Emission Mechanisms of Fast Radio Bursts

Fast radio bursts (FRBs) are recently discovered mysterious single pulses of radio emission, mostly coming from cosmological distances (∼1 Gpc). Their short duration, ∼1 ms, and large luminosity demonstrate coherent emission. I review the basic physics of coherent emission mechanisms proposed for FRBs. In particular, I discuss the curvature emission of bunches, the synchrotron maser, and the emission of radio waves by variable currents during magnetic reconnection. Special attention is paid to magnetar flares as the most promising sources of FRBs. Non-linear effects are outlined that could place bounds on the power of the outgoing radiation.

Annual Changes in the spectrally resolved global and local Earth Energy Imbalance using the Sun as a Reference Radiation Source

<p>A new method is presented to derive spectrally resolved global and local annual changes in the Earth Energy Imbalance (ΔEEI(λ, Δλ)) from measurements of Total and Spectral Solar Irradiance (TSI and SSI) and Total Outgoing Radiation (TOR) and the Spectral Outgoing Radiation (SOR) of the Earth. Since TSI space radiometers provide data with a long-term absolute accuracy <0.1 W m<sup>-2</sup>, the Sun should be used as a TSI referenced radiation source to obtain SSI data using the method of the Solar Auto-Calibrating XUV-IR Spectrometer (SOLACER). By repeatedly calibrating the solar and Earth observation instruments, the degradation should be compensated to accurately determine the outgoing flux Φ(λ, Δλ) entering the instrument. If the instruments on a pointing device are moved within the Angular Range of Sensitivity (ARS) in two angular dimensions through the solar disk, the instruments are also regularly calibrated with regard to their dependence of the angular sensitivity. ARS is independent of the environmental conditions. To improve the accuracy of SOR data, a normalization factor Ω<sub>a</sub> / ARS is used to extend the annual averaged outgoing flux data Φ(λ, Δλ)<sub>a</sub> to the SOR(λ, Δλ)<sub>a</sub>. The strength of the method is demonstrated by describing space-evaluated instruments to be adapted for solar and/or Earth observation from a small satellite. In the spectral range from 120 nm to 3000 nm, spectrometers and highly sensitive photometers with signal-to-noise ratios >1:10<sup>7</sup> are described to generate data records with high statistical accuracy. Given the compactness of the instruments, more than 20 different data sets should be compiled to complement, verify each other and improve accuracy.</p><p> </p>

Preliminary results of relative radiometer to measure the Earth’s outgoing radiation on FY-3F satellite

<p>A space based relative radiometer has been developed and applied to the PICARD mission. It has successfully measured 37 months solar radiation, terrestrial outgoing radiation, and a comparable interannual variation in Earth Radiation Budget (ERB) is inferred from those measurements [1]. However, since the BOS (Bolometric Oscillation Sensor [2]) relative radiometer is originally designed to measure the solar irradiance with 10 seconds high cadence comparing to the absolute radiometer. The high dynamic range of BOS limits its performance to track the Earth’s outgoing radiation in terms of instantaneous field-of-view (iFOV) and the absolute radiation level. Two relative radiometers (RR) will be developed for JTSIM/FY-3F. One is the solar channel relative radiometer aimed to measure the solar irradiance side by side with the cavity solar irradiance absolute radiometer (SIAR). The second RR is acting as a non-scanner instrument to measure the Earth’s outgoing radiation. Comparing to the design of PICRD-BOS. Each RR has included an aperture, for the solar channel it limits its Unobstructed Field of View (UFOV) to about 1.5 degree and for the Earth channel to about 110 degrees, respectively. We also test the possibility to use the Carbon Nanotube coating on the main detector. In this presentation, the design of the earth channel relative radiometer (ERR) will be introduced, including the aperture design, dynamic range and the active temperature control system. The preliminary laboratory test result of the ERR will be discussed in the end.</p><p>[1] <strong>P. Zhu,</strong> M. Wild, M. van Ruymbeke, G. Thuillier, M. Meftah, and Ö. Karatekin. Interannual variation of global net radiation flux as measured from space. J. Geophys. Res. doi:10.1002/2015JD024112, 121:6877–6891, 2016.</p><p>[2] <strong>P. Zhu,</strong> M.van Ruymbeke, Ö. Karatekin, J.-P.Noël, G. Thuillier, S. Dewitte, A. Chevalier, C. Conscience, E. Janssen, M. Meftah, and A. Irbah. A high dynamic radiation measurement instrument: the bolometric oscillation sensor (bos). Geosci. Instrum. Method. Data Syst., 4,89-98,:doi:10.5194/gi–4–89–2015, 2015.</p><p><strong>Acknowledgement</strong>: this work is partly supported by the National Natural Science Foundation of China No. 41974207 and CSC Scholarship No.202004910181</p><p> </p>

Sir John Houghton (30 December 1931 — 15 April 2020) and radiation transfer

<p>IPCC announced that the WGI contribution to AR6 will be dedicated to the memory of leading climate scientist Sir John Houghton. Sir John died of complications from COVID-19 one year ago. He helped creating the IPCC in 1988, and served as Chair and Co-Chair of WGI from 1988 to 2002. In this presentation we focus on two aspects of his work: radiation transfer and cloud radiative forcing. — His book “The Physics of Atmospheres” (third edition, 2002) says: “The equation of radiative transfer through the slab, which includes both absorption and emission, is sometimes known as Schwarzschild’s equation” (Eq. 2.3, p.11). Introducing a constant Ф net flux (Eq. 2.5) being equal to the outgoing radiation, the black-body function B of the atmosphere is given as a function of Ф and the optical depth as B = Ф(χ* + 1)/2π (Eq. 2.12). He says, “it is easy to show that there must be a temperature discontinuity at the lower boundary”: B<sub>g</sub> – B<sub>0</sub> = Ф/2π (Eq. 2.13). Fig. 2.4 displays the net flux at the boundary as half of the outgoing radiation, independently of the optical depth. He notes: “Such a steep lapse rate will soon be destroyed by the process of convection”, and continues: “Combining (2.12) and (2.13) we find Bg = Ф(χ* + 2)/2π ” (Eq. 2.15, section 2.5 The greenhouse effect). We controlled Eq. (2.13) on 20 years of clear-sky CERES EBAF Ed4.1 global mean data and found it satisfied with a difference of -2.28 Wm<sup>-2</sup>. The validity of this equation casts constraint on the surface net radiation and on the corresponding non-radiative fluxes in the hydrological cycle by connecting them unequivocally to half of the outgoing longwave radiation. We constructed the all-sky version of the equation by separating atmospheric radiation transfer from longwave cloud effect, and found it valid within 2.84 Wm<sup>-2</sup>. We computed Eq. (2.15) with a special optical depth of χ* = 2 for clear-sky; it is justified with a difference of -2.88 Wm<sup>-2</sup>. We also created its all-sky version; the difference is 2.46 Wm<sup>-2</sup>. Altogether, the four equations are satisfied on 20-yr of CERES data with a mean bias of 0.035 Wm<sup>-2</sup>. We show that the four equations together determine a clear-sky and an all-sky greenhouse factor as 1/3 and 0.4. Data from Wild et al. (2018) and IPCC AR5 (2013) show g(clear) = (398 – 267)/398 = 0.33 and g(all) = (398 – 239)/398 = 0.3995. The IPCC reports predict an enhanced greenhouse effect from human emissions. According to the above arithmetic solutions, Earth’s observed greenhouse factors are equal to the theoretical ones without any deviation or enhancement. — The first IPCC report states that cloud radiative forcing is governed by cloud properties as cloud amount, reflectivity, vertical distribution and optical depth. Here we show that the TOA net CRF (= SWCRF + LWCRF) in equilibrium is equivalent to TOA net clear-sky imbalance, hence to determine its magnitude only clear-sky fluxes are needed.</p>

Impact of Climate Change on Life

Climate is changing in an accelerating pace. Climate change occurs as a result of an imbalance between incoming and outgoing radiation in the atmosphere. The global mean temperatures may increase up to 5.4°C by 2100. Climate change is mainly caused by humans, especially through increased greenhouse gas emissions. Climate change is recognized as a serious threat to ecosystem, biodiversity, and health. It is associated with alterations in the physical environment of the planet Earth. Climate change affects life around the globe. It impacts plants and animals, with consequences for the survival of the species. In humans, climate change has multiple deleterious consequences. Climate change creates water and food insecurity, increased morbidity/mortality, and population movement. Vulnerable populations (e.g., children, elderly, indigenous, and poor) are disproportionately affected. Personalized adaptation to the consequences of climate change and preventive measures are key challenges for the society. Policymakers must implement the appropriate strategies, especially in the vulnerable populations.

Explorations of the infinite regions of spacetime

An important concept in Physics is the notion of an isolated system. It is used in many different areas to describe the properties of a physical system which has been isolated from its environment. The interaction with the “outside” is then usually reduced to a scattering process, in which incoming radiation interacts with the system, which in turn emits outgoing radiation. In Einstein’s theory of gravitation, isolated systems are modeled as asymptotically flat spacetimes. They provide the appropriate paradigm for the study of gravitational waves and their interaction with a material system or even only with themselves. In view of the emerging era of gravitational wave astronomy, in which gravitational wave signals from many different astrophysical sources are detected and interpreted, it is necessary to have a foundation for the theoretical and numerical treatments of these signals. Furthermore, from a purely mathematical point of view, it is important to have a full understanding of the implications of imposing the condition of asymptotic flatness onto solutions of the Einstein equations. While it is known that there exists a large class of asymptotically flat solutions of Einstein’s equations, it is not known what the necessary and sufficient conditions at infinity are that have to be imposed on initial data so that they evolve into regular asymptotically flat spacetimes. The crux lies in the region near spacelike infinity [Formula: see text] where incoming and outgoing radiation “meet”. In this paper, we review the current knowledge and some of the analytical and numerical work that has gone into the attempt to understand the structure of asymptotically flat spacetimes near spacelike and null-infinity.

Atmospheric correction of multispectral satellite imagery

Atmospheric correction is a necessary step in the processing of remote sensing data acquired in the visible and NIR spectral bands.The paper describes the developed atmospheric correction technique for multispectral satellite data with a small number of relatively broad spectral bands (not hyperspectral). The technique is based on the proposed analytical formulae that expressed the spectrum of outgoing radiation at the top of a cloudless atmosphere with rather high accuracy. The technique uses a model of the atmosphere and its optical and physical parameters that are significant from the point of view of radiation transfer, the atmosphere is considered homogeneous within a satellite image. To solve the system of equations containing the measured radiance of the outgoing radiation in the bands of the satellite sensor, the number of which is less than the number of unknowns of the model, it is proposed to use various additional relations, including regression relations between the optical parameters of the atmosphere. For a particular image pixel selected in a special way, unknown atmospheric parameters are found, which are then used to calculate the reflectance for all other pixels.Testing the proposed technique on OLI sensor data of Landsat 8 satellite showed higher accuracy in comparison with the FLAASH and QUAC methods implemented in the well-known ENVI image processing software. The technique is fast and there is using no additional information about the atmosphere or land surface except images under correction.

Some estimations of errors at problem of continuous medium radiography

The paper deals with a problem of radiography of a continuous medium of unknown chemical composition. The medium is subjected to multiple X-raying at different energy levels. The relative errors at incoming and outgoing radiation are assumed to be known. The paper advances some estimations of absolute errors at the right side of system of equations describing the process of radiation transfer.