Reconstruction of space weather physical parameters on 400-year scale

The main goal of this paper is to get physically informative comprehensive data about dynamics of the solar magnetic field, geomagnetic field, and interplanetary magnetic field over large time scales. The total sunspot magnetic flux, aa and IDV indices of geomagnetic activity, the IMF strength, the dipole-octopole index of the large-scale magnetic field of the Sun, and the open magnetic flux are reconstructed for 400 years. The reconstruction of the π index of the large-scale polar magnetic field of the Sun is performed for 150 years.     

Parametric resonance in the solar corona

When studying microwave emission of active regions on the Sun, an effect of parametric resonance between 5-min velocity oscillations in the solar photosphere and sound oscillations of coronal magnetic loops modulating the microwave emission has been discovered for the first time. The effect shows itself as simultaneous excitation in coronal magnetic loop of oscillations with periods 5, 10, and 3 min, which correspond to the pumping frequency, subharmonic, and the first upper frequency of parametric resonance. The parametric resonance can serve as an effective channel of transporting the energy of photospheric oscillations into the upper layers of the solar atmosphere. This effect opens up the important prospects in understanding the mechanisms of coronal plasma heating.     

Vertical structure of the magnetic field in active regions of the sun at coronal heights

High-altitude measurements and magnetic field distribution in active regions are always an important problem to verify existing models at heights from units to hundreds of Mm. Optical methods of analysis of the magnetic structure work well only at the photosphere level. At the same time, the progress of radio astronomy methods of analyzing the solar radio emission [1] and of the theory of solar plasma radiation [2] facilitates introduction of new methods for measuring the magnetic field strength at various altitudes in the solar atmosphere. In this paper we use multi-wave observations of polarization of the radio emission of active regions in the microwave range together with precise magnetosphere data in order to develop a method of projection for measuring the height distribution of the magnetic field.     

Alfven modes of solar coronal magnetic arches: Excitation of ballooning instability and modulation of flare emission

The effect of Alfven-type oscillations in a coronal magnetic arch on modulation of the gyrosynchrotron radiation and development of the ballooning instability in the arch is considered. On the basis of the energy method and the method of normal modes, the expressions are obtained for increments of ballooning instability at its swinging by natural oscillations of the arch. The conclusion is drawn that bending oscillations, which do not actually compress the plasma and, therefore, represent the Alfven-type modes, unlike the radial oscillations, are capable, under solar corona conditions, to effectively swing ballooning instability and, as a consequence, play a part of a trigger for solar flares. The ballooning instability of coronal arches is shown to be capable of causing formation of helmet-shaped structures in the lower solar corona. On the basis of calculations of the intensity modulation depth and the degree of circular polarization of non-thermal gyrosynchrotron radiation, under the assumption of excited Alfven oscillations of a coronal arch, the conclusion is drawn, that microwave observations at a frequency of > 10 GHz can be used for studying the conditions of excitation and propagation of Alfven modes in flare loops. The consequences of obtained results are discussed using the flare on April 15, 2002 as an example.     

Sunspot oscillations as derived from the <Emphasis Type="Italic">SOHO</Emphasis>/MDI magnetograms

As a result of processing long (up to 144 h) series of sunspot magnetograms obtained on the SOHO (Solar and Heliospheric Observatory) spacecraft with the MDI (Michelson Doppler Imager) instrument it is shown that the mode with a period of 800–1300 min is a limiting low-frequency oscillation mode of the magnetic field of a sunspot as a whole. Its period is essentially and nonlinearly depends on the sunspot magnetic field strength. In addition to this mode, higher harmonics are also revealed in the sunspot oscillation spectra in the bands 40–45, 60–80, 135–170, 220–250, and 480–520 min. The oscillation power in these bands monotonically and rapidly decreases with increasing frequency, which is characteristic for overtones arising due to the nonlinear nature of oscillations. The limiting oscillation mode stably exists in sunspots for 1.5–2 days, which coincides with the average lifetime of a supergranular cell. The mode with the period of 35–48 h observed in the power spectrum is not an eigen mode of sunspots, because its period is independent of its magnetic field strength. Probably, it occurs as a quasiperiod of an external exciting force caused by disturbances from supergranular cells surrounding the sunspot.     

Statistical properties of the fluxes of energetic ions and solar wind in the region of intersection of shock wave fronts in the distant heliosphere

The character of statistical distributions of the intensity of energetic charged particles, solar wind flux, and the interplanetary magnetic field strength is analyzed using the data obtained by the Voyager 1 and Voyager 2 spacecraft in the distant heliosphere. A comparison of the distributions in the region of crossings of shock wave fronts in 1991 and in 2004 is carried out, and their similarities and differences are discussed.     

Geomagnetic effect of launches and flights of large spacecraft

The results of observations of variations in the geomagnetic field that accompanied launches and flights of rockets of different types have been analyzed. The launches were performed in 2002–2010 from different space launch facilities of the world (237 events in total), and variations in the range of periods 1–1000 s were studied. Measurements were performed near the city of Kharkov (distance from the spaceports ranges from 1500 to 9500 km). Statistical analysis and spectral estimations have been made, and three groups of disturbances were revealed. Time delays and disturbance durations increased with increasing distance from spaceports. Typical periods were equal to 6 to 14 min, while amplitudes varied in the range 1–3 nT.     

Longitudinal structure of ballooning MHD disturbances in a model magnetosphere

Large-scale toroidal Pc5 pulsations are commonly treated as Alfven oscillations of a magnetic field line. According to observations, their longitudinal structure is described well by theory. At the same time, the longitudinal structure of azimuthal small-scale poloidal Pc5 pulsations is virtually unknown. These pulsations are associated with ballooning disturbances described by a system of coupled equations for Alfvenic and slow magnetosonic (SMS) modes. In this work, the Voigt model is used to describe the equilibrium finite-pressure plasma configuration in an inhomogeneous magnetosphere plasma in a curved magnetic field. Spectral characteristics and the spatial structure of natural ballooning modes are calculated for this model. The model calculations demonstrate the possibility of different longitudinal scales for transverse and longitudinal magnetic components of oscillations near the top of the field line.     

Topological model of the solar event including a flare and coronal mass ejection on October 19, 2001

Based on the analysis of a strong solar flare X1.6/2B on October 19, 2001 in the active region 9661, accompanied by a coronal mass ejection (CME) of the halo type, a topological model of development of this solar event is suggested. The model considers a unified process of development of CME and a chromosphere flare. According to the model, this process has a common source of energy supply: the turbulent current layer lying between the arcade of flare loops and the surface of CME going away. The structures on the ends of flare bands (SEFB) represent in this model chromosphere feet of the system of large-scale coronal magnetic arches at the initial stage of the dynamic processes whose evolution results in CME. Peripheral structures (PS) of the flare (elongated double bright emission strips beyond the limits of the active region) are interpreted as chromosphere bases of magnetic field lines that form an external shell (braid) of the CME at the late stage of the flare.     

Planetary waves according to simultaneous observations of <Emphasis Type="Italic">GPS</Emphasis> satellites and ground-based magnetic stations

On the basis of measurements made at Japanese magnetic stations and using GPS satellites for the 12 months of 2003, a comparison of simultaneous variations of three components of the magnetic field and total electron content (TEC) was carried out in the range of the planetary waves period. The correlation analysis has shown that almost synchronous variations exist within this range of periods at the ground-based magnetometer stations and in the TEC measurements both during strong magnetic disturbances and in quiet periods. The strong magnetic disturbances could be considered as a possible independent source of ionospheric variations within the planetary waves range, while the accompanying ionospheric storms could be a possible factor changing the conductivity of the lower ionosphere plasma. In quiet periods, the correlation of magnetic variations and disturbances in TEC is caused by the direct impact of atmospheric planetary waves on the lower ionosphere and can be related to variations of ionospheric currents due to the dynamo mechanism.     

The development of compression long-period pulsations on the recovery phase of the magnetic storm on May 23, 2007

The features of the excitation of spatially localized long-period (10–15 min) irregular pulsations with a maximum amplitude of ~200 nT at a geomagnetic latitude of 66° in the morning sector 5 MLT are considered. Fluctuations were recorded against the background of substorm disturbances (maximum AE ~ 1278 nT). Antiphase variations of plasma density and magnetic field accompanied by vortex disturbances of the magnetic field both in the magnetosphere and the ionosphere have been recorded in the magnetosphere in this sector. Compression fluctuations corresponding to a slow magnetosonic wave have been recorded in the interplanetary medium in the analyzed period. It is assumed that pulsations have been excited in the localization of the cloud of injected particles in the plasma sheet by compression fluctuations caused by variations of the dynamic pressure of solar wind.     

Theory of type III radio bursts in the interplanetary space: I. Derivation of permittivity tensor for the system consisting of electron beam and solar wind plasma

The tensor of permittivity for the system “electron beam - plasma of the interplanetary space” is derived in the approximation of geometrical optics. The problem is one-dimensional; all parameters such as density of the beam and of the solar wind plasma, and the induction of the interplanetary magnetic field are assumed to be dependent only on the distance to the Sun. The beam is generated by an active region during a solar flare, and it is a source of radio bursts of type III in the interplanetary space. The tensor of permittivity was obtained to close field equations by a material equation. On the basis of these equations it becomes possible to study theoretically the amplitude-frequency characteristics of the radio bursts as disturbances of the above-described beam-plasma system.     

Energy dependence of the characteristic decay time of proton fluxes in solar cosmic ray events

Energetic solar proton events within the energy interval 1–48 MeV at the stage of their decay are considered over the period of 1974–2001. The dependence of the characteristic decay time on the proton energy in the assumed power-law representation τ(E) =E ^?n is analyzed for the events with an exponential decay form. The dependence of n on the heliolongitude of the flare (the particles source on the Sun) is studied.     

Spectral analysis of ionospheric disturbances in the phase delay and radio signal amplitude at limb paths according to the <Emphasis Type="Italic">COSMIC</Emphasis> data in periods of solar activity

Based on more than 4500 sessions of radio transillumination of Earth’s atmosphere along the satellite–atmosphere–satellite path obtained in the COSMIC experiment, the distribution along latitude and over local time of the spatial spectra of variations in the ionospheric phase delay and signal amplitude has been analyzed. The spatial spectra have been calculated for two height ranges, i.e., 60–80 and 80–100 km. In the phase signal spectrum within the height range 80–100 km, the second maximum in the vicinity of a frequency of 7–8 rad/km is clearly seen. Its diurnal and latitudinal behavior and its decrease towards high latitudes in both hemispheres can also be seen. In the height range of 60–80 km, this maximum is hardly observed. Although solar flares can lead to substantial local changes in the electron concentration, no substantial difference in the behavior of the spectral densities of the amplitude and phase delay at long limb paths was observed within these two height ranges on days of active and quiet sun. The latter fact makes it possible to develop a united algorithm of optimal ionospheric correction of the radio occultation data independent of solar activity.     

Ionospheric disturbances in the north-east region of Russia according to ionosonde data in the periods of equinoxes

Ionospheric disturbances in the equinox periods of 2005–2006 are considered on the basis of the ionosondes of vertical and oblique sounding located in the north-east region of Russia. It is found that the X-ray flares observed in the first half of September 2005 caused an additional increase in the ionization of the lower ionosphere in the daytime, this fact leading to a development of absorption and an increase in the lowest observable frequencies at the Magadan-Irkutsk and Noril’sk-Irkutsk radio paths. Wave-like changes in the maximum observable frequencies and critical frequencies with periods of about 2–2.5 h were detected during the magnetic disturbances. Oscillations of the planetary wave type with periods of 4–5 days were also revealed.     

Model estimations of possible climatic changes in 21st century at different scenarios of solar and volcanic activities and anthropogenic impact

We have made estimations of climatic changes in the 21st century at different scenarios of changes in the solar and volcanic activities using ensemble calculations with the help of a three-dimensional climatic model taking the carbon cycle into account. This model was developed in the Oboukhov Institute of Atmospheric Physics, Russian Academy of Sciences. An ensemble of scenarios is used for possible changes of the solar radiation flux in the 21st century, based on different methods of extrapolation of the data for the period 1610–2000. Along with this, different scenarios of volcanic activity in the 21st century are used. The results of thus made calculations are indicative of a rather small role played by the solar activity variations in changes of the global mean annual near-surface temperature in the 21st century as compared to the expected anthropogenic impact. Model changes of the global near-surface temperature in the 21st century (possible variations of the solar radiation and volcanic activity included) are characterized by a general increase determined in the main by anthropogenic SRES scenarios.     

A mechanism for generating magnetic field by vortex processes in stellar plasma

The difference in viscous properties of proton and electron gases in fully ionized hydrogen plasma is shown to result in a possibility of generation in this plasma of the magnetic field, even if initially there was no field. As an example, a simplified planar stationary model of a magnetohydrodynamic process of the eddy sink type is considered. It is demonstrated that the intensity of the generated magnetic field strongly depends on plasma temperature, so that the range T = 100000–500000 K corresponds to the range of maximum magnetic induction B = 50–2700 G. Such values are frequently observed in ordinary stars, in particular, in solar flares.     

Influence of the interplanetary magnetic field on ULF oscillations of the ionospheric resonator

A weak but statistically reliable dependence of the diurnal activity of oscillations in the ionospheric Alfvén resonator on orientation of the interplanetary magnetic field ahead of the magnetospheric front has been detected based on observations of ULF oscillations at Sayan solar observatory Mondy of the Institute of Solar–Terrestrial Physics. The interpretation of the result has been proposed. The essence is that the electromagnetic fluctuations penetrate into the magnetosphere from the interplanetary environment and influence the ionospheric resonator. The formulation of the problem and the method of solving it are part of the broad program of the experimental and theoretical study of the influence of the interplanetary magnetic field on the oscillation regime of ULF oscillations of the magnetosphere.     

Long-term variations of asymmetry of the solar magnetic field and geometry of the interplanetary magnetic field

A comparative analysis of variations of the mean solar magnetic field and the interplanetary magnetic field over all history of their measurements is performed. Asymmetry of the solar magnetic field and its manifestation in the heliosphere is investigated. Long-term variations of the solar magnetic field and the heliosphere, which manifest themselves in alternation of dominating magnetic polarities of different sign, are discovered. On the basis of the analysis of cumulative sums of the IMF components, long-term variations of the IMF geometry and of the solar wind spiral angle are found. The cumulative sum of the IMF B _z component perpendicular to the ecliptic plane also shows long-term variations. Time intervals are revealed, in which negative values of the IMF B _z component dominate, and an increased geomagnetic activity is observed.