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.
Since the International Geophysical Year (1957), the Lebedev Physical Institute performs the regular measurements of charged particle fluxes in the Earth's atmosphere (from the ground level up to ...30–35km) at several latitudes. The unique experimental data base obtained during 58 years of cosmic rays observations in the atmosphere allows to investigate temporal, spatial and energetic characteristics of galactic and solar cosmic rays as well as the role of charged particles in the atmospheric processes. Analysis of this data base also revealed a special class of numerous events caused by energetic electron precipitation recorded in the atmosphere at polar latitudes. In this paper we present Catalogue of electron precipitation events observed in the polar atmosphere during 1961–2014 and briefly outline the previous results of this data set analysis.
•Regular measurements of cosmic rays in the Earth's atmosphere (0–35km) since 1957.•A special class of events caused by energetic electron precipitation at polar latitudes is defined.•More than 550 events of precipitating electron events are recorded during 58 years of observations.•Characteristics of precipitating electron spectra are determined.•We present the Catalogue of electron precipitation events observed during 1961–2014.
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.
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
Since the middle of 1957 till present time the group of researchers of P.N. Lebedev Physical Institute of the Russian Academy of Sciences has carried out the regular balloon borne measurements of ...charged particle fluxes in the atmosphere. The measurements are performed at polar (northern and southern) and middle latitudes and cover the interval of heights from the ground level up to 30–35
km. Standard detectors of particles (gas-discharged counters) have been used. More than 80,000 measurements of cosmic ray fluxes in the atmosphere have been performed to the present time. In the data analysis the geomagnetic field and the Earth’s atmosphere are used as cosmic ray spectrometers.
The main goals of observations are the investigations of galactic cosmic ray modulation in the heliosphere, solar cosmic ray generation and propagation, precipitation of energetic electrons from the Earth’s magnetosphere, study of the role of charged particles in the atmospheric processes. Now we have got a large amount of unique data on galactic and solar particles in the energy range of 0.1–20
GeV for the period of 50
years (1957–2007).
In this paper, the main results obtained from the long-term measurements of charged particles in the atmosphere on the problems mentioned above are presented.
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.
A study of the long-term modulation of galactic cosmic rays in positive and negative phases of the 22-year solar magnetic cycle, including a period of anomalously low solar activity between 2008 and ...2020 is performed. Solar magnetic field lines reconnect with galactic ones in the negative phases. In the positive phases, there is a magnetic barrier between these fields that must be considered when describing the modulation of galactic cosmic rays.
The effect the three-component heliospheric magnetic field has on the modulation of galactic cosmic rays is considered. Radial and longitudinal components of the model are associated by the familiar ...Parker ratio. The latitudinal component is proportional to the radial one and emerges if the dependence of the latter deviates from the law of inverse squares. The model is tested using the problem of galactic proton modulation.
