Suppression of Weibull-Distributed Clutters Using a Cell-Averaging LOG/CFAR Receiver

The parameters of the Weibull distribution and the threshold level for an adaptive CFAR detector are determined by calculating the mean value and the mean-squared value of the input signal voltage before it passes through a logarithmic amplifier. By using this threshold level an adaptive method for suppressing various VVeibull-distributed clutters is proposed.     

Dynamical behaviour of the corona in association with radio emissions

From a combined analysis of radioheliographic observations and white light images of the Corona, it is shown that metric continua onsets or enhancements are associated with a great variety of dynamical changes of the Corona. It is found that if the most spectacular radio bursts (type IV) are associated with mass ejection transients, the more common noise storm onsets or enhancements are systematically associated with coronal changes which are not necessarly mass ejections.Simultaneous observations of Radio type III bursts and Hα mass ejecta are related. We are looking to the signature at low levels in the corona of the electron beam acceleration triggering type III bursts. The results deal with the relationship between the type III occurrence and optical features : the presence of velocities in Hα, the shape of Hα line which reveals trubulent motions and the probable existence of a shock wave.     

Derivation of OH concentrations from LIMS measurements

Stratospheric concentrations of OH have been derived from LIMS measurements of minor constituents. Two methods have been used. Assuming that HNO₃ and NO₂ are in photochemical steady state, LIMS measurements of these species, with knowledge of appropriate rate constants and a calculation of the HNO₃ photolysis rate, allow nearly global fields of OH to be derived. The derived profiles show satisfactory agreement with observations. As a check on our method, OH has also been derived by calculations of its sources and sinks using LIMS measurements of H₂O. The two methods agree extremely well in low latitudes. At higher latitudes the agreement is less satisfactory. This is discussed in terms of the diurnal behaviour of the species and the time constant of the HNO₃/NO₂ equilibrium.     

Comparison of subpeak electron density profiles deduced from ionograms with the International Reference Ionosphere (IRI)

A comparison is made between the subpeak electron density profiles, obtained at selected local hours by vertical ionospheric sounding at the ionospheric station at Sofia (42.6°N; 23.3°E) and the IRI profiles for spring, summer, winter and two levels of solar activity (R = 10 and 100). It is demonstrated that the ionospheric profiles above Sofia are in rather good agreement with the values computed with IRI.     

Possible adaptation to strong magnetic fields

Animal adaptation to a strong magnetic field was investigated. Mice were exposed to 30-day total-body continuous effects of a constant magnetic field (CMF) of 1.6T, and their physiological responses were assessed. Analysis of the data obtained showed that different parameters varied in a dissimilar manner. Red blood changes returned to normal in the course of the experiment. Leucocytosis and increased content of catecholamines and corticosterone of blood and adrenals persisted throughout the exposure. Changes in the spermatogenic epithelium were most distinct after the exposure. The recovery of certain parameters during the CMF exposure is indicative of adaptation of some physiological systems. The adaptation is, however, incomplete as suggested by the long persisting stress manifestation. Reticulocytopenia and spermatogenetic abnormalities found after exposure are of particular importance.     

The mass spectrum analyzer (MSA) onboard BEPI COLOMBO MMO: Scientific objectives and prototype results

BEPI COLOMBO is a joint mission between ESA and JAXA that is scheduled for launch in 2014 and arrival at Mercury in 2020. A comprehensive set of ion sensors will be flown onboard the two probes that form BEPI COLOMBO. These ion sensors combined with electron analyzers will allow a detailed investigation of the structure and dynamics of the charged particle environment at Mercury. Among the ion sensors, the Mass Spectrum Analyzer (MSA) is the experiment dedicated to composition analysis onboard the Mercury Magnetospheric Orbiter (MMO). It consists of a top-hat for energy analysis followed by a Time-Of-Flight (TOF) section to derive the ion mass. A notable feature of MSA is that the TOF section is polarized with a linear electric field that provides an enhanced mass resolution, a capability that is of importance at Mercury since a variety of species originating from the planet surface and exosphere is expected. MSA exhibits two detection planes: (i) one with moderate mass resolution but a high count rate making MSA appropriate for plasma analysis, (ii) another with a high (above 40) mass resolution though a low count rate making it appropriate for planetology science. Taking advantage of the spacecraft rotation, MSA will provide three-dimensional distribution functions of magnetospheric ions, from energies characteristic of exospheric populations (a few eVs or a few tens of eVs) up to the plasma sheet energy range (up to ∼40 keV/q) in one spin (4 s).     

Physics of ion acceleration in the solar flare on 2005 September 7 determines γ-ray and neutron production

Relativistic neutrons were observed by the neutron monitors at Mt. Chacaltaya and Mexico City and by the solar neutron telescopes at Chacaltaya and Mt. Sierra Negra in association with an X17.0 flare on 2005 September 7. The neutron signal continued for more than 20 min with high statistical significance. Intense emissions of γ-rays were also registered by INTEGRAL, and during the decay phase by RHESSI. We analyzed these data using the solar-flare magnetic-loop transport and interaction model of Hua et al. [Hua, X.-M., Kozlovsky, B., Lingenfelter, R.E. et al. Angular and energy-dependent neutron emission from solar flare magnetic loops, Astrophys. J. Suppl. Ser. 140, 563–579, 2002], and found that the model could successfully fit the data with intermediate values of loop magnetic convergence and pitch-angle scattering parameters. These results indicate that solar neutrons were produced at the same time as the γ-ray line emission and that ions were continuously accelerated at the emission site.     

Solar wind low-energy energetic ion enhancements: A tool to forecast large geomagnetic storms

Predicting the occurrence of large geomagnetic storms more than an hour in advance is an important, yet difficult task. Energetic ion data show enhancements in flux that herald the approach of interplanetary shocks, usually for many hours before the shock arrival. We present a technique for predicting large geomagnetic storms (Kp  7) following the arrival of interplanetary shocks at 1 AU, using low-energy energetic ions (47–65 keV) and solar wind data measured at the L1 libration point. It is based on a study of the relationship between energetic ion enhancements (EIEs) and large geomagnetic storms by Smith et al. [Smith, Z., Murtagh, W., Smithtro, C. Relationship between solar wind low-energy energetic ion enhancements and large geomagnetic storms. J. Geophys. Res. 109, A01110, 2004. doi:10.1029/ 2003JA010044] using data in the rise and maximum of solar cycle 23 (February 1998–December 2000). An excellent correlation was found between storms with Kp  7 and the peak flux of large energetic ion enhancements that almost always (93% of time in our time period) accompany the arrival of interplanetary shocks at L1. However, as there are many more large EIEs than large geomagnetic storms, other characteristics were investigated to help determine which EIEs are likely to be followed by large storms. An additional parameter, the magnitude of the post-shock total magnetic field at the L1 Lagrangian point, is introduced here. This improves the identification of the EIEs that are likely to be followed by large storms. A forecasting technique is developed and tested on the time period of the original study (the training data set). The lead times, defined as the times from the arrival of the shock to the start of the 3-h interval of maximum Kp, are also presented. They range from minutes to more than a day; the average for large storms is 7 h. These times do not include the extra warning time given when the EI flux cross the high thresholds ahead of the shock. Because the data-stream used in the original study is no longer available, we extended the original study (1998–2000) to 2001, in order to: (a) investigate EIEs in 2001; (b) present a validation of the technique on an independent data set; (c) compare the results based on the original (P1) energy channel to those of the replacement (P1′) and (d), determine new EIE thresholds for forecasting geomagnetic storms using P1′ data. The verification of this P1′ training data set is also presented, together with lead times.     

Kinetic-Gasdynamic Modeling of the Heliospheric Interface

Heliospheric energetic neutral atoms (ENAs) that will be measured by the Interstellar Boundary Explorer (IBEX) originate from the heliosheath. The heliosheath is formed as a result of the interaction of the solar wind (SW) with the circum-heliospheric interstellar medium (CHISM). The expected fluxes of ENAs are strongly dependent on the nature of this interaction. In turn, the interaction of the solar wind with the local interstellar cloud has a complex and multi-component nature. Detailed theoretical modeling of the interaction between the SW and the local interstellar medium is required to understand the physics of the heliosheath and to predict and explain the heliospheric ENAs. This paper summarizes current state-of-art kinetic-gasdynamic models of the SW/CHISM interaction. We shall restrict our discussion to the kinetic-gasdynamic and kinetic-magnetohydrodynamic (MHD) models developed by the Moscow group. This paper summarizes briefly the main results of the first self-consistent, two-component, kinetic-gasdynamic model by Baranov and Malama (J. Geophys. Res. 98:15157–15163, 1993), presents new results obtained from the 3D kinetic-MHD model by Izmodenov et al. (Astron. Astrophys. 437:L35–L38, 2005a), describes the basic formulation and results of the model by Malama et al. (Astron. Astrophys. 445:693–701, 2006) as well as reports current developments in the model. This self-consistent model considers pickup protons as a separate non-equilibrium component. Then we discuss a stochastic acceleration model for pickup protons in the supersonic solar wind and in the heliosheath. We also present the expected heliospheric ENA fluxes obtained in the framework of the models.     

Correlation between cell death and induction of non-rejoining PCC breaks by carbon-ion beams.

We have shown a correlation between cell death and induction of non-rejoining chromatin breaks in two normal human cells and three human tumor cell lines irradiated by carbon-ion beams and X rays. Non-rejoining chromatin breaks were measured by counting the number of remaining chromatin fragments detected by the premature chromosome condensation (PCC) technique. Carbon-ion beams were accelerated by the Heavy Ion Medical Accelerator in Chiba (HIMAC). The cells were irradiated by two different mono-LET beams (LET = 13 keV/micrometer and 77 keV/micrometer ) and 200 kV X rays. The RBE values of cell death for carbon-ion beams relative to X rays were 1.1 to 1.4 for 13 keV/micrometer beams and 2.5 to 2.9 for 77 keV/micrometer beams. The induction rate of non-rejoining PCC breaks per cell per Gy was found to be highest for the 77 keV/micrometer beams for all of the cell lines.The results found in this study show that there is a good correlation between cell death and induction of non-rejoining PCC breaks for these human cell lines.