Yu.G. Shafer Institute of Cosmophysical Research and Aeronomy

We study the spatiotemporal variations of ionospheric parameters over the regions of Eurasia by analyzing data from chains of high- and mid-latitude ionosondes during the extreme magnetic storm in May 2024. The analysis of ionospheric parameters allowed us to note strong latitudinal and longitudinal differences in variations of the analyzed parameters under quiet conditions before the onset of the magnetic storm and during its development. Almost immediately after the onset of the storm at 17:00 UT on May 10, 2024, according to data from all ionosondes, a sharp drop in the electron density at the height of the F2-layer maximum was recorded, regardless of the local time at the measurement point. Ionosondes of the high-latitude chain showed a complete absence of data (radio signal blackout) during the main and early recovery phases of the storm until the evening of May 12, 2024, i.e. more than one and a half days. Additional bursts of geomagnetic activity during the recovery phase of the storm were also accompanied by significant and prolonged decreases in the electron density according to ionosonde measurements at all longitudes of Eurasia. The recovery of ionospheric ionization began on May 14–15 at all longitudes of the mid- and high-latitude regions of Eurasia. A long-term negative disturbance of electron density covering a huge territory of mid-latitude Eurasia was caused by an extraordinary, catastrophic drop in the [O]/[N2] ratio according to satellite measurements of GUVI TIMED during the superstorm for almost three days. The response of the thermospheric composition of neutral gas to the processes developing at high latitudes of the Northern Hemisphere on May 10–15, 2024 was global, with penetration of the thermospheric disturbance at almost all longitudes up to the equatorial latitudes (~10° N) and with very low values of the [O]/[N2] ratio ~0.1÷0.4. Significant differences in the spatiotemporal variations of the thermospheric composition of neutral gas were revealed during the most extreme geomagnetic storms of the current 21st century — in May 2024 and October–November 2003 (Halloween storms). The magnetic superstorm in May 2024 was much more geoeffective than the superstorms in October–November 2003, and caused a significantly different ionospheric response at different longitudes and latitudes of the Northern Hemisphere.

The article reports on the study of the dynamics of the IMF turbulent component from the quiet period on May 7, 2024 to the arrival of an interplanetary shock wave in the second half of May 10, 2024. To achieve the stated goal, 1-minute direct measurements of interplanetary medium parameters on the ACE, DSCOVR, and WIND spacecraft are involved in the analysis. Spectral analysis methods are used to study the evolution of power spectra of fluctuations in IMF modulus and MHD waves in the inertial portion of the SW turbulence spectrum at frequencies ~2.5∙10–4–8.3∙10–3 Hz. The contribution of Alfvén, fast, and slow magnetosonic waves to the observed power spectrum of the IMF modulus measured by each of the three spacecraft is determined, and power spectra of MHD waves of these types are identified. It is shown that the power of the spectra of fluctuations in the IMF modulus and MHD waves increases by more than an order of magnitude as the shock wave approaches the point of its recording on the spacecraft. It is concluded that this is due to the generation of MHD waves by fluxes of energetic storm particles (ESP) — cosmic rays with energies ~1 MeV, observed in the region ahead of the interplanetary shock wave front. Analysis of all measurement data allows for the assumption that a significant increase in low-energy CR fluxes (~1 MeV) and SW turbulence levels may lead to a change in the IMF direction in the region adjacent to the IPS front.

In this article we provide the results of the synthesis of graphene films and discuss their potential applications in electronic structures. Graphene films were synthesized on copper foil using the CVD method at 1050 °C. During the initial stage of synthesis, graphene domains with hexagonal shapes and an average size of 10 μm were formed. The orientation and size of the graphene domains are based on the synthesis parameters and the copper foil. As the synthesis time increases, domain cross-linking occurs, resulting in polycrystalline continuous graphene film formation. Graphene films have areas up to 100 cm2 and thicknesses ~ 1 nm to 5 nm. To measure the Raman spectra, graphene films were transferred to SiO2/Si substrates. Graphene films exhibit an intense 2D peak that significantly exceeds the G peak of crystalline graphite. Flexible transparent conductive touch panels were created on the basis of the grown graphene films. A lamination method has been used to create graphene films that can be transferred from copper foil to polymer substrates. A laboratory touch screen with a graphene film acting as a capacitive touch sensor was constructed on the basis of the transferred film, and transparent electrodes for molybdenum disulfide-based photosensitive elements were also created. Resistive humidity sensors based on graphene films were developed and transferred to SiO2/Si and epoxy/Si substrates. The graphene humidity sensor has a low response, high temperature stability, and is highly reliable.

The article considers showers produced by primary particles with energies $$E_{0}\geq 10^{20}$$ eV. The showers were registered in the course of continuous long-term observations at the Yakutsk array of extensive air showers. In the present work, the mathematical processing of showers was repeated and the phenomenology of the charged component, muons with threshold $$\epsilon_{\textrm{thr.}}\geq 1$$ GeV in the region of highest energies was refined. Mass composition of primary particles producing air showers with energy greater than $$10^{20}$$ eV was made based on the muon component.

Rayleigh lidar measurements of temperature from 20 to 60 km have been carried out at the Yu.G. Shafer Institute of Cosmophysical Research and Aeronomy of the SB RAS, from 2004 to 2017. Observations were carried out from late August to mid-May. Dominant IGWs with wavelengths 2–4 km, 5–7 km, and 10–15 km was identified. Local variation maximum of the temperature profile is often observed at stratopause heights during sudden winter stratospheric warmings (SSWs).

Measurements by the world network of neutron monitors during the period 1996–2018 31 are used to identify strong Forbush decreases (>5%) that meet the accepted criteria for event selection. Coordinated spatial distributions of solar wind parameters and drops in the density of cosmic rays are determined via epoch superimposition. It is established that contributions from the mechanisms of the formation of Forbush decreases differ greatly in two groups of events. This difference could be due to Forbush decreases forming in the front of one group and the peripheral part of the disturbance forming in the other group.

The paper presents joint analysis of the characteristics of the electron-photon and Cherenkov components, and muons with a threshold ${ϵ}_{\mathrm{thr}}\ensuremath{\ge}1\text{ }\text{ }\mathrm{GeV}$ and zenith angles less than 60\ifmmode^\circ\else\textdegree\fi{}. The analysis is based on complex data of air shower registration. A quantitative estimation of muons at different distances from the shower axis and the ratio of muons and charged particles at a distance of 600 m are obtained. The empirical relationship found between ${\ensuremath{\rho}}_{\ensuremath{\mu}}(600)/{\ensuremath{\rho}}_{\ensuremath{\mu}+e}(600)$ and the depth of the maximum ${X}_{\mathrm{max}}$ estimated by Cherenkov light data. It allowed to estimate ${X}_{\mathrm{max}}$ in individual showers by fraction of muons ${\ensuremath{\rho}}_{\ensuremath{\mu}}(600)/{\ensuremath{\rho}}_{\ensuremath{\mu}+e}(600)$. From the set of such showers, the dependence of ${X}_{\mathrm{max}}$ on the energy ${E}_{0}$ was found. Mass composition of cosmic rays with highest energies is estimated by comparison of the experimental ${X}_{\mathrm{max}}$ and QGSJetII-04 simulation ${X}_{\mathrm{max}}$ for different primary nuclei. The composition of cosmic rays determined from the muon component of air showers, mainly consists of protons and helium nuclei in the energy range 5--10 EeV. At energies greater than 30 EeV the mass composition is becoming heavier due to CNO and iron nuclei.

We presented the first results of triangulation measurements of the stable auroral red arcs height at the Yakutsk meridian in 2015–2020. The heights of the lower luminosity boundary in arcs of 350–370 km near the maximum and 250–290 km during the minimum of solar activity in the 24th cycle are obtained. The decrease of the red arcs height in the minimum years is due to the significant density decrease of the upper neutral atmosphere.

During the solar eclipse on June 10, 2021 for the JJY40 – Yakutsk radio path the amplitude signal changes were not registered, the phase delay decrease by 0.95 radians (11:14:06 UT) then the phase delay increase by 1.25 radians (12:02:24 UT). For the JJY40 - Tixie Bay path the amplitude increase by 5 dB (11:47:42 UT) and the phase delay increase by 1.2 radians (11:51:54 UT). The normalization coefficient was determined <i>H_{JJY40-Tixie Bay}</i> = 4.93±0.54 km. The maximum change of the effective height of the Earth-ionosphere waveguide JJY40 – Tixie Bay for the maximum shading (11:39:18 UT) is 7.08 km (68° N, 132° E, <i>Φ</i> = 0.883).

In this paper, we examine the relationship of the SME index with magnetic storm characteristics and inter-planetary medium parameters during the main phase of magnetic storms caused by CIR and ICME events. Over the period 1990– 2017, 107 magnetic storms driven by (64) CIR and (43) ICME events have been selected. Close correlation coefficients between SME_aver and the SW electric field have been obtained for CIR and ICME events. SME_aver has been found to increase with the rate of magnetic storm development and |Dst_min|.