Spectral riometry technique for ionisation estimation of the D-region ionosphere

第6回極域科学シンポジウム[OS] 宙空圏11月16日（月）　国立極地研究所 2階 大会議

Secondary electron emission from meteoric smoke particles inside the polar ionosphere

The charging by secondary electron emission (SEE) from particles is known as a significant charging process in astrophysical plasmas. This work aims at evaluating the significance of SEE for charging of meteoric smoke particles (MSPs) in the Earth's polar atmosphere. Here, the atmosphere is subject to a bombardment of energetic electrons from the magnetosphere (and partly the sun). We employ the SEE formalism to MSPs in the upper mesosphere using electron precipitation fluxes for three different precipitation strengths. In addition, we address the possible effect of tertiary electron emission (TEE) from MSPs induced by atmospheric secondary electrons for one precipitation case. The SEE and TEE rates from MSPs of different sizes are compared to plasma attachment and photodetachment and photoionization rates of MSPs. The needed concentration of electrons and ions have been modeled with the Sodankyla Ion and Neutral Chemistry (SIC) model with included electron precipitation spectra as an additional ionization source. We find that secondary electron emission from MSPs is not a relevant charging mechanism for MSPs. The electron attachment to MSPs and photodetachment of negatively charged MSPs are the most important processes also during energetic electron precipitation

Secondary electron emission from meteoric smoke particles inside the polar ionosphere

The charging by secondary electron emission (SEE) from particles is known as a significant charging process in astrophysical plasmas. This work aims at evaluating the significance of SEE for charging of meteoric smoke particles (MSPs) in the Earth's polar atmosphere. Here, the atmosphere is subject to a bombardment of energetic electrons from the magnetosphere (and partly the sun). We employ the SEE formalism to MSPs in the upper mesosphere using electron precipitation fluxes for three different precipitation strengths. In addition, we address the possible effect of tertiary electron emission (TEE) from MSPs induced by atmospheric secondary electrons for one precipitation case. The SEE and TEE rates from MSPs of different sizes are compared to plasma attachment and photodetachment and photoionization rates of MSPs. The needed concentration of electrons and ions have been modeled with the Sodankyla Ion and Neutral Chemistry (SIC) model with included electron precipitation spectra as an additional ionization source. We find that secondary electron emission from MSPs is not a relevant charging mechanism for MSPs. The electron attachment to MSPs and photodetachment of negatively charged MSPs are the most important processes also during energetic electron precipitation

Improving the twilight model for polar cap absorption nowcasts

During Solar Proton Events (SPE), energetic protons ionize the polar mesosphere causing HF radiowave attenuation, more strongly on the dayside where the effective recombination coefficient, αeff, is low. Polar cap absorption (PCA) models predict the 30 MHz cosmic noise absorption, A, measured by riometers, based on real-time measurements of the integrated proton flux-energy spectrum, J. However, empirical models in common use cannot account for regional and day-to-day variations in the day- and nighttime profiles of αeff(z) or the related sensitivity parameter, m=A/√J. Large prediction errors occur during twilight when m changes rapidly, and due to errors locating the rigidity cutoff latitude. Modeling the twilight change in m as a linear or Gauss error-function transition over a range of solar-zenith angles (χl < χ < χu) provides a better fit to measurements than selecting day or night αeff profiles based on the Earth-shadow height. Optimal model parameters were determined for several polar cap riometers for large SPEs in 1998-2005. The optimal χl parameter was found to be most variable, with smaller values (as low as 60°) post-sunrise compared with pre-sunset, and with positive correlation between riometers over a wide area. Day and night values of m exhibited higher correlation for closely spaced riometers. A nowcast simulation is presented in which rigidity boundary latitude and twilight model parameters are optimized by assimilating age-weighted measurements from 25 riometers. The technique reduces model bias, and root-mean-squared errors are reduced by up to 30% compared with a model employing no riometer data assimilation

On the determination of ionospheric electron density profiles using multi-frequency riometry

Radio wave absorption in the ionosphere is a function of electron density, collision frequency, radio wave polarisation, magnetic field and radio wave frequency. Several studies have used multi-frequency measurements of cosmic radio noise absorption to determine electron density profiles. Using the framework of statistical inverse problems, we investigated if an electron density altitude profile can be determined by using multi-frequency, dual-polarisation measurements. It was found that the altitude profile cannot be uniquely determined from a “complete” measurement of radio wave absorption for all frequencies and two polarisation modes. This implies that accurate electron density profile measurements cannot be ascertained using multi-frequency riometer data alone and that the reconstruction requires a strong additional a priori assumption of the electron density profile, such as a parameterised model for the ionisation source. Nevertheless, the spectral index of the absorption could be used to determine if there is a significant component of hard precipitation that ionises the lower part of the D region, but it is not possible to infer the altitude distribution uniquely with this technique alone.</p

Quantitative myocardial perfusion response to adenosine and regadenoson in patients with suspected coronary artery disease

Background The aim of the present study was to compare the quantitative flow responses of regadenoson against adenosine using cardiac O-15-water PET imaging in patients with suspected or known coronary artery disease (CAD). Methods Hyperemic myocardial blood flow (MBF) after adenosine and regadenoson was compared using correlation and Bland-Altman analysis in 21 patients who underwent rest and adenosine O-15-water PET scans followed by rest and regadenoson O-15-water PET scans. Results Global mean (+/- SD) MBF values at rest and stress were 0.92 +/- 0.27 and 2.68 +/- 0.80 mL center dot g center dot min for the adenosine study and 0.95 +/- 0.29 and 2.76 +/- 0.79 mL center dot g center dot min for the regadenoson study (P = 0.55 and P = 0.49). The correlations between global and regional adenosine- and regadenoson-based stress MBF were strong (r = 0.80 and r = 0.77). The biases were small for both global and regional MBF comparisons (0.08 and 0.09 mL center dot min center dot g), but the limits of agreement were wide for stress MBF. Conclusion The correlation between regadenoson- and adenosine-induced hyperemic MBF was strong but the agreement was only moderate indicating that established cut-off values for (15)0-water PET should be used cautiously if using regadenoson as vasodilator

Radar—CubeSat Transionospheric HF Propagation Observations: Suomi 100 Satellite and EISCAT HF Facility

Radio waves provide a useful diagnostic tool to investigate the properties of the ionosphere because the ionosphere affects the transmission and properties of high frequency (HF) electromagnetic waves. We have conducted a transionospheric HF-propagation research campaign with a nanosatellite on a low-Earth polar orbit and the EISCAT HF transmitter facility in Tromsø, Norway, in December 2020. In the active measurement, the EISCAT HF facility transmitted sinusoidal 7.953 MHz signal which was received with the High frEquency rAdio spectRomEteR (HEARER) onboard 1 Unit (size: 10 × 10 × 10 cm) Suomi 100 space weather nanosatellite. Data analysis showed that the EISCAT HF signal was detected with the satellite's radio spectrometer when the satellite was the closest to the heater along its orbit. Part of the observed variations seen in the signal was identified to be related to the heater's antenna pattern and to the transmitted pulse shapes. Other observed variations can be related to the spatial and temporal variations of the ionosphere and its different responses to the used transmission frequencies and to the transmitted O- and X-wave modes. Some trends in the observed signal may also be associated to changes in the properties of ionospheric plasma resulting from the heater's electromagnetic wave energy. This paper is, to authors' best knowledge, the first observation of this kind of “self-absorption” measured from the transionospheric signal path from a powerful radio source on the ground to the satellite-borne receiver

Machine-learning-driven biomarker discovery for the discrimination between allergic and irritant contact dermatitis

Contact dermatitis tremendously impacts the quality of life of suffering patients. Currently, diagnostic regimes rely on allergy testing, exposure specification, and follow-up visits; however, distinguishing the clinical phenotype of irritant and allergic contact dermatitis remains challenging. Employing integrative transcriptomic analysis and machine-learning approaches, we aimed to decipher disease-related signature genes to find suitable sets of biomarkers. A total of 89 positive patch-test reaction biopsies against four contact allergens and two irritants were analyzed via microarray. Coexpression network analysis and Random Forest classification were used to discover potential biomarkers and selected biomarker models were validated in an independent patient group. Differential gene-expression analysis identified major gene-expression changes depending on the stimulus. Random Forest classification identified CD47, BATF, FASLG, RGS16, SYNPO, SELE, PTPN7, WARS, PRC1, EXO1, RRM2, PBK, RAD54L, KIFC1, SPC25, PKMYT, HISTH1A, TPX2, DLGAP5, TPX2, CH25H, and IL37 as potential biomarkers to distinguish allergic and irritant contact dermatitis in human skin. Validation experiments and prediction performances on external testing datasets demonstrated potential applicability of the identified biomarker models in the clinic. Capitalizing on this knowledge, novel diagnostic tools can be developed to guide clinical diagnosis of contact allergies.Peer reviewe

Spectral riometer observation of atmospheric iononization due to energetic electron precipitation

The Tenth Symposium on Polar Science/Special session: [S] Future plan of Antarctic research: Towards phase X of the Japanese Antarctic Research Project (2022-2028) and beyond, Tue. 3 Dec. / Entrance Hall (1st floor) at National Institute of Polar Research (NIPR