Solar Forcing of Climate

Solar activity is evident both in the equatorial activity centres and in the polar magnetic field variations. The total solar irradiance variation is due to the former component. During the extraordinarily long minimum of activity between sunspot cycles 23 and 24, the variations related to the equatorial field components reached their minimum values in the first half of 2008, while those related to the polar field variations had their extreme values rather at the end of 2009 and the first half of 2010. The explanation of this delay is another challenge for dynamo theories. The role of the open solar flux has so far been grossly underestimated in discussions of Sun-climate relations. The gradual increase in the average terrestrial ground temperature since 1610 is related both to the equatorial and polar field variations. The main component (0.077?K/century) is due to the variation of the total solar irradiance. The second component (0.040?K/century) waits for an explanation. The smoothed residual increase, presumably antropogenic, obtained after subtraction of the known components from the total increase was 0.31?K in 1999.     

Quantifying and specifying the solar influence on terrestrial surface temperature

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.     

Global electrical currents

Summary The atmospheric electrical structure of the earth is postulated to be controlled by a motivating force in the lower ionosphere which is produced by interaction between neutral atmosphere tidal circulations and the ionospheric plasma in the presence of the earth's magnetic field. Associated electric fields power the dynamo currents through the Hall effect with a resulting development of a gross electric potential distribution in the lower ionosphere. Asymmetries in these hemispheric potential distributions result in exospheric current flows in lowL-shells and larger differences in potential produced by dynamo return current flows in high magnetic latitudes result in strong currents through highL-shells between auroral zones. Vertical thunderstorm currents with their associated lightning discharges effectively connect the earth to a low potential region of the dynamo circuit and thus supply the earth with an average negative charge which motivates a leakage tropospheric electrical circuit. In addition, the dynamo currents maintain the magnetic polar regions at different potentials with a resulting electrical exchange with the solar wind through the earth's near space. These considerations indicate that observed electrical and variable magnetic phenomena near the earth are all part of a single comprehensive electrical current system.This paper was read byH. Dolezalek in an abbreviated form supplied by the author.     

Forecasting the parameters of sunspot cycle 24 and beyond

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 R_max=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).     

冬季太阳11年周期活动对大气环流的影响

利用气象场的再分析资料和太阳辐射活动资料,对太阳11年周期活动影响北半球冬季(11月~3月)大气环流的过程进行了统计分析和动力学诊断.根据赤道平流层纬向风准两年振荡(QBO)的东、西风状态对太阳活动效应进行了分类讨论,结果表明：东风态QBO时,太阳活动效应主要集中在赤道平流层中、高层和南半球平流层,强太阳活动时增强的紫外辐射加热了赤道地区的臭氧层,造成平流层低纬明显增温,同时加强了南半球的Brewer-Dobson(B-D)环流,引起南极高纬平流层温度增加;而北半球中高纬的环流主要受行星波的影响,太阳活动影响很小.西风态QBO时,太阳活动效应在北半球更为重要,初冬时强太阳活动除了加热赤道地区臭氧层外,还抑制了北半球的B-D环流,造成赤道平流层温度增加和纬向风梯度在垂直方向的变化,从而改变了对流层两支行星波波导的强度;冬末时在太阳活动调制下,行星波向极波导增强,B-D环流逐渐恢复,造成北半球极地平流层明显增温,同时伴随着赤道区域温度的下降.     

The dynamo basis of solar cycle precursor schemes

We investigate the dynamo underpinning of solar cycle precursor schemes based on direct or indirect measures of the solar surface magnetic field. We do so for various types of mean-field-like kinematic axisymmetric dynamo models, where amplitude fluctuations are driven by zero-mean stochastic forcing of the dynamo number controlling the strength of the poloidal source term. In all stochastically forced models considered, the surface poloidal magnetic field is found to have precursor value only if it feeds back into the dynamo loop, which suggests that accurate determination of the magnetic flux budget of the solar polar fields may hold the key to dynamo model-based cycle forecasting.     

Detection of solar activity signatures in OH* temperature fluctuations possibly related to the differential rotation of the Sun

Measurements of the hydroxyl rotational temperatures at about 87 km altitude above Wuppertal (51.3°N, 7.2°E), Germany, are analysed. The time series covers the time interval from 1987 until 2005 and consists of more than 4000 night mean temperature data. Seasonal and longer-term trends are removed from the data set and OH* temperature fluctuations on temporal scales of about 3–40 days are derived. Various spectral analysis techniques (harmonic analysis, maximum entropy method and wavelet transform) are applied. Can – due to the Sun's rotation – the irregular pattern of sunspots on the solar disc lead to OH* temperature fluctuations? Pronounced spectral components in the OH* temperature fluctuations around a period from 27 to 31 days are frequently observed. We tentatively attribute these signatures to the differential rotation of the Sun: Sun's equatorial regions rotate faster (taking only about 27 days) than the polar regions. Sunspots occur at heliographic latitudes at about ±40°, which correspond to a rotation rate of about 27–31 days. The OH* temperature fluctuations within this period range show a long-term modulation of 11 years. Thus, tracking the spectral intensity of the 27- to 31-day component should allow the indirect monitoring of the solar sunspot cycle.     

Cosmic-ray vector anisotropy and local characteristics of the interplanetary medium

Variations in the cosmic-ray vector anisotropy observed on Earth are closely connected with the state of the near-Earth interplanetary medium. Hourly characteristics of vector anisotropy for the period 1957–2013, which were obtained by the global survey method from the data of the worldwide network of neutron monitors, make it possible to study the relationship between the cosmic-ray anisotropy and solar wind parameters. In the present work, we have studied the connection between the equatorial component of anisotropy of cosmic rays with a rigidity of 10 GV and the following parameters: velocity and density of the solar wind; density of the interplanetary magnetic field; and cosmic-ray density variations, in which the spatial gradient of cosmic rays in the interplanetary medium is manifested. The characteristics of cosmic-ray anisotropy at various combinations of the interplanetary medium parameters are compared. The possibility of diagnosing the solar wind state from data on the cosmic-ray anisotropy is discussed.     

An intense SFE and SSC event in geomagnetic H, Y and Z fields at the Indian chain of observatories

Changes in the three components of geomagnetic field are reported at the chain of ten geomagnetic observatories in India during an intense solar crochet that occurred at 1311 h 75° EMT on 15 June 1991 and the subsequent sudden commencement (SSC) of geomagnetic storm at 1518h on 17 June 1991. The solar flare effects (SFE) registered on the magnetograms appear to be an augmentation of the ionospheric current system existing at the start time of the flare. An equatorial enhancement in AH due to SFE is observed to be similar in nature to the latitudinal variation of SQ (H) at low latitude. AF registered the largest effect at 3.6° dip latitude at the fringe region of the electrojet. AZ had positive amplitudes at the equatorial stations and negative at stations north of Hyderabad. The SSC amplitude in the H component is fairly constant with latitude, whereas the Z component again showed larger positive excursions at stations within the electrojet belt. These results are discussed in terms of possible currents of internal and external origin. The changes in the Y field strongly support the idea that meridional current at an equatorial electrojet station flows in the ionospheric dynamo, E.Presently at: School of Physics, University of New South Wales, Sydney, Australia     

Solar cycle evolution of the heliospheric magnetic field: The Ulysses legacy

Important contributions of Ulysses to understanding the solar cycle evolution of the heliospheric magnetic field (HMF) and solar wind are reviewed: a dramatic reorientation of the HMF as the solar dipole rotates between axial and equatorial orientations; solar cycle variation of the total heliospheric magnetic flux and its response to changes in solar magnetic fields; the unusual on-going solar minimum and its effects; a connection between magnetic flux and solar wind mass flux in the heliosphere and at the source; a recurrent north–south heliospheric asymmetry at solar minimum and the equatorial offset of the solar magnetic dipole.     

Possible traces of solar activity effect on the surface air temperature of Turkey

In this study we investigate the effects of solar activity on the surface air temperature of Turkey. This enables us to understand existence of solar activity effects on the temperature. We used surface air temperature, pressure and tropospheric absorbing aerosol data as climate parameters and solar flare index data as solar activity indicator. We considered the parameters temperature and flare index data for the period data ranging from the beginning of January 1976 to the end of December 2006, which cover almost three solar cycles, 21st, 22nd and 23rd. However, only the period interval starting from January 1980 up to December 2005 includes the tropospheric absorbing aerosol data. We found a significant correlation between solar activity and surface air temperature for only cycle 23. We applied multitaper method to obtain the cyclic behavior of surface air temperature data sets. The most pronounced power peaks were found by this transform to be present at 1.2 and 2.5 years, which were reported earlier for some solar activity indicators. We concluded that solar activity effect exists on surface air temperature of Turkey; besides changes of greenhouse gases and tropospheric absorbing aerosols concentration have also a dominant effect on the surface air temperature of Turkey.     

A new time-dependent ionosphere–magnetosphere coupling model: Comparison of field-aligned currents against ST5 observations

By using Tsyganenko's model for the magnetosphere's magnetic field, which links two hemispheres of the ionosphere, and adopting a practical boundary condition for the electric potential around the polar cap, we developed a new ionosphere–magnetosphere coupling model based on prairie view dynamo code (PVDC). The new model takes the variations in solar wind and interplanetary magnetic field, as well as the geomagnetic activity, into account. Rather than the previous version of PVDC that is useful only for quiet conditions, the new model enables to calculate the electric potential and currents in the ionosphere and the field-aligned current (FAC) off the ionosphere in quiet and disturbed times. Comparison of the calculated FAC with the measurements of Space Technology 5 (ST5) mission shows a good agreement.     

Solar response in the vertical structure of ozone and temperature in the tropical stratosphere

The aim of the present paper is to study the solar response in the vertical structure of ozone and temperature over the Indian tropical region and a search for any mutual relationship between their solar coefficients on a decadal scale in the lower stratosphere. For the purpose, the data obtained by ozonesonde and Umkehr methods for the lower stratospheric ozone and that of the total ozone amount from Dobson spectrophotometer during the period 1979–2001 have been analyzed. These data are analyzed using the multi-functional regression model, which takes into account most of the known natural and anthropogenic signals. The NCEP- and MSU-satellite data for the temperature over this region have been used. Results indicate an in-phase correlation of around 0.5 between ozone and solar flux (F10.7) in the vertical structure over the equatorial station, Trivandrum (8.3°N) but no significant correlation over Pune (18.3°N). The solar components of ozone and temperature indicate an in-phase but poor correlation in the lower stratospheric altitudes over both stations. However, when total ozone content data is analyzed, it indicates a very high correlation (⩾0.9) between the solar components of ozone and temperature. The solar trend in the vertical distribution of ozone is found to be of the order of 5–25% per 100 units of F10.7 solar flux for Trivandrum but it is relatively smaller (1.6–15.2%) over Pune. The solar dependence of temperature is found to be quite significant for the entire Indian tropical region with not much latitudinal variation.     

Polar and high latitude substorms and solar wind conditions

All substorm disturbances observed in polar latitudes can be divided into two types: polar, which are observable at geomagnetic latitudes higher than 70° in the absence of substorms below 70°, and high latitude substorms, which travel from auroral (<70°) to polar (>70°) geomagnetic latitudes. The aim of this study is to compare conditions in the IMF and solar wind, under which these two types of substorms are observable on the basis of data from meridional chain of magnetometers IMAGE and OMNI database for 1995, 2000, and 2006–2011. In total, 105 polar and 55 high latitude substorms were studied. It is shown that polar substorms are observable at a low velocity of solar wind after propagation of a high-speed recurrent stream during the late recovery phase of a magnetic storm. High latitude substorms, in contrast, are observable with a high velocity of solar wind, increased values of the Bz component of the IMF, the Ey component of the electric field, and solar wind temperature and pressure, when a high-speed recurrent stream passes by the Earth.     

Equatorial dayside minimum of the neutral gas density and temperature: Formation mechanism

The causes of the formation of neutral gas temperature and density equatorial minimums on the dayside, recently detected from satellite measurements, have been studied based on a global numerical model of the Earth’s upper atmosphere (UAM). The performed numerical experiments made it possible to conclude that these minimums are not related to the magnetospheric sources of energy and momentum and electric fields of the dynamo origin. It has been indicated that the absorbed solar ionizing radiation and rotation of the Earth are responsible for the formation of the neutral gas temperature and density equatorial minimums on the dayside.     

Properties of QBO and SAO generated by gravity waves

In this paper we present an extension for the 2D (zonal mean) version of our numerical spectral mode (NSM) that incorporates Hines’ Doppler spread parameterization (DSP) for small-scale gravity waves (GW). This model is applied to describe the seasonal variations and the semi-annual and quasi-biennial oscillations (SAO and QBO). Our earlier model reproduced the salient features of the mean zonal circulation in the middle atmosphere, including the QBO extension into the upper mesosphere inferred from UARS measurements. The model is extended to reproduce the upwelling at equatorial latitudes that is associated with the Brewer–Dobson circulation — which affects significantly the dynamics of the stratosphere as Dunkerton had pointed out. In the presence of GW, this upwelling is produced in our model with tropospheric heating, which generates also zonal jets outside the tropics similar to those observed. The resulting upward vertical winds increase the period of the QBO. To compensate for that, one needs to increase the eddy diffusivity and the GW momentum flux, bringing the latter closer to values recommended in the DSP. The QBO period in the model is 30 months (mo), which is conducive to synchronize this oscillation with the seasonal cycle of solar forcing. Associated with this QBO are interannual and interseasonal variations that become increasingly more important at higher altitudes — and this variability is interpreted in terms of GW filtering that effectively couples the dynamical components of the mesosphere. The computed temperature amplitudes for the SAO and QBO are in substantial agreement with observations at equatorial and extra-tropical latitudes. At high latitudes, however, the observed QBO amplitudes are significantly larger, which may be a signature of propagating planetary waves not included in the present model. The assumption of hydrostatic equilibrium not being imposed, we find that the effects from the vertical Coriolis force associated with the equatorial oscillations are large for the vertical winds and significant for the temperature variations even outside the tropics, but the effects are small for the zonal winds.     

The solar magnetic flux mid-term periodicities and the solar dynamo

We investigate here the fluctuations in the total, open and closed solar magnetic flux (SMF) for the period 1971–1999 by means of the maximum entropy method in the frequency range 5×10⁻⁹–10⁻⁷ Hz (6 yr to 120 days). We use monthly data for the total, open and closed magnetic solar fluxes. Periodicities found in the series are similar showing that there is some relationship between the fluxes. The most important finding of this work is the existence of fluctuations at around 1.3 and 1.7 yr in the SMF with alternating importance during consecutive even and odd solar cycles. These fluctuations are directly related with variations present in cosmic rays, solar wind parameters and geomagnetic activity indexes. A quasi-triennial periodicity previously found in sunspots and other solar phenomena is also of importance. The SMF is generated by the action of the solar dynamo; therefore, it is through the magnetic flux that the solar dynamo influences several heliospheric phenomena.     

Non-linear dynamo waves in an incompressible medium when the turbulence dissipative coefficients depend on temperature

Non-linear - dynamo waves existing in an incompressible medium with the turbulence dissipative coefficients depending on temperature are studied in this paper. We investigate of - solar non-linear dynamo waves when only the first harmonics of magnetic induction components are included. If we ignore the second harmonics in the non-linear equation, the turbulent magnetic diffusion coefficient increases together with the temperature, the coefficient of turbulent viscosity decreases, and for an interval of time the value of dynamo number is greater than 1. In these conditions a stationary solution of the non-linear equation for the dynamo waves amplitude exists; meaning that the magnetic field is sufficiently excited. The amplitude of the dynamo waves oscillates and becomes stationary. Using these results we can explain the existence of Maunders minimum.     

The initial temporal evolution of a feedback dynamo for Mercury

Various possibilities are currently under discussion to explain the observed weakness of the intrinsic magnetic field of planet Mercury. One of the possible dynamo scenarios is a dynamo with feedback from the magnetosphere. Due to its weak magnetic field, Mercury exhibits a small magnetosphere whose subsolar magnetopause distance is only about 1.7 Hermean radii. We consider the magnetic field due to magnetopause currents in the dynamo region. Since the external field of magnetospheric origin is antiparallel to the dipole component of the dynamo field, a negative feedback results. For an αΩ-dynamo, two stationary solutions of such a feedback dynamo emerge: one with a weak and the other with a strong magnetic field. The question, however, is how these solutions can be realized. To address this problem, we discuss various scenarios for a simple dynamo model and the conditions under which a steady weak magnetic field can be reached. We find that the feedback mechanism quenches the overall field to a low value of about 100–150 nT if the dynamo is not driven too strongly.     

A dynamo model with double diffusive convection for Mercury's core

A recent dynamo model for Mercury assumes that the upper part of the planet's fluid core is thermally stably stratified because the temperature gradient at the core–mantle boundary is subadiabatic. Vigorous convection driven by a superadiabatic temperature gradient at the boundary of a growing solid inner core and by the associated release of light constituents takes place in a deep sub-layer and powers a dynamo. These models have been successful at explaining the observed weak global magnetic field at Mercury's surface. They have been based on the concept of codensity, which combines thermal and compositional sources of buoyancy into a single variable by assuming the same diffusivity for both components. Actual diffusivities in planetary cores differ by a large factor. To overcome the limitation of the codensity model, we solve two separate transport equations with different diffusivities in a double diffusive dynamo model for Mercury. When temperature and composition contribute comparable amounts to the buoyancy force, we find significant differences to the codensity model. In the double diffusive case convection penetrates the upper layer with a net stable density stratification in the form of finger convection. Compared to the codensity model, this enhances the poloidal magnetic field in the nominally stable layer and outside the core, where it becomes too strong compared to observation. Intense azimuthal flow in the stable layer generates a strong axisymmetric toroidal field. We find in double diffusive models a surface magnetic field of the observed strength when compositional buoyancy plays an inferior role for driving the dynamo, which is the case when the sulphur concentration in Mercury's core is only a fraction of a percent.