排序方式： 共有10条查询结果，搜索用时 15 毫秒
1
1.
A non-linear coupling function between sunspot maxima and aa minima modulations has been found as a result of a wavelet analysis of geomagnetic index aa and Wolf sunspot number yearly means since 1844. It has been demonstrated that the increase of these modulations for the past 158 years has not been steady, instead, it has occurred in less than 30 years starting around 1923. Otherwise sunspot maxima have oscillated about a constant level of 90 and 141, prior to 1923 and after 1949, respectively. The relevance of these findings regarding the forecasting of solar activity is analyzed here. It is found that if sunspot cycle maxima were still oscillating around the 141 constant value, then the Gnevyshev–Ohl rule would be violated for two consecutive even–odd sunspot pairs (22–23 and 24–25) for the first time in 1700 years. Instead, we present evidence that solar activity is in a declining episode that started about 1993. A value for maximum sunspot number in solar cycle 24 (87.5±23.5) is estimated from our results. 相似文献
2.
A critical analysis of the theoretical methods for obtaining the ionospheric and induced currents from the geomagnetic variations is performed, and the ionospheric currents in the electrojet are analyzed, through the geomagnetic variations in the proximity of the dip equator in Nigeria. For this purpose, a method, previously introduced by the authors, is applied, which makes it possible to discuss the contribution of the currents induced in the Earth by those variations. The result is compared with that obtained from the variations in the South American area. It is found that the amplifications could be very different in the two areas. 相似文献
3.
Variations in total solar irradiance (TSI) correlate well with changes in projected area of photospheric magnetic flux tubes
associated with dark sunspots and bright faculae in active regions and network. This correlation does not, however, rule out
possible TSI contributions from photospheric brightness inhomogeneities located outside flux tubes and spatially correlated with them. Previous reconstructions of TSI report agreement with radiometry that seems to rule out significant “extra-flux-tube” contributions.
We show that these reconstructions are more sensitive to the facular contrasts used than has been generally recognized. Measurements
with the Solar Bolometric Imager (SBI) provide the first reliable support for the relatively high, wide-band, disk-center
contrasts required to produce 10% rms agreement. Longer term bolometric imaging will be required to determine whether the
small but systematic TSI residuals we see here are caused by remaining errors in spot and facular areas and contrasts or by
extra-flux-tube brightness structures such as bright rings around sunspots or “convective stirring” around active regions. 相似文献
4.
Solar activity is regulated by the solar dynamo. The dynamo is a non-linear interplay between the equatorial and polar magnetic field components. So far, in Sun–climate studies, only the equatorial component has been considered as a possible driver of tropospheric temperature variations. We show that, next to this, there is a significant contribution of the polar component. Based on direct observations of proxy data for the two main solar magnetic fields components since 1844, we derive an empirical relation between tropospheric temperature variation and those of the solar equatorial and polar activities. When applying that relation to the period 1610–1995, we find some quasi-regular episodes of residual temperature increases and decreases, with semi-amplitudes up to ～0.3 °C. The present period of global warming is one of them. 相似文献
5.
The structure of the conductosphere at equatorial latitudes is investigated by analyzing geomagnetic daily variations (GDV) data. To do so the magnetic field induced in a multilayered model by an external source of finite size that reproduces the external part of these variations is computed; latitudinal profiles of the total field produced at ground by the assumed external source are then found and compared with the measured GDV data. Results are applied to equatorial zones in Peru, Africa and India. 相似文献
6.
Electron temperature measurements made with Langmuir probes at E-region heights together with deviative absorption data show that the electrons are not in thermal equilibrium with the neutrals. Moreover, for very quiet days (Ap ? 7, Kp ? 1+ throughout the whole day) and hours close to noon the quotients between the electron and neutral gas temperature profiles have a similar behaviour. In this paper Te profiles measured in situ with Langmuir probes and Tn, profiles given by neutral atmosphere models, both in the specified ionospheric conditions, are used to compute profiles. Each of the profiles thus obtained is fitted by a Lorentzian curve and the variation with F10.7 of its parameters is also fitted by simple mathematical expressions. 相似文献
7.
Solar variability is controlled by the internal dynamo which is a non-linear system. We develop a physical–statistical method for forecasting solar activity that takes into account the non-linear character of the solar dynamo. The method is based on the generally accepted mechanisms of the dynamo and on recently found systematic properties of the long-term solar variability. The amplitude modulation of the Schwabe cycle in dynamo's magnetic field components can be decomposed in an invariant transition level and three types of oscillations around it. The regularities that we observe in the behaviour of these oscillations during the last millennium enable us to forecast solar activity. We find that the system is presently undergoing a transition from the recent Grand Maximum to another regime. This transition started in 2000 and it is expected to end around the maximum of cycle 24, foreseen for 2014, with a maximum sunspot number Rmax=68±17. At that time a period of lower solar activity will start. That period will be one of regular oscillations, as occurred between 1730 and 1923. The first of these oscillations may even turn out to be as strongly negative as around 1810, in which case a short Grand Minimum similar to the Dalton one might develop. This moderate-to-low-activity episode is expected to last for at least one Gleissberg cycle (60–100 years). 相似文献
8.
The problem of the electromagnetic induction produced by a localized and an extended ionospheric current near an ocean coast, over a mantle of infinite conductivity, has been reduced to the solution of an integral equation where the induced current density appears in an implicit form. This formalism is applied to calculate the field induced by the geomagnetic daily variation due to the presence of the ocean at the Peruvian and Nigerian equatorial zones. 相似文献
9.
This investigation is a follow-up of a paper in which we showed that both major magnetic components of the solar dynamo, viz. the toroidal and the poloidal ones, are correlated with average terrestrial surface temperatures. Here, we quantify, improve and specify that result and search for their causes.We studied seven recent temperature files. They were smoothed in order to eliminate the Schwabe-type (11 years) variations. While the total temperature gradient over the period of investigation (1610–1970) is 0.087 °C/century; a gradient of 0.077 °C/century is correlated with the equatorial (toroidal) magnetic field component. Half of it is explained by the increase of the Total Solar Irradiance over the period of investigation, while the other half is due to feedback by evaporated water vapour. A yet unexplained gradient of ?0.040 °C/century is correlated with the polar (poloidal) magnetic field. The residual temperature increase over that period, not correlated with solar variability, is 0.051 °C/century. It is ascribed to climatologic forcings and internal modes of variation.We used these results to study present terrestrial surface warming. By subtracting the above-mentioned components from the observed temperatures we found a residual excess of 0.31° in 1999, this being the triangularly weighted residual over the period 1990–2008.We show that solar forcing of the ground temperature associated with significant feedback is a regularly occurring feature, by describing some well observed events during the Holocene. 相似文献
10.
The geomagnetic daily variations at the Nigerian dip equator have been analyzed with the methodology introduced in a previous paper. It has been found that the height integrated current presents a notoriously higher amplification in Nigeria than in Peru. It has also been found that there exists a strong and inhomogeneous anomaly in the Earth's conductivity in Nigeria. And contrary to what is usually accepted, it is shown that its latitudinal distribution can not be precisely determined until the distribution and magnitude of the ionospheric currents at F-region heights is more accurately known. 相似文献
1