By Viktor ORAYEVSKY, Dr. Sc. (Phys. & Math.), Director of the RAS Institute of Terrestrial Magnetism, Ionosphere and Propagation of Radio-Waves, Vladimir KUZNETSOV, Dr. Sc. (Phys. & Math.), First Deputy Director of the Institute

Today we would like to bring to the attention of our readers one of Russia's unique centers of research - the RAS Institute of Terrestrial Magnetism, Ionosphere and Propagation of Radio-Waves (IZMIRAN). Its main areas of research cover the physics of the Sun and solar-terrestrial physics, magnetism of the Earth and other planets, their ionospheres and magnetospheres and the propagation of radio-waves. Institute scientists also specialize in geophysics, ecology, cartography and other related areas. Brief geomagnetic forecasts prepared by IZMIRAN are shown on Russian TV on a daily basis. All of these studies are being conducted on what we call a comprehensive basis-the principle established by the first IZMIRAN Director, Nikolai Pushkov, Dr. Sc. (Phys. & Math.) (1903 - 1981). The progress of research over the past few decades has proved the viability of this approach.

IZMIRAN GENEALOGY

The predecessor of IZMIRAN - the Scientific Research Institute of Earth Magnetism - was established on October 11, 1939 by a government decree as a center of geomagnetic and ionospheric studies. Its facilities included a magnetic observatory and ionospheric station in Pavlovsk (Leningrad Region) and the Bureau of General Magnetic Surveying (Leningrad). The program of research of the new center, besides studies of the topology of the geomagnetic field, its sources, anomalies and variations in time for the needs of navigation and geological studies, also included observations of the Sun, ionosphere, ionospheric and magnetic disturbances and short-range forecasts of the state of the magnetic field.

During the Great Patriotic War with Nazi Germany (1941 - 1945) institute scientists prepared long-term ionospheric forecasts required by the army, magnetic maps for different arms of the army and the navy and conducted observations of sun-spots and cosmic rays.

In 1944, the Institute returned from evacuation but not back to Pavlovsk, ruined by the Nazis, but to a new location at the 40th kilometer of the Kaluzhskoye Highway near Moscow (now the town of Troitsk*) where it remains to this day. Only a couple of its

* See: V. Matveyev, V. Laptev, "From Cloth Mill to Basic Research", Science in Russia, No. 6, 1999. - Ed.

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departments-of magnetic surveys and magnetic cartography-returned to Leningrad forming the Leningrad (now St. Petersburg) branch of the Institute. The scale of the institute activities was considerably enlarged from 1945 so that its researchers had to prepare ionospheric forecasts required by federal short-wave radio communications agencies and services.

Because of a significant expansion of studies of the ionosphere and radio-wave propagation, the Institute was transferred in 1956 from the administration of the Main Directorate of the State Hydrometeorological Service to the USSR Ministry of Communications and given the official name of the Scientific Research Institute of Terrestrial Magnetism, Ionosphere and Propagation of Radio-Waves.

The historic launch of the first Soviet space satellite in 1957 opened up before the Institute scientists some truly grand and fascinating prospects for studies of the magnetic field and the ionosphere of the Earth and planets, the Sun and solar- terrestrial links. The third Soviet space satellite carried a special magnetometer for magnetic field measurements in near-Earth space. And unique research instruments developed by Institute scientists made it possible to gather unique data on the magnetic fields in near-Earth space and the Moon.

The steadily broadening range of Institute studies on the fundamental problems of solar-terrestrial physics, geophysics and active participation in space research prompted the inclusion in 1959 of the Institute into the system of research centers of what was then the USSR Academy of Sciences with its present name (IZMIRAN). Set up on its basis and with the active participation of its experts in the subsequent years were the Academy's Polar Institute of Geophysics (1960, Murmansk), the Siberian Institute of Terrestrial Magnetism, Ionosphere and Radio-Waves Propagation (1961, Irkutsk)-now the Institute of Solar-Terrestrial Physics- and the Institute of Cosmophysical Studies and Aeronomics (1960s, Yakutsk).

SOLAR-TERRESTRIAL PHYSICS AND SPACE WEATHER

One of the main areas of IZMIRAN research today are studies of our luminary and solar-terrestrial links. Its importance has been accentuated in recent years by the growing awareness in world science of the impact of solar activity on physical processes occurring on this planet, in near-Earth space-magnetosphere and ionosphere, on geological environment and various areas of human activity. These studies are carried out by ground and orbital stations with the latter providing the most significant results, such as observations in the X-ray and ultraviolet bands which can be conducted only from space.

The main "source" of weather in space is the Sun, which is a frequent source of "disturbances" on and around our planet. Suffice it to say that during the 11 -year cycle of solar activity there occur some 37,000 solar flares (according to observations during the 22nd cycle of 1986 - 1996). At the peak of a solar cycle there occurs an average of one flare within one to two hours, and at its minimum-one to two flares per day. At the peak of the cycle there occur 5 - 10 discharges of matter of the solar corona per day on the average. At the present time the luminary is near the peak of its 11 -year cycle (which was in April, 2000), and a high level of solar activity will continue for another two to three years. The maximum of the next-24th cycle, is expected in 2010 - 2013.

During each of these cycles there occur on the Earth due to various factors of solar activity (flares and shock waves they produce, discharges of matter of the corona, high-velocity currents of solar wind, etc.) some 500 magnetic storms. These storms affect the condition of people suffering from various ailments and have some dangerous and even catastrophic impacts upon different technical systems. One such example was an electric blackout for 9 hours in Quebeque, Canada, in March 1989 caused by induced induction current in power transmission networks and deactivation of emergency relays.

IZMIRAN is operating a Center of geophysical prognostication watching the levels of solar activity using ground and space data and informing the agencies concerned of the state of the Earth's magnetic field and expected magnetic storms. For example, a timely warning of an approaching magnetic storm in July, 2000 made it possible to forestall its negative impact on the Russian OKEAN-0 satellite and keep it in orbit (at that time the Japanese lost their expensive ASCA satellite). The Center also provided timely geomagnetic activity forecasts and the associated state of the ionosphere during the dramatic de-orbiting of the Russian MIR station and its sinking in the preplanned area on March 23, 2001.

For studies of the Sun and solar-terrestrial links at different stages of the 11-year solar cycle IZMIRAN scientists have developed the international CORONAS Program (Complex orbital near-Earth observations of solar activity) which is being successfully implemented. Within this program instruments on board the CORONAS- I satellite launched in 1994 observed the luminary near the minimum of its activity, and the CORONAS-F satellite (launched on July 31, 2001) is now investigating solar activity near the maximum of the current 23rd cycle. The orbit of the second probe (inclination-82.49 ^o , minimal distance from the Earth surface-500.9 km, maximum-548.5 km, period of revolution-94.859 min) provides for periodically recurrent sessions of continuous observations of our luminary (of up to 20 days) which is important for the monitoring of most of the solar events.

The main scientific objectives of the CORONAS-F project include studies of the global oscillations of the luminary and on this basis-the seismology of its bowels and inner structure, comprehensive studies of powerful dynamic processes of solar activity (flares, plasma discharges, active areas) within a broad range of wavelengths- from optical to gamma, and also of solar cosmic rays accelerated at periods of solar activity, conditions for their release and propagation in the interplanetary magnetic field, and the

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impact upon the magnetosphere of the Earth.

With the participation of experts from the RAS Lebedev Institute of Physics a new area of astrophysical studies is being implemented with the help of the CORONAS-F satellite. This is X-ray spectroscopy which makes it possible, using monochromatic images of the Sun, to reconstruct its three-dimensional structure and study the dynamics of plasma formations in its atmosphere within a broad range of the existing temperatures- from 50 thous to 50 mln degrees K. Thus it has been possible to identify for the first time plasma structures with temperatures of tens of millions of degrees which is ten times more than the temperature of the solar corona.

The satellite has been used to obtain more than 80,000 pictures of the Sun in different X-ray bands and scientists have reconstructed three-dimensional images and dynamics of the corona for separate periods of solar activity.

The high time and spectral resolution of the X-ray and gamma emissions ensured by the instruments of the satellite offer the researchers some unique data for the comprehension of high-energy phenomena occurring on the Sun. And the registration of solar cosmic rays within the medium-energy bands makes it possible to keep check on the radiation conditions in the near-Earth space and study solar-terrestrial links. CORONAS-F is also used for observations of global fluctuations of the Sun within the most informative ultraviolet band. Thanks to that scientists can better understand the inner structure of the luminary and the physical processes within its bowels.

INTERHELIOZOND, CORONOGRAF ET AL.

The IZMIRAN program of solar studies includes the projects like INTERHELIOZOND, CORONOGRAF and Polar-Ecliptic Patrol.

The program of the first one provides for a space probe in a heliocentric orbit performing numerous gravitational maneuvers near Venus. Because of its gravitational pull, and following a twisting trajectory, the probe will approach the luminary at distances at which it will "hover" over a chosen area of its surface for a week. This will make it possible to establish direct correlations-important for solar- terrestrial links-between phenomena on the Sun and in the interplanetary space. And since the distance of the probe from the luminary at the perihelion will measure one seventh of the distance from the Earth to the Sun, specialists will be able to examine its surface at a high spatial resolution, unattainable for our planet.

Orbiting the Sun in about one third of a year, the INTERHELIOZOND will assume different positions with respect to the Earth-Sun line, and observe the Sun from one side of this line and from the side invisible from the Earth. This will make it possible not only to conduct stereo observations of the Sun's surface and its corona, but to register discharges of solar matter propagating towards the Earth and also magneto- and ionospheric disturbances which would make it possible to conduct timely prognostications of their likely geomagnetic manifestations, such as magnetic storms. At the subsequent stages of its mission the probe, using the same gravitational maneuvers near Venus, will bend the

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place of its orbit with respect to the ecliptic plane and start observing the polar regions of the luminary with the processes of interactions of the magnetic field, spin and convection of solar matter which are important for the understanding of the solar cycle. The project should provide the answers to the key problems of solar-terrestrial physics and astrophysics concerning the mechanisms of heating of the solar corona, origin and acceleration of solar wind and the origin of the most powerful manifestations of solar activity-solar flares and discharges of matter of the corona.

Under the CORONOGRAF project a probe in a near-Earth orbit will "capture" on a monthly basis the shadow of the Moon from the Sun and observe a full solar eclipse- something which can be but seldom done (once in 2 years on the average) from the surface of the Earth. During solar eclipses (only) one can obtain unique images of the lowest strata of the solar corona and conduct detailed studies of their structure.

Under the project entitled "Polar-Ecliptic Patrol" scientists of the Institute will maintain non-stop monitoring of solar activity and solar wind, solar discharges moving in the direction of the Earth and heliospheric disturbances as well as conduct observations of the Sun's polar regions and its reverse side. With this aim in mind two

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minor space probes will be place in polar (or at an angle of 45 ^o to the ecliptic plane) heliocentric orbits at a distance of 0.5 astronomical units from the Sun so that the planes of their orbits will be perpendicular to one another and the probes themselves will be spaced in their orbits by a quarter period (period-about 130 days). With the orbital arrangement of this kind one of the probes will be monitoring without interruptions (and both of these probes for some long period of time) the luminary along the Sun-Earth line. As a result monitoring will be maintained both in the near- ecliptic and near-polar regions. This will make it possible to conduct uninterrupted studies of the low and high-velocity solar wind and will provide a three-dimensional picture of the solar corona and solar discharges. Over separate periods one of the probes will be positioned with respect to the Sun-Earth line in another, than the Earth hemisphere, thus being able to "observe" the reverse side of the Sun, invisible from the Earth.

In a word, the Polar-Ecliptic Patrol Project will supply an uninterrupted flow of information required for space weather monitoring for studies of solar-terrestrial links and for issuing warnings of the coming "terrestrial echos" of solar storms.

MAGNETO- AND IONOSPHERIC PHYSICS

Our scientists have obtained some interesting results in their magnetic studies during the many voyages to the little studied regions of the world ocean of the non-magnetic vessel ZARYA (1970s-1980s). They carried out an analysis of the global data on the secular pattern of the geomagnetic field and built the corresponding analytical models.

In the KHIBINY experiment (1980s) scientists put into practice what they called the method of in-depth electromagnetic sounding, developed with the participation of IZMIRAN, for studies of the geological structure of the earth crust on the basis of induced geomagnetic field disturbances produced with the help of a powerful MHD- generator. Our specialists had a key role to play in the processing and interpretation of data obtained in this experiment both on dry land and on the Barents Sea shelf. These results are of great importance for minerals prospecting and the identification of promising oil and gas-bearing regions on the European territory of Russia.

With the help of bottom magnetic stations developed at IZMIRAN in the 1980s scientists measured geomagnetic field variations in some regions of the Caspian Sea bottom. On the their basis they built models of distribution of conductivity under the bottom of the Caspian Sea (South Caspian megade-pression) which will facilitate studies of the mineral wealth of this region. Within the framework of the international project VENUS-HALLEY COMET (1984 - 1986) scientists placed on board the VEGA-1 and VEGA-2 space probes some instruments developed at IZMIRAN (or with its participation), including a TV guidance transmitter, MIS HA magnetometer and plasma waves analyzer. These instruments helped obtain unique data on the electromagnetic wave processes in the near-comet region, measure electric field amplitudes at low frequencies and assess the magnetic field and its variations near Halley's comet. Our researchers determined the mechanisms of super long-distance propagation of radio short waves and the role of nonuniformities of electron concentration in the ionosphere and the conditions at which an interlayer channel in the ionosphere can provide for a waveguide propagation of radio signals with exceptionally low losses. Also studied were the effects of the non-linear scattering of radio waves leading to their capture in the ionospheric channel and the processes of withdrawal of electromagnetic energy from it. Scientists developed methods of calculation of the trajectory of radio

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signals in the tri-dimensional non-uniform multilayer ionosphere and global models of absorption at radio channels in the short-wave band. The state of the ionosphere was studied by the method of vertical, inclined and reverse-inclined pulsed sounding with the help of instruments developed at IZMIRAN. These included the SOIKA-600 highla automated digital ionospheric station, the BASIS station, a special multi- frequency unit and a multi-frequency device for the phase sounding of ionosphere. These and other such diagnostic instruments designed and built at our center made it possible for a team of Russian scientists to carry out a number of studies of the processes of modification of the ionosphere under the impact of powerful radio emissions.

The launches of the first artificial earth satellites made it possible for specialists of our Institute to gather over the past decades a wealth of factual data on the status and behaviour of the ionosphere. During the 3 years of operation of the INTERCOSMOS- 19, developed under the guidance of IZMIRAN experts and launched in 1979, scientists conducted studies of the ionosphere by the method of pulse sounding. They also studied processes occurring in it above the main maximum of electron concentration, and obtained data on its disturbances caused by powerful radio emissions. The COSMOS-1809 probe (launched in 1986) provided for a global control of the environment, including the condition of the ionosphere, for making forecasts of radio waves propagation and dealing with a range of other applied problems.

Incidentally, it was INTERCOSMOS-19 which first registered the low-frequency noise radio emission which appears in the ionosphere over the areas of earthquakes before and during such events and this triggered studies of the mechanisms of interaction of the lithosphere with the atmosphere and the ionosphere of the Earth. Later on this area of research became one of the major ones at our Institute. It is based on the fact that processes taking place in the earth crust before an earthquake at its center change the composition of ground waters and atmospheric gases, boost the intensity of outbursts of radioactive matter and charged aerosols into the Earth atmosphere. This, in its turn is the cause of developing temperature anomalies in these zones and affects the electrical conductivity of the near-ground atmosphere and electric current parameters in the Earth-ionosphere chain. Thus before an earthquake there occur in the area over the active zone a modification of all the basic characteristics of the ionosphere-magnetic field intensity, rate of transfer of plasma and its ionic composition, electron concentration distribution by height, structure of small-scale ionospheric nonuniformities and lengthwise currents, wave emissions in different frequency bands, etc. The aforesaid disturbances of the medium can be registered by modern space probes. And since they are formed in the ionosphere within hours, days or even weeks (depending on the nature of disturbance) before the onset of a quake they can be regarded as ionospheric forerunners and used for earthquake prognostication. These problems have been put on the agenda of the VULKAN space project and the SEISMO-PROGNOZ-SM experiment on board of the Russian segment of the International Space Station and will be accomplished with the IZMIRAN participation under the aegis of ROSAVIACOSMOS.

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The IZMIRAN staff today consists of some 700 including 330 research scientists. The center includes its St. Petersburg, Kaliningrad and newly formed Vladikavkaz branches.

Our current studies, technical and technological R&D make it possible to "transfer" fundamental knowledge into various areas of human activity, such as navigation, geology, cosmonautics, medicine, ecology, development of various advanced rario systems and so on and so forth.

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