Features of whistling electromagnetic wave propagation descending from above upon the night ionosphere

The results of numerical solution of the wave equations for the oblique incidence of whistling electromagnetic waves upon the night ionosphere from above have been obtained and analyzed. In the studied region of altitudes, within the wavelength scale, charged particle concentration varies drastically, and damping caused by collisions between the charged and neutral particles decreases considerably. Below, the sharp lower boundary of the ionosphere, the refractive index of the whistler wave approaches unity, and plasma turbulence transform into atmospheric electromagnetic waves. The dependences of the whistler reflection factor are found in terms of energy and horizontal magnetic component of the electromagnetic wave near the Earth’s surface on the frequency and the wave vector transverse component for the plain-layered medium model at two values of latitude. Strong dependences have been found on the wave angle of incidence and frequency. At rather small angles of incidence, the wave disturbances reach the Earth’s surface, and the module of reflection coefficient logarithm is in the range of 0.4–1. At large angles of incidence, the reflection coefficient module varies over a wide range depending on specific conditions. The obtained results explain the absence of oscillation modes of plasma magnetosphere maser in the night magnetosphere.     

27-day variation in solar-terrestrial parameters: Global characteristics and an origin based approach of the signals

The Earth and the near interplanetary medium are affected by the Sun in different ways. Those processes generated in the Sun that induce perturbations into the Magnetosphere-Ionosphere system are called geoeffective processes and show a wide range of temporal variations, like the 11-year solar cycle (long term variations), the variation of ～27?days (recurrent variations), solar storms enduring for some days, particle acceleration events lasting for some hours, etc.In this article, the periodicity of ～27?days associated with the solar synodic rotation period is investigated. The work is mainly focused on studying the resulting 27-day periodic signal in the magnetic activity, by the analysis of the horizontal component of the magnetic field registered on a set of 103 magnetic observatories distributed around the world. For this a new method to isolate the periodicity of interest has been developed consisting of two main steps: the first one consists of removing the linear trend corresponding to every calendar year from the data series, and the second one of removing from the resulting series a smoothed version of it obtained by applying a 30-day moving average. The result at the end of this process is a data series in which all the signal with periods larger than 30?days are canceled.The most important characteristics observed in the resulting signals are two main amplitude modulations: the first and most prominent related to the 11-year solar cycle and the second one with a semiannual pattern. In addition, the amplitude of the signal shows a dependence on the geomagnetic latitude of the observatory with a significant discontinuity at approx. ±60°.The processing scheme was also applied to other parameters that are widely used to characterize the energy transfer from the Sun to the Earth: F10.7 and Mg II indices and the ionospheric vertical total electron content (vTEC) were considered for radiative interactions; and the solar wind velocity for the non-radiative interactions between the solar wind and the magnetosphere. The 27-day signal obtained in the magnetic activity was compared with the signals found in the other parameters resulting in a series of cross-correlations curves with maximum correlation between 3 and 5?days of delays for the radiative and between 0 and 1?days of delay for the non-radiative parameters. This result supports the idea that the physical process responsible for the 27-day signal in the magnetic activity is related to the solar wind and not to the solar electromagnetic radiation.     

The Role and Contributions of Energetic Neutral Atom (ENA) Imaging in Magnetospheric Substorm Research

Energetic Neutral Atom (ENA) imaging has contributed substantially to substorm research. This technique has allowed significant advances in areas such as observation and quantification of injected particle drift as a function of energy, observation of dynamics in the tail that are directly related to the effects of imposed (growth phase) and induced (expansion phase) electric fields on the plasma, the prompt extraction of oxygen from the ionosphere during substorms, the relationship between storms and substorms, and the timing of substorm ENA signatures. We present discussion of the advantages and shortcomings of the ENA technique for studying space plasmas. Although the technique is in its infancy, it is yielding results that enrich our understanding of the substorm process and its effects.     

Microthrusters in silicon for aerospace application

This paper reviews the results of the thermal and static analysis of small motor aerospace technology (SMART) propulsion system, constituted of a microthrusters array realised by MEMS technology on silicon wafers. This system has been studied using FEM (NASTRAN) and the results have been verified by the electro-thermic analogy and the FDM method, using, respectively, SPICE and MATLAB codes. The simulation results demonstrated the feasibility of SMART systems for aerospace applications such as attitude control and deorbiting missions for small satellite station-keeping. A theoretical impulse of 20 mNs has been calculated for the SMART system.     

Evolution of UV-B regulation and protection in plants.

Plants have evolved under the influence of UV-B radiation and have acquired systems for monitoring it and investing appropriate resources for protection against it, i.e., filters, quenchers of radicals and reactive oxygen species, and repair systems. An hypothesis for how plants monitor radiation has been presented.     

Induction machine based flywheel energy storage system

This study introduces a field oriented controlled (FOC) induction machine based flywheel energy storage (FES) system fed from a 20 kHz high frequency (HF) ac link and pulse density modulated (PDM) Converter. The feasibility of FES system is investigated both in software and hardware and is demonstrated successfully in both cases. The investigated system offers a good potential as a temporary energy storage system for various applications from automobile industry to aerospace applications.     

Observations of the Acceleration of Polar Solar Wind Near Solar Maximum

In a previous paper (Tappin et al., 1999) we used cross-correlation analysis of high-cadence observations with the LASCO coronagraphs to trace the acceleration of the solar wind at low latitudes. In this paper we present a similar analysis carried out over the North pole of the Sun. The observations which were made in March 2000 with the C3 coronagraph show low bulk flow speeds (comparable to or lower than those seen at the equator in early 1998). We observe the acceleration continuing to the edge of the C3 field of view at about 30 R _⊙. We also observe, as at low latitude, a high-speed tail but now reaching out well beyond 2000 km s⁻¹. We do not see a clear signature of a fast polar bulk flow. We therefore conclude that at this phase of the solar cycle, any fast bulk flow occupies only a small part of the line of sight and is therefore overwhelmed by the denser slow solar wind in these observations. We also show that the fast component is consistent with observed solar wind speeds at 1 AU. This revised version was published online in August 2006 with corrections to the Cover Date.     

Magnetic turbulence at the magnetopause, a key problem for understanding the solar wind/ magnetosphere exchanges

According to ideal MHD, the magnetopause boundary should split the terrestrial environment in two disconnected domains: outside, the solar wind (including its shocked part, the magnetosheath), and inside, the magnetosphere. This view is at variance with the experimental data, which show that the magnetopause is not tight and that a net transfer of matter exists from the solar wind to the magnetosphere; it implies that the frozen-in condition must break down on the magnetopause, either over the whole boundary or at some points. In the absence of ordinary collisions, only short scale phenomena (temporal and/or spatial) can be invoked to explain this breakdown, and the best candidates in this respect appear to be the ULF magnetic fluctuations which show very strong amplitudes in the vicinity of the magnetopause boundary. It has been shown that these fluctuations are likely to originate in the magnetosheath, probably downstream of the quasi-parallel shock region, and that they can get amplified by a propagation effect when crossing the magnetopause. When studying the propagation across the magnetopause boundary, several effects are to be taken into account simultaneously to get reliable results: the magnetopause density gradient, the temperature effects, and the magnetic field rotation can be introduced while remaining in the framework of ideal MHD. In these conditions, the magnetopause amplification has been interpreted in term of Alfvén and slow resonances occurring in the layer. When, in addition, one takes the ion inertia effects into account, by the way of the Hall-MHD equations, the result appears drastically different: no resonance occurs, but a strong Alfvén wave can be trapped in the boundary between the point where it is converted from the incident wave and the point where it stops propagating back, i.e., the point where k _\|=0, which can exist thanks to the magnetic field rotation. This effect can bring about a new interpretation to the magnetopause transfers, since the Hall effect can allow reconnection near this particular point. The plasma transfer through the magnetopause could then be interpreted in terms of a reconnection mechanism directly driven by the magnetosheath turbulence, which is permanent, rather than due to any local instability of the boundary, for instance of the tearing type, which should be subject to an instability threshold and thus, as far as it exists, more sporadic.     

Differential GPS/inertial navigation approach/landing flight testresults

In November 1990, a differential GPS/inertial flight test was conducted to acquire a system performance database and demonstrate automatic landing using an integrated differential GPS/INS with barometric and radar altimeters. Flight test results obtained from postflight data analysis are presented. These results include characteristics of DGPS/inertial error, using a laser tracker as a reference. In addition, data are provided on the magnitude of the differential correlations and vertical channel performance with and without radar altimeter augmentation. Flight test results show one sigma DGPS/inertial horizontal errors of 9 ft and one sigma DGPS inertial vertical errors of 15 ft. Without selective availability effects, the differential corrections are less than 10 ft and are dominated by receiver unique errors over the time period of an approach. Therefore, the one sigma performance of the autonomous GPS (8-ft horizontal and 20-ft vertical) is very similar to the DGPS/inertial performance. Postprocessed results also demonstrate significant improvements in vertical channel performance when GPS/inertial is aided with radar altimeter along with a low-resolution terrain map