The A.I. Kuzmin Cosmic Ray Spectrograph in Yakutsk contains a 24-NM-64 neutron monitor and a system of underground MT and SMT muon detectors for recording muons at levels of 0, 7, 20, and 40 m of water equivalent. The temperature effect of muons observed with MT telescopes on gas-discharge counters has been analyzed in the previous work [Yanchukovsky, 2023]. Here we calculate the temperature effect of muons recorded by SMT telescopes. Distributions of the density of temperature coefficients for muons recorded on the surface and at different depths underground were found from SMT telescope data for the period from January 2016 to December 2018, using data on the altitude profile of the atmosphere temperature over Yakutsk for the same period. In the analysis of multidimensional data, we applied the methods of regression on principal components. When constructing a system of linear equations in the space of principal components, we employed the method of projections to latent structures (PLS2). The obtained results were compared with the results of theoretical calculations. The found distributions of the density of temperature coefficients allow us to correctly take into account the temperature effect in data from SMT muon telescopes.

Correlation curves of the multi-frequency Siberian Radioheliograph (SRH) provide a sensitive indication and demonstrative representation of monitoring the microwave life of the active Sun. We derive approximate relationships and briefly discuss the contribution of the quiet Sun, active regions, radio bursts, satellites, and atmospheric absorption to the radioheliograph’s correlation response. The estimates are obtained under the assumption that the activity centers and the quiet Sun are homogeneous disks of different sizes and brightness. The sensitivity of the correlation curves to weak sources of small angular sizes is due to their wide spatial spectrum. The wide spectrum means that each pair of antennas produces a noticeable interferometric response, so the total response is significant. The correlation curves allow us to estimate spatial sizes of the radio burst source at different frequencies, but do not allow us to calculate the shape of its radio spectrum. Variability in the atmospheric water content over time creates fluctuations of the received solar radio flux. The correlation response is much less susceptible to this factor.

We have examined the response of the lower and upper ionosphere to the passage of extratropical cyclones in 2014–2023, using measurements made at regional ultra-long-wave radio stations and satellites of the Swarm mission in the Far Eastern region of Russia. For twelve cyclones, we have found that disturbances in the lower ionosphere, observed in VLF signal amplitude and phase variations, as well as their associated electron density variations in the upper ionosphere during the active stage of the cyclones, correspond to the passage of atmospheric internal gravity waves and their dissipation, as evidenced by several examples. We have studied the mechanisms of the influence of internal atmospheric waves on the ionosphere, which make it possible to interpret the VLF signal phase variations observed in the lower ionosphere and the electron density variations in the upper ionosphere.

The paper analyzes the description in chronicles of the September 2, 1859 auroras observed in Irkutsk during the Carrington event. The description of the red arc by an eyewitness, the analysis of geomagnetic conditions, publications on visual observations of auroras of various forms at middle and low latitudes during this period, modern instrumental observations of SAR arcs at the latitude of Irkutsk have allowed us to assume that the red arc described in the chronicles is a SAR arc — one of the auroral types at subauroral and middle latitudes observed during geomagnetic storms. We have established that in Irkutsk the SAR arc was observed during the recovery phase of the magnetic superstorm. The intensity of the SAR arc was estimated at ~10–20 kR. The projection of the plasmapause onto the ionosphere on September 2, 1859 at ~12 UT was at the latitude of Irkutsk. We can assume that the description of the aurora borealis on September 2, 1859 in Irkutsk is the first objective description of the SAR arc, a century before its discovery as a phenomenon in 1958.

The Sun showed extraordinary activity related to sunspot area 3664 on May 8–10, 2024, resulting in solar flares considered the most intense in the current solar cycle. Auroras occurred in several regions around the world. Early on May 12, 2024 near the highest peak in the Sultanate of Oman, a team of Omani astrophotography enthusiasts documented the rare event ever observed in this region. Auroras often occur along the so-called auroral oval zones around the geomagnetic poles, where Earth's magnetic field directs charged particles penetrating from the solar wind. This takes place when a cloud of charged particles is thrown toward Earth by a large explosion on the Sun. Sometimes, these particles can make the aurora visible in places where it is exceedingly rare throughout recorded history. The observation from the mountain Jebel Shams, situated far from the polar regions (23 degrees north of the equator), offers a unique chance to study such an event in a region where auroras are exceptionally rare. We explore the factors contributing to the observed aurora in Oman, including geomagnetic conditions and the role of sunspot region AR3664 in solar activity along with local conditions in Oman that contributed to the visibility of this aurora. Understanding this dynamics can enhance our knowledge of the mechanisms driving auroral visibility at lower latitudes and provide valuable insights into the global impact of solar storms. This study also emphasizes how crucial it is to record auroras in regions like the Arabian Peninsula, where they are rarely documented.

The paper reports the results of comprehensive observations of space weather manifestations during geophysical events at the end of October – beginning of November 2021 at the Yakut meridional geophysical network of SHICRA SB RAS equipped with a complex of various scientific instruments installed at the stations Yakutsk, Maimaga, Zhigansk, and Tixie Bay (neutron monitors, an ionosonde, a riometer, receivers of VLF radio noise and signals from navigation radio stations, magnetometers), as well as a complex of optical instruments installed in Maimaga. We present the results of the analysis of phenomena occurring in near-Earth space, Earth’s ionosphere and atmosphere in the North-Eastern sector of Siberia. We examine the properties of the geophysical effects of space weather observed at this time: Forbush decreases of cosmic rays, geomagnetic storm and substorm, riometric absorption, the occurrence of electrojet, quasi-periodic broadband radio hisses, assess changes in the effective height of the Earth—ionosphere waveguide, F2-layer critical frequencies, absorption of short-wave radio waves, temperature of the neutral atmosphere, radiant auroral band in 557.7 and 630.0 nm emissions, as well as the region of intense auroras and auroral red arc (SAR arc).

Using SDO/HMI data, we have studied the dynamics of small-scale magnetic field elements in the photosphere during the formation of small active region USAF/NOAA 12761. The choice of this region is due to the fact that it formed near the central meridian at the minimum of the 11-year solar activity cycle in the absence of strong background magnetic fields. It has been established that two days before the formation of the first pores, the initially observed small-scale structure of the magnetic field forms chains of elements of both polarities. The structure of the chains creates a stable polarity dividing line (PIL). During the first day, the orientation of PIL changes from quasi-latitudinal to quasi-meridional. After comparing observations with a number of theoretical models, we concluded that the observed dynamics of elements of magnetic chains is consistent with the models of emergence of a magnetic flux rope in the photosphere.

We have studied the morphological features of semidiurnal variations in the occurrence of the sporadic Es layer (PEs) and height of the layer (hEs), using data from the Irkutsk DPS-4 ionosonde (52.3° N, 104.3° E) for 2003–2021. By averaging over all the years, we calculate diurnal variations in PEs and hEs for each month. It is observed that the maximum of occurrence PEs is achieved when the height hEs decreases; and there is an asymmetry in the maximum of occurrence PEs: morning maxima are larger than evening ones. These features are interpreted based on the concept of the optimal height for Es formation and the role of photoionization in forming the sporadic layer.

The ionospheric electric potential (EP) is used as a heliogeophysical parameter to analyze tropospheric response to solar impacts during geomagnetic superstorms in solar cycle 23. According to observational data, the response of meteoparameters is shown to concur with EP variations during the November 20, 2003 geomagnetic superstorm caused by an extreme geoeffective event. The tropospheric response is time-shifted versus EP maximum during the July 15, 2000 magnetic superstorm: increased precipitable water is observed in 6 hrs; decreased outgoing longwave radiation, in 12 hrs; increased upper cloudiness, in 18 hrs. We have found that the amplitude of the meteoparameters’ response to EP variations during the July 15, 2000 magnetic superstorm is about half as low as that of the tropospheric response during the November 20, 2003 geomagnetic superstorm.

Since the discovery of the phenomenon of abnormal cooling and sinking of the middle and upper atmosphere in 1993–1998, two concepts have developed which explain its origin by man-made processes. Both focus on different consequences arising from one common cause — the burning of carbon fuels on an industrial scale. The first concept is based on the hypothesis about the key role of the decrease in oxygen content in the atmosphere in this process. The second model, which emerged a little later, attributes the observed effects to the growth of greenhouse gases in the atmosphere, primarily CO2. Over the years, numerous attempts have been made to confirm the assumption of the dominance of the second mechanism in the excitation of the long-term trend of the climate of the middle and upper atmosphere. However, all of them turned out to be futile. At the same time, today, firstly, the validity of the first proposed hypothesis is justified which recognizes the leading role of oxygen in climate change in the upper atmosphere, and secondly, errors that cause the erroneous rejection of this conclusion are revealed. It becomes obvious that man-made processes affecting the atmosphere lead to two multidirectional phenomena: a) global warming of the troposphere; b) global cooling of the thermosphere: an extreme increase in the mass of CO2 heats the lower layers of the atmosphere, and its upper layers are cooled even by an inconspicuous decrease in part of O2 relative to the total mass. Since nothing indicates a decline in the man-made activity of the world civilization in the coming years, in order to adequately predict the consequences of an increase in atmospheric pollution the effect of a decrease in oxygen content on the state of near-Earth outer space should probably be taken into account.