Geoeffectiveness of solar flares in magnetic crochet (sfe) production: II—Dependence on the detection method

During magnetic active periods, disturbances in the geomagnetic field can act as natural noise masking other magnetic variations of small amplitude. In this paper, the influence of these perturbations on the observation of the effects on Earth of solar flares (sfe) has been studied. The diurnal and monthly values of detected sfe have been obtained, as well as the temporal variation of the relative occurrence of events. These numbers show how the irregular distribution of the magnetic observatories is an important limitation in the efficiency of the detection method. Some considerations about the actual method used at the International Service on Rapid Magnetic Variations are finally presented.     

Effect of iron salt counter ion in dose–response curves for inactivation of Fusarium solani in water through solar driven Fenton-like processes

The inactivation of Fusarium solani in water was assessed by solar driven Fenton-like processes using three different iron salts: ferric acetylacetonate (Fe(acac)₃), ferric chloride (FeCl₃) and ferrous sulfate (FeSO₄). The experimental conditions tested were [Fe] ≈ 5 mg L⁻¹, [H₂O₂] ≈ 10 mg L⁻¹ and [Fe] ≈ 10 mg L⁻¹; [H₂O₂] ≈ 20 mg L⁻¹ mild and high, respectively, and pH 3.0 and 5.0, under solar radiation. The highest inactivation rates were observed at high reaction conditions for the three iron salts tested at pH 5.0 with less than 3.0 kJ L⁻¹ of accumulate energy (Q_UV) to achieve over 99.9% of F. solani inactivation. Fe(acac)₃ was the best iron salt to accomplishing F. solani inactivation. The modified Fermi equation was used to fix the experimental inactivation, data showed it was helpful for modeling the process, adequately describing dose–response curves. Inactivation process using FeSO₄ at pH 3.0 was modeled fairly with r² = 0.98 and 0.99 (mild and high concentration, respectively). Fe(acac)₃, FeCl₃ and FeSO₄ at high concentration (i.e. [Fe] ≈ 10 mg L⁻¹; [H₂O₂] ≈ 20 mg L⁻¹) and pH 5.0 showed the highest fitting values (r² = 0.99). Iron salt type showed a remarkable influence on the Fenton-like inactivation process.     

Geoeffectiveness of solar flares in magnetic crochet (sfe) production: I—Dependence on their spectral nature and position on the solar disk

The influence of the spectral nature and position on the solar disk of solar flares related to the production of magnetic effects on earth (from now on, sfe) over a more than 30-year period has been studied. Regarding the spectral issue, we found that the probability of a flare to produce sfe depends on the spectral band in which we observe it, being higher when the flare is important both in Hα and X-ray emissions. On the other hand, Hα and X-ray emissions have been considered in many different divisions of the solar surface and their effectiveness on sfe production have been compared. We found that there is not any privileged region on the solar disk for sfe production. These results end with the controversy generated by distinct conclusions obtained in classical studies on the subject.     

Analyzing observations of multiple small center of solar flares at a wavelength of 195 Å

The duration of elementary eruption process and intervals between them for flares of different importance have been determined based on the photometric data for flares, observed by a TRACE spacecraft at a wavelength of 195 Å. It has been revealed that the values of these parameters increase with increasing flare importance. It is assumed that the appearance of elementary nonstationary flare centers correlates with the origination of solitons at self-organized criticality.     

Some sources of plasma inhomogeneities in the solar wind in front of the Earth’s magnetosphere

The origination of various plasma inhomogeneities in the magnetosheath in front of the Earth’s magnetosphere is analyzed within classical magnetohydrodynamics. The effect of directional discontinuities or tangential and rotational discontinuities of the solar wind on plasma is studied. The origination of inhomogeneities of the type of secondary MHD waves in the magnetosheath is shown; the former equalize plasma parameters when restoring the stationary state. The effect of a rotational discontinuity on the bow shock–Earth’s magnetosphere system is of special interest, with distinguishing of plasma inhomogeneities of the plateau type observed in the near-Earth space.     

Construction of Intensity–Duration–Frequency (IDF) curves for precipitation at Lubumbashi,Congo, under the hypothesis of inadequate data

Abstract

Intensity–Duration–Frequency (IDF) curves for precipitation constitute a probabilistic tool and have proven useful in water resources management. In particular, IDF curves for precipitation enable questions on the extreme character of precipitation to be answered. The construction of IDF curves for precipitation is difficult or impossible in tropical areas due to the lack of long-term extreme precipitation data. A technique is proposed to overcome this shortcoming by combining limited high-frequency information on rainfall extremes with long-term daily rainfall information. It may be regarded as an extension of Koutsoyiannis' approach. Using this technique, IDF curves for precipitation are produced for Lubumbashi in Congo.

Citation Van de Vyver, H. & Demarée, G. R. (2010) Construction of Intensity–Duration–Frequency (IDF) curves for precipitation at Lubumbashi, Congo, under the hypothesis of inadequate data. Hydrol. Sci. J. 55(4), 555–564.     

Manifestation of solar and geodynamic activity in the dynamics of the Earth’s rotation

The relationships between different manifestations of solar and geomagnetic activity and the structural peculiarities of the dynamics of the pole wobble and irregularities in the Earth??s rotation are studied using singular spectrum analysis. There are two close major peaks and several lower ones in the same frequency range (1.1?C1.3 years) in the Chandler wobble (CW) spectrum. Components in the geomagnetic activity were distinguished in the same frequency band (by the Dst and Ap indices). Six- to seven-year oscillations in the Earth??s rotation rate with a complex dynamics of amplitude variations are shown in variations in geomagnetic activity. It is revealed that secular (decade) variations in the Earth??s rotation rate on average repeat global variations in the secular trend of the Earth??s geomagnetic field with a delay of eight years during the whole observation period.     

Construction of the maximal solution of Backus’ problem in geodesy and geomagnetism

The (simplified) Backus’ Problem (BP) consists in finding a harmonic function u on the domain exterior to the three dimensional unit sphere S, such that u tends to zero at infinity and the norm of the gradient of u takes prescribed values g on S. Except for a change of sign, the solution is not unique in general. However, there is uniqueness of solutions in the class of functions with the additional property that the radial component of the gradient of u on S is nonpositive. This is the geodetically relevant case. If a solution u with this property exists, then u is the maximal solution of the problem (and -u the minimal one). In this paper we propose a method of successive approximations to get this particular solution of BP and prove the convergence for functions g close to a constant function.     

Effects of solar and geomagnetic activity in long-term variations in the ionospheric parameters of the auroral zone in 1963–1986

A stable linear relation between foF2 and W with a correlation coefficient of 0.68–0.96 has been revealed as a result of a joint analysis of the foF2 critical frequencies and the virtual minimal heights (h’F) obtained from the data of vertical sounding (VS) of the ionosphere at Dixon Island auroral station, Wolf numbers (W), and PC geomagnetic index from 1963 to 1986. A significant linear relation exists between foF2 and the PC index with a correlation coefficient of r = 0.18–0.67. The correlation between the PC index and W is low in winter and autumn and is r = 0.50 and 0.74 at a significance level of ss = 0.96–0.99 in spring and summer. When the correlation between PC and foF2 is analyzed, it is necessary to consider the effect of solar activity (SA) on both parameters. The multiple correlation coefficients between these parameters have been calculated with regard to the effect of W. They were R = 0.75−0.98; however, the standardized regression coefficients β _W and β _PC indicated that W and PC considerably and insignificantly affect multiple correlation with foF2, respectively, and this effect depends on the season and time of day. It has been detected that the cyclic variations in foF2 and h’F are asymmetric. The amplitudes of these parameters in cycle 20 are smaller than in cycle 21.     

Influence of solar activity on variations in the density of the Earth’s upper atmosphere

This article studies long-period variations in the Earth’s upper atmosphere density over several solar activity cycles, using long-term data on the evolution of motion of three artificial satellites (Intercosmos-19, Meteor-1-2, and Cosmos-1154) in orbits at heights of 400–1000 km. The time interval when the satellites were in the orbits covered three solar activity cycles (partly the 21st, completely the 22nd, and partly the 23rd). It is found that the variations in the average density of the upper atmosphere at heights of 400–600 km in the 1980–2000 period were governed by the changes in the solar activity level.     

In search of potential earthquake source regions in the Chinese mainland in the light of ambient shear stress field

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Role of solar activity in formation of the anomalous El Nin’o current

Monthly indices of Southern Atmospheric Oscillation (SOI) and corresponding Wolf numbers, geoeffective solar flares, magnetic AE indices as well as daily average values of the southward component of the interplanetary magnetic field (IMF B _z) and data on the wind characteristics at Antarctic stations Vostok, Leningradskaya, and Russkaya are analyzed. It is shown that a sharp decrease in the SOI indices, which corresponds to the beginning of El Nin’o (ENSO), is preceded one or two months before by a 20% increase in the monthly average Wolf numbers. In warm years of Southern Atmospheric Oscillation a linear relationship is observed between the SOI indices and the number of geoeffective solar flares with correlation coefficients p < ?0.5. It is shown that in warm years a change in the general direction of the surface wind to anomalous at the above stations is preceded one or two days before by an increase in the daily average values of IMF B _z. An increase in the SOI indices is preceded one or two months before by a considerable increase in the monthly average values of the magnetic AE indices.     

Helicity–vorticity turbulent pumping of magnetic fields in the solar convection zone

We study the effect of turbulent drift of a large-scale magnetic field that results from the interaction of helical convective motions and differential rotation in the solar convection zone. The principal direction of the drift corresponds to the direction of the large-scale vorticity vector. Thus, the effect produces a latitudinal transport of the large-scale magnetic field in the convective zone wherever the angular velocity has a strong radial gradient. The direction of the drift depends on the sign of helicity and it is defined by the Parker–Yoshimura rule. The analytic calculations are done within the framework of mean-field magnetohydrodynamics using the minimal τ-approximation. We estimate the magnitude of the drift velocity and find that it can be a few m/s near the base of the solar convection zone. The implications of this effect for the solar dynamo are illustrated on the basis of an axisymmetric mean-field dynamo model with a subsurface shear layer. The model shows that near the bottom of the convection zone the helicity–vorticity pumping results mostly from the kinetic helicity contributions. We find that the magnetic helicity contributions to the pumping effect are dominant at the subsurface shear layer. There the magnitude of the drift velocity is found to be a few cm/s. We find that the helicity–vorticity pumping effect can have an influence on the features of the sunspot time–latitude diagram, producing a fast drift of the sunspot activity maximum at the rise phase of the cycle and a slow drift at the decay phase of the cycle.     

Observations of the Hα hydrogen emission on Spitsbergen during the proton event of January 22, 2012

The behavior of the Hα hydrogen emission at Barentsburg observatory during precipitation of high-energy solar protons and sudden impulse (SI) on January 22, 2012, was studied. The emission intensity was determined with a spectrometer, which gives the meridian arc spectrum image. It has been shown that the Hα emission luminosity onset coincides with SI and is caused by precipitation of solar wind protons through the cusp.     

Dynamics of the large-scale open solar magnetic field and its specific features in the zone of the main active longitudes in 2006–2012

The dynamics of the absolute global values (Φ) of the large-scale open solar magnetic field (LOSMF) fluxes at an interval of one solar rotation in 2006–2012 has been studied based on the Wilcox Solar Observatory data and using the ISOPAK original package for modeling the solar magnetic field. The reference points and the duration of the final quasi-biennial interval in cycle 23 (January 2006–May 2007; 17 months) and the phases of the cycle 24 minimum (May 2007–November 2009; 30 months), growth (November 2009–May 2012; 30 months), and the beginning of the maximum (May 2012–January 2013) have been determined. It has been indicated that the absolute values (Φ) decreased sharply at the beginning of the minimum, growth, and the maximum phases to ～(2, 1.25, 0.75) × 10²² Mx, respectively. During the entire minimum phase, LOSMF corotated super-quasi-rigidly westward in the direction of solar rotation; at the beginning of the growth phase, this field started corotating mostly eastward. The LOSMF polarity reversal in the current cycle 24 started in May–June 2012 (CR 2123–2124), when fields of southern polarity rushed from the Sun’s southern hemisphere toward the north. The statement that the solar cycle is a continuous series of quasi-biennial LOSMF intervals is confirmed. In particular, the minimum and growth phases are characterized by opposite LOSMF rotation directions, i.e., super-quasi-rigid corotation (twisting) and detwisting, with identical duration at least in cycle 24.     

Variations in solar radiation in the solar activity cycle: Response of Earth’s atmospheric parameters (numerical modeling and analysis of observational data)

The results of a three-dimensional numerical simulation of changes in the temperature and wind within a height range of up to 100 km caused by changes in fluxes in the solar ultraviolet (UV) radiation in the 23rd solar activity cycle (which was characterized by unusually low values of UV-radiation fluxes) and also of global changes in the ozone content are presented. The simulation results showed that the response of the temperature to variations in the UV radiation are substantially of a nonzonal character, which is caused by the presence in the model of sources of quasi-stationary waves corresponding to the observational data.     

Model estimations of wave disturbances of the emission layer’s luminosity as recorded from spacecraft in the vicinity of the solar terminator

A method of recording internal gravitational waves (IGWs) from spacecraft by observing disturbances in the atmospheric emission layer, formed in the vicinity of the solar terminator and emitted in the atmospheric molecular oxygen system (762 ± 5 nm), is considered. The possibility of such observations and the efficiency of recording various characteristics of IGWs passing through the observed emission layer are estimated.