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1.
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
2.
Ronald L. Rosenberg 《Solar physics》1970,15(1):72-78
A simple model is used to present a unified picture of the polarity pattern of the interplanetary magnetic field observed during the solar cycle. Emphasis in this paper is on the field near solar maximum. The heliographic latitude dependence of the dominant polarity of the interplanetary magnetic field is explained in terms of weak poloidal (dipolar) field sources in the sun's photosphere. Unlike the Babcock theory, the author hypothesizes that the dipolar field exists at equatorial latitudes (0–20°), too, (as well as in polar regions) and that the major source of the interplanetary magnetic field observed near the ecliptic plane is the dipolar field from equatorial latitudes. The polarity of the interplanetary field data taken in 1968 and in the first half of 1969 near solar maximum may possibly be explained in terms of a depression of the dipolar field boundary in space. The effect on the solar wind of the greater activity in the northern hemisphere of the sun that existed in 1968 and in the first half of 1969 is believed responsible for this hypothesized depression, especially near solar maximum, of the plane separating the + and - dipolar polarity below the solar equatorial plane in space. Predictions are made concerning the interplanetary field to be observed near the ecliptic plane in each portion of the next solar cycle. 相似文献
3.
S.-I. Akasofu 《Planetary and Space Science》1979,27(8):1055-1062
It is suggested that the solar current sheet, extending from a coronal streamer, develops a large-scale radial deformation, at times with a very steep gradient at the Earth's distance. The associated magnetic field lines (namely, the interplanetary magnetic field (IMF) lines) are expected to have also a large gradient in the vicinity of the current sheet. It is also suggested that some of the major geomagnetic storms occur when the Earth is located in the region where IMF field lines have a large dip angle with respect to the ecliptic plane for an extended period (6–48 h), as a result of a steep radial deformation of the current sheet. 相似文献
4.
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
5.
A. V. Usmanov 《Solar physics》1993,143(2):345-363
An attempt is made to infer parameters of the solar corona and the solar wind by means of a numerical, self-consistent MHD simulation. Boundary conditions for the magnetic field are given from the observations of the large-scale magnetic field at the Sun. A two-region, planar (the ecliptic plane is assumed) model for the solar wind flow is considered. Region I of transonic flow is assumed to cover the distances from the solar surface up to 10R
S (R
S is the radius of the Sun). Region II of supersonic, super-Alfvénic flow extends between 10R
S and the Earth's orbit. Treatment for region I is that for a mixed initial-boundary value problem. The solution procedure is similar to that discussed by Endler (1971) and Steinolfson, Suess, and Wu (1982): a steady-state solution is sought as a relaxation to the dynamic equilibrium of an initial state. To obtain a solution to the initial value problem in region II with the initial distribution of dependent variables at 10R
S (deduced from the solution for region I), a numerical scheme similar to that used by Pizzo (1978, 1982) is applied. Solar rotation is taken into account for region II; hence, the interaction between fast and slow solar wind streams is self-consistently treated. As a test example for the proposed formulation and numerical technique, a solution for the problem similar to that discussed by Steinolfson, Suess, and Wu (1982) is obtained. To demonstrate the applicability of our scheme to experimental data, solar magnetic field observations at Stanford University for Carrington rotation 1682 are used to prescribe boundary conditions for the magnetic field at the solar surface. The steady-state solution appropriate for the given boundary conditions was obtained for region I and then traced to the Earth's orbit through region II. We compare the calculated and spacecraft-observed solar wind velocity, radial magnetic field, and number density and find that general trends during the solar rotation are reproduced fairly well although the magnitudes of the density in comparison are vastly different. 相似文献
6.
C. O. Lee J. G. Luhmann X. P. Zhao Y. Liu P. Riley C. N. Arge C. T. Russell I. de Pater 《Solar physics》2009,256(1-2):345-363
The current solar cycle minimum seems to have unusual properties that appear to be related to weak solar polar magnetic fields. We investigate signatures of this unusual polar field in the ecliptic near-Earth interplanetary magnetic field (IMF) for the STEREO period of observations. Using 1 AU OMNI data, we find that for the current solar cycle declining phase to minimum period the peak of the distribution for the values of the ecliptic IMF magnitude is lower compared to a similar phase of the previous solar cycle. We investigate the sources of these weak fields. Our results suggest that they are related to the solar wind stream structure, which is enhanced by the weak polar fields. The direct role of the solar field is therefore complicated by this effect, which redistributes the solar magnetic flux at 1 AU nonuniformly at low to mid heliolatitudes. 相似文献
7.
The ecliptic as a mean orbital plane of the Sun in Le Verrier's theory is a mean orbital plane determined from the secular parts of the longitude of the ascending node and the inclination of the Sun with respect to a reference plane. On the other hand, the ecliptic in Newcomb's theory is so chosen that the latitude with respect to his ecliptic does not have cosg nor sing whereg is the mean anomaly of the Sun. The two definitions are really different in spite of their apparent similarity. Standish (1981) defined the ecliptic from a kinematical point of view, and it is shown that the ecliptic defined by Standish (in the rotating sense) does coincide with the ecliptic defined by Newcomb. 相似文献
8.
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
9.
L. I. Shestakova 《Solar System Research》2004,38(1):76-84
Prolonged searches for the cold matter brought into the solar corona from the outskirts of the Solar system have finally been crowned with success. After the first prediction about the possibility of detecting emission from certain atoms and low-charge ions made by Shestakova in 1990, several attempts have been made to detect the resonance emission of Ca ions in the solar corona. The wide-field interferometric observations of the corona in the Ca II H and K lines performed by Gulyaev on Shcheglov's facility revealed an extended emission region to the west of the Sun only during the solar eclipse of February 26, 1998. We attempt to construct a model for the motion of Ca ions after their separation from the parent body. The ions move away from the Sun mainly under light pressure. Reasonably good agreement of the model with the observed radial velocities and the emission configuration is achieved by assuming that the chain of parent bodies moves from the south northward in a parabolic orbit almost perpendicularly to the plane of the ecliptic. 相似文献
10.
Previous attempts to produce three-dimensional (3-D) reconstructions of coronal mass ejections (CMEs) have required either
modeling efforts or comparisons with secondary associated eruptions near the solar surface. This is because coronagraphs are
only able to produce sky-plane-projected images of CMEs and it has hence been impossible to overcome projection effects by
using coronagraphs alone. The SECCHI suite aboard the twin STEREO spacecraft allows us to provide the means for 3-D reconstruction
of CMEs directly from coronagraph measurements alone for the first time. We present these measurements from two CMEs observed
in November 2007. By identifying common features observed simultaneously with the LASCO coronagraphs aboard SOHO and the COR
coronagraphs aboard STEREO we have triangulated the source region of both CMEs. We present the geometrical analysis required
for this triangulation and identify the location of the CME in solar-meridional, ecliptic, and Carrington coordinates. None
of the two events were associated with an easily detectable solar surface eruption, so this triangulation technique is the
only means by which the source location of these CMEs could be identified. We present evidence that both CMEs originated from
the same magnetic structure on the Sun, but from a different magnetic field configuration. Our results reveal some insight
into the evolution of the high corona magnetic field, including its behavior over time scales of a few days and its reconfiguration
after a major eruption. 相似文献
11.
Tomoko Nakagawa 《Solar physics》1993,147(1):169-197
Planar magnetic structure (PMS) is an interplanetary magnetic structure in which magnetic field vectors are all parallel to a plane but highly variable in both magnitude and direction in that plane. This magnetic structure corresponds to re-entrant loops of magnetic field lines in the photosphere that emanate into interplanetary space. To find information on the generation site, occurrence properties of PMSs are investigated by using the interplanetary magnetic field data obtained by Sakigake and ISEE-3 spacecraft. No significant correlation is found between PMS occurrence and the solar wind velocity gradient which would suggest interplanetary formation of PMSs. No significant correlation is found between the PMS events and flares or filaments, either. Instead, a half of the PMSs were projected to the vicinity of the sector boundary in the source surface magnetic field, although there are exceptions when PMS appeared in the center of a sector. The PMS planes were not parallel to the current sheet at the sector boundary. Sometimes PMSs were observed recurrently at the same heliospheric longitude in successive rotations of the Sun, suggesting persistence of the source of PMS on the Sun. The orientation of the PMS planes were not conserved in the recurrent PMSs. 相似文献
12.
Gerd-Hannes Voigt 《Planetary and Space Science》1981,29(1):1-20
A quantitative magnetospheric magnetic field model has been calculated in three dimensions. The model is based on an analytical solution of the Chapman-Ferraro problem. For this solution, the magnetopause was assumed to be an infinitesimally thin discontinuity with given geometry. The shape of the dayside magnetopause is in agreement with measurements derived from spacecraft boundary crossings.The magnetic field of the magnetopause currents can be derived from scalar potentials. The scalar potentials result from solutions of Laplace's equation with Neumann's boundary conditions. The boundary values and the magnetic flux through the magnetopause are determined by all magnetic sources which are located inside and outside the magnetospheric cavity. They include the Earth's dipole field, the fields of the equatorial ring current and tail current systems, and the homogeneous interplanetary magnetic field. In addition, the flux through the magnetopause depends on two constants of interconnection which provide the possibility of calculating static interconnection between magnetospheric and interplanetary field lines. Realistic numerical values for both constants have been derived empirically from observed displacements of the polar cusps which are due to changes in the orientation of the interplanetary field. The transition from a closed to an open magnetosphere and vice versa can be computed in terms of a change of the magnetic boundary conditions on the magnetopause. The magnetic field configuration of the closed magnetosphere is independent of the amount and orientation of the interplanetary field. In contrast, the configuration of the open magnetosphere confirms the observational finding that field line interconnection occurs primarily in the polar cusp and high latitude tail regions.The tail current system reflects explicitly the effect of dayside magnetospheric compression which is caused by the solar wind. In addition, the position of the plasma sheet relative to the ecliptic plane depends explicitly on the tilt angle of the Earth's dipole. Near the tail axis, the tail field is approximately in a self-consistent equilibrium with the tail currents and the isotropic thermal plasma.The models for the equatorial ring current depend on the Dst-parameter. They are self-consistent with respect to measured energy distributions of ring current protons and the axially symmetric part of the magnetospheric field. 相似文献
13.
Proton heating at stream interaction regions in the solar wind is investigated based on the solar wind data obtained by Suisei spacecraft between 0.68 and 1.01 AU from the Sun. The deflection angle of the solar wind flow in the ecliptic plane is used to identify the interaction region. In the solar wind flows coming from east of the Sun in low-speed streams and coming from west in high-speed streams, the radial gradient of proton temperature is flattened owing to heating in the interaction region. From comparison of the best-fitted power law dependence of proton temperature on the radial distance in the deflected flow with that in the non-deflected flow, it is suggested that heating in the interaction regions starts around 0.6–0.7 AU from the Sun. 相似文献
14.
The interplanetary magnetic field has been mapped between 0.4 and 1.2 AU in the ecliptic plane, extrapolating from satellite measurements at 1 AU. The structure within sectors and the evolution of sectors are discussed. The development of a solar active region appears to produce magnetic loops in the interplanetary medium that result in the formation of a new sector. 相似文献
15.
The structure of the interplanetary magnetic field within the flare streams as well as associated variations of the geomagnetic disturbancy are considered. It is shown that in the main body of the flare stream the magnetic field is determined by the configuration of the large scale magnetic field on the Sun at the flare region. Within the head part of the flare stream the magnetic field represents by itself the compressed field of the background solar wind and hence is determined by the distribution of the super large scale solar magnetic field outside the flare region.A certain asymmetry in the parameters of the magnetic field within the streams associated with geoeffective and non-effective flares is shown to exist. 相似文献
16.
Rajendra Shelke 《Journal of Astrophysics and Astronomy》2006,27(2-3):101-112
Coronal holes and interplanetary disturbances are important aspects of the physics of the Sun and heliosphere. Interplanetary
disturbances are identified as an increase in the density turbulence compared with the ambient solar wind. Erupting stream
disturbances are transient large-scale structures of enhanced density turbulence in the interplanetary medium driven by the
high-speed flows of low-density plasma trailing behind for several days. Here, an attempt has been made to investigate the
solar cause of erupting stream disturbances, mapped by Hewish & Bravo (1986) from interplanetary scintillation (IPS) measurements
made between August 1978 and August 1979 at 81.5 MHz. The position of the sources of 68 erupting stream disturbances on the
solar disk has been compared with the locations of newborn coronal holes and/or the areas that have been coronal holes previously.
It is found that the occurrence of erupting stream disturbances is linked to the emergence of new coronal holes at the eruption
site on the solar disk.
A coronal hole is indicative of a radial magnetic field of a predominant magnetic polarity. The newborn coronal hole emerges
on the Sun, owing to the changes in magnetic field configuration leading to the opening of closed magnetic structure into
the corona. The fundamental activity for the onset of an erupting stream seems to be a transient opening of pre-existing closed
magnetic structures into a new coronal hole, which can support highspeed flow trailing behind the compression zone of the
erupting stream for several days. 相似文献
17.
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 elevation (geocentric solar ecliptic latitude) and azimuth (geocentric solar ecliptic 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 signals the location of the type III burst projected into the ecliptic can be found. HAWKEYE 1 has its spin axis nearly parallel to the ecliptic plane, hence the elevation of the source may also be determined. The trajectory of the electrons generating the burst, projected onto the ecliptic plane, follows an Archimedean spiral. Out of the ecliptic plane the trajectory is at a nearly constant heliographic latitude. The electrons originate from a region near a solar flare. With direction measurements of elevation and azimuth along with the modulation factor it is possible to determine the source size. Typical half angle source sizes range from 60° at 500 kHz to 40° at 56.2 kHz as viewed from the sun. 相似文献
18.
C. Foullon C. J. Owen S. Dasso L. M. Green I. Dandouras H. A. Elliott A. N. Fazakerley Y. V. Bogdanova N. U. Crooker 《Solar physics》2007,244(1-2):139-165
We examine the near-Earth Interplanetary Coronal Mass Ejection (ICME) apparently related to the intense Solar Energetic Particle (SEP) event of 20 January 2005. Our purpose is to contribute to the understanding of the macroscopic structure, evolution and dynamics of the solar corona and heliosphere. Using Cluster, ACE and Wind data in the solar wind, and Geotail data in the magnetosheath, we perform a multi-spacecraft analysis of the ICME-driven shock, post-shock magnetic discontinuities and ejecta. Traversals by the well-separated near-Earth spacecraft provide a coherent picture of the ICME geometry. Following the shock, the ICME sequence starts with a hot pileup, i.e.,? a sheath, followed by a fast ejecta characterised by a non-compressive density enhancement (NCDE), which is caused essentially by an enrichment in helium. The plasma and magnetic observations of the ejecta are consistent with the outskirts of a structure in strong expansion, consisting of nested magnetic loops still connected to the Sun. Within the leading edge of the ejecta, we establish the presence of a tilted current sheet substructure. An analysis of the observations suggests that the tilted current sheet is draped within the overlying cloud canopy, ahead of a magnetic cloud-like structure. The flux rope interpretation of this structure near L1, confirmed by observations of the corresponding magnetic cloud, provided by Ulysses at 5.3 AU and away from the Sun?–?Earth line, indicates that the bulk of the cloud is in the northwest sector as seen from the Earth, with its axis nearly perpendicular to the ecliptic. This is consistent with the primary direction of travel of the fast halo CME observed at the Sun. Moreover, the NCDE and helium enrichment are consistent with the position near the streamer belt of the flaring active region NOAA 10720 associated with the CME. However, differences between interplanetary and solar observations indicate a large rotation of the erupting filament and overlying arcade, which can be attributed to the flux rope being subject to the helical kink instability. 相似文献
19.
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
20.
A new class of disturbance in the interplanetary magnetic field has been discovered. This disturbance consists of an enhancement in the magnetic field strength lasting tens of minutes to hours. The strength of the enhancement is variable ranging up to over double the background field strength. The peak field pressure can be as high as 10% of the solar wind dynamic pressure. These events occur randomly with respect to the position of the spacecraft relative to Venus but not randomly with respect to Venus solar ecliptic longitude. There is a significant tendency for these events to cluster near certain ecliptic longitudes. The field distortion is often greater in the direction perpendicular to the solar wind flow rather than along it. These characteristics suggest that the source of the disturbances are weakly outgassing objects, possibly dispersed along their orbits such as in meteor streams. 相似文献