排序方式： 共有17条查询结果，搜索用时 15 毫秒
1.
Radio astronomy experiments designed to probe the interplanetary plasma close to the Sun have been carried out at the wavelength = 2.92 m using the occultation method. The experiments are based on a modification of the occultation method by which the sources, in this case quasars, are used to measure the radial dependence of the apparent source size, the scattering angle (R). The radial dependence of this source size (R) reveals that an anomalous enhancement in the scattering appears at radial distances from about 16 to 30 R
, which is associated with the solar wind transsonic region. It is shown by analysis of the theoretical equations that the radial profiles of both the source size (R) and the scintillation index m(R) are consistent in the near solar interplanetary medium (R 40 R
). Combining these two independent applications of the occultation method extends the range of the investigation and provides a powerful new diagnostic of the solar wind transsonic region. 相似文献
2.
N. A. Lotova K. V. Vladimirskii V. N. Obridko B. P. Filippov O. A. Korelov 《Astronomy Letters》2005,31(8):546-556
We study the formation of solar-wind streams in the years of maximum solar activity 2000–2002. We use observations of the scattering of radio emission by solar-wind streams at distances of ～4–60RS from the Sun, data on the magnetic field structure and strength in the source region (R ～ 2.5RS), and observations with the LASCO coronagraph onboard the SOHO spacecraft. Analysis of these data allowed us to investigate the changes in the structure of circumsolar plasma streams during the solar maximum. We constructed radio maps of the solar-wind transition, transonic region in which the heliolatitudinal stream structure is compared with the structure of the white-light corona. We show that the heliolatitudinal structure of the white-light corona largely determines the structure of the solar-wind transition region. We analyze the correlation between the location of the inner boundary of the transition region Rin and the magnetic field strength on the source surface |BR|. We discuss the peculiarities of the Rin = F(|BR|) correlation diagrams that distinguish them from similar diagrams at previous phases of the solar cycle. 相似文献
3.
The studies are based on the experimental mass sounding of the interplanetary plasma near the Sun at radial distances of R = 4−70 R
S, performed at Pushchino RAO, Russian Academy of Sciences, and on the calculated magnetic fields in the solar corona based
on the magnetic field strength and structure measured on the Sun’s surface at J. Wilcox Solar Observatory, United States.
The experimental data make it possible to localize the position of the boundary closest to the Sun of the transition transonic
region of the solar wind in the near-solar space (R ≈ 10−20 R
S) and to perform an interrelated study of the solar wind structure and its sources, namely, the magnetic field components
in the solar corona based on these data. An analysis of the evolution of the flow types in 2000–2007 makes it possible to
formulate the physically justified criterion responsible for the time boundaries of different epochs in the solar activity
cycle. 相似文献
4.
The dependence of the position of the solar wind sonic point on the magnetic field in the solar corona during cycle 23 is studied. This dependence is shown to be rather strong in the rising phase and at the cycle maximum. As the coronal magnetic field grows, the distance to the sonic point decreases. Since the distance to the sonic point has been shown previously to anticorrelate with the solar wind speed, the result obtained suggests a strong positive correlation between the later and the coronal magnetic field. The situation changed dramatically two years after the calendar date of the cycle maximum. Beginning in 2004 the solar wind speed ceased to depend on the magnetic field up until the cycle minimum in December 2008. In 2009 a strong dependence of the wind speed on the coronal magnetic field was restored. It is hypothesized that this effect is associated with two different coronal heating mechanisms whose relative efficiency, in turn, depends on the contribution from magnetic fields of different scales. 相似文献
5.
N. A. Lotova 《Solar physics》1988,117(2):399-406
The morphology and physical characteristics of the extended solar wind transsonic region, an intrinsically unique regime of the heliosphere, are described. It is here where the primary acceleration of the solar wind occurs and both subsonic and supersonic plasma flows co-exist and interact. This concept of mixed flow has evolved from an analysis of interplanetary scintillation (IPS) data that reveal the solar wind stream structure and anomalous scattering within the solar wind transsonic region. 相似文献
6.
An experimental study of the source and formation of large-scale streams in the solar wind is presented. Radio-astronomical data from 1998 are compared with optical SOHO observations and solar coronal magnetic fields calculated from Zeeman data obtained at the Wilcox Observatory. A correlation between the geometry of the solar-wind transition region and the strength of coronal magnetic fields is revealed. For the moderate heliolatitudes studied, this correlation divides into three branches corresponding to three types of coronal magnetic-field structures: open structures with field lines escaping into interplanetary space, closed structures with loop-like field lines, and intermediate structures including both open and closed configurations. High-speed streams of solar wind originate in regions with open magnetic structures. These structures are connected with the lateral lobes of streamers at moderate heliolatitudes. Low-speed flows originate above closed magnetic structures, typical of the main bodies of streamers. The lowest-speed solar-wind flows are not associated with coronal streamer structures, and originate in coronal regions with intermediate magnetic configurations simultaneously containing open and closed field lines. In these regions, the white-light corona becomes an extended and amorphous area with high luminosity, which stratifies into a radial structure with narrow stripes at higher resolution. 相似文献
7.
N.A. Lotova V.N. Obridko K.V. Vladimirskii M.K. Bird P. Janardhan 《Solar physics》2002,205(1):149-163
The large-scale stream structure of the solar wind flow is studied in the main acceleration zone from 10 to 40 solar radii from the Sun. Three independent sets of experimental data were used: radio astronomical observations of radio wave scattering using the large radio telescopes of the Lebedev Physical Institute; dual-frequency Doppler solar wind speed measurements from the Ulysses Solar Corona Experiment during the spacecraft's two solar conjunctions in summer 1991 and winter 1995; solar magnetic field strength and configuration computed from Wilcox Solar Observatory data. Both the experimental data on the position of the transonic region of the solar wind flow and the solar wind speed estimates were used as parameters reflecting the intensity of the solar wind acceleration process. Correlation studies of these data with the magnetic field strength in the solar corona revealed several types of solar wind flow differing in their velocities and the location of their primary acceleration region. 相似文献
8.
Experiments based on multi-source radio occultation measurements of the circumsolar plasma at R∼4.0−70R
S were carried out during 1997 – 2008 to locate the inner boundary of the solar-wind transonic transition region, R
in. The data obtained were used to correlate the solar-wind stream structure and magnetic fields on the source surface (R=2.5R
S) in the solar corona. The method of the investigation is based on the analysis of the dependence R
in=F(|B
R|) in the correlation diagrams, where R
in is the inner boundary of the solar-wind transition region and |B
R| is the intensity of the magnetic field at the source surface. On such diagrams, the solar wind is resolved into discrete
branches, streams of different types. The analysis of the stream types using a continuous series of data from 1997 to 2008
allowed us to propose a physical criterion for delimiting the epochs in the current activity cycle. 相似文献
9.
The scintillation theory is developed for application to the interstellar medium taking into account both the movement of the pulsars and the movement of the interstellar irregularities.It is shown that the velocity of the drifting pattern differs essentially from that for the pulsars. This difference is due to the medium extent effect and to the motion of the irregularities. The pulsar velocityv
0 and the parameters of the motion of the irregularities (
, ) can be derived from the obtained formulae, using the known parameters of the cross-correlation function of scintillations (V
ef, 1,S).In contrast with the interplanetary scintillation, the asymmetry of the form of the cross-correlation function of the interstellar scintillations is caused not only by the motion of the interstellar irregularities, but also by the movement of the source itself. 相似文献
10.
We study the sources and components of the solar-wind spatial stream structure at the maximum of the solar cycle 23. In our analysis, we use several independent sets of experimental data: radio-astronomical observations of scattered radiation from compact sources with the determination of the distance from the Sun to the inner boundary of the transonic-flow transition region (Rin); calculated data on the magnetic-field intensity and structure in the solar corona, in the solar-wind source region, obtained from optical measurements of the photospheric magnetic-field intensity at the Stanford Solar Observatory (USA); and observations of the white-light corona with the LASCO coronograph onboard the SOHO spacecraft. We show that at the solar maximum, low-speed streams with a transition region located far from the Sun dominate in the solar-wind structure. A correlation analysis of the location of the inner boundary Rin and the source-surface magnetic-field intensity |B R | on a sphere R=2.5RS (RS is the solar radius) has revealed the previously unknown lowest-speed streams, which do not fit into the regular relationship between the parameters Rin and |B R |. In the white-light corona, the sources of these streams are located near the dark strip, a coronal region with a greatly reduced density; the nonstandard parameters of the streams probably result from the interaction of several discrete sources of different types. 相似文献