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The geoeffectiveness of single and complex transient structures of the solar wind (SW), formed by coronal mass ejections (CMEs) and associated Forbush decreases (FDs) in the cosmic ray flux is considered. By the example of the period of 2010–2011, it is shown that complex SW structures resulting from the interaction of CMEs with high-speed streams from coronal holes or with other CMEs in the heliosphere more often lead to moderate and strong geomagnetic storms (Dst < –50 nT) in comparison with single CMEs. It is shown that the FD increases with the growth of the SW transient structure duration and the average magnitude of the interplanetary magnetic field of the transient and takes the highest values when the complex structures arrive at the Earth.

The state of the space environment plays a significant role for forecasting of geomagnetic storms produced by disturbances of the solar wind (SW). Coronal mass ejections (CMEs) passing through the heliosphere often have a prolonged (up to several days) trail with declining speed, which affects propagation of the subsequent SW streams. We studied the CME and the post-eruption plasma flows behind the CME rear in the event on 2010 August 18 observed in quadrature by several space-based instruments. Observations of the eruption in the corona with EUV telescopes and coronagraphs revealed several discrete outflows followed by a continuous structureless post-eruption stream. The interplanetary coronal mass ejection (ICME), associated with this CME, was registered by PLAsma and SupraThermal Ion Composition (PLASTIC) instrument aboard the Solar TErrestrial RElations Observatory (STEREO-A) between August 20, 16:14 UT and August 21, 13:14 UT, after which the SW disturbance was present over 3 days. Kinematic consideration with the use of the gravitational and Drag-Based models has shown that the discrete plasma flows can be associated with the ICME, whereas the post-eruption outflow was arrived in the declining part of the SW transient. We simulated the Fe-ion charge distributions of the ICME and post-CME parts of SW using the plasma temperature and density in the ejection region derived from the Differential Emission Measure analysis. The results demonstrate that in the studied event the post-ICME trailing region was associated with the post-eruption flow from the corona, rather then with the ambient SW entrained by the CME., 13 pages, 4 figures

A review of studies of coronal mass ejections (CMEs) and the propagation of the resulting interplanetary coronal mass ejections (ICMEs) in the heliosphere is presented. The main parameters of ICMEs, their differences from other types of solar wind (SW) streams, and correlation of the ICME occurrence rate with the state of solar activity are considered. Special attention is paid to the formation and simulation of the ion composition of the CME/ICME plasma, which is one of the key factors in identifying the types and sources of SW streams, especially in complex structures formed in the heliosphere during the interaction of streams. Models for predicting the parameters of SW streams from observational data are considered. The review also presents the lists of literature sources on coronal ejections and databases on the parameters of SW streams, as well as numerous references to the works on the phenomena under study.

The paper considers the classification of solar wind streams in magnetohydrodynamic parameters (MHD-types); combinations of proton speed, density, temperature, and magnetic field strength, in addition to the classical solar wind separation into high-speed streams from coronal holes, transient streams of coronal mass ejections, and the slow solar wind from the streamer belt. Two classifications of solar wind properties were compared for the events in August 2010 and May 2011, when one could observe the interaction of two coronal mass ejections and a coronal mass ejection with a high-speed solar wind stream from the coronal hole, respectively. It is shown that the classical description of a large-scale structure of wind streams (the ion wind composition especially) in scales of hours and days allows one to determine the type and source of streams, whereas the MHD-parameters allow one to more accurately describe the small-scale structure (in minutes), especially in the cases of several streams interaction in the heliosphere. The detailed study of a small-scale structure of stream interaction regions provides the information required for developing MHD-models describing the processes of propagation and interaction of streams in the heliosphere and for predicting their geoefficiency.

We study the development of a coronal mass ejection (CME) caused by a prominence eruption on 24 February 2011 and properties of a related interplanetary CME (ICME). The prominence destabilized, accelerated, and produced an M3.5 flare, a fast CME, and a shock wave. The eruption at the east limb was observed in quadrature by the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO) and by the Sun Earth Connection Coronal and Heliospheric Investigation (SECCHI) instrument suite on board the Solar-Terrestrial Relations Observatory (STEREO). The ICME produced by the SOL2011-02-24 event was measured in situ on STEREO-B two days later. The diagnostics made from multi-wavelength SDO/AIA images reveals a pre-eruptive heating of the prominence to about 7 MK and its subsequent heating during the eruption by flare-accelerated particles to about 10 MK. The hot plasma was detected in the related ICME as an enhancement in the ionic charge state of Fe, whose evolution was reproduced in the modeling. The analysis of the solar source region allows for predicting the variations of magnetic components in the ICME, while the flux-rope rotation by about $40^{\circ }$ was indicated by observations. The magnetic-cloud propagation appears to be ballistic.

We have considered the possible causes of discrepancies between the predicted and observed at 1 AU parameters of the recurrent solar wind (SW) streams in the maximum of the 24th solar cycle. These discrepancies have been observed in both the SW velocity profile and the SW stream arrival time, as well as in the absence of the expected high-speed SW stream. The degree of discrepancy depends on the model used for the SW prediction; however, in some cases, different prediction methods provide a similar discrepancy with the observed SW parameters at 1 AU. For several cases, we show that the probable cause of the discrepancies can be a deflection of the high-speed SW stream from the radial direction due to the interaction with the transient SW streams at certain configuration of the magnetic fields of high-speed and transient SW sources in the solar corona.

The interaction of the interplanetary coronal mass ejection (ICME) and the high-speed solar wind flux (HSSWF) associated with the coronal hole (CH) is considered. By the examples of two events at the maximum of solar cycle 24 from June 4 to June 16 and from June 30 to July 10, 2012 it is shown that the temperature-dependent parameters of the SW ionic composition appear closer to the values in the HSSWF than in the ICME due to mixing of fluxes in the corona when the ICME source is near the CH boundary.

The SPIRIT telescope aboard the CORONAS-F satellite (in orbit from 26 July 2001 to 5 December 2005), observed the off-limb solar corona in the 175 Å (Fe IX, X and XI lines) and 304 Å (He II and Si XI lines) bands. In the coronagraphic mode the mirror was tilted to image the corona at the distance of 1.1...5 Rsun from the solar center, the outer occulter blocked the disk radiation and the detector sensitivity was enhanced. This intermediate region between the fields of view of ordinary extreme-ultraviolet (EUV) telescopes and most of the white-light (WL) coronagraphs is responsible for forming the streamer belt, acceleration of ejected matter and emergence of slow and fast solar wind. We present here the results of continuous coronagraphic EUV observations of the solar corona carried out during two weeks in June and December 2002. The images showed a "diffuse" (unresolved) component of the corona seen in both bands, and non-radial, ray-like structures seen only in the 175 Å band, which can be associated with a streamer base. The correlations between latitudinal distributions of the EUV brightness in the corona and at the limb were found to be high in 304 Å at all distances and in 175 Å only below 1.5 Rsun. The temporal correlation of the coronal brightness along the west radial line, with the brightness at the underlying limb region was significant in both bands, independent of the distance. On 2 February 2003 SPIRIT observed an expansion of a transient associated with a prominence eruption seen only in the 304 Å band. The SPIRIT data have been compared with the corresponding data of the SOHO LASCO, EIT and UVCS instruments.

The dynamics of parameters of the near-Earth solar wind (SW) and the effect of solar activity on the parameters of three SW components (fast SW from large-scale coronal holes (CHs); slow SW from active regions, streamers, and other sources; and transient flows related to sporadic solar activity) at the beginning of the 24th solar cycle (2009–2011) are analyzed. It is demonstrated that temperaturedependent parameters of ionic composition (C+6/C+5 and O+7/O+6) of the transient SW component in the profound minimum of solar activity in 2009 were correlated with the variation of the rate of weak (type C and weaker) flares. This verifies the presence of a hot component associated with these flares in the SW. The variations in the velocity and the kinetic temperature of fast SW from CHs with an increase in activity are more pronounced in the bulk of the high-speed stream, and the variations of O+7/O+6 and Fe/O ratios and the magnitude of the interplanetary magnetic field are the most prominent in the region of interaction between fast and slow SW streams. The analysis reveals that a value of O+7/O+6 = 0.1 serves as the criterion to distinguish between fast SW streams and interplanetary coronal mass ejections in the 2009 activity minimum. This value is lower than the one (0.145) determined earlier based on the data on the 23rd cycle (Zhao et al., 2009). Therefore, the distinguishing criterion is not an absolute one and depends on the solar activity level.

This work is a continuation of our previous articles (Yermolaev et al. in J. Geophys. Res. 120, 7094, 2015; Yermolaev et al. in Solar Phys. 292, 193, 2017; Yermolaev et al. in Solar Phys. 293, 91, 2018), which describe the average temporal profiles of interplanetary plasma and field parameters in large-scale solar-wind (SW) streams: corotating interaction regions (CIRs), interplanetary coronal mass ejections (ICMEs including both magnetic clouds (MCs) and ejecta), and sheaths as well as interplanetary shocks (ISs). In this work we analyze the average profile of helium abundance N{\alpha}/Np for interval of 1976-2016. Our results confirm main early obtained results: N{\alpha}/Np is higher in quasi-stationary fast streams than in slow ones; it slowly changes in compression regions CIRs and Sheaths from values in undisturbed solar wind to values in corresponding type of piston (HSS or ICME); in Ejecta it is closed to abundance in undisturbed streams and it is maximal in MCs. We obtained for first time that N{\alpha}/Np correlates with plasma {\beta}-parameter in compression regions CIRs and Sheaths and anti-correlates in ICMEs. The N{\alpha}/Np vs. {\beta} dependence is stronger in MCs than in Ejecta and may be used as an indicator of conditions in CME formation place on the Sun., Comment: 12 pages, 6 figures, calculations for new OMNI2 dataset version (without ACE helium measurements), results unchanged

We investigate the case of disagreement between predicted and observed in-situ parameters of the recurrent high-speed solar wind streams (HSSs) existing for Carrington rotation (CR) 2118 (December 2011) in comparison with CRs 2117 and 2119. The HSSs originated at the Sun from a recurrent polar coronal hole (CH) expanding to mid-latitudes, and its area in the central part of the solar disk increased with the rotation number. This part of the CH was responsible for the equatorial flank of the HSS directed to the Earth. The time and speed of arrival for this part of the HSS to the Earth were predicted by the hierarchical empirical model based on EUV-imaging and the Wang-Sheeley-Arge ENLIL semi-empirical replace model and compared with the parameters measured in-situ by model. The predicted parameters were compared with those measured in-situ. It was found, that for CR 2117 and CR 2119, the predicted HSS speed values agreed with the measured ones within the typical accuracy of ±100 km s−1. During CR 2118, the measured speed was on 217 km s−1 less than the value predicted in accordance with the increased area of the CH. We suppose that at CR 2118, the HSS overtook and interacted with complex ejecta formed from three merged coronal mass ejections (CMEs) with a mean speed about 400 km s−1. According to simulations of the Drag-based model, this complex ejecta might be created by several CMEs starting from the Sun in the period between 25 and 27 December 2011 and arriving to the Earth simultaneously with the HSS. Due to its higher density and magnetic field strength, the complex ejecta became an obstacle for the equatorial flank of the HSS and slowed it down. During CR 2117 and CR 2119, the CMEs appeared before the arrival of the HSSs, so the CMEs did not influence on the HSSs kinematics.

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 A. The images in the 193 A describe the geometry of large HCs that represent sources of fast SW well. The images in 171 A 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.

The review is addressed to problems of spectroscopic diagnostics of the solar coronal plasma by its radiation in the X-ray and extreme ultraviolet (EUV) bands. Physical conditions in the corona, elementary processes and mechanisms of radiation formation, and methods and results of the temperature and density diagnostics of diverse coronal structures (such as active and quiet solar regions, coronal holes, and the extended corona) are considered. The types and main parameters of instruments for investigation of the corona by its X-ray and EUV emission in space experiments are given.

The existence of coronal plasmoids has been postulated for many years in order to supply material to streamers and possibly to the solar wind (SW). The W-L SoHO C2 Lasco coronagraph observations were made under the 2.2 solar radii (R0) occulting disk to look at the ultimate sources of the SW; EUV imagers are preferably devoted to the analysis of the corona on and very near the solar disk. Here, in addition to eclipse white-light (W-L) snapshots, we used the new SWAP space-borne imager designed for the systematic survey of coronal activity in the EUV lines near 17.4 nm, over a field of view (FOV) up to 2 R0. Using summed and co-aligned images, the corona can then be evaluated for the 1st time up to the limit of this FOV. At the time of the July 11, 2010, solar total eclipse a 20h continuous run of observations was collected, including images taken during eclipse totality from several ground observing locations where W-L data were collected. A plasmoid-like off-limb event was followed using the SWAP summed

On February 26, 2009, the first data was obtained in the TESIS experiment on the research of the solar corona using imaging spectroscopy. The TESIS is a part of the scientific equipment of the CORONAS-PHO-TON spacecraft and is designed for imaging the solar corona in soft X-ray and extreme ultraviolet regions of the spectrum with high spatial, spectral, and temporal resolutions at altitudes from the transition region to three solar radii. The article describes the main characteristics of the instrumentation, management features, and operation modes.

Photometric methods of image analysis in the extreme ultraviolet (EUV) wavelength range are widely used in solving current scientific problems of solar physics. Types of solar EUV telescopes, their main parameters, effects of space flight and observation conditions on accuracy of the photometric analysis are considered.

On 2017 September 6 and 10, the strongest X9.3 and X8.2 flares of the decade occurred in the active region NOAA Active Region 12673. During these flares, the Sun Watcher with Active Pixels and Image Processing (SWAP) telescope on board the Project for Onboard Autonomy 2 (PROBA2) satellite registered the unusual alternate brightening and darkening of the western corona at the heliocentric distances ≈1.2–1.7 R ☉. The X9.3 flare on 2017 September 6 was accompanied by coronal brightening up to 30%–45% at distances ≈1.35–1.7 R ☉. Numerical simulations showed that this brightening might be produced by resonant scattering of the flare radiation by the Fe ix–Fe xi ions in the coronal plasma at the temperature T ~ 0.8–1 MK, and the densities seriously reduced in comparison with the typical values for the quiet background corona probably moving outward with velocities of 30–40 km s−1. At the maximum of the flare and one hour later, two coronal mass ejections (CMEs) originated, which dimmed the coronal emission in the SWAP 174 A passband above the western limb by 20%–30%. The X8.2 flare on September 10 was accompanied by a CME, which rose up and progressively dimmed the western part of the corona up to 60%. An hour later the darkening, produced by a global rearrangement of the magnetic field structure and an evacuation of a significant part of the coronal plasma, extended over the complete western limb. A differential emission measure (DEM) analysis showed a decrease in the electron density of the background plasma with T ~ 1–2 MK at distances 1.24–1.33 R ☉ by 2–3.5 times after the CME. At the same time, an additional DEM peak at T ≈ 0.8 MK appeared, which may be associated with an additional emission in the SWAP passband produced by the flare radiation resonantly scattered by the coronal plasma.

The CORONAS-Photon spacecraft was successfully launched in January 2009. Its scientific payload included the TESIS complex of telescopes and spectrometers, designed to obtain high spectral, temporal and spatial resolution solar corona images in soft X-ray to far UV spectral range.

TESIS is a set of solar imaging instruments in development by the Lebedev Physical Institute of the Russian Academy of Science, to be launched aboard the Russian spacecraft CORONAS-PHOTON in December 2008. The main goal of TESIS is to provide complex observations of solar active phenomena from the transition region to the inner and outer solar corona with high spatial, spectral and temporal resolution in the EUV and Soft X-ray spectral bands. TESIS includes five unique space instruments: the MgXII Imaging Spectroheliometer (MISH) with spherical bent crystal mirror, for observations of the Sun in the monochromatic MgXII 8.42 A line; the EUV Spectoheliometer (EUSH) with grazing incidence difraction grating, for the registration of the full solar disc in monochromatic lines of the spectral band 280–330 A; two Full-disk EUV Telescopes (FET) with multilayer mirrors covering the band 130–136 and 290–320 A; and the Solar EUV Coronagraph (SEC), based on the Ritchey–Chretien scheme, to observe the inner and outer solar corona from 0.2 to 4 solar radii in spectral band 290–320 A. TESIS experiment will start at the rising phase of the 24th cycle of solar activity. With the advanced capabilities of its instruments, TESIS will help better understand the physics of solar flares and high-energy phenomena and provide new data on parameters of solar plasma in the temperature range 10 5 - 10 7 K . This paper gives a brief description of the experiment, its equipment, and its scientific objectives.

The scientific purpose of the SPIRIT experiment is to study the space-time structures of phenomena of the solar activity using a set of X-ray instruments aboard the Koronas-F satellite. The system consists of the SRT-C six-channel telescope and the RES-C four-channel spectroheliometer for 8.4- to 335-A wavelengths and the SPR-N five-range polarimeter for 20- to 100-keV energies. For a 3.5-yr flight (since July, 2001 to January, 2005), over 40000 observation sessions were conducted and over 1 million spectral pictures were obtained during the SPIRIT experiment. The volume of electronic archive of the experiment reached 220 Gbyte. The software package was developed for prompt control of the scientific system and used in the semiautomatic mode to form the sequence diagrams of energizing, create control files (CFs) via the dialog line, and schedule CF delivery. The software package is based both on the electronic table in the Excel-2000 format, which displays the basic procedures and control events, and on the database in the Access-2000 format, which is automatically filled with the information on all created CFs. For archiving, viewing, and selecting scientific data of the experiment, a graphic database in the Access-2000 format was created. The software for automatic filling of the database and a graphic interface for prompt viewing of the database and retrieval of pictures based on some parameters were designed. An automatic augmentable ballistic database containing basic parameters of the satellite orbit over the full flight period was created.

Aims: Knowledge of properties of the Earth’s upper atmosphere is important for predicting the lifetime of low-orbit spacecraft as well as for planning operation of space instruments whose data may be distorted by atmospheric effects. The accuracy of the models commonly used for simulating the structure of the atmosphere is limited by the scarcity of the observations they are based on, so improvement of these models requires validation under different atmospheric conditions. Measurements of the absorption of the solar extreme ultraviolet (EUV) radiation in the upper atmosphere below 500 km by instruments operating on low-Earth orbits (LEO) satellites provide efficient means for such validation as well as for continuous monitoring of the upper atmosphere and for studying its response to the solar and geomagnetic activity. Method: This paper presents results of measurements of the solar EUV radiation in the 17 nm wavelength band made with the SPIRIT and TESIS telescopes on board the CORONAS satellites and the SWAP telescope on board the PROBA2 satellite in the occulted parts of the satellite orbits. The transmittance profiles of the atmosphere at altitudes between 150 and 500 km were derived from different phases of solar activity during solar cycles 23 and 24 in the quiet state of the magnetosphere and during the development of a geomagnetic storm. We developed a mathematical procedure based on the Tikhonov regularization method for solution of ill-posed problems in order to retrieve extinction coefficients from the transmittance profiles. The transmittance profiles derived from the data and the retrieved extinction coefficients are compared with simulations carried out with the NRLMSISE-00 atmosphere model maintained by Naval Research Laboratory (USA) and the DTM-2013 model developed at CNES in the framework of the FP7 project ATMOP. Results: Under quiet and slightly disturbed magnetospheric conditions during high and low solar activity the extinction coefficients calculated by both models agreed with the measurements within the data errors. The NRLMSISE-00 model was not able to predict the enhancement of extinction above 300 km observed after 14 h from the beginning of a geomagnetic storm whereas the DTM-2013 model described this variation with good accuracy.

Large-scale hot features were detected and observed several times high in the solar corona in the high-temperature Mg XII line (T = 5–20 MK, T max = 10 MK) with the soft X-ray telescope of the SPIRIT instrumentation complex onboard the CORONAS-F spacecraft. These features look like a spider up to 300000 km in size and live up to a few days. Their bright cores observed at heights were from 0.1 to 0.3 solar radii are connected with active regions by darker legs, giant loops. These features are disposed above arcades, which are simultaneously observed in cooler emission lines sensitive to temperatures of 1 to 2 MK. For the core of such a feature observed December 28–29, 2001, Zhitnik et al. (2003a) estimated an electron temperature of 10 MK and a number density of n e ≈ 1010 cm−3. A high activity and an association with eruptive phenomena were found for such features in continuous (up to 20-day) observations with a cadence of 0.6–1.7 min. In the present paper, we discuss the relation of such features to coronal structures, which are known from previous studies. We identify such off-limb features observed with SPIRIT on October 22, November 12, and December 28–29, 2001, with hot upper parts of post-eruptive arcades. The results of multifrequency analysis of these features based on the data obtained in various spectral ranges by different instruments (Yohkoh/SXT, SOHO/EIT, SOHO/LASCO, Nobeyama and SSRT radioheliographs) are briefly discussed. We address the physical conditions of the long-term existence of giant hot coronal structures. It is demonstrated that the post-eruptive energy release must be prolonged and the condition β ≪ 1 is not satisfied in these structures. It is argued that the so-called “standard flare model” should be better considered as a “standard post-eruptive energy release model.”

The SPectroheliographIc X-Ray Imaging Telescope (SPIRIT) aboard the CORONAS-F spacecraft sometimes observes in the Mg XII 8.42 u A line (Tmax ∼ 9MK) large, bright features existing for many hours high in the corona. This fact suggests that plasma beta there might not be small. We identify such a feature observed on 2001 October 22 at a height of 100Mm with a hot part of a post-eruptive arcade. Using multi-spectral data and radio astronomy methods, we estimate the plasma parameters in the arcade and reveal the coronal magnetic configuration. Several hours after the eruption, the temperature in the arcade was 6–8MK, and the plasma density was (5–10) ·10 9 cm −3 . We confirm the results by the accord of the quantities obtained from different observations using different methods and by the extrapolation of the photospheric magnetograms into the corona, from which we have obtained a magnetic field strength of about 7G at that height. Hence, indeed β ≥ 1 in the post-eruptive arcade. The high-beta possibility had previously been stated, e.g., by Ichimoto et al. (1994), but still not investigated. We address this issue in terms of the “standard flare model” elaborated by Shibata and Yokoyama. During this event, Yohkoh/SXT observed McKenzie–Hudson dark moving features. Those features are filled with cold material, if they are not empty, and may affect the arcade.

Based on observations with the EUV SPIRIT telescope aboard the CORONAS-F spacecraft, we analyze large-scale dimmings on the solar disk initiated by halo-type coronal mass ejections (CMEs). We address four powerful geo-effective eruptive events of November 4, 2001; October 28, 29, and November 18, 2003. The SOHO/EIT telescope did not observe the first event. Considering other events, we demonstrate that the CORONAS-F/SPIRIT and SOHO/EIT data well supplement each other in time and spectral coverage. The spatial coincidence of the main dimmings in different-temperature lines hints at their relation to plasma outflow from partly or completely opened magnetic structures in the transition region and corona. For some dimmings whose appearance is dissimilar in different lines, CME-associated variations of the plasma temperature can play a role as well. Peculiar propagating darkening was detected in the SPIRIT 304 A band on November 18 between 08:23 and 09:54 UT. Most probably, the darkening is caused by some absorption of the emission in cold material of the erupted filament.

We present new observational data on the phenomena of extremely high activity on the Sun and in the heliosphere that took place in October-November 2003. A large variety of solar and heliospheric parameters give evidence that the interval under consideration is unique over the entire observation time. Based on these data, comparing them with similar situations in the past and using available theoretical concepts, we discuss possible cause-and-effect connections between the processes observed. The paper includes the first results and conclusions derived by the collaboration "Solar Extreme Events-2003" organized in Russia for detailed inves- tigations of these events. As a result of our consideration, it is beyond question that the physical causes of solar and heliospheric phenomena in October-November 2003 are not exclusively local and do not belong only to the active regions and solar atmosphere above them. The energy reservoirs and driving forces of these processes have a more global nature. In general, they are hidden from an observer, since ultimately their sources lie in the subphotospheric layers of the Sun, where changes that are fast and difficult to predict can sometimes take place (and indeed they do). Solar flares can serve as sufficiently good tracers of these sudden changes and reconstruc- tions on the Sun, although one can still find other diagnostic indicators among the parameters of magnetic fields, motions of matter, and emission characteristics.

Multi-wavelength imaging of the solar corona is a powerful observational method to study CME-related dynamics of structures in spectral bands related to the solar corona and transition region. We analyze large-scale eruptive events caused by halo-type CMEs observed at the solar disk with the CORONAS-F/SPIRIT (175, 304, and 284 A) and SOHO/EIT telescopes on November 4, 2001 and October–November, 2003. For most events, CME-associated dimmings coincide in different bands, but the 304 A dimming in November 4, 2001 event was delayed by hours. In October–November events, coronal waves were observed in 195 A and some in 175 A channel. In a CME event associated with a filament eruption on November 18, the SPIRIT images display a propagating disturbance seen as a darkening in 304 A channel only. This phenomenon was not described earlier.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The images of the solar corona from the limb out to the distance of about 5 solar radii have been obtained for the firs time in the XUV narrow spectral bands and monochromatic lines in the current experiment SPIRIT (SPectroheliographIc soft X-Ray Imaging Telescope). This paper presents the examples of images for the Sun's “quiet” atmosphere as well as for some transient and eruptive events in the corona to illustrate the performance of the instrumentation and to point out the way for future studies. The data obtained will be used for diagnostic purposes and modeling of solar wind acceleration, coronal plasma structures and various active phenomena in the solar corona.

SPIRIT (SPectroheliograph Ic soft X-Ray Imaging Telescope) is the current experiment on board theCORONAS-F satellite launched on July 31, 2001 ( Oraevskii & Sobelman, 2002 ). The main goal of this experiment is to study a structure and dynamics of the solar atmosphere in the wide scale of heights (from the chromosphere to a far corona) and of temperatures (from ten thousands through thirty millions Kelvins) by means of the XUV imaging spectroscopy. Since the launch of the CORONAS-F satellite more than three hundred thousands of images and spectroheliograms have been recorded. For the first time continuous series of monochromatic full Sun images in MgXII lines at 8.42 A (doublet: 8.418 and 8.423 A) were obtained. These series include long-term continuous observations of duration up to 10 days with the cadence of 100 sec as well as temporal sequences with duration of a few minutes and high resolution of 7 sec, synchronized with flares. The spectroheliograms for the whole disk and off-limb regions are also recorded in the spectral bands 177 – 207 and 285 – 335 A providing spectra with high resolution of various coronal structures including eruptive and transient events. This paper presents preliminary results of quick look analysis of some observational data obtained by means of the SPIRIT spectroheliographs.

We consider the effects of the absorption of solar XUV radiation by the Earth's atmosphere that were observed in the solar images obtained with the TEREK-K telescope onboard the Coronas-I satellite in May–June 1994 at low solar activity and with the SPIRIT instrumentation onboard the Coronas-F satellite in October–November 2001 at maximum solar activity. The solar images were recorded during the satellite occultation: in the 175- and 304-A spectral ranges onboard Coronas-I with the TEREK-K telescope and in the 175-, 304-, and 8.42-A ranges onboard Coronas-F with the SPIRIT instrumentation. Based on the XUV solar images obtained during atmospheric sounding, apart from the total absorption, we can determine the direction of the atmospheric density gradient and study the local absorption variations with altitude on spatial scales of less than 1 km. The described method can significantly supplement the data obtained in studies of the upper atmosphere by the methods of mass spectrometry, incoherent radar scattering, and the drag of orbital spacecraft.

The origins of the solar wind and the interplanetary magnetic field sector structure in the beginning of the magnetic polarity reversal of 24th solar cycle were investigated using the Wilcox Solar Observatory magnetic field measurements and their products as well as the solar wind data from ACE and the SDO/AIA EUV images. The dominance of the quadrupole harmonics in the solar magnetic field in this period resulted in a four-sector structure of the interplanetary magnetic field. The dominating source of recurrent high-speed solar wind stream was a large trans-equatorial coronal hole of negative polarity evolving in the course of the polarity reversal process. The contribution of ICMEs to the high-speed solar wind did not exceed 17% of the total flux. The solar wind density flux averaged over the year amounted to 1 × 108 cm−2 s−1 which is considerably lower than the typical long-term value (2–4 × 108 cm−2 s−1 ). The slow-speed component of solar wind density flux constituted in average more than 68% of the total flux, the high-speed component was about 10%, reaching the maximum of 32% in some Carrington rotations.

This review presents the basic characteristics of the SPIRIT instrument onboard the CORONAS-F satellite, description of observation programmes, summary of observation sessions and scientific data obtained, as well as the main results in the research of hot coronal plasma, solar flares and the eruptive phenomena.

We present a summary of the scientific objectives, payload and mission profile of the Space Weather & Ultraviolet Solar Variability Microsatellite Mission (SWUSV) proposed to CNES and ESA (small mission).

The method of imaging XUV spectroscopy was used to study plasma in the transition layer and inner corona of the Sun with temperatures 105–107 K in the TEREK and RES experiments on board KORONAS-I. The observations were carried out in the period from March 12 to July 5, 1994. The spectral images and their correlation with the YOHKOH X-ray images and groundbased observations are important for the study of the physical conditions and modeling of the bulk processes in the quiet Sun plasma, including active regions, corona holes, and overlimb structures.

Some of local sources of the slow solar wind can be associated with spectroscopically detected plasma outflows at edges of active regions accompanied with specific signatures in the inner corona. The EUV telescopes (e.g. SPIRIT/CORONAS-F, TESIS/CORONAS-Photon and SWAP/PROBA2) sometimes observed extended ray-like structures seen at the limb above active regions in 1MK iron emission lines and described as "coronal rays". To verify the relationship between coronal rays and plasma outflows, we analyze an isolated active region (AR) adjacent to small coronal hole (CH) observed by different EUV instruments in the end of July - beginning of August 2009. On August 1 EIS revealed in the AR two compact outflows with the Doppler velocities V =10-30 km/s accompanied with fan loops diverging from their regions. At the limb the ARCH interface region produced coronal rays observed by EUVI/STEREO-A on July 31 as well as by TESIS on August 7. The rays were co-aligned with open magnetic field lines expanded to the streamer stalks. Using the DEM analysis, it was found that the fan loops diverged from the outflow regions had the dominant temperature of ~1 MK, which is similar to that of the outgoing plasma streams. Parameters of the solar wind measured by STEREO-B, ACE, WIND, STEREO-A were conformed with identification of the ARCH as a source region at the Wang-Sheeley-Arge map of derived coronal holes for CR 2086. The results of the study support the suggestion that coronal rays can represent signatures of outflows from ARs propagating in the inner corona along open field lines into the heliosphere., Accepted for publication in Solar Physics; 31 Pages; 13 Figures

Energy release in solar corona is used to attend with plasma heating. For the most powerful processes, temperature of plasma increases up to millions of Kelvin. For this reason, the study of hot coronal plasma is the key for understanding mechanisms of heating of the corona and nature of solar flares. In this chapter, we analyze observation of Mg XII line (10 MK) in series of experiments onboard CORONAS satellites. We studied configuration, dynamics, and temperature distribution in hot plasma structures. The possible mechanisms of heating are discussed.

Results of solar observations in the XUV-region by means of the telescope TEREK aboard the “Phobos-1” spacecraft are presented. Images of the Sun in the HeII 30,4 nm and FeIX-FeXI 17–18 nm lines were obtained with new types of optical elements — multilayer normal incidence XUV-mirrors and CCD-detectors. About 140 images were obtained with an angular resolution up to 15″ and with exposure times 0.1 to 40 s. In the images one sees the structures in the transition layer from corona to chromosphere which has temperatures in the range 5×104 – 1×106 K as well as in the polar and equatorial coronal holes. Besides, a unique phenomenon — a “blob” in outer corona at a distance about 2 solar radii has been observed. Processing of the data revealed a complex correlation between the XUV-images and the magnetic field structure in the photosphere.

An electron-beam deposition method is used to fabricate spherical and flat mirrors with a peak reflectivity of 20% for wavelengths between 120 and 450 Å. It is experimentally shown that the fabricated mirrors can be employed to form an image with a resolution of 1 μm for ultrasoft x rays. The possibility of producing intense directional high-temperature plasma radiation by spherical multilayer mirrors is demonstrated. A radiation intensity of 107 W/cm2 around 182 Å has been experimentally obtained in the laser plasma image plane.

LYRA is the solar UV radiometer that will embark in 2006 onboard Proba2, a technologically oriented ESA micro-mission. LYRA is designed and manufactured by a Belgian–Swiss–German consortium (ROB, PMOD/WRC, IMOMEC, CSL, MPS and BISA) with additional international collaborations. It will monitor the solar irradiance in four UV passbands. They have been chosen for their relevance to Solar Physics, Aeronomy and Space Weather: (1) the 115–125 nm Lyman-α channel, (2) the 200–220 nm Herzberg continuum range, (3) the Aluminium filter channel (17–70 nm) including He II at 30.4 nm and (4) the Zirconium filter channel (1–20 nm). The radiometric calibration will be traceable to synchrotron source standards (PTB and NIST). The stability will be monitored by onboard calibration sources (LEDs), which allow to distinguish between potential degradations of the detectors and filters. Additionally, a redundancy strategy maximizes the accuracy and the stability of the measurements. LYRA will benefit from wide bandgap detectors based on diamond: it will be the first space assessment of a pioneering UV detectors program. Diamond sensors make the instruments radiation-hard and solar-blind: their high bandgap energy makes them insensitive to visible light and, therefore, make dispensable visible light blocking filters, which seriously attenuate the desired ultraviolet signal. Their elimination augments the effective area and hence the signal-to-noise, therefore increasing the precision and the cadence. The SWAP EUV imaging telescope will operate next to LYRA on Proba2. Together, they will establish a high performance solar monitor for operational space weather nowcasting and research. LYRA demonstrates technologies important for future missions such as the ESA Solar Orbiter.

PROBA2 is an ESA technology demonstration mission to be launched in early 2007. The two primary scientific instruments on board of PROBA2 are SWAP (Sun Watcher using Active Pixel System detector and Image Processing) and the LYRA VUV radiometer. SWAP provides a full disk solar imaging capability with a bandpass filter centred at 17.5 nm (FeIX-XI) and a fast cadence of ≈1 min. The telescope is based on an off-axis Ritchey Chretien design while an extreme ultraviolet (EUV) enhanced APS CMOS will be used as a detector. As the prime goal of the SWAP is solar monitoring and advance warning of Coronal Mass Ejections (CME), on-board intellige nce will be implemented. Image recognition software using experimental algorithms will be used to detect CMEs during the first phase of eruption so the event can be tracked by the spacecraft without huma n intervention. LYRA will monitor solar irradiance in four different VUV passbands with a cadence of up to 100 Hz. The four channels were chosen for their relevance to solar physics, aeronomy and space weather: 115-125 nm (Lyman-α), 200-220 nm Herzberg continuum, the 17-70 nm Aluminium filter channel (that includes the HeII line at 30.4 nm) and the 1-20 nm Zirconium filter channel. On-board calibration sources will monitor the stability of the detectors and the filters throughout the duration of the mission.

[1] The extraordinary solar activity of October–November 2003 manifested itself in many powerful eruptive events, including large coronal mass ejections (CMEs) and extremely powerful flares. A number of major events were accompanied by practically all known phenomena of the solar activity, both local and large-scale, and caused severe space weather disturbances. We study large-scale posteruptive activity manifestations on the Sun associated with CMEs, i.e., dimmings and coronal waves, observed with extreme-ultraviolet telescopes, the SPIRIT on the CORONAS-F spacecraft and the EIT on the SOHO. During that period, observations with a cadence of 15 to 45 min were carried out by the SPIRIT in the 175 A and 304 A bands simultaneously. The EIT observed with 12-min cadence in the 195 A band as well as with 6-hour cadence in the 171, 284, and 304 A bands. These data complement each other both in the temporal and spectral coverage. Our analysis reveals that largest-scale dimmings covered almost the whole southern part of the Sun's visible side and exhibited homology, with one homological structure being changed to another configuration on 28 October. These structures show connections between large superactive and smaller regions that constituted a huge activity complex responsible for the extraordinary solar activity of that period. Coronal waves were observed at 175 A as well as at 195 A in some events, in areas where there were no active regions, but in the 175 A images they look fainter. They were not accompanied by deep, long-living dimmings. By contrast, such dimmings were observed in active regions, in their vicinity, and between them. These facts rule out the direct relation of the phenomena of long-term dimmings and coronal waves. On 18 November, a motion of an ejecta was observed at the solar disk as a propagation of a dark feature only in the 304 A band, which can be interpreted as an absorption in a “cloud” formed from material of the eruptive filament, which probably failed to become a CME core.

The paper describes instruments for solar imaging XUV spectroscopy - the TEREK-C telescope array and the RES-C spectroheliograph mounted on board the Russian-Ukrainian CORONAS-I satellite (launched on March 2, 1994). The CORONAS project is carried out under scientific guidance of Prof. V.N. Oraevsky, director of the IZMIRAN (Troitsk,Moscow region, Russia) - leading institute of this project. The instruments were intended to obtain high resolution solarimages and spectra from the transition region and the corona of the Sun within the temperature range of I O - I O K. Theoptical design of the TEREK telescope array includes two Herschelian XUV-telescopes with Mo-Si multilayer mirrors: thefirst one with 3 whole-Sun spectral channels (reflection peaks at X=13.2, 17.5 and 30.4 nm, angular scale 4.7"), the secondchannel - with 4 mirrors, each covering 1/4 of the Sun (2=17.5 nm, angular scale 1"). The RES-C spectroheliograph has fivemeasuring channels with a whole-Sun field of view: two XUV channels with orthogonal dispersion planes, equipped withgrazing incidence gratings and multilayer mirrors to obtain high resolution spectral images in the 19.2

Wide-field EUV telescopes imaging in spectral bands sensitive to 1 MK plasma on the Sun often observe extended ray-like coronal structures stretching radially from active regions to distances of 1.5-2Rsun, which represent the EUV counterparts of white-light streamers. To explain this phenomenon, we investigated the properties of a streamer observed on October 20-21, 2010 by the PROBA2/SWAP EUV telescope together with the Hinode/EIS spectrometer (HOP 165) and the Mauna Loa Mk4 white-light coronagraph. In the SWAP 174 A band comprising the Fe ix - Fe xi lines, the streamer was detected to a distance of 2Rsun. We assume that the EUV emission is dominated by collisional excitation and resonant scattering of monochromatic radiation coming from the underlying corona. Below 1.2Rsun, the plasma density and temperature were derived from the Hinode/EIS data by a line-ratio method. Plasma conditions in the streamer and in the background corona above 1.2Rsun from disk center were determined by forward-modeling the emission that best fit the observational data in both EUV and white light. It was found that plasma in the streamer above 1.2Rsun is nearly isothermal, with a temperature T=1.43+-0.08 MK. The hydrostatic scale-height temperature determined from the evaluated density distribution was significantly higher (1.72+-0.08 MK), which suggests the existence of outward plasma flow along the streamer. We conclude that, inside the streamer, collisional excitation provided more than 90% of the observed EUV emission; whereas, in the background corona, the contribution of resonance scattering became comparable with that of collisions at R > 2Rsun.

For XUV-imaging of the Sun with sub-arc second resolution it is proposed to use the Herschel telescope with aspherical (toroidal) multilayer mirror working at out-of-axis angle 1.5 - 2 degree(s). In that case aberrations (mainly astigmatism) are sufficiently reduced so high resolution better than 1' may be obtained. In comparison with the Ritchey-Chretien two- mirror telescope which is regarded as perspective to reach closely the diffraction limited resolution, the Herschel telescope is more simple, less critical to adjustment and has higher throughput. Toroidal mirrors with diameter D equals 30 mm, focal length F equals 800 mm and ratio of sagittal and meridional radii of curvature Rm/Rs equals 1.001 have been made on super polished fused quartz substrates (roughness better than 7 A). After shape correction mirrors were covered by Mo-Si coating for 175 A wavelength band. The mirrors were used in high resolution channel of the TEREK-C telescope designed for the CORONAS space solar observatory which was launched on March 2, 1994. An example of the solar image obtained by this telescope is presented.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

A number of high-performance normal-incidence multilayer mirrors (MMs) have been fabricated on concave (r equals 1.6 - 2.0 m) fused silica substrates using laser deposition and a magnetron ion sputtering source. The resonance wavelengths (lambda) 0 equals 2nd of the MMs synthesized are proximate to 45, 130, 175, 190, and 304 angstroms. The MMs have been subjected to scrutiny by a spectroscopic technique employing a laser-plasma broadband XUV radiation source. The spectral shapes of the resonance reflection curves, the (lambda) 0 values, and the aperture uniformity (topography) of the mirrors have been determined spectroscopically. Normal-incidence reflection maxima, which correspond to higher-order reflection (k(lambda) equals 2n(lambda )d, k > 1), have been observed for all of the Mo-Si MMs with (lambda) >= 175 angstroms.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

We analyzed brightness variations in widespread dimming regions occurred in several major eruptive events in 2003 and 2005 resulted in fast halo CMEs. In all cases brightness of remote dimming regions show some pre-eruptive growth, then gradual and fast decrease to minimum. The time interval of maximal decrease overlaps with X-flare peak and LASCO CME onset. Brightness variations in some dimmed regions are highly correlated before the CME onset and much less – after. It suggests a break of magnetic connectivity between previously linked coronal structures. Dimmings develop similar at 175 and 195 A being shallower and sometimes delayed at 304 A. In large-scale region (L 250 km/s which is typical for EIT-waves.