To on-board MHD power generation

The electric power generation in on-board MHD generator is considered under conditions of vehicle’s flight in Earth atmosphere. The physical and computational model of on-board MHD power generation is presented. It is shown that electric power of order of 18 – 20 MW (or ∼ 100 W/cm3) can be extracted in ordinary Faraday-type segmented MHD generator. This high level of electric power is achieved at magnetic field about 0.3 – 0.4 tesla and constitutes nearly 9.5% of total enthalpy flux. The main factor limiting the rise of extracted power is a stall of flow due to MHD deceleration.

Trajectory options for a manned mission to Mars using high-thrust propulsion systems

An analysis has been done of performance factors (mission duration, initial mass of the interplanetary crew transfer vehicle, velocity of the re-entry into the Earth atmosphere of the descent vehicle with the crew) for a single-spacecraft manned mission to Mars using high-thrust propulsion systems. Locally optimal solutions (in terms of delta-V budgets for the transfer) were found for the Earth–Mars–Earth transfer, with varying periods of waiting in Mars orbit, minimal distance to the Sun, as well as flight paths (direct Earth–Mars–Earth transfers vs. gravity assist maneuvers at Venus during Earth–Mars or Mars–Earth transfers). The proposed classification for locally optimal solutions is applicable to both high-thrust propulsion systems and low-thrust propulsion systems. A comparison of performance factors has been done for manned Martian mission options based on liquid-propellant engines and nuclear rocket engines with a 12,5 km/s constraint on the velocity of the manned re-entry vehicle in the Earth atmosphere. Key words: Manned mission to Mars, interplanetary transfer trajectory, high-thrust, liquid-propellant rocket engine, nuclear rocket engine, mission duration, initial mass of the interplanetary vehicle, re-entry velocity of a manned vehicle for returning the crew to Earth.

Segmentation of Coronal Features to Understand the Solar EUV and UV Irradiance Variability III. Inclusion and Analysis of Bright Points

The study of solar irradiance variability is of great importance in heliophysics, Earth’s climate, and space weather applications. These studies require careful identifying, tracking and monitoring of features in the solar photosphere, chromosphere, and corona. Do coronal bright points contribute to the solar irradiance or its variability as input to the Earth atmosphere? We studied the variability of solar irradiance for a period of 10 years (May 2010 – June 2020) using the Large Yield Radiometer (LYRA), the Sun Watcher using APS and image Processing (SWAP) on board PROBA2, and the Atmospheric Imaging Assembly (AIA), and applied a linear model between the segmented features identified in the EUV images and the solar irradiance measured by LYRA. Based on EUV images from AIA, a spatial possibilistic clustering algorithm (SPoCA) is applied to identify coronal holes (CHs), and a morphological feature detection algorithm is applied to identify active regions (ARs), coronal bright points (BPs), and the quiet Sun (QS). The resulting segmentation maps were then applied on SWAP images, images of all AIA wavelengths, and parameters such as the intensity, fractional area, and contribution of ARs/CHs/BPs/QS features were computed and compared with LYRA irradiance measurements as a proxy for ultraviolet irradiation incident to the Earth atmosphere. We modeled the relation between the solar disk features (ARs, CHs, BPs, and QS) applied to EUV images against the solar irradiance as measured by LYRA and the F10.7 radio flux. A straightforward linear model was used and corresponding coefficients computed using a Bayesian method, indicating a strong influence of active regions to the EUV irradiance as measured at Earth’s atmosphere. It is concluded that the long- and short-term fluctuations of the active regions drive the EUV signal as measured at Earth’s atmosphere. A significant contribution from the bright points to the LYRA irradiance could not be found.

On the detectability of the meteor pairs created by fragmentation in near-Earth space

<p>Although numerous observers reported that meteors appear in pairs or groups, recent papers based on instrumental observations did not confirm such results. At least, among older meteor showers such grouping was not confirmed. On the other hand, among younger streams, such behaviour is still possible.</p> <p>In our recent paper dedicated to the search of pairs among Geminid meteors, we found that we have no evidence for the physically connected pairs despite the fact that a number of potential candidates have been detected. Monte Carlo statistical test showed that all the cases can be results of coincidental approaches of the particles in a similar space and time.</p> <p>Therefore, we prepared a model of orbital fragmentation of meteoroids in the vicinity of the Earth, which follows trajectories of fragmented particles ejected with different velocities in different directions under  the solar radiation pressure. The collisions with interplanetary particles as the possible source of the pairs are taken into account for the major meteor showers during whole year. </p> <p>The paper will provide constraints on the time of ejection, ejection velocities and ejection angles, which will allow the pairs or groups to be detected in the Earth atmosphere by the video or photographic cameras.</p>

Introduction to the Special Issue “Radiative Transfer in the Earth Atmosphere”

This Special Issue aims at addressing the recent developments towards improving our understanding of the diverse radiative impact of different types of aerosols and clouds [...]

NOMINAL BALLISTIC MISSILE ASCENT OPTIMIZATION WITH THERMAL INVESTAGATION

Ballistic Missile Trajectory is one of the big issues to simulate and also to be optimized. The main objective of this paper is to find a method to obtain the Nominal trajectory for the ballistic missile through finding out the optimal parameters for each ballistic trajectory phases. To define the problem; the paper will list all governing equations and describe the parameters of input and output for each phase of the trajectory. Then, a method to reduce the number of input parameters will be discussed. We study each parameter effect to get the most optimal trajectory for the missile. At the final, optimal flight will be discussed in details. Although, we investigate the thermal effect for entry point from space into the earth atmosphere

Trends in spectrally resolved OLR from 10 years of IASI measurements

<p>The Earth's Outgoing Longwave Radiation (OLR) is a key component in the study of climate. As part of the Earth's radiation budget, it reflects how the Earth-atmosphere system compensates the incoming solar radiation at the top of the atmosphere. At equilibrium, the two quantities compensate each other on average. Any variation of the climate drivers (e.g. greenhouse gases) causes an energy imbalance which leads to a climate response (e.g. surface temperature increase), with the effect of bringing the radiation budget back to equilibrium. Considerable improvements in our understanding of the Earth-atmosphere system and of its long-term changes have been achieved in the last four decades through the exploitation of measurements from dedicated broadband instruments. However, such instruments only provide spectrally integrated OLR over a broad spectral range and are therefore not well suited for tracking separately the impact of the different parameters affecting the OLR.</p><p>Better constraints can, in principle, be obtained from spectrally resolved OLR (i.e. the integrand of broadband OLR, in units of W m<sup>-2</sup> cm<sup>-1</sup>) derived from infrared hyperspectral sounders. Recently, a dedicated algorithm was developed to derive clear-sky spectrally resolved OLR from the Infrared Atmospheric Sounding Interferometer (IASI) at the 0.25 cm<sup>-1</sup> native spectral sampling of the L1C spectra (Whitburn et al. 2020).  Here, we analyze the changes in 10 years (2008-2017) of the IASI-derived OLR and we relate them to known changes in greenhouse gases concentrations (CO<sub>2</sub>, CH<sub>4</sub>, H<sub>2</sub>O, …) and climate phenomena activity such as El Niño-Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO).</p><p>Whitburn, S., Clarisse, L., Bauduin, S., George, M., Hurtmans, D., Safieddine, S., Coheur, P. F., and Clerbaux, C. (2020). <strong>Spectrally Resolved Fuxes from IASI Data: Retrieval algorithm for Clear-Sky Measurements</strong>. Journal of Climate. doi: 10.1175/jcli-d-19-0523.1</p>

How fast the earth surface breathe? Gas transport in high permeability soils and earth surface discontinuities

<p>Gas movement within the earth’s subsurface and its exchange with the atmosphere are some of the principal processes in soil, ecosystem, and atmospheric environments. For a decade, our group has explored the roles played by atmospheric conditions and matrix properties in gas transport at the earth-atmosphere interface, where surface discontinuities, such as fractures, boreholes and aggregated soils, exist and may affect the process.</p><p>The gas transport mechanisms, resulting from the development of a thermal gradient and surface wind, were analyzed both independently and in combination. Two types of experiments were carried out: (1) under field conditions and (2) under highly controlled laboratory conditions. During all studies, temperature and wind conditions across the media and at the media-atmosphere interface were monitored. Results show that the magnitudes of thermal- and wind-induced convection were directly related to the media permeability, given favorable ambient conditions at the media-atmosphere interface. Such ambient conditions included high diurnal temperature amplitude (~± 10 ᵒC) or high surface wind (~2 m/s measured 10 m above ground). In addition, specific results from the field experiment were used to establish an empirical model that predicts gas transport magnitude as a function of wind speed and media permeability.</p><p>With respect to other discontinuities, such as boreholes and fractures, the effect of atmospheric conditions was investigated, namely atmospheric pressure and temperature, on air, CO<sub>2</sub>, and radon transport. Using high-resolution spatiotemporal measurements, it was concluded that diurnal atmospheric pressure oscillations (barometric pumping) and borehole-atmospheric temperature differences (thermal-induced convection) controlled the air transport within the boreholes. For one of the boreholes monitored, the air velocities and CO<sub>2</sub> emissions to the atmosphere were quantified (up to ~6 m/min and ~5 g-CO<sub>2</sub>/min, respectively). This reveals the role of boreholes as a source of greenhouse gas emissions.</p><p>The results and conclusions derived from our studies are expected to improve our understanding of the governing mechanisms controlling gas movement in porous media, fractures, and boreholes, and their functions in gas exchange across the earth-atmosphere interface.</p>

A Comparison of Mechanical Wind Filters for Infrasound Sensor Noise Reduction

Infrasound sensors record the ambient acoustic field that contains not only signals of interest but also noise and clutter. Noise is defined as atmospheric turbulence that is incoherent over the distances of meters, whereas, signals of interest and clutter are acoustic pressure waves that are coherent over 10s of meters to 100s of kilometers. There is a growing interest in monitoring sources that extend across the acoustic spectrum from infrasound (below 20 Hz) into the low-end audible acoustic (20–1000 Hz). Monitoring of these extended band signals with a single sensor is made possible with the development of contemporary infrasound sensors, such as Hyperion IFS-3000 with a flat response from 0.01 to 1000 Hz. Combining infrasound sensors with seismometers provides opportunity to better assess noise contributions for both sensor types and improve characterization of sources that occur close to the solid earth–atmosphere boundary. Because sensors are installed to target these broadband acoustic sources, considerations need to be made when selecting a mechanical wind filter to mitigate the noise, while minimizing the impacts to the signals of interest across these frequency ranges. Motivated by these opportunities, this article compares traditional infrasound wind filter designs, that is, porous hoses rosettes and domes, in an urban setting for frequencies 0.01–45 Hz. Data analysis compares the filters, in terms of their response to noise and signals with direct comparisons of wind filters, as a function of frequency. The quantification of performance of these filters in an urban setting provides insight into their effects on detection of sources of interest in this environment.