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[en] Complete text of publication follows. Post-CME current sheet is a common feature associated with solar eruptions as inferred by CME models. Thin ray-like features in the corona that appear shortly after the eruption in between the ejecta and post-CME loops have been observed by white light coronagraphs on SMM, SOHO/LASCO and MLSO/MK4. They are believed to be the observational evidence of the post-CME current sheet. Magnetic reconnection within the current sheet should produce observational signatures, such as heated plasma and outflows, that can be used to test various models. Observations from SOHO/UVCS and Hinode/XRT support its existence by the high temperature emission that is co-spatial with the ray-like features observed in white light. We present the first attempt to model the UV line emission and the ionic charge state evolution in a post-CME current sheet, and discuss the observational consequences implied from our results.
[en] Complete text of publication follows. This paper describes a new method to obtain the local magnetic index, K, from a global index, Kp, experienced at any location in a wide area having or not a magnetic observatory in the vicinity. The motivation for this work arises from the need to produce accurate data for the predictive Space Weather models. Many models work with global indices as drivers, but if specific regions as some parts of the ionosphere have to be studied, the local indices are more appropriate. However, until now, in the case of not having magnetic observatories in this area, global indices were the only option. The methodology that we used is based on neural networks, and we demonstrated that this method was effective to obtain the local K-index. This tool has a great potential to process information from rather complex systems as the geomagnetic one.
[en] Complete text of publication follows. Recent technological advances suggest that we are on the threshold of a new era in applied magnetic surveys, where acquisition of magnetic gradient tensor data will become routine. In the meantime, modern ultrahigh resolution conventional magnetic data can be used to calculate gradient tensor elements from TMI or TMI gradient surveys. Until the present, not a great deal of attention has been paid to processing and interpretation of gradient tensor data. New methods for inverting gradient tensor surveys to obtain source parameters have been developed for a number of elementary, but useful, models. These include point pole, line of poles, point dipole (sphere), line of dipoles (horizontal cylinder), thin and thick dipping sheets and sloping step models. A key simplification is the use of eigenvalues and associated eigenvectors of the tensor. Rotational invariants can be expressed as combinations of eigenvalues. The scaled source strength (e.g. p/r3 for a point pole, m/r4 for a point dipole) is a particularly useful quantity that can be calculated from the eigenvalues. Gradient tensor data collected over the Tallawang magnetite skarn deposit in New South Wales will be presented to illustrate the methods. A number of methods have been proposed for locating dipole-like sources from spot measurements or isolated profiles of magnetic gradient tensor data. In particular, there is an inherent four-fold ambiguity in obtaining solutions for dipole location and orientation of its moment from point-by-point analysis of gradient tensors. This paper presents a new, simple and efficient method for uniquely determining the location and magnetic moment of a dipole source from a short segment of gradient tensor data that is relatively free of contamination from background gradients. A separate algorithm, which deconvolves gradient tensor data along a profile by separating scalar and vector aspects of the dipole inversion problem, will be described. This enables contamination from background gradients to be estimated and removed, thereby improving estimation of dipole parameters. Besides the geological applications, these algorithms are readily applicable to the detection, location and classification (DLC) of magnetic objects, such as naval mines, UXO, shipwrecks, archaeological artefacts and buried drums.
[en] Complete text of publication follows. Solar flares are characterized by impulsive release of considerable energy in the form of electromagnetic and corpuscular radiation-solar cosmic rays as well as by coronal mass ejections (CMEs). However, recent investigations indicate the presence of flares that are not associated with observable CMEs. The energy of a large solar flare hundreds times exceeds the reserves of chemical energy (coal, oil, gas) of the Earth. Flare development is usually being connected with magnetic field reconnection in region of the solar chromosphere and corona above sun-spots where strong magnetic fields with a tension up to 3000 Gs exist: such magnetic fields in sun-spots ensure solar flare energetics observed. At the same time corona graphic observations by SOLWIND, SMM and SOHO space missions in the last decade revealed more than 1500 new comets, passing very closely to the Sun, so called sungrazers and sunstrikers. Recent theoretical investigations on the evolution of cometary nuclei in the solar atmosphere, carried out taking into account aerodynamic fragmentation and transversal expansion of the fragmented mass, indicate the possibility of generation of solar flares due to explosive release of the kinetic energy of nuclei of comets, sunstrikers, near the solar photosphere. The energetics of such impact-initiated solar photospheric flare corresponds to that observed during large solar flares at cometary nuclei masses of the order of mass of the nucleus of Comet Halley. Synchronic observations of sunstriking comets and solar activity are important for further understanding of solar flare mechanisms. 1. COSPAR Inform. Bull. 1998, 142, 21 // http://sohowww.nascom.nasa.gov/hotshots/2008_06_23/ ; 2. Gopalswamy N., Akiyama S., Yashiro S. Major solar flares without coronal mass ejections // IAU Symposium No. 257 'Universal Heliophysical Processes' Abstracts, Ioannina, Greece, 2008, p. 12 // http://iau257.uoi.gr/submitted_abstracts/ ; 3. Hale G.E. On the probable existence of a magnetic field in sun-spots // Astrophys. J. 1908, v. 28, No. 4, pp. 315-343; 4. Ibadov S., Ibodov F.S., Grigorian S.S. Explosion of sungrazing comets in the solar atmosphere and solar flares // Proc. IAU Symposium No. 257, N. Gopalswamy and D.F. Webb, Eds, Cambridge University Press, 2009, pp. 341-343; 5. Somov B.V. Physical Processes in Solar Flares // Kluwer Academic Publisheres, Dordrecht/Boston/London, 1992, 249 p.; 6. Sweet P.A. Mechanisms of solar flares // Ann. Rev. Astron. Astrophys. 1969, v. 7, p. 149-176.
[en] Complete text of publication follows. In our study, we combine the geomagnetic field (poloidal and toroidal parts) at the core-mantle boundary (CMB), the related fluid-flow close to the CMB and the CMB topography to determine core-mantle coupling torques. This combined electromagnetic and topographic coupling torques are used to compute the related variations of Earth's orientation parameters (EOPs). Their comparison with observed EOPs is used to check consistency of input models with observations to select particular models (e.g. of CMB topography) accordingly. For the computation of the EM coupling torque, we have to calculate the poloidal and toroidal geomagnetic field at the CMB. We apply the non-harmonic downward continuation (Ballani et al., 2002; GJI 149) to the observed poloidal geomagnetic field for its computation at the CMB. For the determination of the toroidal geomagnetic field at the CMB, we need the fluid-flow velocity, which will be inferred from the poloidal geomagnetic field at the CMB by fluid flow inversion according to Wardinski (2005; GFZ STR 05/07). We solve the initial boundary value problem for the toroidal field and can determine the toroidal geomagnetic field in the whole conducting part of the Earth's mantle. Moreover, we investigate the influence of different electric conductivity models of the mantle on the geomagnetic field at the CMB and both coupling torques. Based on the time-dependent fluid-flow velocities, the TOP coupling torque is determined consistently. The combined coupling torques provide us the possibility to deduce equivalent excitation functions for the forward modelling of EOPs on the decadal time scale. Inconsistencies with the observed variation of length-of-day (LOD) rule out some combination of conductivity and CMB topography models.
[en] Complete text of publication follows. We use the multi-spacecraft mission Cluster to make observational estimates of the local energy conversion across the dayside high-latitude magnetopause. The energy conversion is estimated during eleven complete magnetopause crossings under steady south-dawnward interplanetary magnetic field (IMF). We describe a new method to determine the reconnection rate from the magnitude of the local energy conversion. The reconnection rate as well as the energy conversion varies during the course of the eleven crossings and is typically much higher for the outbound crossings. This supports the previous interpretation that reconnection is continuous but its rate is modulated. These results have been compared to results of the BATSRUS global MHD simulation based on the observed IMF conditions. We found that BATSRUS correctly reproduce the energy conversion observed by Cluster and the magnitude of the estimated energy conversion from Cluster and the model are in good agreement. Our results may be used to validate and scale BATSRUS to improve predictions of the total energy input to the magnetosphere, which is of importance for Space Weather.
[en] Complete text of publication follows. The relationships between double-onset substorms, bursty bulk flows (BBFs), and the variations of the interplanetary magnetic field (IMF) are comparatively studied by using two events respectively observed by Geotail and THEMIS. Five (four) consecutive bursts of Pi2 pulsations for the Geotail (THEMIS) event occurred successively and simultaneously at the ground stations from high to low latitudes. Especially for both events, the last pair of Pi2 bursts are accompanied by magnetic bays at high latitudes and preceded by earthward BBFs in the plasma sheet. Polar UVI images show auroral activations at each Pi2 onset. The ground-based magnetometers and geosynchronous orbit sensed magnetic perturbations like the one affected by the formation of the substorm current wedge. The horizontal magnetic variation vectors, consisting of H and D components, had the vortex patterns like the ones induced by the upward and downward field-aligned currents during substorm times. These observations display two similar events of double-onset substorm. The mapping of ground Pi2 onset timing to the IMF observations at ∼1 AU just in front of Earth's magnetopause shows that they appear under the same variation cycles of north-to-south and then north. The comparison of both events suggests that double-onset substorms are externally triggered and driven by earthward BBFs as expected to result from magnetotail reconnection in association with the IMF variations.
[en] Complete text of publication follows. The magnetic field of the Earth acts like a shield against the solar wind, leading to a magnetopause position many planetary radii away from the planet, in contrast to the situation at non or weakly magnetized planets such as Mars and Venus. Despite this there is significant ion outflow from the cusp and polar cap region of the Earth's ionosphere. Effective interaction regions form, in particular in the ionospheric projection of the cusp, where ionospheric plasma flow up along the field-lines in response to magnetospheric energy input. Strong wave particle interaction at altitudes above the ionosphere further accelerate the particles so that gravity is overcome. For the particles to enter a direct escape path the particles must be accelerated along open magnetic field lines so that they cross the magnetopause or reach a distance tailward of the tail reconnection point. Else the Earth's magnetic field will transport the particles back towards the Earth. This return flow may also be either lost to space or returned to the atmosphere. Throughout this transport chain the heating and acceleration experienced by the particles will have an influence on the final fate of the particles, as well as determine which populations can be measured by particle instruments. We will present quantitative estimates of centrifugal acceleration and perpendicular heating along the escape path from the cusp, through the high altitude polar cap / mantle. We will see what factors determines the observed number flux, and present some preliminary results based on fluxes observed further downstream in the tail, including both outflow and return flow.
[en] Complete text of publication follows. One of the most important and most effective tools in the investigation and monitoring of the magnetosphere is the sounding of this region by electromagnetic signals traversing / propagating through this magnetized, inhomogeneous, in some cases moving medium. To reach this goal it is necessary to use accurate, full wave propagation models. In these models the media are complex and inhomogeneous; the signals are in most cases UWB signals with general shapes. This presentation will give an overview of the common, general characteristics of these new, accurate and effective models for the computation of the signal propagation in the magnetosphere (and in the atmosphere of other planets, too). These common characteristics are the base of the description of the parameters and dynamics of the magnetosphere deriving by the inversion of the accurate propagation models, and the results depend on the structure and characteristics of the applied model.
[en] Complete text of publication follows. We present results from a study of the response of the magnetosphere-ionosphere system to southward turnings of the Interplanetary Magnetic Field. This is the period during which the M-I system is preconditioned for a subsequent substorm expansion phase onset. The loading process is manifested in the ionospheric current system and we show extensive observations of challenging the 'standard DP1-DP2 model'. We find significant differences in the response of the auroral electrojet system in the dark ionosphere vs. the sunlit ionosphere. This indicates a discontinuity located near or at the terminator.