An overview is presented of basic results and recent developments in the field of cosmic ray induced ionisation in the atmosphere, including a general introduction to the mechanism of cosmic ray ...induced ion production. We summarize the results of direct and indirect measurements of the atmospheric ionisation with special emphasis to long-term variations. Models describing the ion production in the atmosphere are also overviewed together with detailed results of the full Monte-Carlo simulation of a cosmic ray induced atmospheric cascade. Finally, conclusions are drawn on the present state and further perspectives of measuring and modeling cosmic ray induced ionisation in the terrestrial atmosphere.
The paper summarizes the properties of precipitation of magnetospheric electrons with energy above several hundred keV recorded by observing X‐ray bremsstrahlung in the polar stratosphere above the ...Murmansk region, Russia, in 1961–2019. Precipitation occurrence rate demonstrates a clear dependence on the solar activity with a maximum at the decay phase of the 11‐year solar cycle, similarly to the variability in occurrences of the high‐speed solar wind streams (HSSWS). The energetic electron precipitation (EEP) event series is often initiated by a moderate geomagnetic storm caused by a HSSWS and continues during geomagnetic storm recovery. EEP demonstrates the seasonal rate variation with the maxima in occurrence rate around the spring and the autumn solstices and correlates with fluences of relativistic electrons in the outer radiation belt. For 59 years, 589 events of precipitation were observed. Analysis of the long‐term time series revealed a growing trend in the rate of precipitation occurrence, especially in the 1990s to 2000s that is not properly explained yet.
Plain Language Summary
Since the beginning of the 1960s, the group from Lebedev Physical Institute watches the precipitation of energetic electrons from the outer radiation belt to the atmosphere. The precipitation reflects the condition in the interplanetary space and in the magnetosphere, that is, it is governed by solar activity. In the 1990s, solar activity started weakening: the maximum annual mean of sunspot number decreased from 233 in Solar Cycle 21 to 116 in Cycle 24. But the occurrence rate of precipitation increased, which has not found an explanation yet.
Key Points
Balloon observations allow recording precipitation of magnetospheric electrons via bremsstrahlung in the atmosphere
Since 1961 till 2019, 589 electron precipitation events were observed in the Murmansk region
An unexpected increase of precipitation occurrence rate was found in the 1990s to 2000s
We compare the quasi-biennial variations and Rieger-type variations (on a timescale of less than 1 year) in solar activity, interplanetary magnetic field, and galactic cosmic-ray flux modulation. We ...show that, in comparison with the 11-year cycle, the quasi-biennial variations are less suppressed in the interplanetary medium than on the Sun. Although the Rieger-type variations are adjacent in frequency to the quasi-biennial variations, they differ noticeably from them in the degree of reproduction in the interplanetary medium and the influence on the cosmic-ray modulation.
Abstract
Using measurements from the PAMELA and ARINA spectrometers on board the Resurs-DK1 satellite, we have examined the 27 day intensity variations in galactic cosmic ray (GCR) proton fluxes in ...2007–2008. The PAMELA and ARINA data allow for the first time a study of time profiles and the rigidity dependence of the 27 day variations observed directly in space in a wide rigidity range from ∼300 MV to several gigavolts. We find that the rigidity dependence of the amplitude of the 27 day GCR variations cannot be described by the same power law at both low and high energies. A flat interval occurs at rigidity
GV with a power-law index
γ
= −0.13 ± 0.44 for PAMELA, whereas for
R
≥ 1 GV, the power-law dependence is evident with index
γ
= −0.51 ± 0.11. We describe the rigidity dependence of the 27 day GCR variations for PAMELA and ARINA data in the framework of the modulation potential concept using the force-field approximation for GCR transport. For a physical interpretation, we have considered the relationship between the 27 day GCR variations and solar wind plasma and other heliospheric parameters. Moreover, we have discussed possible implications of MHD modeling of the solar wind plasma together with a stochastic GCR transport model concerning the effects of corotating interaction regions.
This paper provides insight into heliospheric processes and galactic cosmic ray (GCR) modulation occurring due to the presence of two branches of solar activity in this solar layer. According to the ...topology of solar magnetic fields, these branches are called toroidal (active regions, sunspots, flares, coronal mass ejections, etc.) and poloidal (high-latitude magnetic fields, polar coronal holes, zonal unipolar magnetic regions, etc.). The main cause of different manifestations of the two branches on the solar surface and in the heliosphere — the layer at the base of the heliosphere in which the main energetic factor is the magnetic field — is formulated. In this case, the magnetic fields of the poloidal branch, which have a larger scale but a lower intensity, gain an advantage in penetrating into the heliosphere. A connection is shown between the poloidal branch and the heliospheric characteristics (solar wind velocity field, size of the heliosphere, form of the heliospheric current sheet, regular heliospheric magnetic field and its fluctuations) that, according to modern notions, determine GCR propagation in the heliosphere.
An analysis of the data of spacecraft that scanned large areas of the heliosphere, as well as the results of magnetohydrodynamic calculations, indicates that corotating interaction regions of solar ...wind (SW), which are almost always present in the low- and mid-latitude heliosphere, sometimes strongly change the large-scale characteristics of the heliosphere that are important for long-term variations in the intensity of galactic cosmic rays (GCRs). In particular, for Carrington rotation no. 2066 (January–February 2008), these regions enhance magnetic fields in the inner (
r
< 3–5 AU) heliosphere and weaken them in the middle and far heliosphere, as well as significantly changing the polarity distribution of heliospheric magnetic fields. The assumption is made that in this situation the influence of the corotating interaction regions should lead to an increase in the GCR intensity in many regions of the heliosphere. This paper discusses the process of changing the polarity distribution of heliospheric magnetic fields due to the interaction of SW streams for Carrington rotation no. 2066 of different speeds, the simple model of the heliospheric magnetic field without an interaction between the SW streams of different speeds, as well as the results of numerical two-dimensional finite-difference calculations of longitude-averaged GCR intensity with the use of this model in comparison with a three-dimensional Monte Carlo calculation based on three-dimensional magnetohydrodynamic simulation of the heliosphere.
The effects of the 22-year variation of solar magnetic fields in the galactic cosmic ray (GCR) intensity were first observed and interpreted as manifestations of inversion of the high-latitude solar ...magnetic field in properties of heliospheric magnetic fields by the Lebedev Physical Institute team in 1973. Since then, these effects have been studied already for 50 years.
The situation with the heliospheric magnetic field is clear for periods of medium and low sunspot activity — the heliosphere consists of two unipolar “hemispheres” separated by a wavy global heliospheric current sheet and characterized by a general polarity A (unit quantity with the sign of the radial component of the heliospheric magnetic field in the northern hemisphere). Yet there is no consensus on what the inversion of the heliospheric magnetic field is and which effects in the GCR intensity are connected with this phenomenon.
In this article, we briefly formulate general concepts of the 22-year variation in characteristics of the Sun, heliosphere, and GCR intensity and discuss the observed effects in the GCR intensity, which we attribute to the heliospheric magnetic field reversal. Models for this phenomenon and the results of GCR intensity calculations with these models will be discussed in the next article.
The regions of interaction between solar wind streams of different speed, known as corotating interaction regions, form an almost constantly existing structure of the inner heliosphere. Using ...observational data on the main characteristics of the heliosphere, important for GCR modulation, and the results of 3D MHD modeling of corotating interaction regions, and Monte Carlo simulation of recurrent GCR variations, we analyze the importance of the corotating interaction regions for longitude-averaged characteristics of the heliosphere and GCR propagation, and possible ways for simulating long-term GCR intensity variations with respect to the corotating interaction regions.
On the basis of the temporal behavior of the galactic cosmic rays and the heliospheric factors observed in 2007–2008 and 2014–2015, their average heliolongitude distributions are formed and compared. ...In addition to the neutron monitor data, the provisional database of daily average galactic cosmic ray proton intensities measured by the PAMELA satellite-borne experiment in 2006–2015 is used. It is shown that the properties of the heliolongitude distributions in the above periods are substantially different.
This article presents the results of comparative analysis of diffusion and chemical processes running upon contact interaction with processed material of a regular cutting tool and of a tool with the ...surface layer of the working part modified by the impact of gas discharge.
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