Solar-terrestrial Relationships Research Articles

Testing the effect of solar wind parameters and geomagnetic storm indices on Galactic cosmic ray flux variation with automatically-selected Forbush decreases

Forbush decrease (FD), discovered by Scott E. Forbush about 80 years ago, is referred to as the non-repetitive short-term depression in Galactic cosmic ray (GCR) flux, presumed to be associated with large-scale perturbations in solar wind and interplanetary magnetic field (IMF). It is the most spectacular variability in the GCR intensity which appears to be the compass for investigators seeking solar-terrestrial relationships. The method of selection and validation of FD events is very important to cosmic ray (CR) scientists. We have deployed new computer software to determine the amplitude and timing of FDs from daily-averaged CR data at Oulu Neutron Monitor station. The code selected 230 FDs between 1998 and 2002. In an attempt to validate the new FD automated catalog, the relationship between the amplitude of FDs, and IMF, solar wind speed (SWS) and geomagnetic storm indices (Dst, kp, ap) is tested here. A two-dimensional regression analysis indicates significant linear relationship between large FDs (CR(%) ≤ –3) and solar wind data and geomagnetic storm indices in the present sample. The implications of the relationship among these parameters are discussed.

FEATURES OF DISTRIBUTION OF SEISMIC ACTIVITY IN DIFFERENT REGIONS OF EARTH OVER PHASES OF THE 11-YEAR SOLAR CYCLE

We discuss the relationship of solar activity with the seismicity of Earth and reasons for the differences in the results of studies of various authors. Using the epoch superposition method, we analyze the differences in seismic activity distribution over phases of the 11-year solar cycle for the whole world, hemispheres, sectors, latitudinal belts, and individual regions. The northeastern sector of Earth has been shown to make the main contribution to the planetary distribution of seismic activity over phases of the 11-year solar cycle. We have revealed a pattern in the distribution of seismic activity over latitudinal belts: the solar cycle phases, at which the main maximum of seismic activity occurs, increase with increasing latitude in both hemispheres. For some regions, the results may differ from the generalized results for Earth due to the influence of local geodynamic conditions during the destruction of the earth's crust. In middle latitudes, the maximum number of earthquakes is shifted to the later phases of the solar cycle from west to east, which was not found for the northern regions. We discuss possible reasons for various manifestations of solar-terrestrial relationships for different regions, taking into account their different structure and geodynamic development modes. The presence of pronounced maxima of the seismic activity distribution over the 11-year solar cycle phases allows us to use them for refining the “time” parameter in the medium-term prediction of dangerous earthquakes.

Особенности распределения сейсмической активности в разных регионах Земли по фазам 11-летнего солнечного цикла

We discuss the relationship of solar activity with the seismicity of Earth and reasons for the differences in the results of studies of various authors. Using the epoch superposition method, we analyze the differences in seismic activity distribution over phases of the 11-year solar cycle for the whole world, hemispheres, sectors, latitudinal belts, and individual regions. The northeastern sector of Earth has been shown to make the main contribution to the planetary distribution of seismic activity over phases of the 11-year solar cycle. We have revealed a pattern in the distribution of seismic activity over latitudinal belts: the solar cycle phases, at which the main maximum of seismic activity occurs, increase with increasing latitude in both hemispheres. For some regions, the results may differ from the generalized results for Earth due to the influence of local geodynamic conditions during the destruction of the earth's crust. In middle latitudes, the maximum number of earthquakes is shifted to the later phases of the solar cycle from west to east, which was not found for the northern regions. We discuss possible reasons for various manifestations of solar-terrestrial relationships for different regions, taking into account their different structure and geodynamic development modes. The presence of pronounced maxima of the seismic activity distribution over the 11-year solar cycle phases allows us to use them for refining the “time” parameter in the medium-term prediction of dangerous earthquakes.

Historical Database of Geomagnetic and Auroral Activity for the Study of Solar–Terrestrial Relationships

In situ data on geomagnetic and auroral activity obtained in recent years has contributed to a greater understanding of solar–terrestrial processes. However, because space exploration began only in the middle of the 20th century, in situ data are insufficient to analyze geomagnetic variations and solar-activity variations on a time scale from decades to centuries. The Russian network of magnetic and meteorological observatories provides one of the longest data series. For example, the magnetograms from St. Petersburg (SPE), Pavlovsk (SLU), and Voeikovo (LNN) stations provide long series of continuous records of variations of declination (D) and horizontal (H) and vertical (Z) components of the geomagnetic field. The aim of this paper is to make this data publicly available. For this purpose, a specialized database has been developed for the study of various aspects of solar–terrestrial relationships, including heliobiomagnetology. The database contains (1) digital images of analog magnetograms from SPE (1869–1877) and SLU (1878–1921, images for 1921–1941 are still being scanned), (2) hourly values of declination D and horizontal H and vertical Z components of the geomagnetic field obtained at SPE and SLU stations for 1869–1914, (3) data on geomagnetic storms from the SLU station for 1878–1941 and from the LNN station for 1947–1954, and (4) data on aurora borealis observed at 141 stations of the Russian Meteorological Network for 1837–1909. The database is designed to provide online access to the Russian collection of historical data on geomagnetic and auroral activity. On this basis, it is possible to carry out research on various aspects of space weather and climate and use it, among other things, to solve problems of heliomagnetobiology. Users are provided with easy access to individual magnetograms at different zoom levels. Online access will allow a wide range of researchers to use these databases to solve problems related to historical space weather data.

Resurrecting Maunder’s ghost: John ‘Jack’ Eddy, the Maunder Minimum, and the rise of a dilettante astrophysicist

SUMMARYDuring the 1970s, widespread scientific interest in the risks of climate change prompted John A. Eddy (1931–2009), an astrophysicist with the National Center for Atmospheric Research in Boulder, CO, to investigate whether sunspots could be used to predict future climate changes. Methodologically, Eddy’s investigations were uniquely historical in nature. By interrogating old manuscripts of solar observations since the early seventeenth century, he identified what appeared to be a correlation between the so-called Maunder Minimum – a virtual cessation of sunspots between 1645 and 1715 – and severely cold temperatures during the Little Ice Age. While he could not identify the physical mechanisms that governed solar-climate relationships, this historical episode fostered his curiosity. Fortuitously, Eddy’s solar-climate research coincided with efforts to use satellites to monitor and record variations in solar energy output, which in context constituted a significant development in managing environmental and technological risk.But using the Maunder Minimum to advance the frontiers of knowledge about solar-terrestrial relationships was not Eddy’s only – or even primary – motivation. In the mid-1840s, German astronomer Heinrich Schwabe (1789–1875) discovered what appeared to be a decadal sunspot cycle, the existence of which inspired generations of astrophysicists to more precisely estimate its length as well as determine its underlying causes. Eddy, however, came to believe that the astronomical community failed to consider the implications of subsequent evidence suggesting that Schwabe's solar cycle was not an enduring characteristic of the sun. Instead, he reasoned that evidence offered by nineteenth-century European astronomers Gustav Sporer and Edward Maunder in the 1880s and 1890s had been entirely overlooked. But rather than arguing that their evidence was overlooked in error, Eddy identified what he cast as a conspiracy of wilful ignorance on the part of a staid and conservative astronomical community. By utilizing Eddy's private hand-written notes as they appeared in undergraduate lectures, public speeches and academic talks, as well as his appreciation for the seminal views of sociologist of science Thomas Kuhn, I show that Eddy sought to rectify this injustice by proposing a contrasting vision of science as an interdisciplinary, collaborative and creative process of exploring the ignored areas between scientific disciplines.

Exposure of the solar system and the earth to external influences

The present review article is devoted to the consideration of the causes of the practically crisis state of study and unsuccessful attempts to explain the solar–terrestrial relationships. It substantiates the need to take into account the endogenous activity of the Earth, (in addition to solar activity and fluxes of galactic cosmic rays). Solar activity and fluxes of galactic cosmic rays contribute to their respective roles and share of external impact on the Earth. When all three external factors of influence on the Earth are taken into account, mechanisms, cyclicity, energetics, polar asymmetry, synchronism, variations in the shape of the Earth, the level of the ocean, gravity, seismicity and volcanism become understandable, as well as the previously unexplained events and processes of manifestation solar–terrestrial relationships. Endogenous activity of the Earth is caused by the gravitational actions of the Moon, the Sun and other planets in the process of barycentric motion of the solar system in the gravitational field of the Galaxy. It is shown that, under external influence on the solar system, the Earth’s shells respond to it synchronously with the responses of the observed layers of the Sun’s atmosphere.

A Heuristic Approach to Remove the Background Intensity on White-light Solar Images. I. STEREO/HI-1 Heliospheric Images

Abstract White-light coronal and heliospheric imagers observe scattering of photospheric light from both dust particles (the F-Corona) and free electrons in the corona (the K-corona). The separation of the two coronae is thus vitally important to reveal the faint K-coronal structures (e.g., streamers, co-rotating interaction regions, coronal mass ejections, etc.). However, the separation of the two coronae is very difficult, so we are content in defining a background corona that contains the F- and as little K- as possible. For both the LASCO-C2 and LASCO-C3 coronagraphs aboard the Solar and Heliospheric Observatory (SOHO) and the white-light imagers of the SECCHI suite aboard the Solar Terrestrial Relationships Observatory (STEREO), a time-dependent model of the background corona is generated from about a month of similar images. The creation of such models is possible because the missions carrying these instruments are orbiting the Sun at about 1 au. However, the orbit profiles for the upcoming Solar Orbiter and Solar Probe Plus missions are very different. These missions will have elliptic orbits with a rapidly changing radial distance, hence invalidating the techniques in use for the SOHO/LASCO and STEREO/SECCHI instruments. We have been investigating techniques to generate background models out of just single images that could be used for the Solar Orbiter Heliospheric Imager and the Wide-field Imager for the Solar Probe Plus packages on board the respective spacecraft. In this paper, we introduce a state-of-the-art, heuristic technique to create the background intensity models of STEREO/HI-1 data based solely on individual images, report on new results derived from its application, and discuss its relevance to instrumental and operational issues.

Effects of Forbush decreases of galactic cosmic rays on anticyclone activity at middle latitudes

The baric response of the lower atmosphere to Forbush decreases of galactic cosmic rays (GCRs) is investigated. It is shown that Forbush decreases are accompanied by a weakening of cyclonic activity and a strengthening of anticyclonic activity at the extratropical latitudes (45°–70°) of the Northern and Southern hemispheres. These results show an important role of cosmic rays in solar-terrestrial relationships.

Reconstructing Holocene geomagnetic field variation: new methods, models and implications

Reconstructions of the Holocene geomagnetic field and how it varies on millennial timescales are important for understanding processes in the core but may also be used to study long-term solar-terrestrial relationships and as relative dating tools for geological and archaeological archives. Here, we present a new family of spherical harmonic geomagnetic field models spanning the past 9000 yr based on magnetic field directions and intensity stored in archaeological artefacts, igneous rocks and sediment records. A new modelling strategy introduces alternative data treatments with a focus on extracting more information from sedimentary data. To reduce the influence of a few individual records all sedimentary data are resampled in 50-yr bins, which also means that more weight is given to archaeomagnetic data during the inversion. The sedimentary declination data are treated as relative values and adjusted iteratively based on prior information. Finally, an alternative way of treating the sediment data chronologies has enabled us to both assess the likely range of age uncertainties, often up to and possibly exceeding 500 yr and adjust the timescale of each record based on comparisons with predictions from a preliminary model. As a result of the data adjustments, power has been shifted from quadrupole and octupole to higher degrees compared with previous Holocene geomagnetic field models. We find evidence for dominantly westward drift of northern high latitude high intensity flux patches at the core mantle boundary for the last 4000 yr. The new models also show intermittent occurrence of reversed flux at the edge of or inside the inner core tangent cylinder, possibly originating from the equator.

The STARE/SABRE story

Abstract. In January 1977 a new type of radar aurora experiment named STARE (Scandinavian Twin Aurora Radar Experiment) commenced operation in northern Scandinavia. The purpose of the experiment was two-fold: to make observations of the nature of radar auroras, and to contribute to the study of solar–terrestrial relationships (or space weather). The experiment was designed for automatic continuous operation, and for nearly two and a half decades it provided estimates of electron flows with good spatial coverage and resolution and good time resolution. It was a successful experiment that yielded a wealth of observations and results, pertaining to, and based on, the observed time variations of the electron flows and to the spatial flow pattern observed at any given time. This radar system inspired the creation of a similar system, SABRE (Sweden And Britain Radar Experiment), which increased the field of view towards the southwest of STARE. This system commenced operation in 1982.

Atmospheric pressure variations at extratropical latitudes associated with Forbush decreases of galactic cosmic rays

Changes of troposphere pressure associated with short-time variations of galactic cosmic rays (GCRs) taking place in the Northern hemisphere’s cold months (October–March) were analyzed for the period 1980–2006, NCEP/NCAR reanalysis data being used. Noticeable pressure variations during Forbush decreases of GCRs were revealed at extratropical latitudes of both hemispheres. The maxima of pressure increase were observed on the 3rd–4th days after the event onsets over Northern Europe and the European part of Russia in the Northern hemisphere, as well as on the 4th–5th days over the eastern part of the South Atlantic opposite Queen Maud Land and over the d’Urville Sea in the Southern Ocean. According to the weather chart analysis, the observed pressure growth, as a rule, results from the weakening of cyclones and intensification of anticyclone development in these areas. The presented results suggest that cosmic ray variations may influence the evolution of extratropical baric systems and play an important role in solar-terrestrial relationships.

Spatial Distribution of Seismicity: Relationships with Geomagnetic Z-Component in Geocentric Solar Magnetospheric Coordinate System

For 173477 epicenters of earthquakes with М ≥ 4.5, which occurred at the globe in 1973-2010, the geomagnetic Z-component in Geocentric Solar Magnetospheric (GSM) coordinate system were evaluated for the moment of earthquake occurrence on the base of the International Geomagnetic Reference Field model (IGRF-10). It is found that in the regions, where the ZGSM reaches large positive value (low and middle latitudes), earthquake occurrence is higher than in the regions where ZGSM is mainly negative (high latitudes). In the area of strongest seismicity at the globe, which is located in the longitudinal ranges of about 1200E - 1700W, the values of ZGSM are the most high at the globe. It is found that statistically significant dependence, with correlation coefficient R = 0.91, exists between the maximal possible magnitude of earthquake (Mmax) and the logarithm of absolute value of ZGSM . We suggest that earthquake occurrence is triggered by the perturbations, which in first occur at the magnetopause due to reconnection of the magnetic field of the solar wind with the Earth’s magnetic field, and then propagate into the solid earth via the GEC, which is considered at present as a main applicant for a physical mechanism of solar-terrestrial relationships. It is clear that much work remains to further verify this speculative assertion and to find the physical processes linking seismicity with the main geomagnetic field structure.

Reconstructing the Holocene geomagnetic field

Knowledge of the Holocene evolution of Earth's magnetic field is important for understanding geodynamo processes in the core, is necessary for studying long-term solar-terrestrial relationships, and can provide useful age constraints for archeologicaland stratigraphic applications. Continuous time-varying global field models based on archeo- and paleomagnetic data are useful tools in this regard. We use a comprehensive data compilation and recently refined modelling strategies to produce CALS10k.1b, the first time-varying spherical harmonic geomagnetic field model spanning 10 ky. The model is an average obtained from bootstrap sampling to take account of uncertainties in magnetic components and ages in the data (and hence has version number 1b instead of 1). This model shows less spatial and temporal resolution than earlier versions for 0–3 ka, and particularly aims to provide a robust representation of the large-scale field at the core-mantle boundary (CMB). We discuss the geomagnetic dipole evolution and changes in Holocene magnetic field morphology at the CMB as shown by the new reconstruction. The results are compatible with earlier models ( CALS3k.3 and CALS3k.4) for 0–3 ka, but reveal some clear deficiencies in the 0–7 ka CALS7K.2 model prior to 3 ka. CALS10k.1b is able to resolve mobile and structurally-evolving high latitude radial field flux lobes at the CMB in both hemispheres, as well as persistent non-zonal structure, in the 10 ky average. Contributions to the average field from time-varying structures in the equatorial Indonesian–Australian region are particularly striking.

Global factors in dynamics of petrophysical processes

In classical description of structural-tectonic fragments of earth crust vast territories of ancient platforms are represented as geodynamically passive elements of lithosphere. That is why nature of various phenomena occurring on platform (landslides and karst-suffosion processes, rock bursts and gas explosions in mines, pipeline breaks, etc.) is usually associated solely with processes of exogenous changes in geological environment, formed by rocks of sedimentary cover [Natural Hazards in Russia, 2002]. However, results of many years investigations of geodeformation regimes of geodynamically (seismically) active and platform regions allowed experimentally establish [Rudakov, 2009] that in preparation of catastrophic geodynamic phenomena (earthquakes and volcanic eruptions) prominent role played by processes of global change of stress-strain state of lithosphere due to processes of self-organization under influence of Earth velocity rotation variations. In particular, it was shown that these processes are reflected in changes of fluid dynamic regimes of fault structures of East European Platform (EEP), influencing processes of exogenous geological environment transformation, and, appearing in rocks of sedimentary cover by local geodynamic processes and phenomena. For example, it was found that dynamics of accidents on routes of gas pipeline networks of EEP is connected with wave motion of platform, as well as with processes of cyclic fluid transmission in fault transcontinental and regional tectonic formations that form dynamics of karst-suffosion processes in territories of Moscow depression [Rudakov, 2008]. Continuing to investigate links in chain of cause-effect dependence of local geodynamic phenomena and processes from processes of global change in stress-strain state of earth's crust, we made spectral and correlation analysis of a half century (49 years) time series of mean annual cases of karst gap formation in Dzerzhinsk, Nizhny Novgorod region in comparison with variations of water level in Oka River, which flows in area, variations in Earth's rotation and change in solar activity. It allowed to trace development of karst-suffosion processes influenced by changes in fluid dynamic regimes in region controlled by variations in stress-strain state of earth's crust in region associated with variations in Earth's rotation and changes in solar activity, controlling climate changes on Earth as a whole, and in each particular region of planet. Note that problem of assessing influence of solar-terrestrial relationships in processes of terrestrial atmosphere, hydrosphere, and even biosphere, after A.L. Chizhevsky concerned by many researchers [Rivin, 1989] but geological and geophysical aspects of this problem are practically not affected. Especially not enough investigated processes that control in platform conditions development of exogenous processes, such as karst-suffosion. And in this respect opportunity to examine longterm observations, of the Dzerzhinsk karst observatory” of Nizhny Novgorod region allowed, as it seems to us, to take another step toward assessing extent of planetary processes influence on dynamics of geodynamic processes of local scale. Fig. 1 shows original time series of mean annual variations of Earth's rotation velocity (relative value), solar activity (Wolf numbers), cases of karst gaps in Dzerzhinsk and water level in Oka river, which were analyzed on basis of calculation spectral-temporal and correlation characteristics of these time series and their components identified by energy filtering. Fig. 2 shows calculated values of cross-correlation function (CCF) between analyzed time series.

A novel technique to measure intensity fluctuations in EUV images and to detect coronal sound waves nearby active regions

Context. In the past years, evidence for the existence of outward-moving (Doppler blue-shifted) plasma and slow-mode magnetoacoustic propagating waves in various magnetic field structures (loops in particular) in the solar corona has been found in ultraviolet images and spectra. Yet their origin and possible connection to and importance for the mass and energy supply to the corona and solar wind is still unclear. There has been increasing interest in this problem thanks to the high-resolution observations available from the extreme ultraviolet (EUV) imagers on the Solar TErrestrial RElationships Observatory (STEREO) and the EUV spectrometer on the Hinode mission. Aims. Flows and waves exist in the corona, and their signatures appear in EUV imaging observations but are extremely difficult to analyse quantitatively because of their weak intensity. Hence, such information is currently available mostly from spectroscopic observations that are restricted in their spatial and temporal coverage. To understand the nature and origin of these fluctuations, imaging observations are essential. Here, we present measurements of the speed of intensity fluctuations observed along apparently open field lines with the Extreme UltraViolet Imagers (EUVI) onboard the STEREO mission. One aim of our paper is to demonstrate that we can make reliable kinematic measurements from these EUV images, thereby complementing and extending the spectroscopic measurements and opening up the full corona for such an analysis. Another aim is to examine the assumptions that lead to flow versus wave interpretation for these fluctuations. Methods. We have developed a novel image-processing method by fusing well established techniques for the kinematic analysis of coronal mass ejections (CME) with standard wavelet analysis. The power of our method lies with its ability to recover weak intensity fluctuations along individual magnetic structures at any orientation, anywhere within the full solar disk, and using standard synoptic observing sequences (cadence <3 min) without the need for special observation plans. Results. Using information from both EUVI imagers, we obtained wave phase speeds with values on the order of 60−90 km s −1 , compatible with those obtained by other previous measurements. Moreover, we studied the periodicity of the observed fluctuations and established a predominance of a 16-min period, and other periods that seem to be multiples of an underlying 8-min period. Conclusions. The validation of our analysis technique opens up new possibilities for the study of coronal flows and waves, by extending it to the full disk and to a larger number of coronal structures than has been possible previously. It opens up a new scientific capability for the EUV observations from the recently launched Solar Dynamics Observatory. Here we clearly establish the ubiquitous existence of sound waves which continuously propagate along apparently open magnetic field lines.

Search for periodicities of the Solar Irradiance Data from Earth Radiation Budget Satellite (ERBS) using Rayleigh Power Spectrum Analysis

The solar irradiance data plays a very important role for understanding of Solar internal Structure and the solar terrestrial relationships. The Total Solar Irradiance (TSI) is integrated solar energy flux over the entire spectrum which arrives at the top of the atmosphere at the mean sun earth distance. TSI has been monitored from several satellites, e.g. Nimbus 7, Solar Maximum Mission (SMM), The NASA, Earth Radiation Budget Satellite (ERBS), NOAA9, NOAA10, Eureca and the Upper Atmospheric Research Satellite (UARS) etc. From these observations it reveals that the total solar irradiance varies about a small fraction of 0.1 over solar cycle being higher during maximum solar activity condition. In the present paper we have analysed the solar irradiance data from ERBS during the time period from October 15, 1984 to October 15, 2003. First filtering the data by Simple Exponential Smoothing we have applied the Rayleigh Power Spectrum Analysis on the processed data in order to search for its time variation. Study exhibits multi-periodicities on these data around 7, 11, 42, 80, 104, 130, 160, 254, 536, 752, 1142, 1388, 2474 and 4951 days with very high confidence levels (more than 95%). Apart from these strong periods there are some other weak periods around 22, 47, 53, 67, 69, 149, 167, 365, 489 and 683 days. These periods are significantly similar with the periods of other solar activities which may suggest that solar irradiance may be associated with other solar activities.

Sixty-five years of solar radioastronomy: flares, coronal mass ejections and Sun–Earth connection

This paper will review the input of 65 years of radio observations to our understanding of solar and solar–terrestrial physics. It is focussed on the radio observations of phenomena linked to solar activity in the period going from the first discovery of the radio emissions to present days. We shall present first an overview of solar radio physics focussed on the active Sun and on the premices of solar–terrestrial relationships from the discovery to the 1980s. We shall then discuss the input of radioastronomy both at metric/decimetric wavelengths and at centimetric/millimetric and submillimetric wavelengths to our understanding of flares. We shall also review some of the radio, X-ray and white-light signatures bringing new evidence for reconnection and current sheets in eruptive events. The input of radio images (obtained with a high temporal cadence) to the understanding of the initiation and fast development in the low corona of coronal mass ejections (CMEs) as well as the radio observations of shocks in the corona and in the interplanetary medium will be reviewed. The input of radio observations to our knowledge of the interplanetary magnetic structures (ICMEs) will be summarized; we shall show how radio observations linked to the propagation of electron beams allow to identify small scale structures in the heliosphere and to trace the connection between the Sun and interplanetary structures as far as 4AU. We shall also describe how the radio observations bring useful information on the relationship and connections between the energetic electrons in the corona and the electrons measured in-situ. The input of radio observations on the forecasting of the arrival time of shocks at the Earth as well as on Space Weather studies will be described. In the last section, we shall summarize the key results that have contributed to transform our knowledge of solar activity and its link with the interplanetary medium. In conclusion, we shall indicate the instrumental radio developments at Earth and in space, which are from our point of view, necessary for the future of solar and interplanetary physics.

The atmospheric global electric circuit: An overview

Research work in the area of the Global Electric Circuit (GEC) has rapidly expanded in recent years mainly through observations of lightning from satellites and ground-based networks and observations of optical emissions between cloud and the ionosphere. After reviewing this progress, we critically examine the role of various generators of the currents flowing in the lower and upper atmosphere and supplying currents to the GEC. The role of aerosols and cosmic rays in controlling the GEC and linkage between climate, solar–terrestrial relationships and the GEC has been briefly discussed. Some unsolved problems in this area are reported for future investigations.

The contribution of this country's scientists to research on the ionosphere and solar-terrestrial relationships

This paper analyzes the achievements of our country's scientists in heliogeophysical studies in the period after the first International Geophysical Year (1957-58), the experience of which was taken into account in organizing and carrying out an array of projects in solar-terrestrial physics. The use of the first geophysical rockets and later of scientific satellites in the study of the ionosphere showed that fundamental improvements were needed in the theory of the formation of the ionosphere. It was necessary to construct de novo empirical and theoretical models of the spectra and fluxes of short-wavelength solar radiation from the x-ray to the UV range. To do this, a model of the sun's upper atmosphere was created in which the main role belongs to the transitional region between the chromosphere and the corona. © 2005 Optical Society of America

The Role of Nuclei-Nuclei Interactions in the Production of Gamma-ray Lines in Solar Flares

Dramatic extensions of experimental possibilities (spacecraft RHESSI, CORONAS-F and others) in solar gamma-ray astronomy call for urgent, detailed theoretical consideration of a set of physical problems of solar activity and solar-terrestrial relationships that earlier may have only been outlined. Here we undertake a theoretical analysis of issues related to the production of gamma-radiation in the processes of interactions of energetic (accelerated) heavy and middle nuclei with the nuclei of the solar atmosphere (the so-called i-j interactions). We also make an estimate of the contribution of these interactions to the formation of nuclear and isotopic abundances of the solar atmosphere in the range of light and rare elements. The analysis is carried out for solar flares in the wide range of their intensities. We compare our theoretical estimates with RHESSI observations for the flare of 2002 July 23. It was shown that the 24Mg gamma-ray emission in this event was produced by the newly generated Mg nuclei. With a high probability, the gamma-ray line emission of 28Si nuclei from this flare was generated by the same processes.