Evaluation of the IRI model for the European region

The aim of this paper is to investigate various aspects of the International Reference Ionosphere (IRI) performance in European area and to evaluate its accuracy and efficiency for: long term prediction of the critical frequencies foF2 and the maximum usable frequencies (MUF); using storm-time correction option (ST); the total electron content (TEC) and the maximum observable frequency (MOF) updating. Data of foF2, TEC, MOF are related to 2005. It is obtained that median values of foF2 can be predicted with the mean error σ(med)∼ 0.49 MHz. For median values of MUF absolute σ was 1.39 MHz and relative σ_r was 8.8%. For instanteneous values estimates are increased to 1.58σ(med) MHz for foF2 and could reach 3.84 MHz for MUF. Using correction ST-option and TEC values provided ∼30% improvement but TEC seems to be more preferable. However, from considered parameters of the IRI updating (ST-factor, TEC, MOF) the best results were demonstrated by MOF. Using the IRI2007 to calculate TEC gives 20–50% improvement of TEC correspondence to experimental values but this improvement is not enough to treat TEC without the IRI model adaptation.     

Detrend effect on the scalograms of GPS power scintillation

The study of amplitude scintillation on GPS radio links is usually done after detrending the time series of the transmitted power so to define scintillations as the chaotic fluctuation around a unitary value. In a sense, the choice of how to detrend the time series is part of the definition of scintillation.     

An analytical model for the prediction of a micro-dosimeter response function

A rapid analytical procedure for the prediction of a micro-dosimeter response function in low Earth orbit (LEO), correlated with the Space Transportation System (STS, shuttle) Tissue Equivalent Proportional Counter (TEPC) measurements is presented. The analytical model takes into consideration the energy loss straggling and chord length distribution of the detector, and is capable of predicting energy deposition fluctuations in a cylindrical micro-volume of arbitrary aspect ratio (height/diameter) by incoming ions through both direct and indirect (δ ray) events. At any designated (ray traced) target point within the vehicle, the model accepts the differential flux spectrum of Galactic Cosmic Rays (GCRs) and/or trapped protons at LEO as input. On a desktop PC, the response function of TEPC for each ion in the GCR/trapped field is computed at the average rate of 30 s/ion. The ionizing radiation environment at LEO is represented by O’Neill’s GCR model (2004), covering charged particles in the 1 ? Z ? 28 range. O’Neill’s free space GCR model is coupled with the Langley Research Center (LaRC) angular dependent geomagnetic cutoff model to compute the transmission coefficient in LEO. The trapped proton environment is represented by a LaRC developed time dependent procedure which couples the AP8MIN/AP8MAX, Deep River Neutron Monitor (DRNM) and F10.7 solar radio frequency measurements. The albedo neutron environment is represented by the extrapolation of the Atmospheric Ionizing Radiation (AIR) measurements. The charged particle transport calculations correlated with STS 51 and 114 flights are accomplished by using the most recent version (2005) of the LaRC deterministic High charge (Z) and Energy TRaNsport (HZETRN) code. We present the correlations between the TEPC model predictions (response function) and TEPC measured differential/integral spectra in the lineal energy (y) domain for both GCR and trapped protons, with the conclusion that the model correctly accounts for the increase in flux at low y values where energetic ions are the primary contributor. We further discuss that, even with the incorporation of angular dependency in the cutoffs, comparison of the GCR differential/integral flux between STS 51 and 114 TEPC measured data and current calculations indicates that there still exists an underestimation by the simulations at low to mid range y values. This underestimation is partly related the exclusion of the secondary pion particle production from the current version of HZETRN.     

Analysis of total visual and CCD V-broadband observations of Comet C/1995 O1 (Hale-Bopp): 1995–2001

We developed a general method for determination of water production rates from groundbased visual observations and applied it to Comet Hale–Bopp. Our main objective is to extend the method to include total visual magnitude observations obtained with CCD detector and V filter in the analysis of total visual magnitudes. We compare the CCD V-broadband careful observations of Liller [Liller, W. Pre-perihelion CCD photometry of Comet 1995 O1 (Hale-Bopp). Planet. Space Sci. 45, 1505–1513, 1997; Liller, W. CCD photometry of Comet C/1995 O1 (Hale-Bopp): 1995–2000. Int. Comet Quart. 23(3), 93–97, 2001] with the total visual magnitude observations from experienced international observers found in the International Comet Quarterly (ICQ) archive. A data set of ∼400 CCD observations covering about the same 6 years time span of the ∼12,000 ICQ selected total visual magnitude observations were used in the analysis. A least-square method applied to the water production rates, yields power laws as a function of the heliocentric distances for the pre- and post-perihelion phases. The average dimension of the nucleus as well as its effective active area is determined and compared with values published in the literature.     

Physical mechanism of the vertical electric field generation over active tectonic faults

The concept of the Global Electric Circuit (GEC) provides an explanation of the existence of a vertical atmospheric electric field and coupling between the ground and ionosphere. Presently, ionospheric physics pays more attention to electric fields and coupling processes in the polar and auroral regions, whereas in other areas the potential difference between the ground and ionosphere usually is not taken into account. Regional processes exist, however, that are able to significantly affect the GEC parameters and through modification of the ionospheric potential to create plasma density irregularities of different scales within the ionosphere. One such source of ionosphere modification is air ionization in the vicinity of active tectonic faults, which takes place due to increased radon emanation. This paper considers the process of local modification of the GEC and corresponding ionospheric variability due to tectonic activity.     

Increased BLSS closure using mineralized human waste in plant cultivation on a neutral substrate

The purpose of this work was to study the full-scale potential use of human mineralized waste (feces and urine) as a source of mineral elements for plant cultivation in a biological life support system (BLSS). Plants that are potential candidates for a photosynthesizing link were grown on a neutral solution containing human mineralized waste. Spring wheat Triticum aestivum L., peas Pisum sativum L. Ambrosia cultivar and leaf lettuce Lactuca sativa L., Vitaminny variety, were used. The plants were grown hydroponically on expanded clay aggregates in a vegetation chamber in constant environmental conditions. During plant growth, a determined amount of human mineralized waste was added daily to the nutrient solution. The nutrient solution remained unchanged throughout the vegetation period. Estimated plant requirements for macro-elements were based on a total biological productivity of 0.04 kg day⁻¹ m⁻². As the plant requirements for potassium exceeded the potassium content of human waste, a water extract of wheat straw containing the required amount of potassium was added to the nutrient solution. The Knop’s solution was used in the control experiments.     

Cosmic ray studies at Moussala – Past,present and future

We review the main activities carried out at Moussala peak (2925 m above sea level, 42°11′N, 23°35′E) station in Bulgaria, connected with cosmic ray investigations during the last five decades. Several important results obtained at the station are reported. The detector design and corresponding methodological studies of the presently operational devices are shown as well, precisely the Cherenkov light telescope, lead free neutron monitor and muon telescope. The scientific potential of the existing complex is discussed.     

Longitudinal structure of ballooning MHD disturbances in a model magnetosphere

Large-scale toroidal Pc5 pulsations are commonly treated as Alfven oscillations of a magnetic field line. According to observations, their longitudinal structure is described well by theory. At the same time, the longitudinal structure of azimuthal small-scale poloidal Pc5 pulsations is virtually unknown. These pulsations are associated with ballooning disturbances described by a system of coupled equations for Alfvenic and slow magnetosonic (SMS) modes. In this work, the Voigt model is used to describe the equilibrium finite-pressure plasma configuration in an inhomogeneous magnetosphere plasma in a curved magnetic field. Spectral characteristics and the spatial structure of natural ballooning modes are calculated for this model. The model calculations demonstrate the possibility of different longitudinal scales for transverse and longitudinal magnetic components of oscillations near the top of the field line.     

Comment on “Inversion of all principal submatrices of amatrix”

The paper by Koc and Chen (1994) includes new formulas for computational complexity, but the method itself is already known and has dubious numerical stability. A poorly conditioned example is shown     

SPOT-2 and TOPEX/Poseidon precise orbit determination from DORIS doppler tracking

The French earth observation satellite SPOT-2 has served as a testbed for precise orbit determination from DORIS doppler tracking in anticipation of the TOPEX/Poseidon mission. Using the most up-to-data gravity field model, JGM-2, a radial orbit accuracy of about 2–9 cm was achieved, with an rms of fit of the tracking data of about 0.64 mm/s. Furthermore, it was found that the coordinates of the ground stations can be determined with an accuracy of the order of 2–5 cm after removal of common rotations, and translations.

Using a slightly different model for atmospheric drag, but the same gravity model, precise orbits of TOPEX/Poseidon from DORIS tracking data were determined with a radial orbit accuracy of the order of 4–5 cm, which is far within the 13 cm mission requirement. This conclusion is based on the analysis of 1-day overlap of successive 11-day orbits, and the comparisons with orbits computed from satellite laser tracking (SLR) and from the combination of SLR and DORIS tracking. Results indicate a consistency between the different orbits of 1–4 cm, 4–20 cm, and 6–13 cm in the radial, cross-track, and along-track directions, respectively. The residual rms is about 4–5 cm for SLR data and 0.56 mm/s for DORIS tracking. These numbers are roughly twice as large as the system noise levels, reflecting the fact that there are still some modeling errors left.