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1.
The long-time series of daily means of cosmic-ray intensity observed by four neutron monitors at different cutoff rigidities (Calgary, Climax, Lomnický tít and Huancayo/Haleakala) were analyzed by means of the wavelet transform method in the period range 60 to 1000 days. The contributions of the time evolution of three quasi-periodic cosmic-ray signals (150 d, 1.3 yr and 1.7 yr) to the global one are obtained. While the 1.7-yr quasi-periodicity, the most remarkable one in the studied interval, strongly contributes to the cosmic ray intensity profile of solar cycle 21 (particularly in 1982), the 1.3-yr one, which is better correlated with the same periodicity of the interplanetary magnetic field strength, is present as a characteristic feature for the decreasing phases of the cycles 20 and 22. Transitions between these quasi-periodicities are seen in the wavelet power spectra plots. Obtained results support the claimed difference in the solar activity evolution during odd and even solar activity cycles. 相似文献
2.
Muammer Dizer 《Astrophysics and Space Science》1992,189(2):289-301
This paper presents the results of the study on the periodicity in filament activity. The spectral analysis of the number of filaments shows a basic period at 141 (10.5 yr), at 138 (10.3 yr), and at 144 (10.7 yr) Carrington rotation in the northern and southern hemisphere, respectively.The time series concerning the index of filament activity shows also a typical period at 135 Carrington rotation (10.1 yr) at 144 Carrington rotation (10.7 yr) and at 133 Carrington rotation (9.9 yr), respectively, in the northern and southern hemisphere.The power spectrum analysis of the time series of the filamentary activity in the short-term also yields less pronounced but still noticeable peaks which are statistically significant. 相似文献
3.
The probable connection between cosmic rays and the electromagnetic state of the interplanetary medium was recognized by Hannes Alfvén as early as 1949 (Alfvén, 1949, 1950); he pointed out that the properties of cosmic rays necessitate a mechanism, external to Earth but within the solar system, capable of accelerating particles to extremely high energies. In advocating the view of local origin for part of the cosmic-ray spectrum, Alfvén and his colleagues developed a very general type of acceleration mechanism called magnetic pumping. The unique data set of the two Voyagers extends over an entire decade (1977–1987) and is most suitable to explore the problem of acceleration of charged particles in the heliosphere. The energy coverage of the Low Energy Charged Particle (LECP) experiment covers the range 30 keV to several hundred MeV for ions and 22 keV to several MeV for electrons. Selected observations of interplanetary acceleration events from 1 to 25 AU are presented and reviewed. These show frequent acceleration of ions to several tens of MeV in association with shocks; highest energies (220 MeV oxygen) were measured in the near-perpendicular (
Bn
87.5°) shock of January 5, 1978 at 1.9 AU, where electron acceleration was also observed. Examples of ion acceleration in association with corotating interaction regions are presented and discussed. It is shown that shock structures have profound effects on high-energy (70 MeV) cosmic rays, especially during solar minimum, when a negative latitudinal gradient was observed after early 1985 at all energies from 70 MeV down to 30 keV. By early 1987, most shock acceleration activity in the outer heliosphere (25 to 30 AU) had ceased both in the ecliptic (Voyager-2) and at higher (30°) ecliptic latitudes (Voyager-1). The totality of observations demonstrate that local acceleration to a few hundred MeV, and as high as a few GeV is continually present throughout the heliosphere. It should be noted that in 1954 when Alfvén suggested local acceleration and containment of cosmic rays within the solar system, no one treated his suggestion seriously, at any energy. The observations reviewed in this paper illustrate once more Alfvén's remarkable prescience and demonstrate how unwise it is to dismiss his ideas.Paper dedicated to Professor Hannes Alfvén on the occasion of his 80th birthday, 30 May 1988. 相似文献
4.
A study is made of Lyman continuum observations of solar flares, using data obtained by the Harvard College Observatory EUV spectroheliometer on the Apollo Telescope Mount. We find that there are two main types of flare regions: an overall mean flare coincident with the H flare region, and transient Lyman continuum kernels which can be identified with the H and X-ray kernels observed by other authors. It is found that the ground level hydrogen population in flares is closer to LTE than in the quiet Sun and active regions, and that the level of Lyman continuum formation is lowered in the atmosphere from a mass column density m 5/sx 10–6 g cm–2 in the quiet Sun to m 3/sx 10–4 g cm–2 in the mean flare, and to m 10–3g cm–2 in kernels. From these results we derive the amount of chromospheric material evaporated into the high temperature region, which is found to be - 1015g, in agreement with observations of X-ray emission measures. A comparison is made between kernel observations and the theoretical predictions made by model heating calculations, available in the literature; significant discrepancies are found between observation and current particle-heating models. 相似文献
5.
Two sequences of OSO-4 spectroheliograms in Mg x and Si xii obtained during October–November 1967 and covering the intervals of 83 and 22 hr, respectively, have been analyzed to reveal quasi-periodic oscillations of EUV flux from solar sources with a periodicity of 5–14 hr. The oscillation periods of the emission flux from local sources over sunspots and magnetic field enhancements in plages without spots have been investigated in correlation with characteristics of the respective AR and plages. The greatest periods (> 8 hr) are shown to be peculiar of small sunspots or sunspot groups at the initial or final stage of their development, whereas the smallest periods ( 5–6 hr) are observed in the case of large well-developed groups at the maximum stage of development. In quiet regions on the Sun and plages without spots, the oscillation periods are 6–8 hr. The surface areas in which the oscillations are synchronous and coincide in phase have typical dimensions of 1 in quiet and 1 to 5 in active regions. These areas form a spatial structure similar to the chromospheric network and supergranules. The characteristic lifetime of the structure elements is 1.5–2 days. 相似文献
6.
On the persistence of the 22 y solar cycle 总被引：2，自引：0，他引：2
We briefly discuss the existence of precise periodicities of the Hale cycle (-22 y), the Gleissberg cycle (-88 y), and -132 y cycle, in various direct and indirect indicators (as aurorae, 14C from tree rings and 10Be from polar ice) of solar activity. We consider also the behaviour of the 11y cycle and its first harmonic in modern sunspot series. It appears that the frequencies of -1 c/88 y and -1 c/132 y might be two subharmonics of the Hale cycle. The results support the hypothesis that the Sun behaves as a nonlinear system forced by an oscillator having the Hale frequency. The forcing element inside the Sun can be identified with a magnetofluid torsional oscillator. 相似文献
7.
N.Z. Scoville 《Astrophysics and Space Science》1999,266(1-2):149-155
Recent high resolution near infrared (HST-NICMOS) and mm-interferometric imaging have revealed dense gas and dust accretion disks in nearby ultra-luminous galactic nuclei. In the best studied ultraluminousIR galaxy, Arp 220, the 2m imaging shows dust disks in both of the merging galactic nuclei and mm-CO line imaging indicates molecular gasmasses 109M for each disk. The two gas disks in Arp 220 are counterrotating and their dynamical masses are 2×109
M
, that is, only slightly largerthan the gas masses. These disks have radii 100 pc and thickness 10-50 pc. The high brightness temperatures of the CO lines indicatethat the gas in the disks has area filling factors 25-50% and mean densitiesof 104 cm-3. Within these nuclear disks, the rate of massive star formation is undoubtedly prodigious and, given the high viscosity of the gas, there will also be high radial accretion rates, perhaps 10 M yr -1. If this inflow persists to very small radii, it is enough to feed even the highest luminosity AGNs. 相似文献
8.
The radial brightness distribution of the quiet Sun at 8.6 mm is synthesized from observations using a sixteen element east-west interferometer in Nagoya. The observed brightness is flat from the disk center to 0.8R
. A slight darkening appeared between 0.8R
and the limb. No evidence of the bright ring near the limb is found. The radio radius at 8.6 mm is 1.015±0.005R
. In addition there exists a coronal component just outside the radio limb. 相似文献
9.
Paul N. Swanson 《Solar physics》1973,32(1):77-80
The radio radius of the Sun is determined from an analysis of the radio contact times of the 7 March, 1970 and 10 July, 1972 solar eclipses from = 3 mm to = 31 cm. Agreement with other eclipse measurements is good. A best fit curve through the several points gives the radio radius to within approximately ±0.01 of the photosheric radius below -5 cm. 相似文献
10.
The power spectra for line intensities of several lines formed in the upper transition region around 100000 to 250000 K are presented. A period of 5 min is clearly present in lines due to Oiii, Oiv, and Ov. In one dataset a period approaching 10 min is present for 40 min. The size of the emitting features is limited to 7 arc sec squared. In all datasets examined, there is excess power below 4 mHz everywhere along the slit, although the observed periods do not always come from the most intense regions. In 40% of instances clear periods are observable in the 2–5 mHz range with the largest power peak at 3.0 mHz. In all regions, the 5.0 mHz power peak is smaller. For the frequencies investigated there are no significant time delays in any of the datasets examined. This finding may not be entirely unexpected as the formation temperatures of Oiii (100000 K) and Ov (250000 K) may be too close in order to result in an observable phase shift.The observations are discussed in terms of trapped magnetic modes below the transition region and resonant absorption of MHD waves. For resonant absorption we derive from the observed period of 5 min and the observed extent of the structure a typical magnetic field strength of about 2 G. This value is in good agreement with results from MDI for quiet-Sun regions. Our results seem to imply that resonant waves can play a role in the heating of the quiet Sun. We discuss the effect of observing without tracking on the power spectrum and show that the effect is small. 相似文献
11.
Two dimensional source brightness distributions at 26.4 MHz for solar bursts of spectral type II, III, IV, and V are derived from observations with a multiple-baseline, time-sharing interferometer system. It was designed explicitly to study the large angle (40 halo) component of low frequency solar bursts first reported by Weiss and Sheridan (1962). Thirty-two bursts occurring in the interval of June–August, 1975, were fit with a circular gaussian core and an elliptical gaussian halo component. Half-power halo diameters (E-W×N-S) averaged 30×28 for type III bursts and 42×27, 28×37, 30×25 for type V, II and IV bursts respectively. Typical core sizes fell in the range of 10±4 giving 31 halo to core size ratio. All burst types were found to have some large angle structure: the specific intensity was 10% compared to the core but the total power in each component was comparable. Two processes for producing the core-halo structure of type III bursts are compared: scattering and refraction of a point source and refraction from many sources over an extended region. It is concluded that the core can be explained by either model but the halo is more consistent with emission from an extended source region of 40° in longitude. 相似文献
12.
M.I. Wanas 《Astrophysics and Space Science》1997,252(1-2):237-248
A non-LTE study of the Type IIb supernova 1993J in the galaxy M81 taking into account nonthermal ionization and line blocking effects is carried out. Hydrodynamical models and theoretical spectra clearly show that nonthermal ionization and excitation dominate after the second maximum, at day 30, and play a decisive role in reproducing both the smooth tail of the light curve and the emergence of helium lines in the spectrum, similar to those observed. Based on our model of supernova 1993J, we predict that the light curves of Type Ib supernovae should be subject to nonthermal ionization and excitation at earlier times than even those for supernova 1993J. In our model, the outburst of supernova 1993J is interpreted as the explosion of a 4 M red supergiant, which underwent core collapse and left a neutron star in a binary system. The progenitor is supposed to have a helium core mass of 3 M, corresponding to a 13 M main-sequence star. Supernova 1993J adds evidence to the scenario that Type Ib supernovae originate from moderately massive stars on the main sequence that have lost their hydrogen envelopes in interacting binary systems. 相似文献
13.
Y. Dryagin I. Lapkin V. Vdovin I. Zinchenko K. Kuittinen E. Oinaskallio J. Peltonen 《Experimental Astronomy》1994,5(3-4):279-287
A 3 mm low noise beam-lead Schottky diode mixer has been developed. At cryogenic temperatures the conversion loss is 6.3 dB, and the DSB mixer noise temperature is 75 K, respectively. The mixer was installed into the cooled receiver for radioastronomical observations at the Metsähovi 13.7-m radio telescope. Total DSB noise temperature of the cooled receiver with an ultra low noise HEMT IF amplifier was 110 K at 103 GHz. The tuning range of the mixer mount was from 70 GHz to 115 GHz. 相似文献
14.
Kenneth R. Lang 《Earth, Moon, and Planets》1978,19(2):185-198
Dense molecular clouds within the Taurus and NGC 2264 regions have undergone gravitational collapse and fragmentation to form groups of low mass (1M
) T-Tauri stars which are still embedded within the clouds and which are kinematically associated with them. Molecular column densities on the order of 1014 cm–2 are inferred from the emission lines of OH and NH3. Emission line widths are 2 km s–1 and the antenna beamwidths include linear extents of order 0.1 pc. The OH emission appears to be in a condition of local thermodynamic equilibrium, and it cannot arise from circumstellar sheils similar to those surrounding the masing infrared stars. The OH and NH3 emission occurs in clouds of 1 pc in extent with optical depths of 0.1 to 1.0 and excitation temperatures of the order of 10 K. The molecular clouds have radii of 0.5 pc, molecular hydrogen densities of 4000 cm–3, masses of 100 solar masses, and kinetic temperatures of 20 K. The observed data are not inconsistent with the molecular clouds being in a state of hydrostatic equilibrium.Paper presented at the Conference on Protostars and Planets, held at the Planetary Science Institute, University of Arizona, Tucson, Arizona, between January 3 and 7, 1978. 相似文献
15.
The temporal and spatial variations of EUV emission from a small growing active region were investigated. Frequent localized short term ( few minutes) fluctuations in EUV emission were observed throughout the 7.2 hr interval when the most continuous observations were acquired. Approximately 20% of the 5 x 5 pixels had intensity variations exceeding a factor of 1.3 for the chromospheric L line, a factor of 1.5 for lines formed in the chromospheric-coronal transition region and a factor of 1.4 for the coronal Mg x line. A subflare in the region produced the largest intensity enhancements, ranging from a factor of 2.3 for the chromospheric L line to 8 for the transition region and coronal lines. The EUV fluctuations in this small active region are similar to those observed in coronal bright points, suggesting that impulsive heating is an important, perhaps dominant form of heating the upper chromospheric and lower coronal plasmas in small magnetic bipolar regions. The responsible mechanism most likely involves the rapid release of magnetic energy, possibly associated with the emergence of magnetic flux from lower levels into the chromosphere and corona. 相似文献
16.
From the variations in equivalent width of a selected set of Fraunhofer lines, we derived the variation of effective temperature and microturbulence velocity between the equator and the regions at heliographic latitude of - 72°. The reliability of the results (T/T = 0 ± 0.6%, / = 6% ± 13%) needs further investigations, but from the analysis of our data we can state that temperature variations, if any, are very small. Some suggestions for more fruitful measurements are also given. 相似文献
17.
From an analysis of the interstellar extinction we conclude that interstellar grains are of three main kinds: graphite spheres of radii 0.02 m making up 10% of the total grain mass, small dielectric spheres of radius about 0.04 m making up 25% of the mass, and hollow dielectric cylinders containing metallic iron with diameters of 2/3 m making up 45% of the mass. The remaining 20% consists of other metals and metal oxides. The main dielectric component of the grains appears to be comprised of organic material. 相似文献
18.
P. R. Amnuel O. H. Guseinov H. I. Novruzova Yu. S. Rustamov 《Astrophysics and Space Science》1984,107(1):19-50
On the basis of empirical (D)-dependency at the frequency of 5 GHz constructed using 15 planetary nebulae with the independently measured distances (10–171×10–20 W m–2 Hz–1 ster–1), we evaluated distances of 335 objects. Independent evidence of the correctness of the accepted scale are given. Then(D)-dependency is constructed and it is shown that atD<0.08 pc the mean electron density is higher than the one determined by the Seaton method. We showed that the filling factor diminishes with the increase of the PN diameter (1 atD0.08 pc and 0.2 atD0.4 pc). the ionized mass of 33 PNs is determined. With the diameter increase the ionized mass grows and atD0.4 pc reaches the valueM0.07M
. We used the new distance scale when investigating the space distribution of PNs. The mean scale height =130±15 pc and the mean gradient of the change of surface densitym=0.37, which allowed us to estimate the total number of nebulae in the GalaxyN4×104. We divided the PNs according to their velocities (withV
LSR>35 km s–1 andV
LSR<35 km s–1) and permitted us to confirm that the PN belong to different sub-systems of the Galaxy. The estimated local formation rate of PNs [=(4.6±2.2)×10–12 pc–3 yr–1] is a little higher than the one of the white dwarfs. That can be explained by a large number of PNs having binary cores, which used in our sample. The statistical estimation of PN expansion velocity showed thatV
ex increases from 5–7 km s–1 (atD0.03 pc) to 40–50 km s–1 (atD0.8 pc). 相似文献
19.
The relative Doppler and non-thermal velocities of quiet-Sun and active-region blinkers identified in Ov with CDS are calculated. Relative velocities for the corresponding chromospheric plasma below are also determined using the Hei line. Ov blinkers and the chromosphere directly below, have a preference to be more red-shifted than the normal transition region and chromospheric plasma. The ranges of these enhanced velocities, however, are no larger than the typical spread of Doppler velocities in these regions. The anticipated ranges of Doppler velocities of blinkers are 10–15 km s–1 in the quiet Sun (10–20 km s–1 in active regions) for Hei and 25–30 km s–1 in the quiet Sun (20–40 km s–1 in active regions) for Ov. Blinkers and the chromosphere below also have preferentially larger non-thermal velocities than the typical background chromosphere and transition region. Again the increase in magnitude of these non-thermal velocities is no greater than the typical ranges of non-thermal velocities. The ranges of non-thermal velocities of blinkers in both the quiet Sun and active regions are estimated to be 15–25 km s–1 in Hei and 30–45 km s–1 in Ov. There are more blinkers with larger Doppler and non-thermal velocities than would be expected in the whole of the chromosphere and transition region. The recently suggested mechanisms for blinkers are revisited and discussed further in light of the new results. 相似文献
20.
Muammer Dizer 《Astrophysics and Space Science》1990,173(1):127-144
This paper presents the results of the study on the periodicity and the distribution of the sudden disappearance of the solar prominences (SD) on the chromosphere. The spectral analysis of the SD, from 1039 to 1762 Carrington rotation number, shows a typical period at 138 (10.3 yr) solar rotations in the northern hemisphere and at 153 (11.4 yr) solar rotations in the southern hemisphere of the Sun. The power spectral analysis of the asymmetry index yields a primary peak at 155 (11.6 yr) solar rotations. By plotting the distribution of SD along the Carrington longitude, it can be seen that the distribution of the SD is nearly uniform. 相似文献