Heating efficiency in hydrogen-dominated upper atmospheres

Context. The heating efficiency is defined as the ratio of the net local gas-heating rate to the rate of stellar radiative energy absorption. It plays an important role in thermal-escape processes from the upper atmospheres of planets that are exposed to stellar soft X-rays and extreme ultraviolet radiation (XUV). Aims. We model the thermal-escape-related heating efficiency of the stellar XUV radiation in the hydrogen-dominated upper atmosphere of the extrasolar gas giant HD 209458b. The model result is then compared with previous thermal-hydrogen-escape studies which assumed heating efficiency values between 10-100%. Methods. The photolytic and electron impact processes in the thermosphere were studied by solving the kinetic Boltzmann equation and applying a Direct Simulation Monte Carlo model. We calculated the energy deposition rates of the stellar XUV flux and that of the accompanying primary photoelectrons that are caused by electron impact processes in the H2 to H transition region in the upper atmosphere. Results. The heating by XUV radiation of hydrogen-dominated upper atmospheres does not reach higher than 20% above the main thermosphere altitude, if the participation of photoelectron impact processes is included. Conclusions. Hydrogen-escape studies from exoplanets that assume heating efficiency values that are >= 20 % probably overestimate the thermal escape or mass-loss rates, while those who assumed values that are < 20% probably produce more realistic atmospheric-escape rates.Comment: 7 pages, 4 figures, accepted to A&

Homogenization of UV-Visible NDACC spectrometers reprocessing for ozone and NO2

SAOZ is a ground-based UV-Visible zenith-sky spectrometer deployed since 1988 at a number of NDACC (Network for the Detection of Atmospheric Composition Change) stations at all latitudes on the globe. The instrument is providing ozone and NO2 total columns at sunrise and sunset using the Differential Optical Absorption Spectroscopy (DOAS) technique in the visible spectral range. SAOZ observations have been used extensively to validate various atmospheric chemistry satellite instruments such as nadir viewing TOMS, GOME, SCIAMACHY, OMI and GOME-2. The NDACC UV-Visible working group initiated a tentative homogenization of ozone and NO2 processing of all UV-Vis zenith sky spectrometers as one of its objectives. The first recommendation is concerning the total ozone retrieval. A significant change for the SAOZ network is the use of different cross-sections (O3, NO2, H2O, O4, and Ring calculations) and different spectral window fitting range, which leads to a recalculation of the slant columns. In addition, it is recommended to use a climatological air mass factor (AMF) instead of an annual AMF usually used in standard SAOZ processing. Here we present the results of comparisons between TOMS (since 1988), GOME (since 1995), SCIAMACHY (since 2002), OMI (since 2004), GOME-2 (since 2006) and SAOZ at all latitudes - tropics, mid-latitudes and Polar Regions - in both hemispheres. In the case of ozone, the NDACC recommendations resulted in a significant improvement of the differences between ground-based SAOZ and measurements from space. Preliminary results of NO2 SAOZ columns, using climatological AMF, are also presented and compared to different satellites, such as GOME, SCIAMACHY and OMI

Progression of obstructive sleep apnoea after renal denervation is not associated with hypertension exaggeration

Abstract Purpose In a cohort, observational prospective trial, we assessed the long-term dynamics of sleep-disordered breathing in patients with resistant hypertension after renal denervation and their association with blood pressure change at remote follow-up. Materials and methods Twenty-eight patients with stable hypertension who were recruited for endovascular radiofrequency renal denervation in 2012–2019 and had valid both baseline and follow-up sleep study, were included in the analysis. All patients underwent physical examination, anthropometry, office and ambulatory blood pressure measurements, blood and urine tests, kidney visualization, and full polysomnography before and within 12–36 months after renal denervation. Results The average follow-up comprised 30.1 ± 8.4 months. At long-term follow-up, no significant changes in creatinine level, estimated glomerular filtration rate, body mass index were registered. There was a significant increase in sleep apnea severity indices: the mean change in apnea-hypopnea index comprised 9.0(-21.1;25.2) episodes/h, in oxygen desaturation index 6.5(-16.8;35.9) episodes/h, in the average SpO2 -1.7(-5.6;1.9)%. Over 12-month follow-up, there were no significant differences in blood pressure response in patients with and without sleep apnea. The baseline apnea-hypopnea and oxygen desaturation indices and the mean SpO2 were associated with the circadian blood pressure profile at follow-up, but did not correlate with the blood pressure response. Conclusions Although the severity of sleep apnea worsens at > 12 months follow-up after renal denervation, this is not associated with hypertension exaggeration