Vladimir Salingereevich Makhmutov

Dimethylsulfide (DMS; CH₃SCH₃) from marine phytoplankton is a major source of atmospheric sulfur ¹. Its oxidation products include sulfuric acid (SA; H₂SO₄) and methanesulfonic acid (MSA; CH₃SO₃H), which has a higher yield than SA below 10 °C ². Whereas SA is known to drive the formation of new particles ³, which may subsequently grow and act as cloud condensation nuclei (CCN), the role of MSA remains unclear ⁴. Here, in experiments performed under atmospheric conditions at the CERN CLOUD (Cosmics Leaving OUtdoor Droplets) chamber, we show that MSA nucleates together with ammonia (NH₃) below −10 °C, at rates comparable to SA-NH₃. Moreover, MSA and SA nucleate synergistically below −10 °C, forming multi-acid molecular clusters with NH₃. Even at ultra-low NH₃ levels, MSA drives particle growth at or near the kinetic limit below 9 °C and above 40 % relative humidity (RH). Since MSA and SA generally coexist at similar concentrations in cool marine regions, our findings indicate that nucleation rates may be accelerated up to tenfold and growth rates up to twofold compared with SA-NH₃ alone. Our global model simulations indicate that MSA can enhance CCN concentrations, especially in polar regions. We propose that MSA might be an important driver of biogenic particles in cool, pristine marine regions of both the present-day and pre-industrial atmospheres, and yet is unaccounted for in global climate models ⁵.

This paper explores the possibility of using machine learning methods for analyzing observations from the “Solntse-Terahertz” scientific equipment, developed at the Lebedev Physical Institute for installation on the Russian segment of the ISS. The scientific equipment consists of eight detectors, with target frequencies ranging from 0.4 to 12.0 THz. One of the primary goals of the experiment is to study solar flares whose spectra in this range often have a U-shaped form. The primary focus in determining the spectral parameters is on identifying spectral indices of the decaying and rising parts of the spectrum, as well as the position of the turnover point. The algorithms were trained using model data on the intensity of radiation passing through optical paths of the instrument. The data was obtained by numerical integration methods. The analysis has shown that the Stacking algorithm demonstrates the highest accuracy in determining the spectral parameters and can be integrated into the data processing system for future experiment on the ISS, enabling the automatic preliminary restoration of solar flare spectrum parameters.

This paper explores the possibility of using machine learning methods for analyzing observations from the “Solntse-Terahertz” scientific equipment, developed at the Lebedev Physical Institute for installation on the Russian segment of the ISS. The scientific equipment consists of eight detectors, with target frequencies ranging from 0.4 to 12.0 THz. One of the primary goals of the experiment is to study solar flares whose spectra in this range often have a U-shaped form. The primary focus in determining the spectral parameters is on identifying spectral indices of the decaying and rising parts of the spectrum, as well as the position of the turnover point. The algorithms were trained using model data on the intensity of radiation passing through optical paths of the instrument. The data was obtained by numerical integration methods. The analysis has shown that the Stacking algorithm demonstrates the highest accuracy in determining the spectral parameters and can be integrated into the data processing system for future experiment on the ISS, enabling the automatic preliminary restoration of solar flare spectrum parameters.

The paper presents the results of an analysis of solar and geomagnetic activity and cosmic-ray flux variations during the period of May 10–11, 2024. During that time, the largest geomagnetic storm in the past 20 years occurred, caused by the arrival of several coronal mass ejections to the Earth, which triggered a Forbush decrease in galactic cosmic rays (GCRs) over that period. This event was recorded by the global network of ground-based neutron monitors (NMs). It is a distinctive feature of this period that, along with a significant decrease in GCR fluxes during the main phase of the geomagnetic storm, a flux of high-energy solar cosmic rays (SCR) was detected in near-Earth space by the GOES and SOHO spacecraft. The source of these particles was a powerful solar flare of class X5.8/2B (coordinates S17W44), which began on May 11 at 01:10 UT. SCR fluxes across a wide energy range were first observed almost simultaneously on spacecraft, and at ~02:10 UT, a short-term increase in cosmic-ray intensity was recorded by high-latitude ground-based NMs, identified as GLE 74. Thus, ground-based instruments showed a complex behavior of particle fluxes due to the superposition of SCR fluxes on the modulated GCR fluxes during the Forbush decrease. The main focus of the study is to assess the possible contribution of SCR fluxes to the observed increase in NM count rates. The analysis uses data from the network of ground-based NMs as well as cosmic ray measurements from the KOVER instrument and neutron detectors located at the Dolgoprudny Scientific Station of the Lebedev Physical Institute (Russia), at Eurasian National University (Kazakhstan), and at the CASLEO astronomical complex (Argentina). The SCR energy spectra are determined using measurement data from the GOES and SOHO satellites. The cosmic-ray flux measurements are analyzed in conjunction with solar, interplanetary, and geomagnetic activity data.

Results are presented from analyzing variations in cosmic rays and the solar and geomagnetic activity of May 9‒15, 2024. The authors use data from a network of ground-based neutron monitors and measurements of cosmic rays, made by the CARPET instruments and neutron detectors at the Lebedev Physical Institute’s Dolgoprudny Scientific Station; the Eurasian National University in Astana, Kazakhstan; and the CASLEO astronomical complex in the Argentinian Andes. Characteristics of the Forbush decrease in the cosmic ray fluxes on May 10, 2024, are studied, along with the subsequent rise in cosmic rays on May 11. Results show these effects differed in nature.

Exposure to anthropogenic atmospheric aerosol is a major health issue, causing several million deaths per year worldwide. The oxidation of aromatic hydrocarbons from traffic and wood combustion is an important anthropogenic source of low-volatility species in secondary organic aerosol, especially in heavily polluted environments. It is not yet established whether the formation of anthropogenic secondary organic aerosol involves mainly rapid autoxidation, slower sequential oxidation steps or a combination of the two. Here we reproduced a typical urban haze in the ‘Cosmics Leaving Outdoor Droplets’ chamber at the European Organization for Nuclear Research and observed the dynamics of aromatic oxidation products during secondary organic aerosol growth on a molecular level to determine mechanisms underlying their production and removal. We demonstrate that sequential oxidation is required for substantial secondary organic aerosol formation. Second-generation oxidation decreases the products’ saturation vapour pressure by several orders of magnitude and increases the aromatic secondary organic aerosol yields from a few percent to a few tens of percent at typical atmospheric concentrations. Through regional modelling, we show that more than 70% of the exposure to anthropogenic organic aerosol in Europe arises from second-generation oxidation.

The study of precipitation of high-energy electrons from the magnetosphere into the Earth’s atmosphere is important for studying the physical mechanisms of electron acceleration during interplanetary disturbances in near-Earth space, the processes of formation of trapped electron fluxes in the magnetosphere and their subsequent precipitation into the atmosphere. In addition, the precipitating electrons affect the spacecraft operation and often lead to significant destruction of mesospheric ozone, etc. Since 1957, the Dolgoprudny Scientific Station of the Lebedev Physical Institute has been conducting continuous measurements of cosmic ray fluxes at altitudes of 0–30 km in the atmosphere of polar latitudes (Murmansk oblast, Antarctica) and at middle latitude (Moscow oblast). During this time, almost 600 cases of electron precipitation were recorded, mainly from the Earth’s outer radiation belt near its polar boundary due to measurement in Murmansk oblast. At the same time, several cases of electron precipitation were recorded at mid-latitude (Moscow oblast) and at the Mirny station in Antarctica, in particular, in 2022–2023. The paper discusses interplanetary and geomagnetic conditions during these events. Analysis of measurement data in the stratosphere made it possible to establish the absorption spectra of secondary bremsstrahlung photons and, on their basis, using the method we developed, to determine the primary energy spectra of precipitating magnetospheric electrons.

The future space experiment «Sun-Terahertz» is aimed at studying the Sun in the unexplored terahertz range, obtaining new data on the terahertz radiation of the Sun, solar active regions and solar flares. The scientific equipment being developed is a set of eight detectors sensitive to radiation of various frequencies in the range 0.4–12.0 THz. The Golay cell optoacoustic receiver was used as a sensitive element of the detectors. This paper examines the problem of changing the sensitivity of receivers of this type when their own temperature changes (temperature effect). Using a test bench based on a single-channel model of scientific equipment and a black body simulator, the linear section of the temperature dependence of the receiver was determined. A method for compensating the temperature effect of optoacoustic converters Golay cell has been developed and the results of its testing on a test bench are presented. This technique will be useful in the development of scientific equipment based on Golay cells, the operation of which is expected under conditions of temperature changes in the surrounding space.

The main nucleating vapor in the atmosphere is thought to be sulfuric acid (H ₂ SO ₄ ), stabilized by ammonia (NH ₃ ). However, in marine and polar regions, NH ₃ is generally low, and H ₂ SO ₄ is frequently found together with iodine oxoacids [HIO _x , i.e., iodic acid (HIO ₃ ) and iodous acid (HIO ₂ )]. In experiments performed with the CERN CLOUD (Cosmics Leaving OUtdoor Droplets) chamber, we investigated the interplay of H ₂ SO ₄ and HIO _x during atmospheric particle nucleation. We found that HIO _x greatly enhances H ₂ SO ₄ (-NH ₃ ) nucleation through two different interactions. First, HIO ₃ strongly binds with H ₂ SO ₄ in charged clusters so they drive particle nucleation synergistically. Second, HIO ₂ substitutes for NH ₃ , forming strongly bound H ₂ SO ₄ -HIO ₂ acid-base pairs in molecular clusters. Global observations imply that HIO _x is enhancing H ₂ SO ₄ (-NH ₃ ) nucleation rates 10- to 10,000-fold in marine and polar regions.