Automatic target detection and localization using ultra-wideband radar

<span>The pulse ultra-wide band (UWB) radar consists of switching of energy of very short duration in an ultra-broadband emission chain, and the UWB signal emitted is an ultrashort pulse, of the order of nanoseconds, without a carrier. These systems can indicate the presence and distances of a distant object, call a target, and determine its size, shape, speed, and trajectory. In this paper, we present a UWB radar system allowing the detection of the presence of a target and its localization in a road environment based on the principle of correlation of the reflected signal with the reference and the determination of its correlation peak.</span>

Seismogenic Anomalies in Atmospheric Gravity Waves as Observed from SABER/TIMED Satellite during Large Earthquakes

Atmospheric disturbances caused by seismic activity are a complex phenomenon. The Lithosphere–Atmosphere–Ionosphere Coupling (LAIC) (LAIC) mechanism gives a detailed idea to understand these processes to study the possible impacts of a forthcoming earthquake. The atmospheric gravity wave (AGW) is one of the most accurate parameters for explaining such LAIC process, where seismogenic disturbances can be explained in terms of atmospheric waves caused by temperature changes. The key goal of this work is to study the perturbation in the potential energy associated with stratospheric AGW prior to many large earthquakes. We select seven large earthquakes having Richter scale magnitudes greater than seven ( M > 7.0 ) in Japan (Tohoku and Kumamoto), Mexico (Chiapas), Nepal, and the Indian Ocean region, to study the intensification of AGW using the atmospheric temperature profile as recorded from the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) satellite. We observe a significant enhancement in the potential energy of the AGW ranging from 2 to 22 days prior to different earthquakes. We examine the conditions of geomagnetic disturbances, typhoons, and thunderstorms during our study and eliminate the possible contamination due to these events.

A Semianalytic Afterglow with Thermal Electrons and Synchrotron Self-Compton Emission

We extend previous work on gamma-ray burst afterglows involving hot thermal electrons at the base of a shock-accelerated tail. Using a physically motivated electron distribution based on first-principles simulations, we compute the broadband emission from radio to TeV gamma rays. For the first time, we present the effects of a thermal distribution of electrons on synchrotron self-Compton emission. The presence of thermal electrons causes temporal and spectral structure across the entire observable afterglow, which is substantively different from models that assume a pure power-law distribution for the electrons. We show that early-time TeV emission is enhanced by more than an order of magnitude for our fiducial parameters, with a time-varying spectral index that does not occur for a pure power law of electrons. We further show that the X-ray closure relations take a very different, also time-dependent, form when thermal electrons are present; the shape traced out by the X-ray afterglows is a qualitative match to observations of the traditional decay phase.

MEASUREMENT OF PARAMETERS OF BROADBAND EMISSION USING MINI-SPECTROMETERS

On the basis of mini-spectrometers, a reference lamp of the SIRSH type with a known color temperature, and line spectrum sources, an inexpensive hardware complex has been created for measuring the emission parameters of heterodiodes and interference filters. Examples of recording the emission of heterodiodes (full width at half maximum is 17–30 nm) with a maximum of emission in the region of 659 and 764 nm and measurement of an interference filter (FWHM of the bandwidth is 12 nm) with a maximum transmission of 727 nm are given. The emission parameters of the SIRSH standard lamp are introduced into the program for measuring and processing data, due to which it is possible to significantly refine the value of the wavelength of the maximum emission and transmission.

Demonstration of Near Edge X-ray Absorption Fine Structure Spectroscopy of Transition Metals Using Xe/He Double Stream Gas Puff Target Soft X-ray Source

A near 1-keV photons from the Xe/He plasma produced by the interaction of laser beam with a double stream gas puff target were employed for studies of L absorption edges of period 4 transitional metals with atomic number Z from 26 to 30. The dual-channel, compact NEXAFS system was employed for the acquisition of the absorption spectra. L1–3 absorption edges of the samples were identified in transmission mode using broadband emission from the Xe/He plasma to show the applicability of such source and measurement system to the NEXAFS studies of the transition metals, including magnetic materials.

Coherent Emission in Pulsars, Magnetars, and Fast Radio Bursts: Reconnection-driven Free Electron Laser

We develop a model of the generation of coherent radio emission in the Crab pulsar, magnetars, and fast radio bursts (FRBs). Emission is produced by a reconnection-generated beam of particles via a variant of the free electron laser mechanism, operating in a weakly turbulent, guide field-dominated plasma. We first consider nonlinear Thomson scattering in a guide field-dominated regime, and apply it to explain emission bands observed in Crab pulsar and in FRBs. We consider particle motion in a combined field of the electromagnetic wave and the electromagnetic (Alfvénic) wiggler. Charge bunches, created via a ponderomotive force, Compton/Raman scatter the wiggler field coherently. The model is both robust to the underlying plasma parameters and succeeds in reproducing a number of subtle observed features: (i) emission frequencies depend mostly on the scale λ t of turbulent fluctuations and the Lorentz factor of the reconnection-generated beam, ω ∼ γ b 2 ( c / λ t ) —it is independent of the absolute value of the underlying magnetic field. (ii) The model explains both broadband emission and the presence of emission stripes, including multiple stripes observed in the high frequency interpulse of the Crab pulsar. (iii) The model reproduces correlated polarization properties: the presence of narrow emission bands in the spectrum favors linear polarization, while broadband emission can have an arbitrary polarization. (iv) The mechanism is robust to the momentum spread of the particle in the beam. We also discuss a model of wigglers as nonlinear force-free Alfvén solitons (light darts).

Ground-based Ku-band microwave observations of ozone in the polar middle atmosphere

Ground based observations of 11.072 GHz atmospheric ozone (O3) emission have been made using the Ny Ålesund Ozone in the Mesosphere Instrument (NAOMI) at the UK Arctic Research Station (latitude 78°55’0” N, longitude 11°55’59” E), Spitsbergen. Seasonally averaged O3 vertical profiles in the Arctic polar mesosphere lower thermosphere region for night-time and twilight conditions in the period 15 August 2017 to 15 March 2020 have been retrieved over the altitude range 62–98 km. NAOMI measurements are compared with corresponding, overlapping observations by the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) satellite instrument. The NAOMI and SABER data are binned according to the SABER instrument 60 day yaw cycles into 3 month ‘winter’ (15 December–15 March), ‘autumn’ (15 August–15 November), and ‘summer’ (15 April–15 July) periods. The NAOMI observations show the same year-to-year and seasonal variabilities as the SABER 9.6 μm O3 data. The winter night-time (solar zenith angle, SZA ≥ 110°) and twilight (75° ≤ SZA ≤ 110°) NAOMI and SABER 9.6 μm O3 volume mixing ratio (VMR) profiles agree to within the measurement uncertainties. However, for autumn twilight conditions the SABER 9.6 μm O3 secondary maximum VMR values are higher than NAOMI over altitudes 88–97 km by 47 % and 59 % respectively in 2017 and 2018. Comparing the two SABER channels which measure O3 at different wavelengths and use different processing schemes, the 9.6 μm O3 autumn twilight VMR data for the three years 2017–19 are higher than the corresponding 1.27 μm measurements with the largest difference (58 %) in the 65–95 km altitude range similar to the NAOMI observation. The SABER 9.6 μm O3 summer daytime (SZA < 75°) mesospheric O3 VMR is also consistently higher than the 1.27 μm measurement, confirming previously reported differences between the SABER 9.6 μm channel and measurements of mesospheric O3 by other satellite instruments.