Terahertz (THz) technology is one of emerging technologies that will change our life. A lot of attractive applications in security, medicine, biology, astronomy, and non-destructive materials testing have been demonstrated already. However, the realization of THz emitters and receivers is a challenge because the frequencies are too high for conventional electronics and the photon energies are too small for classical optics. As a result, THz radiation is resistant to the techniques commonly employed in these well established neighbouring bands.

https://www.degruyter.com/document/doi/10.2478/s11772-011-0033-3/pdf

Terahertz detectors and focal plane arrays

In the paper, issues associated with the development and exploitation of terahertz (THz) radiation detectors are discussed. The paper is written for those readers who desire an analysis of the latest developments in different type of THz radiation sensors (detectors), which play an increasing role in different areas of human activity (e.g., security, biological, drugs and explosions detection, imaging, astronomy applications, etc.). The basic physical phenomena and the recent progress in both direct and heterodyne detectors are discussed. More details concern Schottky barrier diodes, pair braking detectors, hot electron mixers, and field-effect transistor detectors. Also the operational conditions of THz detectors and their upper performance limits are discussed.

https://www.degruyter.com/downloadpdf/j/oere.2010.18.issue-1/s11772-009-0029-4/s11772-009-0029-4.xml

THz radiation sensors

We present a multiwavelength study of five methanol maser sites which are not directly associated with a strong ($>100$ mJy) radio continuum source: G 31.28+0.06, G 59.78+0.06, G 173.49+2.42 (S231, S233IR), G 188.95+0.89 (S252, AFGL5180) and G 192.60-0.05 (S255IR). These radio-quiet methanol maser sites are often interpreted as precursors of ultra-compact \ion{H}{ii} regions or massive protostar sites. In this work, the environment of methanol masers is probed from mid-IR to millimetre wavelengths at angular resolutions of $8''-34''$. Spectral energy distribution (SED) diagrams for each site are presented, together with mass and luminosity estimates. Each radio-quiet maser site is always associated with a massive ($>50$ M$_{\odot}$), deeply embedded ($A_v>40$ mag) and very luminous ($>10^4$ S L$_{\odot}$) molecular clump, with $L_{total}{\propto}M_{gas}^{0.75}$. These physical properties characterise massive star-forming clumps in earlier evolutionary phases than \ion{H}{ii} regions. In addition, colder gas clumps seen only at mm-wavelengths are also found near the methanol maser sites. These colderclumps may represent an even earlier phase of massive star formation. These results suggest an evolutionary sequence for massive star formation from a cold clump, seen only at mm wavelengths, evolving to a hot molecular core with a two-component SED with peaks at far-IR and mid-IR wavelengths, to an (ultra-compact) \ion{H}{ii} region. Alternatively, the cold clumps might be clusters of low-mass YSOs, in formation near the massive star-forming clusters. Finally, the values of the dust grain emissivity index ($\beta$) range between 1.6 and 1.9.

/pdf/star-forming-protoclusters-associated-with-methanol-masers-ajshvu2r2s.pdf

Star-forming protoclusters associated with methanol masers

We analyze the 2019 sudden stratospheric warming event that occurred in the Southern Hemisphere through its impact on the Antarctic ozone Using temperature, ozone, and nitric acid data from the Infrared Atmospheric Sounding Interferometer (IASI), our results show that the average increase in stratospheric temperature reached a maximum of 344° on September 20th in the [60‐90]°S latitude range when compared to the past three years Dynamical parameters suggest a locally‐reversed and weakened zonal winds and a shift in the location of the polar jet vortex This led to air masses mixing, to a reduced polar stratospheric clouds formation detected at a ground station, and as such to lower ozone and nitric acid depletion 2019 total ozone columns for the months of September, October, and November, were on average higher by 29%, 28%, and 26% respectively when compared to the 11‐year average of the same months

/pdf/antarctic-ozone-enhancement-during-the-2019-sudden-402l9gjirf.pdf

Antarctic Ozone Enhancement During the 2019 Sudden Stratospheric Warming Event

AbstractBased on the NCEP–NCAR reanalysis dataset covering 1958–2012, this paper demonstrates a statistically significant relationship between the occurrence of major stratospheric sudden warming events (SSWs) in midwinter and the seasonal timing of stratospheric final warming events (SFWs) in spring. Specifically, early spring SFWs that on average occur in early March tend to be preceded by non-SSW winters, while late spring SFWs that on average take place up until early May are mostly preceded by SSW events in midwinter. Though the occurrence (absence) of SSW events in midwinter may not always be followed by late (early) SFWs in spring, there is a much higher (lower) probability of late SFWs than early SFWs in spring after SSW (non-SSW) winters, particularly when the winter SSWs occur no earlier than early January or in the period from late January to early February. Diagnosis shows that, corresponding to an SSW (non-SSW) winter and the following late (early)-SFW spring, intensity of planetary wave acti...

Occurrence of Winter Stratospheric Sudden Warming Events and the Seasonal Timing of Spring Stratospheric Final Warming

Winter 2018 major sudden stratospheric warming impact on midlatitude mesosphere by microwave radiometer measurements

The paper describes a 3mm cryogenic mixer receiver using high doping density (“room-temperature”) Schottky diodes The measured equivalent noise temperature Teq of the diodes is 109 K at 20 K, which is much higher than the Teq of the low doping density (“cryogenic”) diodes In spite of this, the double-sideband (DSB) noise temperature of the cryogenic receiver developed is 55 K at 110 GHz, owing to the low conversion loss of the mixer and ultra-low noise of the PHEMT IF amplifier This is the lowest noise temperature ever reported for a Schottky diode mixer receiver The results obtained are useful for the development of submm receivers in which high doping density Schottky diodes are used

High Doping Density Schottky Diodes in the 3MM Wavelength Cryogenic Heterodyne Receiver

We developed a high-sensitivity receiving and measuring facility designed for observations of the ozone O3 and carbon monoxide CO spectral lines by the method of ground-based remote sensing of the atmosphere in the 90–116 GHz frequency range. The measurement and calibration procedure is described in detail. The results of observations of the O3 and CO emission lines at frequencies 110.836 amd 115.271 GHz, respectively, are presented. The sensitivity level of the receiving and measuring facility, which was implemented in the experiment using a filter-bank analyzer and a Fourier spectrum analyzer is determined.

3-mm wave spectroradiometer for studies of atmospheric trace gases

The paper describes an uncooled front-end of the Schottky diode receiver system, which may be applied for observations of middle atmospheric ozone and carbon monoxide thermal emission lines at frequencies 110.8 GHz and 115.3 GHz, respectively. The mixer of the front-end has utilized high-quality Schottky diodes that allowed us to reduce the mixer conversion loss. The combination of the mixer and an ultra-low-noise IF amplifier in the one integrated unit has resulted in double-sideband (DSB) receiver noise temperature of 260 K at a local oscillator (LO) frequency of 113.05 GHz in the instantaneous IF band from 1.7 to 2.7 GHz. This is the lowest noise temperature ever reported for an uncooled ozone receiver system with Schottky diode mixers.

An Uncooled Very Low Noise Schottky Diode Receiver Front-End for Middle Atmospheric Ozone and Carbon Monoxide Measurements

An fpga-based fourier ffts-160 spectrometer for atmospheric molecular radiation research

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