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1.
The 1974–1988 Crimean measurements of the solar line-of-sight velocity continue to show the presence of a statistically significant periodicity P
1 = 160.009 (±) min with an average harmonic amplitude of about 21 cm s–1. The period is supposed to be that of the global pulsation of the Sun but with a little-known physical mechanism of excitation.The new observations give some evidence for the existence of a second periodicity, P
1 = 160.014 (±) min. It is hypothesized that the appearance of P
1 might be a sidelobe mode (of the P
0-oscillation) induced by rapid rotation of the central solar core.It is also noted that the spacing, in frequency, between P
0 and P
1, corresponds to a beat period of 10 ± 3 yr, which happens to be in good agreement with the average duration of the 11 yr cycle of the magnetic activity of the Sun. Accordingly, we suppose that the phase shift of the P
0-mode between the 1974–1982 and 1986–1988 time intervals reflects a remarkable change of the general magnetic field of the Sun in the course of the 22 yr solar cycle. 相似文献
2.
The solar corona – one of the most spectacular celestial shows and yet one of the most challenging puzzles –
exhibits a spectrum of structures related to both the quiet Sun and active regions. In spite of dramatic differences in appearance
and physical processes, all these structures share a common origin: they are all related to the solar magnetic field. The
origin of the field is beneath the turbulent convection zone, where the magnetic field is not a master but a slave, and one
can wonder how much the coronal magnetic field “remembers” its dynamo origin. Surprisingly, it does.
We will describe several observational phenolmena that indicate a close relationship between coronal and sub-photospheric
processes. 相似文献
3.
W. Landgraf 《Solar physics》1992,142(2):403-406
From astrometric observations of minor planet (1566) Icarus from 1949 to 1987 were made solutions for improved orbital elements of Icarus and the quadrupole moment of the Sun. The formal result was J2 = -0.6±5.8 &d 10–6. From this we can conclude that J
2 is very probably less than 2 · 10–-5. 相似文献
4.
Power spectra based on Pioneer 6 interplanetary magnetic field data in early 1966 exhibit a frequency dependence of f
–2 in the range 2.8 × 10–4 to 1.6 × 10–2 cps for periods of both quiet and disturbed field conditions. Both the shape and power levels of these spectra are found to be due to the presence of directional discontinuities in the microstructure (< 0.01 AU) of the interplanetary magnetic field. Power spectra at lower frequencies, in the range of 2.3 × 10–6 to 1.4 × 10–4 cps, reflect the field macrostructure (> 0.1 AU) and exhibit a frequency dependence roughly between f
–1 and f
–3/2. The results are related to theories of galactic cosmic-ray modulation and are found to be consistent with recent observations of the modulation. 相似文献
5.
We measure the separation velocity of opposite poles from 24 new bipoles on the Sun. We find that the measured velocities range from about 0.2 to 1 km s–1. The fluxes of the bipoles range over more than two orders of magnitude, and the mean field strength and the sizes range over one order of magnitude. The measured separation velocity is not correlated with the flux and the mean field strength of the bipole. The separation velocity predicted by the present theory of magnetic buoyancy is between 7.4Ba
–1/4 cot and 13 cot km s–1, where is the elevation angle of the flux tube at the photosphere (see Figure 9), B is the mean field strength, and a is the radius of the observed bipole. The rising velocity of the top of flux tubes predicted by the theory of magnetic buoyancy is between 3.7Ba
–1/4 and 6.5 km s–1. The predicted separation velocity is about one order of magnitude higher than those measured, or else the flux tubes are almost vertical at the photosphere. There is no correlation between the measured separation velocity and the theoretical value, 7.4Ba
–1/4. The predicted rising velocity is also higher than the vertical velocity near the line of inversion in emerging flux regions observed by other authors. 相似文献
6.
It is shown that if the Sun passed through a T Tauri stage, then a mass loss of only 15% would be sufficient to despin the Sun to an angular velocity of 0 (10–5 rad/sec) at 107 years without the additional braking effect of an enhanced magnetic field. Thus the present Sun could have a core rotating at most ten times faster than its surface. 相似文献
7.
The 1968–2000 data on the mean magnetic field (MMF, longitudinal component) of the Sun are analysed to study long-time trends of the Sun's magnetic field and to check MMF calibration. It is found that, within the error limits, the mean intensity of photospheric magnetic field (the MMF strength, |H|), did not change over the last 33 years. It clearly shows, however, the presence of an 11-year periodicity caused by the solar activity cycle. Time variations of |H| correlate well with those of the radial component, |B
r|, of the interplanetary magnetic field (IMF). This correlation (r=0.69) appears to be significantly higher than that between |B
r| and the results of a potential source-surface extrapolation, to the Earth's orbit, of synoptic magnetic charts of the photosphere (using the so-called `saturation' factor –1 for magnetograph measurements performed in the line Fei 525.0 nm; Wang and Sheeley, 1995). It seems therefore that the true source surface of IMF is the `quiet' photosphere – background fields and coronal holes, like those for MMF. The average `effective' magnetic strength of the photospheric field is determined to be about 1.9 G. It is also shown that there is an approximate linear relation between |B
r| and MMF intensity |H| (in gauss)|B
r|(H
0)min×(1+C|H|)where =1.5×10–5 normalizes the photospheric field strength to 1 AU distance from the Sun, (H
0)min=1.2 G is some minimal `effective' intensity of photospheric background fields and C=1.3 G–1 an empirical constant. It is noted that good correlation between time variations of |H| and |B
r| makes suspicious a correction of the photospheric magnetic fields with the use of saturation factor –1. 相似文献
8.
D.V. Erofeev 《Solar physics》2001,198(1):31-50
To investigate the relationship between solar activity and the large-scale axisymmetric magnetic field of the Sun, we inferred from sunspot data over the period 1964–1985 a latitude–time distribution of magnetic field associated with active regions. This has been done allowing for both bipolar structure of the active regions and inclination of their axes to parallels of latitude, so the inferred magnetic field characterizes latitudinal separation of magnetic polarities which might be related to the large-scale magnetic field of the Sun according to the Babcock–Leighton model. The inferred magnetic field, A
z, is compared with the longitude-averaged (zonal) magnetic field of the Sun, B
z, derived from series of magnetograms obtained at Mount Wilson Observatory in the years 1964–1976, and at Kitt Peak National Observatory during the period from 1976 to 1985. The inferred magnetic field, A
z, exhibits a complex structure distribution of magnetic polarities with respect to latitude and time. Apart from concentration of the different polarity magnetic fields inside the high- and low-latitude portions of the sunspot belts, bipolar active regions produce an intensive, shorter-scale component of the magnetic field which varies on the time scale of about 2 years. Such a short-term variation of A
z reveals substantial correlation with the short-term component of B
z which has the form of the poleward-drifting streams of magnetic field. Most significant correlation takes place between the short-term variations of A
z occurring at latitudes below 20° and those of the large-scale magnetic fields occurring at middle latitudes of 40–50°. Moreover we analyze harmonic coefficients a
l and b
l obtained by expanding A
z and B
z into series in terms of the spherical harmonics. Power spectra of the time-dependent harmonic coefficients indicate that both A
z and B
z reveal a number of resonant modes which oscillate either with the 22-year period in the case of the anti-symmetric (odd-l) modes or with periods of about 2 years in the case of the symmetric (even-l) modes, but the resonant modes of A
z have significantly larger values of the spherical harmonic degree l (and, hence, smaller spatial scales) as compared to those of B
z. It is found that there is a close relationship between the harmonic coefficients b
l and a
m for which either m–l16 (even l=4,...,10) or m–l=4 (odd l=5,...,15). 相似文献
9.
For an observer in space the intensities and anisotropies of solar cosmic-ray events are governed by the duration and the functional shape of the injection processes near the Sun and by the propagation along the interplanetary magnetic field from the Sun to the observer. We study the influence of four different types of solar injections (Gaussian, exponential, step-function and coronal diffusion), and of a purely diffusive interplanetary propagation, where the diffusion coefficient has a power law dependence on the radial distance from the Sun, =Mr
on both the time-intensity and the time-anisotropy profiles at 1 AU. The main results are as follows: A slow quasi-exponential decay of the intensity can be modelled in some cases; all finite injections produce high anisotropies during the main phase of an event; an effective solar injection length can be determined from simultaneous inspection of the intensities and anisotropies; the intensities and anisotropies do to first order not depend on the analytic shape of the various injection profiles. The model is applied to the November 18, 1968 solar event as observed by Pioneer 9 in the 7.5–21.5 MeV and 21.5–60 MeV energy channels. We obtain local diffusion coefficients in the range M= (2.5–5) × 1021 cm2 s–1 and injection periods of the order of 10–20 hr. Closer inspection reveals the change of interplanetary propagation conditions during the event. 相似文献
10.
The magnetic field in an axisymmetric pore is current free and can be represented by a flux tube with a magnetic potential of the formAJ
0(kr)e
-kz. For a given magnetic flux the field in this pore model is uniquely defined if the magnetic pressure balances the gas pressure at two levels. For models with fluxes of 0.5–3.0 × 1020 mx the surface radius varies from 1100–2700 km (diameters of 3–8 arc-sec) and the Wilson depression is estimated at 200 km. As the flux increases, the field becomes nearly horizontal at the edge of the pore and eventually a penumbra is formed. The distinction between pores and sunspots is investigated; the critical flux is about 1020 Mx, corresponding to a radius of 1500 km.Visitor, as a member of the High Altitude Observatory Solar Project, at Sacramento Peak Observatory, Sunspot, N.M., U.S.A. 相似文献
11.
We investigate a latitude–time distribution of polar faculae observed at Ussuriysk Observatory in years 1966–1986. The distribution is compared with the longitude-averaged (zonal) magnetic field of the Sun calculated from the data obtained at Mount Wilson Observatory in the years 1966–1976, and at Kitt Peak National Observatory during the period from 1976 to 1985. We found that slow, poleward-directed migration of the polar faculae zones occurring during the course of the solar cycle is not a continuous process, but it contains several episodes of appearance and fast poleward drift of new zones of polar faculae. At the rising phase of the solar cycle, new zones of polar faculae appear at latitudes as low as 40°, but the ones observed during the declining phase of the solar cycle originate at higher latitudes of 50–55°. Such episodes of appearance and fast migration of the polar faculae zones are associated with the poleward-directed streams of magnetic field originated at low latitudes. Moreover, we found some evidence for existence of an additional component of the polar faculae activity that reveals an equatorward migration during the course of the solar cycle. We also investigated a relationship between the number of polar faculae, n, and absolute magnetic flux z of the zonal mode of the solar magnetic field. We found that within the polar zones of the Sun, substantial correlation between temporal variations of n and z takes place both on the time scale of the solar cycle and on a shorter time scale of 2–4 years. The relationship between the number of polar faculae and magnetic flux may be approximated by a linear dependence n=0.12z (where z is expressed in 1021 Mx), except for time interval 1977 through 1980 for which the factor of proportionality is found to have a systematically larger value of 0.20. 相似文献
12.
Based on spectral observations of active region NOAA 8545 on 19 May 1999, we describe the processes responsible for non-thermal long-lasting radio emission and for narrow-band non-drifting bursts observed at the same time. Non-thermal long-lasting radio emission consisted of two components: short-duration (1–2 s) microbursts with fluxes about 0.001 s.f.u. and continuum emission with growing spectrum in the range of 1000–2000 MHz. Energetic electrons continuously existed in the active region for more than 2.2 hours. The nature and parameters of microbursts were discussed by Bogod, Mercier, and Yasnov (2001). Here we consider the continuum source nature. It is shown that the model, taking into account the cyclotron loss-cone instability of hot electrons and the generation of plasma waves at the upper hybrid frequency, may explain the observed continuum source parameters. For the narrow-band non-drifting bursts we consider two models: the first taking into account an excitation of weak shock waves across the magnetic field and the second with an excitation of the upper hybrid waves under the double plasma resonance. Continuum source parameters are close to the last model. Our estimations for the magnetic field strength are as follows: H=120–126 G, which is valid for the region where the electron density of background plasmas n=(1.4–1.9) ×109 cm–3; H=180–190 G for the region where n=(3.0–4.3) ×109 cm–3; H=290 G for the region where n
e=2.5×1010 cm–3; and H=350 G for the region where n
e=3.5×1010 cm–3. The speed of the fast electrons is about 0.10–0.14 c. 相似文献
13.
Poleward migration of the magnetic neutral line on the Sun has been calculated for the periods 1945–1950 and 1955–1981 using synoptic charts based on H observations. Epochs of sign reversal of the solar magnetic field at latitudes 50° to 90° have been determined for these periods. During the cycles 19 and 20 a threefold sign reversal took place in the northern hemisphere. During all the above cycles both the solar poles were of one polarity for a period ranging from 0.5 to 1 year. The poleward drift velocity of the magnetic neutral line varies from 6 to 29 m s–1 and seems to depend on the strength of the cycle. 相似文献
14.
Whistlers recorded at low latitude ground stations of Gulmarg, Nainital and Varanasi were used to infer the east-west component of electric field on the nightside plasmasphere atL=1.2, 1.12, and 1.07 during magnetic storm periods. The method of measuring electric field from the observed cross-L motions of whistler ducts within the plasma-sphere, indicated by changes in nose frequency of whistlers has been outlined. The nose frequencies of the non-nose whistlers under consideration have been deduced from Dowden-Allocock linear Q-technique. The results show eastward electric fields of 0.7 mVm–1 in the equatorial plane of Gulmarg and 0.3 mVm–1 in the equatorial plane of Nainital in the premidnight local time sector. Near midnight, there is a sharp transition from eastward field to a westward electric field of 0.2–0.7 mV m–1 for Gulmarg, 0.3–0.5 mV m–1 for Nainital and 0.1–0.3 mVm–1 for Varanasi. 相似文献
15.
Time series of 2-dimensional spectro-polarmetric data were obtained with the intent of studying the temporal behavior of velocity, magnetic flux, and characteristics of the Stokes V profile in a small region of a larger sunspot. Full Stokes profiles in I, Q, U, and V were obtained. Velocity oscillations were found at frequencies of 3.3 mHz in each of the profiles. Acoustic power maps indicate that locations of highest power correspond to areas in which the polarization signal was greatest, therefore no conclusion about the type of wave mode participating in the oscillations can be made. Velocity amplitudes were I: 71 m s–1, Q: 47 m s–1, U: 65 m s–1 and V: 86 m s–1. Oscillatory behavior was also detected in longitudinal field strength, with an r.m.s. amplitude of 22 G, at 2.6 and 3.3 mHz. The power was localized at the umbral/penumbral boundary. A phase analysis indicates a –130° phase difference with Stokes V velocity oscillations at 3.3 mHz and a 75° difference at 2.6 mHz. Results are consistent with magnetic field lines swaying in response to a p-mode driver. No oscillatory behavior was seen in Stokes V asymmetry or amplitude splitting. 相似文献
16.
The mean coronal magnetic field determined from HELIOS Faraday rotation measurements 总被引：1，自引：0，他引：1
M. Pätzold M. K. Bird H. Volland G. S. Levy B. L. Seidel C. T. Stelzried 《Solar physics》1971,109(1):91-105
Coronal Faraday rotation of the linearly polarized carrier signals of the HELIOS spacecraft was recorded during the regularly occurring solar occultations over almost a complete solar cycle from 1975 to 1984. These measurements are used to determine the average strength and radial variation of the coronal magnetic field at solar minimum at solar distances from 3–10 solar radii, i.e., the range over which the complex fields at the coronal base are transformed into the interplanetary spiral. The mean coronal magnetic field in 1975–1976 was found to decrease with radial distance according to r
–, where = 2.7 ± 0.2. The mean field magnitude was 1.0 ± 0.5 × 10 –5 tesla at a nominal solar distance of 5 solar radii. Possibly higher magnetic field strengths were indicated at solar maximum, but a lack of data prevented a statistical determination of the mean coronal field during this epoch. 相似文献
17.
J. Javaraiah 《Journal of Astrophysics and Astronomy》2000,21(3-4):167-170
Using the data on sunspot groups compiled during 1879&#x2013;1975, we determined variations in the differential rotation
coefficientsA andB during the solar cycle. The variation in the equatorial rotation rateA is found to be significant only in the odd numbered cycles, with an amplitude &#x223C; 0.01 &#x03BC; rads-1. There exists a good anticorrelation between the variations of the differential rotation rateB derived from the odd and even numbered cycles, suggesting existence of a &#x2018;22-year&#x2019; periodicity inB. The amplitude of the variation ofB is &#x223C; 0.05 &#x03BC; rad s-1. 相似文献
18.
Martin Beech 《Astrophysics and Space Science》1985,116(1):207-212
We consider the various methods used to constrain the possible field strength of the present day intergalactic field and findB
0(G)<10–10 as a probable upper bound. It is suggested that the observed intergalactic magnetic field might not be primordial in origin but rather the result of magnetic flux leakage from galaxies and clusters of galaxies. 相似文献
19.
Dust grains of radiir
g
3×10–6 cm, injected into the intercloud medium at speeds in the range 107–108 cm s–1, may be stochastically accelerated to speeds 0.1c due to scattering by irregularities in the galactic magnetic field. 相似文献
20.
A. H. Gabriel G. Grec J. Charra J. -M. Robillot T. Roca Cortés S. Turck-Chièze R. Bocchia P. Boumier M. Cantin E. Cespédes B. Cougrand J. Crétolle L. Damé M. Decaudin P. Delache N. Denis R. Duc H. Dzitko E. Fossat J. -J. Fourmond R. A. García D. Gough C. Grivel J. M. Herreros H. Lagardère J. -P. Moalic P. L. Pallé N. Pétrou M. Sanchez R. Ulrich H. B. van der Raay 《Solar physics》1995,162(1-2):61-99
The GOLF experiment on the SOHO mission aims to study the internal structure of the sun by measuring the spectrum of global oscillations in the frequency range 10–7 to 10–2 Hz. Bothp andg mode oscillations will be investigated, with the emphasis on the low order long period waves which penetrate the solar core. The instrument employs an extension to space of the proven ground-based technique for measuring the mean line-of-sight velocity of the viewed solar surface. By avoiding the atmospheric disturbances experienced from the ground, and choosing a non-eclipsing orbit, GOLF aims to improve the instrumental sensitivity limit by an order of magnitude to 1 mm s–1 over 20 days for frequencies higher than 2.10–4 Hz. A sodium vapour resonance cell is used in a longitudinal magnetic field to sample the two wings of the solar absorption line. The addition of a small modulating field component enables the slope of the wings to be measured. This provides not only an internal calibration of the instrument sensitivity, but also offers a further possibility to recognise, and correct for, the solar background signal produced by the effects of solar magnetically active regions. The use of an additional rotating polariser enables measurement of the mean solar line-of-sight magnetic field, as a secondary objective. 相似文献