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Statistical properties of the daily averaged values of the solar activity (sunspot numbers, total solar irradiance and 10.7 cm radio emission indices), the solar wind plasma and the interplanetary magnetic field parameters near the Earth’s orbit are investigated for a period from 1964 to 2002 covering the maxima of four solar cycles from 20th to 23rd. Running half-year averages show significant solar cycle variations in the solar activity indices but only marginal and insignificant changes in comparison with background fluctuations for heliospheric bulk plasma and magnetic field parameters. The current 23rd cycle maximum is weaker than 21st and 22nd maxima, but slightly stronger than 20th cycle in most of solar and heliospheric manifestations.

We analyze solar origins of intense geomagnetic perturbations recorded during 2002. All of them were related to coronal mass ejections (CMEs). The initiation of CMEs was documented using the SPIRIT instrument (SPectrohelIographic Soft X-Ray Imaging Telescope) onboard the CORONAS-F satellite. Monochromatic full Sun images taken in the Mg XII doublet at 8.418 and 8.423 A showed the appearance of free energy release sites at altitudes up to 0.4 solar radii. CMEs were initiated at these sites and propagated in interplanetary space under appropriate local conditions including the geometry of the magnetic fields.

The problem of the observed fast damping of longitudinal waves in solar coronal magnetic loops is studied. According to some data, the radiation effect, which plays a key role in the cooling of coronal loops that are observed in the extreme UV wavelength range, is used to explain this phenomenon. The dispersion relation for slow magnetosonic modes of a cylindrical magnetic tube has been obtained with regard to the radiation effect. It has been indicated that the radiation actually results in the fast damping of the slow magnetosonic modes of coronal magnetic loops.

Preliminary results of an analysis of satellite and ground-based measurements during extremely strong magnetic storms at the end of October 2003 are presented, including some numerical modeling. The geosynchronous satellites Ekspress-A2and Ekspress-A3, and the low-altitude polar satellites Coronas-F and Meteor-3M carried out measurements of charged particles (electrons, protons, and ions) of solar and magnetospheric origin in a wide energy range. Disturbances of the geomagnetic field caused by extremely high activity on the Sun were studied at more than twenty magnetic stations from Lovozero (Murmansk region) to Tixie (Sakha-Yakutia). Unique data on the dynamics of the ionosphere, riometric absorption, geomagnetic pulsations, and aurora observations at mid-latitudes are obtained.

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.

The available experimental data and theoretical reasons allow us to point out only the upper limit of Phobos' magnetic moment, which does not exceed 1018 G cm3.

The free energy transformations leading to the observed solar cycle variations of the total solar irradiance are not known. The energy of magnetic fields and their dissipation related to the solar activity manifestations in large scale structures on the Sun do not look to be sufficient energy reservoirs and channels for producing the total solar radiation variations with the relative amplitudes of the order of 10−3. Other types of the free energy should be also involved in the solar cycle and the longer time variability. They could be nuclear power, gravity, mechanical motions, electromagnetic radiation, heat. The main open question remains: what are the energy, momentum and mass distributions and fluxes in space and time inside the Sun during the cycles?

Quite an unusual behavior of the low-energy ion fluxes measured with the LECP and CRS instruments onboard Voyager 1, which is located in the outer heliosphere at a distance of about 90 AU, has been observed since July 2002 until recently (February 2003). This behavior can be interpreted as a possible manifestation of a combination of the global heliospheric disturbance produced by solar activity and the precursor of the outer heliosphere with its termination shock. The extremely large variability of the enhanced ion fluxes since the second half of 2002 in several energy channels from 0.5 to several MeV/nucleon is presumed to be associated with the sources of their acceleration near the termination shock. The simultaneous increase in the flux of protons with energies above 70 MeV may result from the easier penetration of Galactic cosmic rays because of the reduction in modulation at the declining phase in the current solar cycle 23 after the maximum in 2000 and from an admixture of the anomalous component accelerated at the termination shock.

A short account of theoretical and observational studies is presented supporting ideas about complicated topological properties of the coronal and heliospheric magnetic fields and their changes during the solar cycle.

A database is compiled for the study of solar and heliospheric causes of geomagnetic perturbations with the daily average index Aр > 20 that were observed in the period 1997–2000. The number of such events (more than 200) progressively increased and fluctuated as the current solar cycle developed. It is established that geomagnetic storms are generated by dynamical processes and structures near the center of the solar disk in a zone of several tens of degrees, and these processes are responsible for the appearance in the Earth's region, within several tens of hours, of quasistationary and transient solar wind streams with a sufficiently strong southward component of the heliospheric magnetic field. These streams lasted more than a few hours. The following structures can serve as morphological indicators for the prediction of the appearance of such streams: (1) active and disappearing filaments derived from synoptic Нα-maps of the Sun, (2) solar flares, (3) coronal holes and evolving active regions, and (4) the heliospheric current sheet. The geometry of coronal mass ejections needs further observational study.

Solar wind and interplanetary magnetic field parameters are investigated using the data obtained at the Earth's orbit for the 20–23 solar cycles. The time-epoch analysis and hysteresis curves of the heliospheric parameters show some general and specific properties of the cycles. We have found specific hysteresis behaviour when the solar wind energy flow and the induced electric field are plotted against the sunspot number during 20–22 solar cycles. Based on these finding and using measured heliospheric parameters during the rising phase of the current 23-rd solar cycle we are able to present some semi-quantitative estimations of the expected solar wind energy flux and the induced electric field for the time period after the solar maximum. The similarity between the rising phases of the 23-rd and 20-th solar cycles presents additional grounds for expectations of the lower maximum of the current solar cycle and the geomagnetic activity in the present solar cycle as compared with the 21-st and 22-nd solar cycles.

The dynamics of the interplanetary proton spectra in the energy range 1–40 MeV have been investigated using the data obtained on board the IMP-8 (1973–1992) and Meteor (1970–1996) satellites. Phase diagrams of the proton events are constructed in the two-parametric space { Y,g }, where Y=g −1 lg( I p ), g is the differential energy spectral index, I p represents the >1 MeV proton intensity. The results show that the phase trajectories allow separation of the background proton fluxes, proton populations accelerated mainly in the solar flares, at the propagating interplanetary shocks associated with coronal mass ejections and also in the corotating interaction regions between fast and slow solar wind streams. The estimations of the maximal and minimal >1 MeV proton fluxes in the near Earth heliosphere are obtained.

We report on observations of the solar luminosity variations in the Fe xii line (195 A) over the period 1996–1999, which corresponds to the minimum and rising phase of the current 23rd solar cycle. The relatively or rather high temporal cadence and spatial resolution of the Extreme-ultraviolet Imaging Telescope (EIT) on board the Solar and Heliospheric Observatory (SOHO) allowed a nearly continuous measurement of intensity of different structures on the Sun. We find that a significant contribution to the longitudinal asymmetry, and thus to the 27-day variability of the solar EUV radiation, is produced by the numerous intermediate brightness elements that are globally distributed over large areas (up to about \( \sim \frac{2}{3} \) of the whole surface of the Sun). When activity is low, this component even becomes dominant over the contribution from localized active regions and bright points. This suggests that weak magnetic field areas outside active regions constitute an important factor through which solar activity modulates the solar EUV luminosity.

The periods 1975–1977, 1985–1987 and 1995–1997 were selected between pivot points of the solar cycles to analyze available spacecraft data for three successive solar minima. The mean values of the solar wind velocity, dynamic pressure, and temperature are decreasing during each indicated time interval. All variations are of several 0.1. The interplanetary magnetic field is minimal at solar minima. There is no strong difference between solar wind and interplanetary magnetic field parameters as well as solar activity indices for these solar cycles. Nevertheless, the proton cosmic ray intensities and spectra during these especially quiet periods possibly show the remarkable 22-year variation with the minimal proton fluxes in 1985–1987.

A simple analytical model for the global magnetic configuration in the heliosphere is described as a superposition of the solar magnetic multipoles and a thin equatorial current sheet. Polar plumes are tracing these global field lines and inhomogeneous field-aligned currents. Both internal and external boundary conditions are important for the polar plume formation and dynamics.

The coupling between small and large scale structures and processes on the Sun and in the heliosphere is important in the relation to the global magnetic configuration. Thin heliospheric current sheets play the leading role in this respect. The simple analytical model of the magnetic field configuration is constructed as a superposition of the three sources: 1) a point magnetic dipole in the center of the Sun, 2) a thin ring current sheet with the azimuthal current density j ϕ ∼ r −3 near the equatorial plane and 3) a magnetic quadrupole in the center of the Sun. The model reproduces, in an asymptotically correct manner, the known geometry of the field lines during the declining phase and solar minimum years near the Sun (the dipole term) as well as at large distances in the domain of the superalfvenic solar wind in the heliosphere, where the thin current sheet dominates and ∥ B r ( θ )∥ = const according to Ulysses observations (Balogh et al., 1995; Smith et al., 1995). The model with the axial quadrupole term is appropriate to describe the North-South asymmetry of the field lines. The model may be used as a reasonable analytical interpolation between the both extreme asymptotic domains (inside the region of the intermediate distances ∼ (1−10R bd) when considering the problems of the solar wind dynamics and cosmic ray propagation theories.

The cyclic evolution of the heliospheric plasma parameters is related to the time-dependent boundary conditions in the solar corona. “Minimal” coronal configurations correspond to the regular appearance of the tenuous, but hot and fast plasma streams from the large polar coronal holes. The denser, but cooler and slower solar wind is adjacent to coronal streamers. Irregular dynamic manifestations are present in the corona and the solar wind everywhere and always. They follow the solar activity cycle rather well. Because of this, the direct and indirect solar wind measurements demonstrate clear variations in space and time according to the minimal, intermediate and maximal conditions of the cycles. The average solar wind density, velocity and temperature measured at the Earth’s orbit show specific decadal variations and trends, which are of the order of the first tens per cent during the last three solar cycles. Statistical, spectral and correlation characteristics of the solar wind are reviewed with the emphasis on the cycles.

Time series of the solar wind and interplanetary magnetic field parameters, as well as solar and geomagnetic indexes were compared during different phases of the 20, 21 and 22-d solar cycles. General trends and solar cycle variations are evaluated and compared with published results. Points of correspondence and differences are noticed. New features in the density and the temperature are found. Possible interpretations are suggested using the concepts of the magnetically open, closed and intermittent types of the solar wind sources. We conclude that the observed variations at the Earth's orbit are related to the space-time evolution of the mentioned sources on the Sun and their different proportions during different solar cycle phases. Magnetic fields of the Sun and the heliospheric current sheet play the mediating role.

Observational evidence of 3 and 5 min vertical oscillations of a filament on the disk are recorded. Wave activity was observed before, during and after a filament disappearance, inside and around the filament. Both an Hα brightening and, later, a blowing out of a faint soft X-ray (Yohkoh) loop system occuring in connection with a flare were noticed. The wave activity seems to be a dynamically important ingredient of this erupting prominence.Propagating MHD waves and convective structures bring their energy and momentum from the photosphere towards the chromosphere up to the coronal heights where they are partially reflected and/or dissipated. The transition from the laminar to the turbulent state of the whole prominence enhances the dissipation rate of the external waves inside this system, adding energy to produce the heating and lifting of the plasma. Internal plasma instabilities could trigger this transition in the framework of a prominence disappearance.

A possible acceleration mechanism by the magnetic force is suggested for a plasmoid, modeled as a spherical body with a magnetic dipole situated in its center of mass. The governing equations of the motion of a dipole in an inhomogeneous magnetic field are solved analytically and numerically. Both methods show the possibility for the plasmoid to be accelerated in the direction of the external field gradient.

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.

We present the results of measurements of the solar energetic particle (SEP) flows in the Earth polar caps obtained from KORONAS-I on April 14, 1994. The maximum energy of protons was 12 MeV and the maximum energy of electrons was 1.3 MeV. The asymmetry of the North-South flows was observed several hours after their peak intensity. We determined the propagation characteristics of SEP in the isotropic diffusion model. Although the SEP enhancement has not been related to the solar flaring event, the genetic relationship of this effect with one of the largest-scale dynamical events on the Sun measured from YOHKOH is obvious. The possible sources of particle acceleration are discussed.

Enhancements of protons with energiesEp=1–4.5 MeV were observed from the KORONAS-I satellite in the period from March to June 1994. They represent part of a long series of corotating particle enhancements registered by the ULYSSES spacecraft outside the ecliptic plane. An about 5-day nearly constant shift between the maximum times was recorded by the two space vehicles. The assumptions of acceleration area localization and fast proton propagation conditions in the heliosphere are discussed on the basis of a joint analysis of the results presented here and the related experimental data.

A short review of the recent studies of the three-dimensional structure of the heliosphere is presented. The main progress is due to direct plasma and magnetic field measurements from the Ulysses spacecraft outside the ecliptic plane in heliolatitudes of up to ±80°.The new data are used for the development of theoretical models.

Short duration bursts—1–3 s or 0.05–0.15° MLAT—of 32 eV to several hundred eV electrons are regularly observed in the polar rain and mantle precipitation regions by the DMSP satellites. The spacing between bursts is typically 9–12 s (70–90 km) and is sometimes regular but more often irregular. Sometimes quasi-periodic trains of 4 or 5 evenly spaced bursts occur. Electron spectra in the bursts are variable, but typically represent an enhancement of an order of magnitude in the spectral differential energy flux, but without showing signs of field-aligned acceleration. Previous reports of bursty polar cap precipitation consisted of precipitation with large scale (hundreds of km) spatial inhomogeneity of plasma sheet origin under northward IMF conditions. The bursts described herein occur for southward as well as northward IMF Bz, and represent fine structure (7.5 km) within regions that are of magnetosheath origin and which are homogenous over larger spatial scales (>∼100 km). We suggest that the observed phenomena may be related to the nonstationary processes in the outer high latitude magnetosphere.

The self-consistent 1D kinetic Harris-like model of a collisionless current sheet is developed for the case of the current sheet experiencing the impact of an external uniform gravity field. The ambipolar Pannekoek-Rosseland electric field appears in the system as a result of the additional drift motion of ions and electrons. This produces separation of charges, which is responsible for corresponding changes of the current sheet form. The presence of gravitation leads to formation of asymmetric distributions of the magnetic field as well as the plasma and the current density changes. Our estimations show that gravity-forced disruptions of the current sheet profile may occur in the Mercurial magnetosphere and, most probable, in the Io plasma torus near the Jupiter. Also, the model can be applied to magnetospheres of exoplanets.

The coronal mass ejection (CME) that occurred on April 28, 2015 is analyzed. The passage of the ejection did not cause geoeffective disturbances in the near-Earth space. At the same time, the CME had a significant impact on the flux of cosmic rays registered on the Earth's surface by the muon hodoscope URAGAN.

[1] The global electron content (GEC) derivation is initiated by summing up the total electron content of each cell of Global Positioning System GPS-TEC global map multiplied by the cell area. Algorithm of GEC calculation is improved in the present paper using the electron density varying with height through the total volume of a spherical layer in near-Earth space up to 20,200 km (GPS orbit) reconstructed from TEC with the International Reference Ionosphere model extended to the Plasmasphere (IRI-Plas). An analytical model is first derived for two-phase typical GEC storm profile by a common epoch analysis of 10 storms during 2001–2011 with the starting time put at the origin of the negative phase of GEC departure from the quiet reference (5 day median). It is found that GEC depletion occurs synchronously with decrease of the solar wind velocity and the outset of recovery of the magnetospheric ring current (the equatorial Dst index) and the auroral electrojet (AE index). Thus, the GEC is an indicator of the plasma injection in the ionosphere and plasmasphere with the solar wind energy inducing the positive phase of GEC storm during 24 h with electron number increased by 10–20% followed by a negative phase with GEC decrease by 10–20% during 40 h of a plasma release (ejection) into the magnetosphere tail beyond the three Earth radii (GPS orbit).

[1] We investigate the average properties of geomagnetic storms using the global and local Dxt indices at four Dst stations in 1932–2009. Imposing the condition of complete data availability during storms, our study includes 1268/362/134/59 storms with Dxt minimum less than −50/−100/−150/−200 nT, respectively. The global Dxt minima were, on an average, −94/−156/−216/−275 nT, while deepest storm-time local Dxt minima were −137/−214/−285/−350 nT. Accordingly, the local Dxt minima are typically 25–30% stronger than the global Dxt minima. The distribution of largest storm-time disturbances is strongly peaked at 18 local time (LT), challenging local midnight as the dominant ion source. Relative timing of local minima verifies that stations at earlier LT hour observe their minimum a couple of hours after the deepest minimum, in agreement with westward drift of ions. Storm-time maximum asymmetries were found to increase with storm intensity level from about 70 nT to 150 nT for −50 to −200 nT storms. However, strong storms are relatively more symmetric than weak storms when compared to the typical level of local disturbance. During individual storms the asymmetry can be more than 200 nT. The rate of evolution of storm-time asymmetry is found to be roughly twice as fast for large storms. We emphasize that the unique database of local Dxt indices proves to be very useful in studying the average spatial distribution and temporal evolution of storms.

The possibility of a large scale non-steady state interaction between the solar wind and the local interstellar medium (LISM) is investigated. Due to the non-uniqueness of the nonlinear steady-state solutions of the balance and structure equations, regular or irregular oscillations with time scales of the order of months and years may be expected.

We describe the fine structure of white light polar plumes observed using SOHO/LASCO C2 coronagraph. The evolving helical structures of different scales are clearly seen on processed images (the processing is made to reveal the faint contrast objects). The observed structures trace the magnetic field lines, so the electric currents flow along the axes of plumes. An MHD model of a plume which takes into account field-aligned electric currents is developed. The model permits to understand the existence of high-density plasma inside the plume due to the balance between the magnetic forces and the transverse pressure gradient.

From a broader perspective, the heliosphere and planetary magnetospheres provide a test bed to explore the plasma physics of the Universe. In particular, the underlying nonlinear coupling of different spatial and temporal scales plays a key role in determining the structure and dynamics of space plasmas and electromagnetic fields. Plasmas and fields exhibit both laminar and turbulent properties, corresponding to either well organized or disordered states, and the development of quantitative theoretical and analytical descriptions from physics based first principles is a profound challenge. Limited observations and complications introduced by geometry and physical parameters conspire to complicate the problem. Dimensionless scaling analysis and statistical methods are universally applied common approaches that allow for the application of related ideas to multiple physical problems. We discuss several examples of the interplay between the scales in a variety of space plasma environments, as exemplified in the presentations of the IAGA session From Micro- to Macro-scales in the Heliosphere and Magnetospheres.

More than 20 years ago V.P. Shabansky suggested that the magnetic system installed aboard the satellite, could be used as a physical instrument for studying the processes which occur in the near Earth space. The corresponding space scales of an artificial “magnetosphere”—“magnisphere”—are ∼ 10 m in the experiment with relatively small magnets in the ionosphere and ∼ 100 m in the solar wind. The corresponding similarity criteria are estimated. The possible scheme of the experiment with a superconducting magnet (magnetic moment ∼ 10 5 A · m 2 ) installed aboard the satellite is considered. The experimental complex includes a number of systems for measuring the fluxes of charged particles in a wide energy range, DC electric and magnetic fields, the electromagnetic fields in different frequency bands (from X-rays to radio). The scientific objectives are discussed in detail.

When the large-scale spectrometer AMS-02 with the super-conductive coils will be installed at ISS, their residual magnetic field could be effective dipole-like obstacle to form a so called “Magnisphere” in front of AMS due to its interaction with the plasma of ionosphere under conditions of super-sonic, but sub-alfvenic ISS velocity. The boundary (between magnetic field and plasma, at distance RN ∼ 5÷8 m from AMS) of such “Magnisphere” or other mini-magnetospheres, could essentially disturb the whole plasma and electromagnetic environments of ISS due to various small- and large-scale plasma instabilities or waves generation. Therefore we discuss a relevant actual problem and specific features of “Magnisphere” formation, structure and dynamics under essentially non-MHD conditions of the interaction between a dipole and plasma flow, when its directed ion Larmor is in a few times larger than R N . Preliminary data of the laboratory and numerical simulations for such extremely non-MHD dipole-plasma interaction are presented.

International audience; Several important issues are open in the field of solar variability and they wait their solution which up to now was attempted using critical ground-based instrumentations. However, accurate photometric data are attainable only from space. New observational material should be collected with high enough spatial and spectral resolution, covering the whole visible range of the electromagnetic spectrum as well infrared and ultraviolet to reconstruct the total solar irradiance: (1) the absolute contributions of different small-scale structural entities of the solar atmosphere from the white light flares and from micro-flares are still poorly known; (2) we do not know the absolute contributions of different structural elements of the solar atmosphere to the long-term and to the cyclic variations of the solar irradiance, including features of the polar regions of the Sun; (3) the variations of the chromospheric magnetic network are still poorly evaluated; (4) only scarce information is available about the spectral variations of different small-scale features in the high photosphere. Variability of the Sun in white light can be studied with higher spectral, spatial and time resolution using space-born telescopes, which are more appropriate for this purpose than ground based observatories because of better seeing conditions, no interference of the terrestrial atmosphere and a more precise calibration procedure. Scientific requirements for such observations and the possible experimental tools proposed for their solution. Suggested solar studies have broader astrophysical importance.

New planned orbiter missions to Mercury have prompted renewed efforts to investigate the surface of Mercury via ground-based remote sensing. While the highest resolution instrumentation optical telescopes (e.g., HST) cannot be used at angular distances close to the Sun, advanced ground-based astronomical techniques and modern analytical and software can be used to obtain the resolved images of the poorly known or unknown part of Mercury. Our observations of the planet presented here were carried out in many observatories at morning and evening elongation of the planet. Stacking the acquired images of the hemisphere of Mercury, which was not observed by the Mariner 10 mission (1974–1975), is presented. Huge features found there change radically the existing hypothesis that the “continental” character of a surface may be attributed to the whole planet. We present the observational method, the data analysis approach, the resulting images and obtained properties of the Mercury’s surface.

New planned orbiter missions to Mercury have prompted renewed efforts to investigate the surface of Mercury via ground-based remote sensing. While the highest resolution instrumentation optical telescopes (e.g., HST) cannot be used at angular distances close to the Sun, advanced ground-based astronomical techniques and modern analytical and software can be used to obtain the resolved images of the poorly known or unknown part of Mercury. Our observations of the planet presented here were carried out in many observatories at morning and evening elongation of the planet. Stacking the acquired images of the hemisphere of Mercury, which was not observed by the Mariner 10 mission (1974–1975), is presented. Huge features found there change radically the existing hypothesis that the “continental” character of a surface may be attributed to the whole planet. We present the observational method, the data analysis approach, the resulting images and obtained properties of the Mercury’s surface.

Strong X-flares and solar energetic particle (SEP) fluxes are considered as sources of topside ionospheric disturbances observed by the ROCSAT-1/IPEI instrument during the Bastille Day event on 14July 2000 and the Halloween event on 28October–4 November 2003. It was found that within a prestorm period in the dayside ionosphere at altitudes of ~600 km the ion density increased up to ~80% in response to flare-associated enhancements of the solar X-ray emission. Ionospheric response to the SEP events was revealed both at sunlit and nightside hemispheres, where the ion density increased up to ~40% and 100%, respectively. We did not find any prominent response of the ion temperature to the X-ray and SEP enhancements. The largest X-ray and SEP impacts were found for the X17 solar flare on 28October 2003, which was characterized by the most intense fluxes of solar EUV (Tsurutani et al., 2005) and relativistic solar particles (Veselovsky et al., 2004). Solar events on 14July 2000 and 29October 2003 demonstrate weaker impacts with respect to their X-ray and SEP intensities. The weakest ionospheric response is observed for the limb X28 solar flare on 4November 2003. The topside ionosphere response to the extreme solar events is interpreted in terms of the short-duration impact of the solar electromagnetic radiation and the long-lasting impact of the SEP.

We investigate possible links between the activity manifestations in the solar corona and conditions in the solar wind. For the reduction of this immense task we have selected 206 events in the solar wind in 1997 – 2000 corresponding to geomagnetic events with Ap > 20 (compiled into a database at http://alpha.sinp.msu.ru/apev). Up to now, 24 events during the epoch of low solar activity (January 1997 – January 1998) are investigated. The solar wind conditions monitored by ACE and WIND spacecraft were traced back to the solar corona observed by SOHO/EIT. The search for coronal signatures which are probably associated with the disturbed solar wind conditions was performed. The coronal sources of these 24 events are identified, namely: eruptions in active regions, filament eruptions and coronal holes. It is shown that halo and partial halo CMEs observed within the SOHO/LASCO sensitivity limits are not necessary indicators of Earth‐directed eruptions, and coronal EUV dimmings can be used as a complementary indicator. We also found that a structure now conventionally called a “sigmoid” cannot be represented as a single S‐shaped loop (flux tube), but exhibits an assembly of many smaller structures. It could be formed and destroyed via eruptions.

A short review is presented of the dissipative and radiative MHD, electromagnetic and plasma kinetic scaling approaches which are useful for sorting out different physical processes according to their relative importance. The ‘velocity-emission’ ratio Ve, the Faraday number F and ‘Trieste numbers’ T are described together with more familiar dimensionless parameters. The concepts of the turbosphere and turbopause around the Sun are outlined.

The mosaic structure of the magnetic field in the heliosphere is described. It is formed by multiple corotating and propagating magnetic domains which are especially numerous during solar maximum years.

The tilted rotator model is considered using the collisionless supersonic and superalfvenic approximation. The results show that the maximal and minimal solar wind corotating stream velocities appear at the intermediate heliospheric latitudes depending on the tilt angle. The high-speed streams with the strongest velocity difference between maximal and minimal values are expected to be observed at the middle heliolatitudes near 45 degrees. Other consequences of the model are indicated and may be checked during the rapid pole-to-pole Ulysses passage in 1994–1995.

A kinematic model of the stationary electromagnetic fields in interplanetary space with finite conductivity is considered. The electrodynamic problem is solved for a medium with uniform conductivity and radial plasma outflow from a spherical source. Simple analytical formulae are obtained for electric and magnetic fields, currents and charges in the case of a uniformly-magnetized rotating sphere.

Fast-streaming solar-wind plasma with high conductivity screens the heliosphere from the penetration of the interstellar electric and magnetic fields. The simplest model with the constant solar wind conductivity and radial velocity is considered and the boundary electrodynamic problem is solved for static external fields. The results show that screening of the external fields takes place in the heliosphere according to the exponential law.

Mercury’s surface is thought to be covered with highly space-weathered silicate material. The regolith is composed of material accumulated during the time of planetary formation, and subsequently from comets, meteorites, and the Sun. Ground-based observations indicate a heterogeneous surface composition with SiO2 content ranging from 39 to 57 wt%. Visible and near-infrared spectra, multi-spectral imaging, and modeling indicate expanses of feldspathic, well-comminuted surface with some smooth regions that are likely to be magmatic in origin with many widely distributed crystalline impact ejecta rays and blocky deposits. Pyroxene spectral signatures have been recorded at four locations. Although highly space weathered, there is little evidence for the conversion of FeO to nanophase metallic iron particles (npFe0), or “iron blebs,” as at the Moon. Near- and mid-infrared spectroscopy indicate clino- and ortho-pyroxene are present at different locations. There is some evidence for no- or low-iron alkali basalts and feldspathoids. All evidence, including microwave studies, point to a low iron and low titanium surface. There may be a link between the surface and the exosphere that may be diagnostic of the true crustal composition of Mercury. A structural global dichotomy exists with a huge basin on the side not imaged by Mariner 10. This paper briefly describes the implications for this dichotomy on the magnetic field and the 3 : 2 spin : orbit coupling. All other points made above are detailed here with an account of the observations, the analysis of the observations, and theoretical modeling, where appropriate, that supports the stated conclusions.