Interplanetary scintillations of an ensemble of radio sources during the solar activity minimum of cycles 23/24

The results of observations of interplanetary scintillations of a statistical ensemble of radio sources in the period of 2007–2011 are presented. Observation were carried out in the monitoring regime with the BSA LPI radio telescope at the frequency 111 MHz. Fluctuations of radio emission flux of all sources (a few hundred in total) were recorded 24 hours a day. Those sources were investigated, which had a scintillating flux greater than 0.2 Jy and fell within the sky band of 8° width in declination, corresponding to radio telescope’s 16-beam system. The statistical ensemble of radio sources is characterized by the mean variance of a scintillating radiation flux, which is proportional to the squared scintillation index. It follows from the obtained data that the radial dependence of a mean scintillation index during a deep solar activity minimum of 2008–2009 occurs to be weaker than one could expect in the case of spherically symmetric geometry of the solar wind. Suppression of a radial dependence of the mean scintillation index is explained by the effect of the heliospheric current sheet, which reveals itself in a high density of solar wind’s turbulent plasma in the helioequator plane. It is shown that the level of scintillations, averaged over monthly series of observations, was changing synchronously with the solar activity level.     

Peculiarities of the development of active regions on the Sun prior to strong X-class flares: Joint analysis of data from the RATAN-600 radio telescope and SDO space observatory

Complex analysis is performed for five active regions on the Sun where strong X-class solar flares occurred in 2011–2012. Radio emissions from the regions were investigated based on daily multi-wave observation of the Sun with the RATAN-600 radio telescope in the 1.6–8.0 cm wavelength range. It is shown that, as in eruptive events that were investigated earlier using the RATAN-600 radio telescope, 1–2 days (in some cases 14–17 h) prior to a strong flare one observes a developing source over the neutral line of photospheric magnetic field, which is projected on the region of the maximum approach of fields of opposite signs. In most cases this source became a dominant component in the microwave emissions of the active region prior to a flare. Simultaneously, analyzing magnetographic measurements of the same active regions, based on the data of the SDO space observatory, it has been shown that development of X-class flares proceeds at sufficiently high levels (F ～10²² Mx) of magnetic flux in groups of sunspots and at sharp growth of flux gradient (G ～ 20 × 10²⁰ Mx/deg), which reflects the geometric approach of sunspots with opposite polarities of the magnetic field. These results can be used to develop methods for forecasting strong flares on the Sun.     

Observations of March 29, 2006 solar eclipse in the radio range at wavelengths of 3.2 and 4.9 cm

We present observations and processing of the March 29, 2006 solar eclipse data at the radio telescopes RT-3 (λ = 4.9 cm) and RT-2 (λ = 3.2 cm) of the Kislovodsk Solar Station of the Pulkovo Astronomical Observatory of RAS. Registration of the emission flux was conducted by electron method with a time resolution of 0.5 s. Compact sources on the solar disk are identified, and the contribution of coronal holes into the integral flux is determined. Comparisons to observations in the optical and X-ray ranges are performed. The intensity of sources behind the solar limb is estimated. The ratio of the intensity of residual radiation in the maximum phase to the solar emission before the eclipse was equal to 3.7 and 5.9% for 3.2 and 4.9 cm, respectively.     

Solar cycle variation of “killer” electrons at geosynchronous orbit and electron flux correlation with the solar wind parameters and ULF waves intensity

To construct models for hazard prediction from radiation belt particles to satellite electronics, one should know temporal behavior of the particle fluxes. We analyzed 11-year variation in relativistic electron flux (E>2 MeV) at geosynchronous orbit using measurements made by GOES satellites during the 23rd sunspot cycle. As it is believed that electron flux enhancements are connected with the high-speed solar wind streams and ULF or/and VLF activity in the magnetosphere, we studied also solar cycle changes in rank order cross-correlation of the outer radiation belt electron flux with the solar wind speed and both interplanetary and on-ground wave intensity. Data from magnetometers and plasma sensors onboard the spacecraft ACE and WIND, as well as magnetic measurements at two mid-latitude diametrically opposite INTERMAGNET observatories were used. Results obtained show that average value of relativistic electron flux at the decay and minimum phases of solar activity is one order higher than the flux during maximum sunspot activity. Of all solar wind parameters, only solar wind speed variation has significant correlation with changes in relativistic electron flux, taking the lead over the latter by 2 days. Variations in ULF amplitude advance changes in electron flux by 3 days. Results of the above study may be of interest for model makers developing forecast algorithms.     

Properties of Sharp and Large Changes in the Solar Wind Ion Flux (Density)

The results of a detailed study of large (by 20% and more) and sharp (faster than ten minutes) changes of the ion flux in the solar wind are presented. The data are provided by regular measurements onboard the INTERBALL-1 satellite in the period 1996–1999. Using statistical analysis, we obtained the distribution of these changes in their absolute and relative strength. It is shown that, for a considerable proportion of the events, such sharp and large changes of the ion flux (density) take place under conditions of fairly constant values of the solar wind velocity and of both the magnitude and components of the interplanetary magnetic field.     

Features of solar wind streams on June 21–28, 2015 as a result of interactions between coronal mass ejections and recurrent streams from coronal holes

Coronal sources and parameters of solar wind streams during a strong and prolonged geomagnetic disturbance in June 2015 have been considered. Сorrespondence between coronal sources and solar wind streams at 1 AU has been determined using an analysis of solar images, catalogs of flares and coronal mass ejections, solar wind parameters including the ionic composition. The sources of disturbances in the considered period were a sequence of five coronal mass ejections that propagated along the recurrent solar wind streams from coronal holes. The observed differences from typical in magnetic and kinetic parameters of solar wind streams have been associated with the interactions of different types of solar wind. The ionic composition has proved to be a good additional marker for highlighting components in a mixture of solar wind streams, which can be associated with different coronal sources.     

Identification of coronal sources of the solar wind from solar images in the EUV spectral range

Methods of localizing coronal sources of the solar wind (SW), such as coronal holes, quasi-stationary fluxes from active regions, and transient sources associated with small-scale active phenomena are considered based on vacuum-ultraviolet (EUV) images of the corona at low solar activity during the initial period of the 24th solar cycle (2010). It is shown that a SW velocity profile can be calculated from the relative areas of coronal holes (CH) at the central part of the disk based on the images in the ranges of 193 and 171 Å. The images in the 193 Å describe the geometry of large HCs that represent sources of fast SW well. The images in 171 Å are a better visualization of small CHs, based on which the profile of a slow SW component was calculated to a high accuracy (up to 65 km/s). According to Hinode/EIS data of October 15, 2010, using the Doppler spectroscopy method at the streamer base over the active region 11112, the source of the outgoing plasma flux with the mean velocity of 17 km/s was localized in the magnetic field region with an intensity of less than 200 Gauss. According to the estimate, the density of the plasma flux from this source is an order of magnitude greater than the value required for explaining the distinction between the calculated and measured profiles of a slow SW velocity. For finding the transient SW component based on small-scale flare activity, SW parameters were analyzed for the periods of flares accompanied by coronal mass ejections (CMEs), and for the periods without flares, according to the data obtained in 2010 from the ACE and GOES satellites and by coronagraphs on the STEREO-A and -B spacecraft. The ion ratios C⁺⁶/C⁺⁵ and O⁺⁷/O⁺⁶ and the mean charge of Fe ions for periods with flares were shown to be shifted toward large values, suggesting the presence of a hot SW component associated with flare activity. A noticeable correlation between the maximum charge of Fe ions and the peak power of a flare, previously observed for flares of a higher class, was confirmed. The mean value of the SW flux density during the periods of flares was 30% higher than that in the periods without flares, which is possibly associated also with the growth of fluxes from other sources with an increasing solar activity level. Based on the example of a series of flares of October 13–14, 2010, it was supposed that transient SW fluxes from the weak flares at low solar activity can manifest themselves in the form of interplanetary ICME-transients.     

Intermittency of solar wind density fluctuations and its relation to sharp density changes

The paper presents the study of turbulent properties of the solar wind plasma, namely, the intermittency of fluctuations of the solar wind ion flux in the earlier unexplored region of comparatively high frequencies (0.01–1 Hz). Special attention is given to a comparison of intermittency for solar wind observation intervals containing sharp (shorter than 10 min) and high-amplitude (greater than 20%) changes of the ion flux to intervals without such changes. The solar wind observation intervals containing sharp changes of the flux are found to be essentially more intermittent than the intervals of quiet solar wind. Such a comparison allows one to reveal the fundamental difference in turbulent properties of the solar wind depending on the presence or absence of sharp boundaries in plasma structures.     

Space missions for SETI.

Radio Telescopes for SETI searches are less demanding than general purpose astronomical radio telescopes. This provides an opportunity to exploit economical approaches in designing SETI systems. Radio Telescopes in low Earth orbit offer no discernible advantages to SETI; indeed, they probably would perform more poorly than a telescope in any other location. Telescopes in geosynchronous orbits would be sufficiently far from Earth to mitigate greatly the deleterious effect of human radio transmissions. Telescopes on the far side of the moon would be superb both from a radio interference standpoint, and from a civil engineering standpoint. Single-reflector telescopes as large as 50 kilometers in diameter could be constructed with conventional materials. However, their costs appear prohibitive. The asteroid belt and the outer solar system are unpromising places to place a large radio telescope. Perhaps the ultimate radio telescope would utilize the sun as a gravitational lens, focusing radiation on free-flying 10-meter class or possibly larger radio telescopes located at distances of the order of 1000 A.U. from the sun. Such a combination has an energy collecting area at 10 centimeters wavelength equivalent to that of a radio telescope about 11 kilometers in diameter, or of the order of 3000 Arecibo radio telescopes. Such a system could detect transmitters with EIRP of the order of a gigawatt at a distance of the order of the distance to the galactic center.     

不同内边界条件下SEP事件实例的集合数值模拟及其在SEP事件预报中的应用

太阳高能粒子（SEP）事件的定量数值预报是空间态势感知的重要方面之一。SEP事件主要来自于日冕物质抛射（CME）所驱动的激波扩散加速（DSA）。文章在三个有关模型的基础上,结合1 AU处卫星的太阳风观测参数和日冕仪的CME观测参数,建立了一套可用于预报SEP事件的数值方法。利用该方法对一次SEP实例进行数值模拟,并将模拟结果与GOES卫星观测结果进行比较。结果表明:数值模拟得到的＞10 MeV的高能粒子的通量和观测较为吻合,＞100 MeV的高能粒子的通量高于观测值。针对此事件进一步开展了不同CME抛射速度和不同内边界背景太阳风温度条件下的集合模拟试验,结果表明:CME抛射速度对SEP事件中高能粒子通量和能谱影响较大,而内边界背景太阳风温度的改变对于高能粒子通量和能谱的影响几乎可以忽略不计。     

Catalog of large-scale solar wind phenomena during 1976–2000

The main goal of this paper is to compile a catalog of large-scale phenomena in the solar wind over the observation period of 1976–2000 using the measurement data presented in the OMNI database. This work included several stages. At first the original OMNI database was supplemented by certain key parameters of the solar wind that determine the type of the solar wind stream. The following parameters belong to this group: the plasma ratio β, thermal (NkT) and kinetic (mNV ²) pressures of the solar wind, the ratio T/T _exp of measured and expected temperatures, gradients of the plasma velocity and density, and the magnetic field gradient. The results of visualization of basic plasma parameters that determine the character of the solar wind stream are presented on the website of the Space Research Institute, Moscow. Preliminary identification of basic types of the solar wind stream (FAST and SLOW streams, Heliospheric Current Sheet (HCS), Corotating Interaction Region (CIR), EJECTA (or Interplanetary Coronal Mass Ejections), Magnetic Cloud (MC), SHEATH (compression region before EJECTA/MC), rarified region RARE, and interplanetary shock wave IS) had been made with the help of a preliminary identification program using the preset threshold criteria for plasma and interplanetary magnetic field parameters. Final identification was done by comparison with the results of visual analysis of the solar wind data. In conclusion, histograms of distributions and statistical characteristics are presented for some parameters of various large-scale types of the solar wind.     

Sporadic structures and small-scale irregularity in the nighttime polar ionosphere in the period of high solar activity according to the data of radio occultation measurements on satellite-to-satellite paths

Results of the analysis of 327 sessions of radio occultation on satellite-to-satellite paths are presented. The data are taken in the nighttime polar ionosphere in the regions with latitudes of 67°–88°, and in the period of high solar activity from October 26, 2003 to November 9, 2003. Typical ionospheric changes in the amplitude and phase of decimeter radio waves on paths GPS satellites-CHAMP satellite are presented. It is demonstrated that these data make it possible to determine characteristics of the sporadic E _s structures in the lower ionosphere at heights of 75–120 km. Histograms of distribution of the lower and upper boundaries, thickness, and intensity of the E _s structures are presented. Dispersion and spectra of amplitude fluctuations of decimeter radio waves caused by small-scale irregularity of the ionospheric plasma are analyzed. The relation of the polar E _s structures and intensity of small-scale plasma irregularity to various manifestations of solar activity is discussed. The efficiency of monitoring the ionospheric disturbances caused by shock waves of the solar wind by the radio occultation method on satellite-to-satellite paths is demonstrated.     

Long-term variations of fluxes of solar protons and helium isotopes

The fluxes of hydrogen and helium isotopes in the solar wind are reconstructed over a long time scale since the present time up to 600 million years back. Abundances of helium isotopes, obtained in the helium isotopic analysis made for 8 lunar soil samples, were used as initial data in the reconstruction procedure. Samples were taken off from various levels of the 1.6-m core of lunar soil delivered by the automatic Luna-24 station in 1976. The data on modern hydrogen and helium fluxes were used as well. The developed reconstruction procedure allowed one to select various solar wind components in a ??gross?? composition. Proton flux variations over the interval of 600 million years do not exceed a value of 40 %. Helium flux variations reach a value of 1.5?C2 relative to the average value. Most likely, this circumstance is caused by considerable variations of a number of coronal mass ejections (CME) enriched by helium. The arguments in favor of solar activity polycyclicity on a long time scale are discussed.     

Study of radiation conditions onboard the International space station by means of the Liulin-5 dosimeter

For estimating radiation risk in space flights it is necessary to determine radiation dose obtained by critical organs of a human body. For this purpose the experiments with human body models are carried out onboard spacecraft. These models represent phantoms equipped with passive and active radiation detectors which measure dose distributions at places of location of critical organs. The dosimetric Liulin-5 telescope is manufactured with using three silicon detectors for studying radiation conditions in the spherical tissue-equivalent phantom on the Russian segment of the International space station (ISS). The purpose of the experiment with Liulin-5 instrument is to study dynamics of the dose rate and particle flux in the phantom, as well as variations of radiation conditions on the ISS over long time intervals depending on a phase of the solar activity cycle, orbital parameters, and presence of solar energetic particles. The Liulin-5 dosimeter measures simultaneously the dose rate and fluxes of charged particles at three depths in the radial channel of the phantom, as well as the linear energy transfer. The paper presents the results of measurements of dose rate and particle fluxes caused by various radiation field components on the ISS during the period from June 2007 till December 2009.     

Motion and transport of solar cosmic rays in heliospheric traps: The event on January 28–31, 2001

The results of studying the enhancement of solar cosmic ray fluxes on January 28?C31, 2001 in a wide energy range are presented using the ACE spacecraft data. A comparative analysis of temporal variations of the fluxes of charged particles and of the interplanetary medium parameters (interplanetary magnetic field and solar wind) has been performed on the basis of the ??reflection?? model of motion, accumulation, and modulation of cosmic rays. It is shown that a magnetic trap for solar cosmic rays was created by a plasma stream and flare ejection from an active region in the western part of the solar disk. Particles of low energies (<10 MeV) were captured inside the trap; the dispersion of distribution of particles with different energies inside the trap being determined by its complicated magnetic structure. The power-low dependence of the time of maximum for the flux of particles on their energy is found, and softer energy spectrum inside the trap is explained.     

Malfunction of satellite navigation systems GPS and GLONASS caused by powerful radio emission of the Sun during solar flares on December 6 and 13, 2006, and October 28, 2003

Poor quality of functioning of GPS during solar flares on December 6 and 13, 2006 is analyzed in this paper. These flares were accompanied by extremely high (unexampled) level of the solar radio emission flux. A comparison is made of these events with the solar flare on October 28, 2003. Statistically reliable experimental evidence is obtained that GPS positioning was partially paralyzed on the sunlit side of the Earth during the strongest bursts of solar radio emission. The obtained results give a serious ground to revise the role played by space weather factors in operation of modern satellite systems and to take these factors into account more carefully, when such systems are designed and exploited.     

Relative occurrence rate and geoeffectiveness of large-scale types of the solar wind

We investigate the relative occurrence rate for various types of the solar wind and their geoeffectiveness for magnetic storms with Dst < —50 nT. Both integrated effect for the entire time 1976–2000 and variations during this period of 2.5 cycles of solar activity are studied As raw data for the analysis we have used the catalog of large-scale types of the solar wind for the period 1976-2000 (see ftp://ftp.iki.rssi.ru/omni/) created by us with the use of the OMNI database (http://omni.web.gsgc.nasa.gov) [1] and described in detail in [2]. The average annual numbers of different type of events are as follows: 124 ±81 for the heliospheric current sheet (HCS), 8 ±6 for magnetic clouds (MC), 99 ±38 for Ejecta, 46 ±19 for Sheath before Ejecta, 6 ±5 for Sheath before MC, and 63 ±15 for CIR. The measurements that allowed one to determine a source in the solar wind were available only for 58% of moderate and strong magnetic storms (with index Dst < —50 nT) during the period 1976–2000. Magnetic clouds (MC) are shown to be the most geoeffective (~61%). The CIR events and Ejecta with Sheath region are three times less geoeffective (~20–21 %). Variations of occurrence rate and geoeffectiveness of various types of the solar wind in the solar cycle are discussed.     

System of maintaining the thermal regime of a space radio telescope

We present the results of developing a system of thermal regime maintenance for the onboard complex of scientific instruments of the space radio telescope installed on the Spektr-R spacecraft. The structure of the system of thermal regime maintenance is presented that includes a set of autonomous systems of constructive elements of the radio telescope. Basic schemes and composition of aggregates are presented, and main principles of operation of the autonomous systems supporting the thermal regime of the radio telescope are considered.     

Ascending flows in the solar atmosphere and formation of the solar wind

Some morphological features of solar magnetic fields in the chromosphere and corona are considered based on studying various observational data. These data are compared to the results of observation of the solar wind and interplanetary magnetic field, as well as to the data on fluxes of solar cosmic rays. New specific features are found in the solar wind structure, and new additional indications of sources of the solar wind are obtained. The properties of the active regions and coronal holes are considered. A model of the ascending stream-like plasma flow is suggested. It flows around the discrete arched magnetic field tubes in the solar atmosphere and stretches them out into interplanetary space.