Geomagnetism and Aeronomy最新文献

In solar activity, in addition to the 11-year Schwabe cycle, there are also shorter-period oscillations in the range from 27 days to 11 years, which are called mid-term oscillations. In our study, we identify quasi-6-year oscillations in solar activity expressed by the sunspot number SN using wavelet analysis and investigate the characteristics of these variations during 1750–2020. The analysis shows that the ~6-year cycle in SN is a real independent oscillation. A similar quasi-6-year periodicity has been found in the monthly mean records of geomagnetic field components at the Sitka and Honolulu observatories during 1910–2020. It was found that the variations of the geomagnetic field in the range of 5–6-year periods can be caused by the effect of variations in solar activity in the same frequency range. In addition, in the SN series and geomagnetic field variations, a quasi-biennial cycle is well observed, the amplitude of which in some time intervals exceeds the amplitude of the cycle with a period of 5–6 years.

For the first time, several flare events are analyzed based on multifrequency observations using the Radio Solar Telescope Network. The purpose of the analysis is to identify signs of flare preparation. In all considered cases, preflare quasi-periodic fluctuations (QPFs) of radio emission were detected. The duration of preflare wavetrains is 6–20 min. Wavetrains consist of 3–5 pulses. QPFs at lower frequencies (200–600 MHz) begin later than those at high frequencies by 2–6 min. QPFs at frequencies of 2695–8800 MHz occur almost synchronously. The highest amplitude of QPFs is observed at a frequency of 4995 MHz. The observed QPFs can be explained by the force-free magnetic rope model (Solov’ev and Kirichek, 2023).

In this article we continue studying the influence of solar activity on the main trajectories of extratropical cyclones (storm tracks) in different parts of the North Atlantic during the cold half of the year (period of intense cyclogenesis). Long-term oscillations in the latitude of storm tracks in the areas located west and east of the Greenwich meridian are compared. It is shown that secular oscillations in latitudes of storm tracks (with periods of ∼80–100 years) are most distinctly pronounced in the western North Atlantic (longitudes 60°–40° W), weaken in the area of the Icelandic Low (30°−10° W), and completely disappear in the eastern part (0°−20° E), where multidecadal oscillations with periods of ∼50–60 years dominate. Bidecadal oscillations in cyclone trajectories (northward shift of trajectories during the declining phase and at the minima of even-numbered solar cycles) have the greatest amplitude in the region of the Icelandic Low and noticeably weaken east of Greenwich. It is shown that the shift of cyclone trajectories to the north in even cycles occurs under increased galactic cosmic ray (GCR) intensity compared to odd cycles. The data providing evidence for the influence of the stratospheric polar vortex on the position of North Atlantic cyclone trajectories are presented. It is suggested that possible reasons for oscillations in the vortex intensity are changes in the chemical composition and temperature regime of the middle polar stratosphere caused by variations in GCR fluxes and geomagnetic activity.

The study demonstrates the synchronicity of the positive and negative phases of summer irradiation of the Northern Hemisphere in the precession cycle with periods of global climate warming and cooling for the Late Pleistocene and Holocene. The cold phase 50–41.5 ka BP corresponds to the Shestikhinsky cooling in Eastern Europe and the development of glaciation in North America. The warm phase 41–30 ka BP accounts for climate warming in Europe (Bryansk interstadial, Paudorf, Gotwei warming) and in North America (Plum Point Interstadial). The period of maximum development of glaciation in Europe and North America is synchronized with the cold phase 29.5–17.5 ka BP. The warm phase 17–5.5 ka BP is associated with the transition from the cold Pleistocene to the relatively warm Holocene. The Little Ice Age falls on the cold phase 5 ka BP – 5000 CE. It is expected that warming of the climate with respect to the present will correspond to the Warm Epoch 5000–13 000 CE. Changes in solar radiation arriving in the first astronomical half of the year in 5° latitude zones were determined for all astronomical months of the tropical year for climatic precession extrema. This makes it possible to compare spatiotemporal changes in Earth’s solar climate during years of climate precession extrema.

In the recent work by Usoskin et al. (2021) a series of annual sunspot indices for the years 971 to 1899 was reconstructed. Using this series, we study behavior of the “length-amplidude rule” (LAR), according to which the mininum-to-minimum length of a given 11-year solar cycle anticorrelates with the amplitude of the next one. We show that approximately since the 14th century two regimes exist in the series: I) epochs of normal activity, when the LAR is observed; II) epochs of the Maunder, Spörer and Wolf grand minima, when there were no significant links between the amplitudes and lengths of the 11-year cycles. Before the 14th century the LAR and its relation to the level of global activity of the Sun is less pronounced, which, probably, is a consequence of inaccuracies of the 11-year cycle parameters determination in this epoch.

Сorotating interaction regions of solar wind flows with different velocities have actively been magnetohydrodynamically simulated for many years. However, the main goal is to predict heliospheric characteristics in Earth’s orbit, and so calculations are performed to distances of 1–1.5 AU. In the last decade, systematic magnetohydrodynamic calculations of corotating interaction regions up to much larger distances have appeared, which are necessary for studying recurrent variations in the intensity of galactic cosmic rays. Based on one of these calculations, we previously showed that, at least for one rotation of the Sun (Carrington rotation 2066, January–February 2008), the effect of corotating interaction regions on large-scale characteristics of the heliosphere that are important for GCR modulation and, therefore, the intensity averaged over longitude is significant. We assumed that the main principles of this effect of corotating interaction regions on GCRs can be studied both by 3D modeling of the GCR intensity and in much simpler 2D models. In this paper, we discuss the results, prospects, and shortcomings of such a 2D description of the effect of corotating interaction regions on the GCR intensity.

The cause of the asymmetry in the sunspot distribution in the northern and southern hemispheres of the Sun at the end of the Maunder Minimum is studied. It is demonstrated that the expected asymmetry of generation sources is insufficient for such an explanation. To study the influence of asymmetry of generation sources, numerical simulation is used, based on modifications to the Parker model.

The results of observations of coronal jets on the Sun are briefly reviewed. Data on jets of different types (jets, jetlets) were collected. Their properties are considered, such as lifetime, length, width, velocities, coupling to the magnetic field, and their putative role in hot plasma and energy transfer into the corona. Observational data obtained with ground-based and space telescopes were used. There is growing evidence that jets play a key role in imparting mass to the corona and solar wind and can provide sufficient energy to power the solar wind (see, e.g., (Tian et al., 2014)). Modern observations by the Parker Solar Probe and Solar Orbiter spacecraft will contribute to the understanding of solar jets and related phenomena.

The results of analyzing the relationship between large-scale epidemics (pandemics) caused by the Ebola, influenza AH1N1, and AH7N9 viruses and the MERS-CoV coronavirus with global solar factors for the period from 2008 to 2019 (24th cycle of solar activity) are presented. A variable change in the annual values of pandemic cases has been established, corresponding to the regular course of F10.7 cm (r ~ 0.65), MF (r ~ 0.85) and λ315 nm (r ~ 0.83) in the 24th SA cycle. It was concluded that the dynamics of the spread of pandemics depend on temporary changes in UVB radiation power, in particular, at the boundary of the spectral bactericidal efficiency curve (λ315 nm).

Here we studied the planetary features of the spatiotemporal distribution of ionospheric electrojets recorded in the onset of a substorm and in time on the activity maximum of three very intense substorms (with an AL-index from –1200 to –1700 nT) observed during the main phase of the strong magnetic storm on March 23−24, 2023. We have analyzed the substorms by applying the global maps of the planetary distribution of high-latitude ionospheric currents, compiled from simultaneous magnetic measurements on 66 low-orbit satellites of the AMPERE project, as well as ground-based magnetograms from the Scandinavian IMAGE profile and mid-latitude IZMIRAN stations located in the same longitudinal region. It was established that the onset of all the studied substorms on the IMAGE meridian was accompanied by the development of a nighttime current vortex with clockwise rotation, which is an indicator of an increase in downward field-aligned currents. The ground-based mid-latitude observations at the IZMIRAN station network confirmed that the center of the current wedge of the substorm was located in the nighttime sector significantly east of the IMAGE meridian. In the time of the substorm intensity maximum, a similar but more extensive current vortex was observed in the morning sector, which is probably typical of intense substorms.