共查询到20条相似文献，搜索用时 31 毫秒
1.
A. Geranios 《Astrophysics and Space Science》1982,81(1-2):333-343
Hourly interplanetary plasma data measured by Helios-1 satellite over the period 10 December 1974–31 December 1977 are analysed. This analysis showed that the slow solar wind first increases its speed with heliocentric distance and then becomes more or less constant; the mean speed in the range 0.3 to 1.0 AU is 350 km s–1 for the slow solar plasma, while for the fast the mean value is between 650 and 700 km s–1.It seems, particularly in the neighbourhood of the earth, that except for the two dominated types of solar wind (fast and slow) an additional (intermediate) appears at 450 km s–1.During the phase of enhanced solar activity (11-yr solar cycle) the slow solar wind only is present, while at solar minimum all three types of the solar wind are equally represented.The dependence of the proton temperature on the solar wind speed, in the general solar wind, is the same irrespectively of the phase of solar activity. But, the same dependence is stronger during the compression at the leading edge than during the expansion at the trailing edge of a solar wind stream. 相似文献
2.
Based on analyzing corona images taken by the LASCO C1, C2, and C3 instruments, a study is made of the behavior of the streamer belt spanning one half of the 1996–2001 cycle of solar activity, from minimum to maximum activity, in the absence of coronal mass ejections. It is shown that: (1) The position of the streamer belt relative to the solar equator is generally characterized by two angles: o and E, where o is the latitudinal position (near the solar surface) of the middle of the base of the helmet, the top of which gradually transforms to a ray of the streamer belt with a further distance from the Sun, and E is the latitude of this ray for R>5–6 R
from the Sun's center where the ray becomes radial. (2) Only rays lying at some of the selected latitudes o retain their radial orientation (oE) throughout their extent. Namely: o0° (equator), o±90° (north and south poles), and the angle o lying in the range ±(65°–75°) in the N- and S-hemispheres. (3) A deviation of rays from their radial orientation in the direction normal to the surface of the streamer belt occurs: for latitudes o<|65°–75°| toward the equator (>0°) reaching a maximum in the N and S hemispheres, respectively, when OM40°, and OM–42° for latitudes o>|65°–75°| toward the pole (<0°). The regularities obtained here are a numerical test which can be used to assess of the validity of the theory for describing the behavior of the Sun's quasi-stationary corona over a cycle of solar activity. 相似文献
3.
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
4.
The radial dependencies of four solar wind parameters (plasma density N, velocity V, temperature T, and magnitude of the interplanetary magnetic field B) are derived from remote sensing data of the solar corona and from in situ measurements in the heliosphere (Helios-1, 2, Pioneer-10, 11, and Voyager-1, 2). Using doubly logarithmic scaling (solar wind parameter vs radial distance from the Sun) one finds two distinct intervals in the ecliptic, i.e., an exponential section within, approximately, the inner heliosphere and a linear section - up to at least 61 AU - in the outer heliosphere. 相似文献
5.
A. K. R. Anantharamaiah B. Pradeep Gothoskar C. T. J. Cornwell 《Astrophysics and Space Science》1996,243(1):77-81
We present Very Large Array observations at wavelengths of 2, 3.5, 6, and 20 cm, of angular broadening of radio sources due to the solar wind in the region 2–16 solar radii. Angular broadening is anisotropic with axial ratios in the range 2–16. Larger axial ratios are observed preferentially at smaller solar distances. Assuming that anisotropy is due to scattering blobs elongated along magnetic field lines, the distribution of position angles of the elliptically broadened images indicates that the field lines are non-radial even at the largest heliocentric distances observed here. At 5R
, the major axis scattering angle is 0.7 at =6 cm and it varies with heliocentric distance asR
–1.6. The level of turbulence, characterized by the wave structure function at a scale of 10 km along the major axis, normalized to =20 cm, has a value 20±7 at 5R
and varies with heliocentric distance asR
–3. Comprison with earlier results suggest that the level of turbulence is higher during solar maximum. Assuming a power-law spectrum of electron density fluctuations, the fitted spectral exponents have values in the range 2.8–3.4 for scales sizes between 2–35 km. The data suggests temporal fluctuations (of up to 10%) in the spectral exponent on a time scale of a few tens of minutes. The observed structure functions at different solar distances do not show any evidence for an inner scale; the upper limits are 1 km at 2R
and 4 km at 13R
. These upper limits are in conflict with earlier determinations and may suggest a reduced inner scale during solar maximum. 相似文献
6.
Spectrum scans of the head of Comet Bradfield (1980t) covering the wavelength range 365–640 nm were made on two nights when the heliocentric distance of the comet varied from 0.55 to 0.58 AU. The emission features of the CN band at 388 nm and Swan band sequence of C2 at 474 nm, 516 nm, and 563 nm are identified and absolute fluxes in these bands as well as in the continuum are derived. The continuum energy distribution curves of the comet have been compared with those of the Sun and the star Crv (G5 III). An estimate of the number of C2 and CN molecules in the head of the comet has been made through the measured intensities of their respective bands lying in this region. 相似文献
7.
Short-Term Periodicities in the Time Series of Solar Radio Emissions at Different Solar Altitudes 总被引：1，自引：0，他引：1
A spectral analysis of the time series of daily values of 12 parameters, namely, ten solar radio emissions in the range 275–1755 MHz, 2800 MHz solar radio flux, and sunspot numbers for six continuous intervals of 132 values each during June 1997–July 1999 showed considerable differences from one interval to the next, indicating a nonstationary nature. A 27-day periodicity was noticed in Interval 2 (26.8 days), 3 (27.0 days), 5 (25.5 days), 6 (27.0 days). Other periodicities were near 11.4, 12.3, 13.3, 14.5, 15.5, 16.5, 35, 40, 50–70 days. Periodicities were very similar in a large vertical span of the coronal region corresponding to 670–1755 MHz. Above this region, the homogeneity disappeared. Below this region, there were complications and distortions due to localized solar surface phenomena. 相似文献
8.
We show that within distances from the Sun's surface less than the height of a streamer helmet, each of two neighboring rays of the streamer belt, as they approach the solar surface, bends around the helmet on either side of it. Also, a minimum angular diameter of the rays of d2°–3° remains virtually constant within R=1.2–6.0 R
. A density inhomogeneity (`blob') can be produced above the helmet top visible to at least R6 R
. In this case the initial velocity of the `blob' increases with solar distance from where it is generated to something like the velocity of the bulk solar wind with which the `blob' is carried away. 相似文献
9.
Solar Wind Velocity and Anisotropic Coronal Kinetic Temperature Measured with the O Vi Doublet Ratio
Doppler dimming of the Ovi resonance lines (1032 Å, 1037 Å) in an expanding corona is calculated including the pumping effect on the Ovi 1037.61 Å of both Cii lines at 1036.34 Å and 1037.02 Å, and the effect of the width of the absorption profiles of the coronal oxygen ions along the incident radiation. The pumping effect of the Cii line at 1036.34 Å allows us to extend to approximately 450 km s–1 the measurement of solar wind velocities with the Ovi line ratio technique. Since the emissivity ratio of the Ovi doublet depends on the width of the oxygen coronal absorbing profiles, this ratio can provide an accurate measurement of the solar wind velocity in the case that the width of the absorbing profile along the direction of the incident radiation is independently determined. However, if on the one hand the ratio of the emissivities of the Ovi doublet has limitations in probing the wind velocity, on the other hand it can be used as a diagnostics for inferring the velocity distribution of the coronal Ovi ions along the radial, and detecting possible velocity anisotropies. This diagnostics, applied to recent observational results, allows us to infer that the velocity distribution of the oxygen ions is much broader in the direction perpendicular to the magnetic field direction, and that the acceleration of the fast solar wind in the first 2 solar radii is high. 相似文献
10.
A study of the properties of the cosmic radiation of energy - 10 MeV generated by solar flares is reported. Data from four Pioneer spacecraft in interplanetary orbits, and separated by 180° in heliocentric longitude are employed. Attention is restricted to the properties evident at times in excess of 1 day after the occurrence of the parent flare. The anisotropic character of the radiation; the gradients in heliocentric longitude; the decay time constants; and the energy spectra of the radiation are all studied in detail.It is found that the equilibrium anisotropy assumes a direction - 45° E of the satellite-Sun line at very late times. It is suggested that the anisotropy at such times is parallel to E × B. This observation confirms that convection is the determining process in the escape of the solar cosmic rays from the solar system. It indicates that a positive radial gradient of solar cosmic radiation density has builtup at orbit of Earth some 4 days after a flare. This results in an effective convective velocity of approximately 1/2 the solar wind velocity. Direct measurements indicate the presence of strong gradients in heliocentric longitude even at very late times ( 4 days). These gradients are essentially invariant with respect to time, e-folding angles of n - 30° have been observed at - 10 MeV. The presence of these gradients has a major effect on the temporal variation of the cosmic ray flux during the decay phase of the flare effect. Thus, the observed decay time constant is either increased or decreased relative to the convective value depending on the position of the observer relative to the centroid of the cosmic ray population injected by the flare. The effect of the gradient becomes more pronounced at lower energies, and may even exceed the convective removal rate. The observed decay time constant, the characteristics of the anisotropy, and the gradient in longitude are shown to be inter-related as demanded by theory. It is shown that the exponent of the cosmic ray spectrum is dependent on the location of the observer relative to the centroid of the cosmic ray population injected by the parent flare. At a given point in the frame of reference of the cosmic ray population, the spectral exponent is invariant with time.Now at CSIRO, G.P.O. Box 124, Port Melbourne, Victoria 3207, Australia.On leave from Physical Research Laboratory, Ahmedabad, India. 相似文献
11.
S. I. Akasofu 《Solar physics》1981,71(1):175-199
It is shown that major geomagnetic storms (¦Dst¦ > 100) tend to develop at about the time of the passage of the solar current sheet or disk at the location of the Earth, provided this passage is associated with (1) a large impulsive increase of the IMF magnitude B, (2) a negative value of the IMF angle (Theta), and (3) an increasing solar wind speed. The passage occurs in association with the 27-day rotation of the warped current disk or a temporal up-down movement of the latter. The period in which ¦Dst¦/t< 0 during major storms coincides approximately with the period when the solar windmagnetosphere energy coupling function becomes 1019 erg s–1. These conclusions do not depend on the phase of the sunspot cycle.These results may be interpreted as follows: A high speed solar wind flow, originating either from flare regions or coronal holes, tends to push the solar current disk to move upward or downward for either a brief period (1 3 days) or an extended period (2 weeks). A relatively thin region of a large IMF B > 10 is often present near the moving current disk. Waves are also generated on the moving current disk, and some of them cause large changes of . A high value of is found in the region of a large IMF B near the wavy solar current disk, where has a large negative value. 相似文献
12.
Andreev V. E. Efimov A. I. Samoznaev L. N. Chashei I. V. Bird M. K. 《Solar physics》1997,176(2):387-402
A statistical study of Faraday rotation fluctuations (FRF) has been performed using polarization angle data of S-band (f = 2.3 GHz) radio spacecraft signals. The measurements were recorded during the recurring superior conjunctions of the Helios probes, during which the solar proximate point of the radio ray path reached heliocentric distances between 3 and 34 R. The most commonly found temporal FRF spectra are power laws with an average spectral index 1.5 over the frequency range from 1 mHz < v < 10 mHz. The FRF variance decreases with heliocentric distance, the falloff exponent being 8 for R < 6 R and 3 for distances 8 < R < 6 R < 16 R. The results are interpreted under the assumption that the FRF are produced by Alfvén waves propagating in the coronal plasma. For the applicable range of heliocentric distances it is shown that Alfvén waves are in a regime of free propagation and probably transfer much of their energy to the kinetic energy of the solar wind. The spatial power spectrum of magnetic field fluctuations is inferred to be strongly anisotropic, the irregularities extending along the background magnetic field with axial ratios of the order of 10. 相似文献
13.
We study the effects of the sector structure of the interplanetary magnetic field (IMF) on the Galactic cosmic ray (GCR) anisotropy at solar minimum by using Global Network neutron monitor data. The hourly neutron monitor data for 1976 were averaged for the positive (+) and negative (–) IMF sectors (+ and – correspond to the antisolar and solar directions of magnetic field lines, respectively) and then processed by the global survey method. We found that the magnitude of the GCR anisotropy vector is larger in the positive IMF sector and that the phase shifts toward early hours. The derived GCR components A
r, A
, and A
for the different + and – sectors are then used to calculate the angle ( 46°) between the IMF lines and the Sun–Earth line, the solar wind velocity U ( 420 km/s), the ratio of the perpendicular (K
) and parallel (K
||) diffusion coefficients K
/K
|| = ( 0.33), and other parameters that characterize the GCR modulation in interplanetary space. 相似文献
14.
The interplanetary sector structure observed by the IMP-1 satellite during three solar rotations in 1963–4 is compared with the photospheric magnetic field structure observed with the solar magnetograph at Mt. Wilson Observatory. The interplanetary sector structure was most prominent on the sun in latitudes between 10 °N and 20 °N, although the average heliographic latitude of the satellite was 3 1/2 °S. A superposed-epoch analysis of the calcium plage structure obtained from the Fraunhofer Institute daily maps of the sun is used to discuss the relation between the structure of the plages and the interplanetary sector structure. A possible explanation for the observations is discussed in terms of a North-South asymmetry in the flow of the solar wind. It is suggested that these observations favor the equinoctial hypothesis as compared with the axial hypothesis for the explanation of the semi-annual maxima in geomagnetic activity. 相似文献
15.
The analysis of solar wind He++ and H+ ion distribution functions, collected over five months by the satellite Prognoz 1, shows that these are in general maxwellian but that often tails appear at higher speeds. The existing relation V-T, the observation of ratios of T/Tp 3.83 and V/Vp 1.035 give evidence of preferential He++ ion heating and acceleration. The criteria for heating by dissipation of hydromagnetic waves proposed by Barnes and Hung (1973) are tested experimentally. Finally, multifluid models are likely to predict certain observations such as dependence of the velocity ratio V/Vp on the solar wind flux. 相似文献
16.
. . .
, 相似文献
Transfer of resonance radiation in infinite medium is considered as a process of random walks of photons. Close relation is shown to exist between the problems of transfer of line radiation and the stable distributions of the probability theory. This relation is used as a basis of a new method for the investigation of the asymptotic properties of the radiation field far from the sources.
, 相似文献
17.
J. F. Valdés Galicia X. Moussas J. J. Quenby F. M. Neubauer R. Schwenn 《Solar physics》1984,91(2):399-413
Pitch angle scattering of energetic particles (100 MeV) in the interplanetary medium are studied using Helios 1 and 2 magnetometer and plasma data during 1976 near the minimum of solar activity. An IMF configuration was used in the computer experiments which allowed the pitch angle diffusion coefficient, D
and hence the parallel mean free path,
to be determined. The radial mean free path was found to vary as
r r
-0.9 between 0.4 and 1 AU, but between 0.3 and 0.4 AU it decreases significantly. To reconcile our value of
r at 1 AU, lying between 0.01 and 0.02 AU, with the average prompt solar proton event profile, an increasing value of
r at lower radial distances would be required. 相似文献
18.
Kunitomo Sakurai 《Solar physics》1971,17(2):459-467
Except for protons, the chemical composition of solar cosmic rays is very similar to the abundance of the elements at the photosphere of the Sun. If we consider the relative abundance ratio of protons to -particles (P/) at constant rigidity, this ratio is highly variable from one solar cosmic ray event to another. This ratio observed at the Earth, however, decreases monotonically with time from the onset of solar flares and, furthermore, is dependent on the heliocentric distance of the parent flares from the central meridian of the solar disk. P/'s which have been measured before the onset of SC geomagnetic storms change from 1.5 to 50 or more, being a function of the westward position of the source from the east limb of the Sun. These variations with respect to time and heliocentric distance suggest that the propagation of solar cosmic rays is strongly modulated in the interplanetary space. The major part of the -particles seem to propagate as if they are trapped within the magnetic clouds which produce SC geomagnetic and cosmic ray storms at the earth.The chemical composition and rigidity spectra of solar cosmic rays suggest that solar cosmic rays are mainly accelerated by the Fermi mechanism in solar flares. The observed variation of P/'s is produced mainly through the difference between the propagation characteristics of protons and -particles.NAS-NRC Associate with NASA. 相似文献
19.
J. L. Bertaux E. Kyrölä E. Quémerais R. Pellinen R. Lallement W. Schmidt M. Berthé E. Dimarellis J. P. Goutail C. Taulemesse C. Bernard G. Leppelmeier T. Summanen H. Hannula H. Huomo V. Kehlä S. Korpela K. Leppälä E. Strömmer J. Torsti K. Viherkanto J. F. Hochedez G. Chretiennot R. Peyroux T. Holzer 《Solar physics》1995,162(1-2):403-439
On board the SOHO spacecraft poised at L1 Lagrange point, the SWAN instrument is mainly devoted to the measurement of large scale structures of the solar wind, and in particular the distribution with heliographic latitude of the solar wind mass flux. This is obtained from an intensity map of the sky Lyman emission, which reflects the shape of the ionization cavity carved in the flow of interstellar H atoms by the solar wind. The methodology, inversion procedure and related complications are described. The subject of latitude variation of the solar wind is shortly reviewed: earlier Lyman results from Prognoz in 1976 are confirmed by Ulysses. The importance of the actual value of the solar wind mass flux for the equation of dynamics in a polar coronal hole is stressed. The instrument is composed of one electronic unit commanding two identical Sensor Units, each of them allowing to map a full hemisphere with a resolution of 1°, thanks to a two-mirrors periscope system. The design is described in some details, and the rationale for choice between several variants are discussed. A hydrogen absorption cell is used to measure the shape of the interplanetary Lyman line and other Lyman emissions. Other types of observations are also discussed : the geocorona, comets (old and new), the solar corona, and a possible signature of the heliopause. The connexion with some other SOHO instruments, in particular LASCO, UVCS, SUMER, is briefly discussed. 相似文献
20.
A cross-correlation study for time-lags of ±5 yrs between eleven ground based ozone stations (1957–1985) for = 40°N–75° N and = 30° E-114° W and five volcanic emissivity indices has shown their close connection: significant correlations well above 90% were obtained. Intepretation of these positive/negative correlations () was based on the global wind circulation (aided also by a 2-D, 3-D representation between, , ), and the types of volcanic aerosols leading to heterogeneous chemical reactions with ozone. 相似文献