutov  V. S.  Costa  J. E. R.  Raulin  J.-P.  Kaufmann  P.  Lagrotta  P.R.  Giménez de Castro  C.G.  Magun  A.  Arzner  K. 《Solar physics》1998,178(2):393-403

The onset phase of the 22 October 1989 great solar burst was observed at 48 GHz using the multiple beam technique, which allows unambiguous flux determination irrespective of spatial angular position changes in time. We found strong quasi-periodic pulsating structures as the flux started to rise. Two significantly different time scales of 2.5–4.5 s and 0.2–0.5 s have been observed. These pulsations might be related to magnetohydrodynamic perturbations in the active region. However the fast component also might be a signature of the acceleration and/or injection of energetic electrons.  相似文献