Why does the total pressure on the subsolar magnetopause differ from the solar wind dynamic pressure?

Based on analysis of MHD equations and the results of numerical simulation in the magneto-sheath it is demonstrated that the total pressure on the magnetopause differs from the solar wind dynamic pressure in the majority of cases. From the equation of motion it follows that the total pressure is reduced due to deflection from the Sun-Earth line. At the same time, it increases because of formation of a magnetic barrier. This result is consistent with experimentally observed expansion of the magnetosphere for the radial direction of the interplanetary magnetic field, when no magnetic barrier is formed. In this paper we compare the behavior of pressure along the Sun-Earth line for the northward and radial interplanetary field, using the results of numerical MHD simulation and observational data from THEMIS. In the isotropic MHD approximation, the difference between the total pressure on the subsolar magnetopause at northern and radial IMFs does not exceed 10–12 percent. However, in the anisotropic approximation this difference increases up to 15–20 percent. The results of anisotropic modeling well agree with observed averaged profiles of pressure components in the subsolar magnetosheath.     

Anomalies in radiation-collisional kinetics of Rydberg atoms induced by the effects of dynamical chaos and the double Stark resonance

Radiative and collisional constants of excited atoms contain the matrix elements of the dipole transitions and when they are blocked one can expect occurring a number of interesting phenomena in radiation-collisional kinetics. In recent astrophysical studies of IR emission spectra it was revealed a gap in the radiation emitted by Rydberg atoms (RA  ) with values of the principal quantum number of n≈10$n\approx 10$. Under the presence of external electric fields a rearrangement of RA emission spectra is possible to associate with manifestations of the Stark effect. The threshold for electric field ionization of RA   is E≈3·10⁴$E\approx 3·{10}^4$ V/cm for states with n>10$n>10$. This means that the emission of RA   with n≥10$n\ge 10$ is effectively blocked for such fields. In the region of lower electric field intensities the double Stark resonance (or Förster resonance) becomes a key player. On this basis it is established the fact that the static magnetic or electric fields may strongly affect the radiative constants of optical transitions in the vicinity of the Föster resonance resulting, for instance, in an order of magnitude reduction of the intensity in some lines. Then, it is shown in this work that in the atmospheres of celestial objects lifetimes of comparatively long-lived RA states and intensities of corresponding radiative transitions can be associated with the effects of dynamic chaos via collisional ionization. The Föster resonance allows us to manipulate the random walk of the Rydberg electron (RE) in the manifold of quantum levels and hence change the excitation energies of RA, which lead to anomalies in the IR spectra.     

Linear and circular structures of the Bohemian Massif — Comparison of satellite and geophysical data

Two structural schemes of the Bohemian Massif are presented and compared. The first one is a result of interpretation of various geophysical data and the second one is compiled on the basis of decoding of space imagery from different sources (Kosmos, Landsat etc.). Both schemes have many structural features in common, but there are diversities namely in the hierarchy of directions and regional distribution of linear structures. These problems are discussed in detail. For example, the most impressive system of structures is the NW-SE system in both schemes, whereas the NE-SW is more remarkable in the geophysical scheme; the N-S and the E-W systems are best expressed in the scheme of photolineaments. These facts are due to the genesis, age, development and dynamic characteristics of respective structural systems. The circular structural features namely those of large size are mostly remarkable in space imagery. At present, they are not distinguished genetically but only described regionally.     

Ionospheric oscillations caused by geomagnetic Pi2 pulsations and their observations by multipoint continuous Doppler sounding; first results

In 2004, we started operating a continuous Doppler sounding system to investigate ionospheric signatures of infrasonic, short period acoustic gravity waves and geomagnetic pulsations. Since January 2007, four stable 3.59 MHz transmitters have been in operation in the western part of the Czech Republic. Multipoint measurements enable us to investigate horizontal propagation of waves and disturbances in the ionosphere and to estimate horizontal distances over which these waves (disturbances) are correlated.     

Theoretical modeling for the stereo mission

We summarize the theory and modeling efforts for the STEREO mission, which will be used to interpret the data of both the remote-sensing (SECCHI, SWAVES) and in-situ instruments (IMPACT, PLASTIC). The modeling includes the coronal plasma, in both open and closed magnetic structures, and the solar wind and its expansion outwards from the Sun, which defines the heliosphere. Particular emphasis is given to modeling of dynamic phenomena associated with the initiation and propagation of coronal mass ejections (CMEs). The modeling of the CME initiation includes magnetic shearing, kink instability, filament eruption, and magnetic reconnection in the flaring lower corona. The modeling of CME propagation entails interplanetary shocks, interplanetary particle beams, solar energetic particles (SEPs), geoeffective connections, and space weather. This review describes mostly existing models of groups that have committed their work to the STEREO mission, but is by no means exhaustive or comprehensive regarding alternative theoretical approaches.     

Open framework for objective evaluation of crater detection algorithms with first test-field subsystem based on MOLA data

Crater Detection Algorithms (CDAs) applications range from estimation of lunar/planetary surface age to autonomous landing on planets and asteroids and advanced statistical analyses. A large amount of work on CDAs has already been published. However, problems arise when evaluation results of some new CDA have to be compared with already published evaluation results. The problem is that different authors use different test-fields, different Ground-Truth (GT) catalogues, and even different methodologies for evaluation of their CDAs. Re-implementation of already published CDAs or its evaluation environment is a time-consuming and unpractical solution to this problem. In addition, implementation details are often insufficiently described in publications. As a result, there is a need in research community to develop a framework for objective evaluation of CDAs. A scientific question is how CDAs should be evaluated so that the results are easily and reliably comparable. In attempt to solve this issue we first analyzed previously published work on CDAs. In this paper, we propose a framework for solution of the problem of objective CDA evaluation. The framework includes: (1) a definition of the measure for differences between craters; (2) test-field topography based on the 1/64° MOLA data; (3) the GT catalogue wherein each of 17,582 craters is aligned with MOLA data and confirmed with catalogues by N.G. Barlow et al. and J.F. Rodionova et al.; (4) selection of methodology for training and testing; and (5) a Free-response Receiver Operating Characteristics (F-ROC) curves as a way to measure CDA performance. The handling of possible improvements of the framework in the future is additionally addressed as a part of discussion of results. Possible extensions with additional test-field subsystems based on visual images, data sets for other planets, evaluation methodologies for CDAs developed for different purposes than cataloguing of craters, are proposed as well. The goal of the proposed framework is to contribute to the research community by establishing guidelines for objective evaluation of CDAs.     

Rigidity dependence of Forbush decreases in the energy region exceeding the sensitivity of neutron monitors

Applicability of our present setup for solar modulation studies in a shallow underground laboratory is tested on four prominent examples of Forbush decrease during solar cycle 24. Forbush decreases are of interest in space weather application and study of energy-dependent solar modulation, and they have been studied extensively. The characteristics of these events, as recorded by various neutron monitors and our detectors, were compared, and rigidity spectrum was found. Linear regression was performed to find power indices that correspond to each event. As expected, a steeper spectrum during more intense extreme solar events with strong X-flares shows a greater modulation of galactic cosmic rays. Presented comparative analysis illustrates the applicability of our setup for studies of solar modulation in the energy region exceeding the sensitivity of neutron monitors.     

Are Boltzmann plots of hydrogen Balmer lines a tool for identifying a subclass of S1 AGN?

It is becoming clear that we can define two different types of nearby AGN belonging to the Seyfert 1 class (S1), on the basis of the match of the intensities of their Broad Balmer Lines (BBL) with the Boltzmann Plots (BP). These two types of S1 galaxies, that we call BP-S1 and NoBP-S1, are characterized, in first approximation, by Broad Line Regions (BLR) with different structural and physical properties. In this communication, we show that these features can be well pointed out by a multi-wavelength analysis of the continuum and of the broad recombination Hydrogen lines, that we carry out on a sample of objects detected at optical and X-ray frequencies. The investigation is addressed to verify whether BP-S1 are the ideal candidates for the study of the kinematical and structural properties of the BLR, in order to derive reliable estimates of the mass of their central engine and to constrain the properties of their nuclear continuum spectrum.     

Small-scale deformation of the bow shock

The prediction of the bow shock location is a proof of our understanding of the processes governing the solar wind – magnetosphere interaction. However, the models describing the bow shock location as a function of upstream parameters are based on a statistical processing of bow shock crossings observed by a single spacecraft. Such crossings locate the bow shock in motion, i.e., in a non-equilibrium state and this fact can be a source of significant errors. We have carefully analyzed a long interval of simultaneous observations of the bow shock and magnetopause and another interval of bow shock observations at two well-separated points. Our results suggest that often a small-scale deformation of the bow shock front due to magnetosheath fluctuations is the most appropriate interpretation of observations. Since the low-frequency magnetosheath variations exhibit largest amplitudes, a simultaneous bow shock displacement over a distance of 10–15 R_E can be observed. We suggest that bow shock models can be probably improved if the tilt angle would be implemented as a parameter influencing the bow shock location in high latitudes.     

A new approach to solar wind monitoring

The monitoring of solar wind parameters is a key problem of the space weather program. We are presenting a new solution of plasma parameter determination suitable for small and fast solar wind monitors. The first version will be launched during the SPECTR-R project into a highly elongated orbit with apogee ∼350,000 km. The method is based on simultaneous measurements of the total ion flux and ion integral energy spectrum by six identical Faraday cups. Three of them are dedicated to determination of the ion flow direction, the other three (equipped with control grids supplied by a retarding potential) are used for determination of the density, temperature, and speed of the plasma flow. The version under development is primarily designed for the measurements in the solar wind and tail magnetosheath, thus for velocities range from 270 to 750 km/s, temperatures from 1 to 30 eV, and densities up to 200 cm⁻³. However, the instrument design can be simply modified for measurements in other regions with a substantial portion of low-energy plasma as a subsolar magnetosheath, cusp or low-latitude boundary layer. Testing of the engineering model shows that the proposed method can provide reliable plasma parameters with a high time resolution (up to 8 Hz). The paper presents not only the method and its technical realization but it documents all advantages and peculiarities of the suggested approach.