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1.
SOHO/LASCO data were used to obtain the latitudinal and radial distributions of the brightness of the K- and F-corona in the
period of 1996 – 2007, and their solar-cycle variations were studied. Then an inversion method was employed to obtain the
radial distributions of the electron density N
e(R,θ) for various latitude values on the coronal images. Our values of N
e(R,θ) are in good agreement with the findings of other authors. We found that in an edge-on streamer belt the electron density,
like the K-corona brightness, varies with distance more slowly in the near-equatorial rays than in near-polar regions. We
have developed a method for assessing the maximum values of the electron density at the center of the face-on streamer belt
in its bright rays and depressions between them. Not all bright rays observed in the face-on streamer belt are found to be
associated with an increased electron density in them. Mechanisms for forming such rays have been suggested. 相似文献
2.
Synoptic maps of white-light coronal brightness from SOHO/LASCO C2 and distributions of solar wind velocity obtained from
interplanetary scintillation are studied. Regions with velocity V≈300 – 450 km s−1 and increased density N>10 cm−3, typical of the “slow” solar wind originating from the belt and chains of streamers, are shown to exist at Earth’s orbit,
between the fast solar wind flows (with a maximum velocity V
max ≈450 – 800 km s−1). The belt and chains of streamers are the main sources of the “slow” solar wind. As the sources of “slow” solar wind, the
contribution from the chains of streamers may be comparable to that from the streamer belt. 相似文献
3.
A technique is proposed for separating the rays of the streamer belt with quasi-stationary and non-stationary solar wind (SW) flows. It is shown that the lifetime of rays with a quasi-stationary SW can exceed 20 days. A new method has been developed for measuring the relative density distribution of a quasi-stationary slow SW flowing along the streamer belt's ray of increased brightness, based on the LASCO/SOHO data. It is shown that the density n for such SW flows varies with the radius R according to the relationship nR
–, where =13.3–3.9 within 4 R
0 R 6 R
0 (here R
0 is the solar radius), and decreases gradually further away. It is also shown that the V(R)-profiles in some rays of the streamer belt differ little from each other, although the value of the mass flow density, j
E, at the Earth's orbit in them can vary more than by a factor of 4. This distinguishes in a crucial respect a slow SW in the streamer belt's rays from a fast SW originating in coronal holes, for which j
Econstant and the dependences V(R) in different fast flows can differ greatly. 相似文献
4.
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
5.
R. P. Kane 《Solar physics》2007,246(2):471-485
Many methods of predictions of sunspot maximum number use data before or at the preceding sunspot minimum to correlate with
the following sunspot maximum of the same cycle, which occurs a few years later. Kane and Trivedi (Solar Phys. 68, 135, 1980) found that correlations of R
z(max) (the maximum in the 12-month running means of sunspot number R
z) with R
z(min) (the minimum in the 12-month running means of sunspot number R
z) in the solar latitude belt 20° – 40°, particularly in the southern hemisphere, exceeded 0.6 and was still higher (0.86)
for the narrower belt > 30° S. Recently, Javaraiah (Mon. Not. Roy. Astron. Soc.
377, L34, 2007) studied the relationship of sunspot areas at different solar latitudes and reported correlations 0.95 – 0.97 between minima and maxima of sunspot areas at low latitudes
and sunspot maxima of the next cycle, and predictions could be made with an antecedence of more than 11 years. For the present
study, we selected another parameter, namely, SGN, the sunspot group number (irrespective of their areas) and found that SGN(min) during a sunspot minimum year at latitudes > 30° S had a correlation
+0.78±0.11 with the sunspot number R
z(max) of the same cycle. Also, the SGN during a sunspot minimum year in the latitude belt (10° – 30° N) had a correlation +0.87±0.07 with the
sunspot number R
z(max) of the next cycle. We obtain an appropriate regression equation, from which our prediction for the coming cycle 24 is R
z(max )=129.7±16.3. 相似文献
6.
P. Démoulin K.-L. Klein C. P. Goff L. van Driel-Gesztelyi J. L. Culhane C. H. Mandrini S. A. Matthews L. K. Harra 《Solar physics》2007,240(2):301-313
Radio emissions of electron beams in the solar corona and interplanetary space are tracers of the underlying magnetic configuration
and of its evolution. We analyse radio observations from the Culgoora and WIND/WAVES spectrographs, in combination with SOHO/LASCO
and SOHO/MDI data, to understand the origin of a type N burst originating from NOAA AR 10540 on January 20, 2004, and its
relationship with type II and type III emissions. All bursts are related to the flares and the CME analysed in a previous
paper (Goff et al., 2007). A very unusual feature of this event was a decametric type N burst, where a type III-like burst, drifting towards
low frequencies (negative drift), changes drift first to positive, then again to negative. At metre wavelengths, i.e., heliocentric distances ≲1.5R
⊙, these bursts are ascribed to electron beams bouncing in a closed loop. Neither U nor N bursts are expected at decametric
wavelengths because closed quasi-static loops are not thought to extend to distances ≫1.5R
⊙. We take the opportunity of the good multi-instrument coverage of this event to analyse the origin of type N bursts in the
high corona. Reconnection of the expanding ejecta with the magnetic structure of a previous CME, launched about 8 hours earlier,
injects electrons in the same manner as with type III bursts but into open field lines having a local dip and apex. The latter
shape was created by magnetic reconnection between the expanding CME and neighbouring (open) streamer field lines. This particular
flux tube shape in the high corona, between 5R
⊙ and 10R
⊙, explains the observed type N burst. Since the required magnetic configuration is only a transient phenomenon formed by reconnection,
severe timing and topological constraints are present to form the observed decametric N burst. They are therefore expected
to be rare features. 相似文献
7.
Tuula Summanen 《Astrophysics and Space Science》2000,274(1-2):143-148
In this work we have modelled the solar wind proton flux which varies as a function of distance to the heliomagnetic equator
and its effects on the interplanetary Lyman α radiation. The results imply that a groove observed in Lyman α intensity patterns
toward the upwind direction Bertaux et al. disappears when the tilt angle of the heliomagnetic equator is larger than 20°.The observations by Bertaux et al. were measured during the solar wind minimum when the tilt angle of the streamer belt is low. During the solar wind maximum
when the tilt angle of the streamer belt is large the Lyman α groove should disappear according to our results.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
8.
It is shown on the basis of analyzing the LASCO/SOHO data that the main quasi-stationary solar wind (SW), with a typical lifetime of up to 10 days, flows in the rays of the streamer belt. Depending on R, its velocity increases gradually from V3 km s–1 at R1.3 R
to V170 km s–1 at R15 R
. We have detected and investigated the movement of the leading edge of the main solar wind at the stage when it occupied the ray, i.e., at the formative stage of a quasi-stationary plasma flow in the ray. It is shown that the width of the leading edge of the main SW increases almost linearly with its distance from the Sun. It is further shown that the initial velocity of the inhomogeneities (`blobs') that travel in the streamer belt rays increases with the distance from the Sun at which they originate, and is approximately equal to the velocity of the main solar wind which carries them away. The characteristic width of the leading edge of the `blob' R
, and remains almost unchanging as it moves away from the Sun. Estimates indicate that the main SW in the brightest rays of the streamer belt to within distances at least of order R3 R
represents a flow of collisional magnetized plasma along a radial magnetic field. 相似文献
9.
We present for the first time a three-dimensional reconstruction of the electron density in the corona at distances from 1.5R ⊙ to 4R ⊙ using COR1 STEREO observations. The reconstruction is performed using a regularized tomography inversion method for two biweekly periods corresponding to Carrington Rotations 2058 and 2066. Images from the two STEREO spacecraft are used to compare the reconstructed density structures with coronal features located by triangulation. We find that the location of a bright tip of a helmet streamer obtained from the tomographic reconstruction is in good agreement with the location obtained by triangulation. The reconstructed density structure of the equatorial streamer belt is largely consistent with the variation of the current sheet derived from a potential magnetic field extrapolation for most of the equatorial region and for an MHD model of the corona. A zero-value density region in the reconstruction is identified with a low-density region seen in an EUVI image below the reconstruction domain. 相似文献
10.
11.
A rocket-borne coronagraph utilizing external occulting disks was used to photograph the solar corona from 3 to 9 R
s at 1931 UT on 7 March, 1970. Comparison of the rocket and ground-based observations shows a one-to-one correspondence between major streamers from the inner to the outer corona. In particular streamers over the poles are clearly visible against the background corona from 3 to 8 R
s. These rocket data had a scattered light level of 1.2 × 10–10
B
s. The derived quiet equatorial and polar K + F corona was within 10% of the absolute brightness of standard coronal models and displayed identical radial gradients to those models. The photometric profiles of the NE limb streamer were analyzed assuming a model in which the core density follows a Gaussian distribution in directions perpendicular to the radius vector. This streamer was assumed to be rooted on the visible disk at 55 to 60° from the plane-of-the-sky as based on K-coronameter and XUV data. An uncertainty of as much as a factor of three still remains for the value of the axis density owing to uncertainty in the line-of-sight dimension of the streamer. 相似文献
12.
J. David Bohlin 《Solar physics》1970,13(1):153-175
A unique combination of photographic and K-coronameter data were used to study the structure and evolution of two known coronal streamers. In addition, two other K-coronameter enhancements were studied as representing ideal second examples of the known streamers. As a general rule the observations indicate that these features were direct coronal manifestations of photospheric bipolar magnetic regions (BMR) and were of two basic types:active region, by which is meant a coronal streamer which develops radially over a low-latitude active region; andhelmet which denotes a streamer whose structure and development appear to be a consequence of a long-lived complex of activity, composed of both trailing magnetic fields and a parent center of disk activity.The similarity of growth rates during the first solar rotation of life led to derivation of a total streamer density of 4–5 × 108 cm–3 atr = 1.125R
. This density may represent a characteristic maximum density at the base of streamers. The intensity gradient of the inner (r1.5R
) corona was used to establish a qualitative evolutionary model of streamers which synthesizes the observations. Briefly, streamers initially develop over active regions; the streamer growth rate may be as rapid as the disk activity, or at worst lags flare activity by
solar rotation. The streamer can be the cause of interplanetary and geomagnetic effects at 1 AU within a solar rotation after birth. Thereafter the streamer follows an evolution dictated by the underlying solar magnetic fields. In any case the lowest level of the coronal enhancement has a lifetime not exceeding that of the solar disk activity. 相似文献
13.
A large equatorial coronal streamer observed in the outer corona (3R
) grew in brightness and size during successive limb passages between October 6, 1973 and January 10, 1974 (solar rotations 1606–1611). Unlike previous studies of streamers and their photospheric associations, no definite surface feature could be identified in the present case. This suggests that the streamer is associated with the large scale photospheric magnetic field. Comparison of the streamer growth with observed underlying photospheric magnetic flux changes indicated that as the streamer increased in brightness, areal extent, and density, the photospheric magnetic flux decreased. Three possible explanations for the streamer's growth are presented; the conceptually simplest being that the decrease in photospheric field results in an opening of the flux tubes under the streamer which permits an increased mass flux through the streamer.The National Center for Atmospheric Research is sponsored by the National Science Foundation. 相似文献
14.
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
15.
The analysis of a storm of type III solar radio bursts observed in August 1968 between 5 and 0.2 MHz by the RAE-1 satellite has yielded the storm morphology, a possible relation to meter and decameter storms, and an average exciter speed of 0.37 c between 10 and 40 R
(Fainberg and Stone, 1970a, b). A continuation of the analysis, based on the apparent dependence of burst drift rate on heliographic longitude of the associated active region, now provides a distance scale between plasma levels in the streamer, an upper limit to the scale size of coronal streamer density inhomogeneities, and an estimate of the solar wind speed. By fixing one level the distance scale is utilized to determine the electron density distribution along the streamer between 10 and 40 R
. The streamer density is found to be 16 times that expected for the solar minimum quiet solar wind. An upper limit to the scale size of streamer density inhomogeneities is estimated to be of the order of 1 or 2 solar radii over the same height range. From the progressive delay of the central meridian passage (CMP) of the lower frequency emission, a streamer curvature is inferred which in turn implies an average solar wind speed of 380 km/sec between 14 and 36 R
within the streamer. 相似文献
16.
The transfer of wave energy to plasma energy is a very crucial issue in coronal holes and helmet streamer regions. Mixed mode
Alfvén waves, also known as kinetic Alfvén wave (KAW) can play an important role in the energization of the plasma particles
because of their potential ability to heat and accelerate the plasma particles via Landau damping. This paper presents an
investigation of the growth of a Gaussian perturbation on a non-uniform kinetic Alfvén wave having Gaussian wave front. The
effect of the nonlinear coupling between the main KAW and the perturbation has been studied. The dynamical equations for the
field of the main KAW and the perturbation have been established and their semi-analytical solution has been obtained in the
low (β≪ me/mi≪ 1) and the high (β≫ me/mi≪ 1) β cases. The critical field of the main KAW and the perturbation has been evaluated. Nonlinear evolution of the main
KAW and the perturbation into the filamentary structures and its dependence on various parameters of the solar wind and the
solar corona have been investigated in detail. These filamentary structures can act as a source for the particle acceleration
by wave particle interaction because the KAWs are mixed modes and Landau damping is possible. Especially, in the solar corona,
the low β and the high β cases could correspond to the coronal holes and the helmet streamer. The presence of the primary
and the secondary filaments of the perturbation may change the spectrum of the Alfvénic turbulence in the solar wind. 相似文献
17.
S. Koutchmy 《Solar physics》1972,24(2):373-384
A Hydrodynamical Study of the Large NE Coronal Streamer Observed during the 7th March Eclipse.
The photometry of the large coronal streamer located on the N-E limb of the Sun observed on the 7th March 1970 in Mexico has been performed using compensated plates in unpolarized light as well as in tangentially and radially polarized light. The measured polarizations permit us to locate the streamer in space using a generally used method. The density distribution in the core of the streamer and for r > 1.5 R
is given as well as the half-widths of the density distribution perpendicular to the axis of the streamer. Densities n(r) in the 1(R
) < r < 1.5(R
) region are obtained assuming hydrostatic equilibrium (4) for 1.5 < r < 2.The axial values of n(r) are given which agree with those of others models. The values of parameters for the model given are tabulated.The variation of the expansion velocity has been derived from the hydrodynamical continuity equation. This velocity becomes supersonic [v > 150(km s–1)] above the height of minimum cross section of the streamer, r = 3.5 (R
). This result is verified by a simple calculation based on the observed curvature of the streamer's stalk. The velocity corresponding to the garden hose effect considered has a lower value equal to 60(km s–1). The radial distribution of the expansion velocity is shown. Our model allows us to extrapolate in order to obtain the value of v(r) at the Sun's surface. This value, v 0.07 (km s–1) can be compared with the value of the differential rotation velocity of the foot of the streamer. The values of the corpuscular flux of the streamer are calculated [F=2.4 × 1034( s-1] and agree with the value of the flux corresponding to the density enhancements of the solar wind, measured in situ. This shows the importance of large streamers for the coronal expansion processus. 相似文献
18.
Atsuma Yamasaki 《Astrophysics and Space Science》2005,296(1-4):277-280
New BV light curves of the A-type W UMa star AQ Psc (P = 0.476d) have been observed and are described. A few times of minimum light are obtained and the ephemeris is improved.
The light curves are analyzed for the binary parameters with a light curve synthesis method. Combining the results with Lu
and Rucinski’s spectroscopic mass ratio we determined the masses and radii of the components: M
1 = 1.69M
⊙, M
2 = 0.38M
⊙, R
1 = 1.77R
⊙, and R
2 = 0.89R
⊙. 相似文献
19.
F. Sánchez-Bajo E. García-Melendo J. M. Gómez-Forrellad 《Astrophysics and Space Science》2007,312(3-4):151-159
New ephemeris and the absolute parameters—masses, radii and luminosities—of the contact systems VW LMi and BX Dra have been
obtained, by means of the analysis of the minima data available in the literature (for the determination of the ephemeris)
and combining the previously published spectroscopic information and the results of the Wilson-Devinney method using photometric
data (for the determination of the absolute parameters). The VW LMi O−C analysis confirms the multiplicity of the system detected previously from the spectroscopic data. Masses of the VW LMi contact
system primary and secondary components are 1.67 ± 0.02M
⊙ and 0.70 ± 0.02M
⊙, respectively. The corresponding radii are 1.709 ± 0.007R
⊙ and 1.208 ± 0.006R
⊙, respectively. For the BX Dra contact system the masses are 2.19 ± 0.13M
⊙ and 0.63 ± 0.06M
⊙, and the radii, 2.13 ± 0.04R
⊙ and 1.26 ± 0.03R
⊙, for the primary and secondary, respectively. In both cases, the estimated luminosities seem to be slightly greater that
the values derived from the Hipparcos distances. 相似文献
20.
We present the results of our infrared observations of WR 140 (=V1687 Cyg) in 2001–2010. Analysis of the observations has
shown that the J brightness at maximum increased near the periastron by about 0
m
.3; the M brightness increased by ∼2
m
in less than 50 days. The minimum J brightness and the minimum L and M brightnesses were observed 550–600 and 1300–1400 days after the maximum, respectively. The JHKLM brightness minimum was observed in the range of orbital phases 0.7–0.9. The parameters of the primary O5 component of the
binary have been estimated to be the following: R(O5) ≈ 24.7R
⊙, L(O5) ≈ 8 × 105
L
⊙, and M
bol(O5) ≈ −10
m
. At the infrared brightness minimum, T
g ∼ 820–880 K, R
g ≈ 2.6 × 105
R
⊙, the optical depth of the shell at 3.5 μm is ∼5.3 × 10−6, and its mass is ≈1.4 × 10−8
M
⊙. At the maximum, the corresponding parameters are ∼1300 K, 8.6 × 104
R
⊙, ∼2 × 10−4, and ∼6 × 10−8
M
⊙; the mean rate of dust inflow (condensation) into the dust structure is ∼3.3 × 10−8
M
⊙ yr−1. The mean escape velocity of the shell from the heating source is ∼103 km s−1 and the mean dispersal rate of the shell is ∼1.1 × 10−8
M
⊙ yr−1. 相似文献