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1.
The Earth's climate is not constant, and has experienced major changes in the past on all timescales. The causes of these changes, although still incompletely understood, vary according to the timescale considered. Some of the most important causal mechanisms include continental drift, changes in the Earth's orbital parameters, volcanic activity and solar variations. Solar variations have been invoked to explain climatic change on almost all timescales from 1 to 109 yr. Unfortunately, even though the Sun is a prime candidate for explaining many changes in past climate, the use of past climate as a proxy for solar luminosity changes is fraught with difficulty. For example:
  1. In many cases observed changes in climate can be adequately explained without recourse to solar variations as a causal factor. In fact, on the longest timescales the Earth's climate was remarkably similar to today in spite of a considerably lower solar output.
  2. For most timescales of climatic change there are, as yet, no plausible theories giving similar timescale variations in solar activity, so that a vital link between cause and effect is missing.
  3. There are considerable uncertainties in the record of past climates.
  4. On short timescales many proposed solar activity-climate links have failed to stand up to rigorous statistical analysis.
This paper reviews past changes in climate and proposed causal mechanisms on timescales of from 1 to 109 yr. The evidence for solar activity-climate links is discussed with special reference to the above points.  相似文献   

2.
Interpretations of current and past results from ground-based solar diameter measurements, as well as the planning of scientific programs for the 1980's, are strongly dependent on the perceived level of the degrading effects of the Earth's atmosphere. One of the more effective approaches has been to design the observing program and the subsequent data analysis such that the solar diameter measurements themselves could provide an evaluation of atmospheric effects. Many important results have been obtained in studies of this type and these results are collected here to help in appraising the current situation. This evidence all points in one direction: the Earth's atmosphere, while complicating the design of observational programs, is not the source of the oscillations observed in solar diameter measurements. Further, this same evidence indicates that the Earth's atmosphere will not pose any serious limitations in ground-based solar diameter studies during the 1980's.  相似文献   

3.
New physical principles for an explanation of seasonal variations in the Earth's rate of rotation are proposed. It is thought that the variations are caused by a variation of the total energy of the Earth's atmosphere in the course of the planet's revolution about the Sun in elliptic orbit. Jacobi's virial equation for the Earth's atmosphere is derived from the Eulerian equations. The virial theorem is obtained. The existence of the relationship between Jacobi's function and potential energy of the atmosphere is confirmed. In the framework of this relationship, Jacobi's equation is reduced to the equation of unperturbed virial oscillations. The solution of the above-mentioned equation expresses the periodic virial oscillations of Jacobi's function (moment of inertia) of the Earth's atmosphere with time. The solution of the perturbed virial oscillation problem of the atmosphere-solid Earth system is obtained. The perturbation term in Jacobi's virial equation regards, in explicit form, the energy changes occurring in the atmosphere in the course of the planet's revolution about the Sun in elliptic orbit. The annual and semi-annual periodic variations in the Earth's rate of rotation can be considered as an astrometrical result following from the obtained solution. A satisfactory accord of the theoretical results with experimental data is shown.  相似文献   

4.
The solar ultraviolet irradiance measurements in the 120–400 nm wavelength range are reviewed and compared showing still important discrepancies between the irradiance values deduced from the most recent observations.The possible variations of the solar ultraviolet irradiances with the 27-day rotation period of the Sun and with the 11-year activity cycle are presented and discussed on the basis of the available irradiation fluxes obtained during the rising phase of solar cycle 21.The spectral features of both kinds of variation are clearly related to the solar atmospheric layer from which the corresponding radiation is emitted.Proceedings of the 14th ESLAB Symposium on Physics of Solar Variations, 16–19 September 1980, Scheveningen, The Netherlands.  相似文献   

5.
In this paper we compute the rate of solar EUV heating in the upper atmosphere by photo-dissociation and photo-ionization, taking care to include properly the effects of oblique incidence of solar flux, sphericity of the atmosphere and ellipticity of the Earth's orbit. The time and latitudinal variations of the computed heat function are revealed by numerical Fourier analysis of the heat function into harmonics of the yearly cycle. It is shown that EUV absorption contains a ‘latitude independent’ semi-annual component of heating with the ‘proper phase’ to account for the semi-annual density variations. Further, the annual component of the heat function predicts the existence of ‘summer polar’ density increases in the northern and southern hemispheres.  相似文献   

6.
The solar extreme ultraviolet (EUV) irradiance, the dominant global energy source for Earth's atmosphere above 100 km, is not known accurately enough for many studies of the upper atmosphere. During the absence of direct solar EUV irradiance measurements from satellites, the solar EUV irradiance is often estimated at the 30–50% uncertainty level using both proxies of the solar irradiance and earlier solar EUV irradiance measurements, primarily from the Air Force Geophysics Laboratory (now Phillips Laboratory) rockets and Atmospheric Explorer (AE) instruments. Our sounding rocket measurements during solar cycle 22 include solar EUV irradiances below 120 nm with 0.2 nm spectral resolution, far ultraviolet (FUV) airglow spectra below 160 nm, and solar soft X-ray (XUV) images at 17.5 nm. Compared to the earlier observations, these rocket experiments provide a more accurate absolute measurement of the solar EUV irradiance, because these instruments are calibrated at the National Institute of Standards and Technology (NIST) with a radiometric uncertainty of about 8%. These more accurate sounding-rocket measurements suggest revisions of the previous reference AE–E spectra by as much as a factor of 2 at some wavelengths. Our sounding-rocket flights during the past several years (1988–1994) also provide information about solar EUV variability during solar cycle 22.  相似文献   

7.
The rate of production of NO in the thermosphere is expected to vary greatly over the course of an 11-year solar cycle because the fluxes of both extreme ultraviolet radiation and auroral particles are known to increase substantially from solar minimum to solar maximum. In the stratosphere, NO participates in a catalytic cycle which constitutes the dominant photochemical destruction mechanism for stratospheric ozone. If appreciable long range transport of NO from the thermosphere to the upper stratosphere occurs, its effects should therefore be manifested in upper atmospheric ozone density variations over the 11-year solar cycle. In this paper, model predictions of the seasonal and latitudinal variations in upper stratospheric O3 associated with NO transport for different levels of solar activity are compared to satellite observations of upper stratospheric ozone abundances.  相似文献   

8.
Adding the angular velocity of sidereal solar rotation and the apparent rotational effect of the Earth's revolution vectorially, a new synodic solar rotation vector has been obtained. The sidereal and synodic solar rotation axes (and equators) are separated. Using the known parameters of the Earth's orbital motion, the synodic rotation angular velocity and the inclination of the synodic equator, the corresponding sidereal rotation parameters have been calculated (ω1 = 2.915 × 10#X2212;6 rad s#X2212;1 and i 1 = 6.076). Various linear rotational velocities at the solar globe are briefly described.  相似文献   

9.
AXIOM (Advanced X‐ray Imaging Of the Magnetosphere) is a concept mission which aims to explain how the Earth's magnetosphere responds to the changing impact of the solar wind using a unique method never attempted before; performing wide‐field soft X‐ray imaging and spectroscopy of the magnetosheath, magnetopause and bow shock at high spatial and temporal resolution. Global imaging of these regions is possible because of the solar wind charge exchange (SWCX) process which produces elevated soft X‐ray emission from the interaction of high charge‐state solar wind ions with primarily neutral hydrogen in the Earth's exosphere and near‐interplanetary space (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

10.
Results of the analysis of the Comet Halley spectrophotometry,which has been carried out by H.K. Nazarchuk in 1985 with the TVscanner of the 6-meter telescope (SAO, Russia) are presented. Timevariations in the intensities of the CN, CH, C2 and NH2bands were investigated using the series of spectra obtained inthe spectral region λλ=410÷ 510 nm. Theauto-correlation functions for all the bands, thecross-correlation functions for C2 lines and their Fouriertransformations are calculated to determine the frequencies andperiods of the variations. A possibility is considered thathigh-amplitude fast variations of spectral lines in Comet Halleyare caused by solar flares. The daily numbers of solar spots andproton fluxes with energies of more then 1 MeV are compared withthe spectral variations of these lines. It is shown that in theobservation periods the comet was projected onto an active regionof the Sun, but, among all the kinds of solar activity, mainlythe solar proton flux with energies less than 4 MeV coincides intime with fast intensity variations in the spectral lines. Analgorithm of cross-correlation analysis of discrete samplingseries with gaps is built, and average cross-correlation coefficientsare calculated.  相似文献   

11.
Periodicity in the 13–14 day range for full-disk UV fluxes comes mainly from episodes of solar activity with two peaks per rotation, produced by the solar rotational modulation from two groups of active regions roughly 180° apart in solar longitude. Thirteen-day periodicity is quite strong relative to the 27-day periodicity for the solar UV flux at most wavelengths in the 1750–2900 Å range, because the rapid decrease in UV plage emission on average with increasing solar central angle shapes the UV variations for two peaks per rotation into nearly a 13-day sinusoid, with deep minima when the main groups of active regions are near the limb. Chromospheric EUV lines and ground-based chromospheric indices have moderate 13-day periodicity, where the slightly greater emission of regions near the limbs causes a lower strength relative to the 27-day variations than in the above UV case. The lack of 13-day periodicity in the solar 10.7 cm flux is caused by its broad central angle dependence that averages out the 13-day variations and produces nearly sinusoidal 27-day variations. Optically thin full-disk soft X-rays can have 13-day periodicity out of phase with that of the UV flux because the X-ray emission peaks when both groups of active regions are within view, one group at each limb, when the optically thick UV flux is at a rotational minimum. The lack of 13-day periodicity in the strong coronal lines of Fexv at 284 Å and Fexvi at 335 Å during episodes of 13-day periodicity in UV and soft X-ray fluxes shows that the active region emission in these strong lines is not optically thin; resonant scattering is suggested to cause an effective optical depth near unity in these hot coronal lines for active regions near the limb.  相似文献   

12.
The spatial distributions of energetic ion and electron bursts observed on the IMP 7 and 8 satellites in the Earth's magnetotail were studied. It was found that the ion bursts were more frequently detected in the dusk than in the dawn quarter of the neutral sheet whereas the electron bursts, more frequently in the dawn than the dusk quarter. The degree of dawn-dusk asymmetry is however energy dependent; the distribution for higher energy particle bursts exhibits higher degree of asymmetry. The morphologies of the distributions manifest themselves as seasonal variations of the most probable solar ecliptic latitudes at which the ion and electron bursts were observed. The amplitudes of the variations are about 25° with the seasonal variation for ions leading that for electrons by about 2 months.  相似文献   

13.
M.R. Sanad 《New Astronomy》2010,15(8):688-694
We present ultraviolet spectra of the AE Aqr binary system taken by the International Ultraviolet Explorer (IUE) during the period from 1978 to 1993, to accomplish a large scale study of what happens to the ultraviolet fluxes of different emission lines during different orbital phases. Five profiles of AE Aqr binary system show variations of line fluxes at different orbital phases are presented. We concentrated on studying N V emission line at 1240 Å, O I emission line at 1306 Å, He II emission line at 1640 Å, N III emission line at 1749 Å and Si III emission line at 1892 Å, produced in the line emitting gas (Eracleous et al., 1994, Eracleous and Horne, 1996), by calculating the line fluxes of these spectral lines. Our results show that there are spectral variations of line fluxes for the aforementioned emission lines at different times, similar to the light curves found for AE Aqr binary system by using ASCA, XMM – Newton and Chandra X-ray observations (Mauche, 2006). We attributed these spectral variations to the variations of the mass-transfer rate (Ikhsanov et al., 2004) and to the collisions between the compact blobs and the fluffy blobs, where the collisions are supersonic, shocking the gas, causing heating, then expansion (Eracleous et al., 1994, Eracleous and Horne, 1996, Horne, 2009).  相似文献   

14.
The ionosphere shows a large degree of variability on time scales from hours to the solar cycle length. This variation is associated with magnetospheric storms, the Earth's rotation, the season, and the level of solar activity. To make accurate predictions of key ionospheric parameters all these variations must be considered. Neural networks, which are data driven non-linear models, are very useful for such tasks. In this work we examine if the F2 layer plasma frequency, foF2, at a single ionospheric station can be predicted 1 to 24 hours in advance by using information of past foF2 observations, magnetospheric activity, and time as inputs to neural networks. Particular attention has been paid to periods when great geomagnetic storms were in progress with the aim to develop a successful ionospheric storm forecasting tool.  相似文献   

15.
The synodic rotation period and power spectra of solar microwave sources are investigated using accurate data in the interval 1956 to 1970. The variation of the approximate 27 day period is obtained over a complete solar cycle and is thought to be a result of the latitude change over the solar cycle of the origins of the radio emissions. High resolution power spectra have also been obtained and revealed the existence of a double peaked line near 160 day period. This line is attributed to changes in either the Eartn's heliographic latitudes or the Earth's inclination to the Earth-Sun line.  相似文献   

16.
Recent results of charge exchange emission from solar system objects observed with the Japanese Suzaku satellite are reviewed. Suzaku is of great importance to investigate diffuse X‐ray emission like the charge exchange from planetary exospheres and comets. The Suzaku studies of Earth's exosphere, Martian exosphere, Jupiter's aurorae, and comets are overviewed (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

17.
The results of simultaneous measurements of variations of UV radiation (in a band near the hydrogen Lα line, 121.6 nm) and hard X-ray and gamma-ray radiation (50 keV-200 MeV) performed by the VUSS-L and SONG instruments, respectively, onboard the CORONAS-F spacecraft are presented for periods of solar flares. Variations in the Lα ultraviolet radiation during the impulsive phase of a flare are shown to be synchronous with those of hard X-ray radiation. Temporal variations of UV and X-ray fluxes correspond to the progressive heating of higher and higher regions of the solar atmosphere and the energy transfer from the lower layers of the solar atmosphere to the coronal areas of flare regions. The energy of electrons in beams arising during the impulsive phase of flares can be as high as 500 keV. The velocity of the energy propagation from the regions of its release to the upper layers of the solar atmosphere can reach several tens of kilometers per second.  相似文献   

18.
The height of the source region of Si II emission lines characterizes the height of the bottom layer of solar atmosphere's transition region. The correlation analysis of the intensities of ultraviolet spectral lines and the threedimensional structure of magnetic field yielded by force-free extrapolation is a new method for determining the height of ultraviolet emission lines’ source region. It has been found that the height thus obtained is larger than that given by traditional viewpoint. Because the existing numerical analyses with this method are scarce, this result has to be further verified with more observational materials. In this work, this method is applied to the Si II emission lines observed by SOHO/SUMER for the solar surface region beneath the solar coronal hole at southern pole and to the magnetic fields measured by National Solar Observatory/Kitt Peak (NSO/KP) in U.S.A. The correlation height of the source region of Si II emission lines in coronal hole region is approximately 5.0 Mm. This result supports the conclusion that the height of the bottom layer of transition region in coronal hole region is larger than that in quiet regions. Moreover, some new phenomena have been discovered and their causes are probed.  相似文献   

19.
We present the first orbit-resolved ultraviolet spectroscopic observations of the two polar systems EU UMa and ST LMi obtained with the Hubble Space Telescope Faint Object Spectrograph (HST FOS) and International Ultraviolet Explorer (IUE) during their intermediate- and low-luminosity states in the period between 1982 and 2003. Different line profiles of the two systems showing variations of line fluxes at different orbital phases are presented. This paper focuses on the C IV emission line at 1550 Å produced in the accretion stream, presenting calculations of spectral line fluxes, ultraviolet luminosities, and accretion rates for the two systems. Our analysis of the spectroscopic data reveals changes with orbital phase of the emission line profiles that correspond to the light curve variations of both EU UMa and ST LMi in the optical and infrared bands. The variations of line fluxes are attributed to variations of both density and temperature as a result of a changing rate of mass transfer from the secondary star to the white dwarf. The ultraviolet luminosity and accretion rate of EU UMa are smaller than the ultraviolet luminosity and accretion rate of ST LMi.  相似文献   

20.
The theoreticl treatment of several geophysical problems presupposes the solution of field equations of the magnetic field in the Earth's mantle. The field equations are given in a scalar form for a spherical model of the Earth. It will be shown that analytical solutions are possible in all cases. The boundary conditions are discussed with regard to the dynamo process in the Earth's core and the existence of a field representation, which is investigated on the Earth's surface. The question is discussed, to what extend the mantle's field is given by this field representation, when some special assumptions about the Earth's model are made.  相似文献   

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