Laboratory of X-ray Astronomy of the Sun

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Solar Space Experiments in LPI

TESIS team

The Physics Institute of the Russian Academy of Sciences is one of the world leaders and the undisputed leader in Russia in the field of creating high-precision telescopes and spectrometers for space experiments to study the Sun on board of the artificial Earth satellites. In total, over the half-century history of research, the equipment built in the Lebedev Physics Institute worked on board of more than 30 spacecrafts satellites and geophysical rockets. At present, the LPIs space experiments are carried out within the framework of the CORONAS program of the Russian Academy of Sciences (Complex Orbital Observations Near-Earth of Activity of the Sun). The Head of Research and the Chief Constructor of these experiments is Sergey Vadimovich Kuzin.

Experiment on the second Earths artificial satellite (Sputnik-2)

The second Earths artificial satellite.
Left: installation of a container with scientific equipment. Right: Apparatus for studying the radiation of the Sun.

Experimental and theoretical studies of the solar x-ray radiation began at the Lebedev Physics Institute in the second half of the 1950s. Already on board of the second Earths artificial satellite, launched on 3 November 1957, using the equipment which was built at the Lebedev Physical Institute, was conducted the world's first satellite experiment measuring short-wave solar radiation. The Sun observations were carried out in several spectral ranges from 1 to 120 A, emitted by organic and metal filters. During this experiment, for the first time in the world, particles of the Earth's radiation belts were detected. Afterward, this discovery was confirmed in a similar experiment conducted by James Van Allen (James Van Allen) on the American first Earths artificial satellite Explorer-I

The first USSR rocket observations of the Sun and stations of the ELECTRON series

Artificial satellites, ELECTRON series.
Above: Electron-1 in two projections. Below: Electron-2 in two projections.

In 1959-1962, for the first time in the USSR, the LPI carried out rocket observations of the Sun in the x-ray range. Radiation from the Sun was recorded immediately in two spectral regions, which made it possible to determine the effective electron temperature of the plasma in the corona.

Since 1960, first on board of the spacecrafts, and afterward on the space stations Electron-2, Electron-4 and Venus-2, experiments had begun on a long-term (several months) research of solar activity. During these continuous solar observations, the relationship was established between long-term variations in the flux and spectral composition of x-ray radiation with the physical characteristics of active regions on the solar surface. It was also possible to locate the sources of x-ray radiation in the atmosphere of the Sun and establish that it is generated in the corona mainly above the active zones of the Sun.

The first photos x-ray photos of the Sun (USA, USSR)

The first x-ray photograph of the sun.
Received on 19 April, 1960 at the US Marine Research Laboratory in the spectrum of 20-60 Å.

The first x-ray photograph of the sun in the USSR.
Taken by the Lebedev Physical Institute on June 6, 1963.

Subsequently, the systematic satellite studies of the solar ultraviolet and x-ray radiation had started, which were simultaneously carried out at the Physics Institute of the USSR Academy of Sciences (FIAN) under the leadership of S.L. Mandelstam and the US Marine Research Laboratory (Naval Research Laboratory) under headed by Herbert Friedman.

The first photograph of the solar corona was taken on 19 April 1960 by the Friedmans team in the spectral range of 20-60 Å. This image showed that the short-wave radiation of the Sun is distributed unevenly in the corona and most of it comes from compact x-ray active regions located above the bright chromospheric floccules visible in the K line of ionized calcium CaII. The discovered sources of x-ray radiation coincided approximately in the same position as the solar decimeter radiation sources. The equipment used in the experiment was a simple camera- obscura with an aperture of 0.125 mm in diameter covered by an aluminized organic film and gave a resolution of about 0.1 of the solar diameter. Due to the rotation of the equipment, the taken images were blurred up to 170 on an arc.

The first Soviet experiment in taking the image of the Sun in the spectrum of short wavelength was carried out by the Lebedev Physics Institute on 6 June 1963 launched on the geophysical rocket. The experiment was used as a container with a triaxial orientation in space, which helped to make possible the reduction of the angular velocity of rotation of the equipment and at that moment to take clearer photographs.

The camera obscure used in the first soviet experiment had an aperture of 0.2 mm with the length (distance from the inlet to the film) of 200 mm which gave a spatial resolution of about 3 minutes of arc, accordingly.

First Soviet satellites to study the Sun (Cosmos-166, Cosmos-230)

The satellite Cosmos-166 for the solar short-wave radiation research
1 - compartment for the electronic unit of scientific equipment, 2 - screen-vacuum thermal insulation, 3 - solar panel, 4 - sensors of scientific equipment, 5 - solar system orientation sensor.

In 1967 and 1968, at the initiative of the Lebedev Physics Institute and with its active participation, were launched the first Soviet satellites to study the Sun, Cosmos-166 and Cosmos-230. Especially for this experiment the laboratory developed and built the x-ray heliographs and photometers of an original design which made it possible to take more than 1000 images of the Sun in five spectral ranges with an angular resolution of about 20 seconds. In the course of the experiment was received substantially new data on the structure of x-ray flares. In particular, the dynamics of their development was traced for the first time, and at the setting of the active zone beyond the limb, its height was estimated - about 20 thousand km above the photosphere.

In the same period, the first experiments had begun in obtaining the spectrum of the Sun in the short-wavelength region by using the diffraction gratings and Bragg crystals. During these experiments, the world's first photograph of the x-ray spectrum was obtained in the wavelength region shorter than 9.5 A (angstroms). In total the spectrum was recorded up to a wavelength of 1.7 A and was achieved a unique resolution of λ/Δλ~104. This made possible to clarify the abundance of elements in the atmosphere of the Sun and also to detect macroscopic movements in coronal condensations at a line-of-sight velocity up to 100 km/s. The lines of MgXI, FeIX, FeX, and FeXVII ions were detected in the spectrum of solar flares

The INTERCOSMOS program and the rockets of the Vertical series

The satellite "Intercosmos-1" for a solar short-wave radiation research.

In the 70s and early 80s, systematic research of the Sun continued on the Intercosmos satellites and the rockets of the Vertical series at the Lebedev Physics Institute. The equipment for these experiments was built at the Lebedev Physics Institute as a part of the international cooperation with Poland and Czecho-Slovakia. During the experiments, it was possible to register and identify a number of hotlines located in the wavelength region of 1.70-1.95 Å, from their analysis the physical parameters of the hot plasma component of solar flares were established. For the first time was identified the line corresponding to the magnetic quadrupole transition in the solar x-ray spectrum

CORONAS program (1994 2008)

Earths artificial satellite CORONAS I (1994 2001).

Earths artificial satellite CORONAS I (1994 2001).

Earths artificial satellite CORONAS PHOTON (launched in January 2009)

Since 1990, the LPI space experiments have been carried within a framework of the CORONAS program of the Russian Academy of Sciences (Complex Orbital Observations Near-Earth of Activity of the Sun).

As part of this program, two solar observatories, CORONAS-I (1994) and CORONAS-F (2001), were put into orbit. On board of the first spacecraft, the Lebedev Physics Institute conducted a TEREC experiment to observe the Sun in the extreme ultraviolet and X-ray spectral regions. During this experiment, systematic research of solar plasma in the wavelength regions of 132, 175 and 304 Å with a spatial resolution of several angular seconds was first carried out, and the first monochromatic spectrograms of the Sun were obtained in the ranges of 8.41-8.43 A and 180-209 Å.

On board the second satellite, CORONAS-F, the LPI carried out the SPIRIT experiment, which is the most successful experiment in the history of solar research in Soviet and Russian science. In a period more than four years of observations, at about 300,000 high-precision images of the Sun were taken in a nine spectral channels characterizing the spatial structure and dynamics of the plasma of the solar atmosphere in the temperature range from 70 thousand to 10 million degrees and in the range of heights from the upper chromosphere to the corona at altitude more than the radius of the sun. During the experiment, new structures and phenomena were discovered in a hot solar plasma, the contribution of a plasma with a temperature of 6-10 MK to the thermal energy deposits of flares (up to 80%) was determined, and the distribution of matter (differential emission measure) in the temperature range above 5 MK for various structures and dynamics was obtained in the flare process, was recorded the spatiotemporal distribution of the electron density and temperature gradient of the flare plasma, was established the relationship between large-scale eruption and transformation of the magnetic field of the solar corona, a relationship between the density and speed of the solar wind and the integral solar fluxes in the transition layer lines and coronal lines was also revealed; together with the Research Institute of Nuclear Physics of Moscow State University a high (close to 100%) degree of polarization of x-ray radiation in the flare was detected for the first time, the altitude structure of coronal holes investigated and the relationship of their structure with high-speed solar wind flows were shown; investigated the periodic processes in the MgXII hot line; investigated the density variations of the Earths upper atmosphere.

At present, the LPI is completing the building of a complex of the telescopes and imaging spectrometers TESIS which will be installed on board the third spacecraft of the CORONAS program, the satellite CORONAS-FOTON. The launch of the spacecraft and the start of the TESIS experiment was scheduled for June 2008. During the TESIS experiment, it is expected to take more than a million images of the Sun in the extreme ultraviolet and X-ray range with a spatial resolution of fewer than two seconds of arc. A significant part of the results of the experiment will be open for the first time and accessible in the catalogs and image galleries updated on a daily basis.