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

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

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

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

Relationship between the fluxes of relativistic electrons at geosynchronous orbit and the level of ULF activity on the Earth’s surface and in the solar wind during the 23rd solar activity cycle

We present the results of a cross-correlation analysis made on the basis of Spearman’s rank correlation method. The quantities to correlate are daily values of the fluence of energetic electrons at a geosynchronous orbit, intensities of ground and interplanetary ultra-low-frequency (ULF) oscillations in the Pc5 range, and parameters of the solar wind. The period under analysis is the 23rd cycle of solar activity, 1996–2006. Daily (from 6 h to 18 h of LT) magnetic data at two diametrically opposite observatories of the Intermagnet network are taken as ground-based measurements. The fluxes of electrons with energies higher than 2 MeV were measured by the geosynchronous GOES satellites. The data of magnetometers and plasma instruments installed on ACE and WIND spacecraft were used for analysis of the solar wind parameters and of the oscillations of the interplanetary magnetic field (IMF). Some results elucidating the role played by interplanetary ULF waves in the processes of generation of magneospheric oscillations and acceleration of energetic electrons are obtained. Among them are (i) high and stable correlation of ground ULF oscillations with waves in the solar wind; (ii) closer link of mean daily amplitudes of both interplanetary and ground oscillations with ‘tomorrow’ values of the solar wind velocity than with current values; and (iii) correlation of the intensity of ULF waves in the solar wind, normalized to the IMF magnitude, with fluxes of relativistic electrons in the magnetosphere.     

Effect of large and sharp changes of solar wind dynamic pressure on the earths’s magnetosphere: analysis of several events

The magnetosphere and ionosphere response to arrival of large changes of the solar wind dynamic pressure with sharp fronts to the Earth is considered. It is shown that, under an effect of an impulse of solar wind pressure, the magnetic field at a geosynchronous orbit changes: it grows with increasing solar wind pressure and decreases, when the solar wind pressure drops. Energetic particle fluxes also change: on the dayside of the magnetosphere the fluxes grow with arrival of an impulse of solar wind dynamic pressure, and on the nightside the response of energetic particle fluxes depends on the interplanetary magnetic field (IMF) direction. Under the condition of negative Bz-component of the IMF on the nightside of the magnetosphere, injections of energetic electron fluxes can be observed. It is shown, that large and fast increase of solar wind pressure, accompanied by a weakly negative Bz-component of the IMF, can result in particless’ precipitation on the dayside of the auroral oval, and in the development of a pseudobreakup or substorm on the nightside of the oval. The auroral oval dynamics shows that after passage of an impulse of solar wind dynamic pressure the auroral activity weakens. In other words, the impulse of solar wind pressure in the presence of weakly negative IMF can not only cause the pseudobreakup/substorm development, but control this development as well.     

Space weather forecast: Principles of the construction and boundaries of the implementation (experience of three cycles)

All significant short-term disturbances of the near-Earth space are caused exclusively by solar flare events and regions in the solar corona with the magnetic field open into the interplanetary space (coronal holes). Flare processes occur as a consequence of the interactions of new emerging magnetic fluxes within (flares) and outside (filament ejections) the active regions with already existing magnetic fields. The observation of emerging new magnetic fluxes and the estimate of their magnitude and the emerging rate allow one to forecast solar flares and filament ejections and estimate their degree of geoeffectiveness. The main agents that visualize the propagation of disturbance from solar flares and filaments in the solar corona and the interplanetary space are coronal mass ejections, the characteristics of which ideally allow one to estimate the possible disturbance of the geomagnetic field, the possible growth of high-energy charged particle fluxes in the near-Earth space. For successful forecast of geoeffective active phenomena on the Sun and their consequences in the near-Earth space, it is necessary to know the situation on the Sun for the last 3 days taking into account the development and characteristics of the current cycle and the epoch of solar activity.     

Characteristics of the decay phase of proton fluxes in solar events as a function of observer’s heliolongitude

Events in energetic solar protons with the energy > 4 MeV at the stage of their decay are considered for the period from 1974 to 2001. It is shown that in the events with the exponential shape of decay for west flares (relative to the observation point), the characteristic decay time τ and the power index γ of the energy spectrum decrease with an increase in the angular distance between the observer and the source of the particles on the Sun, while this effect is absent for east flares.     

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

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

The Earth's Magnetosphere Response to Solar Wind Events according to the INTERBALL Project Data

The results of studying the interaction of two types of the solar wind (magnetic clouds and solar wind of extremely low density) with the Earth's magnetosphere are discussed. This study is based of the INTERBALL space project measurements and on the other ground-based and space observations. For moderate variations of the solar wind and interplanetary magnetic field (IMF) parameters, the response of the magnetosphere is similar to its response to similar changes in the absence of magnetic clouds and depends on a previous history of IMF variations. Extremely large density variations on the interplanetary shocks, and on leading and trailing edges of the clouds result in a strong deformation of the magnetosphere, in large-scale motion of the geomagnetic tail, and in the development of magnetic substorms and storms. The important consequences of these processes are: (1) the observation of regions of the magnetosphere and its boundaries at great distances from the average location; (2) density and temperature variations in the outer regions of the magnetosphere; (3) multiple crossings of geomagnetic tail boundaries by a satellite; and (4) bursty fluxes of electrons and ions in the magnetotail, auroral region, and the polar cap. Several polar activations and substorms can develop during a single magnetic cloud arrival; a greater number of these events are accompanied, as a rule, by the development of a stronger magnetic storm. A gradual, but very strong, decrease of the solar wind density on May 10–12, 1999, did not cause noticeable change of geomagnetic indices, though it resulted in considerable expansion of the magnetosphere.     

Some features of solar cosmic ray penetration into the Earth’s magnetosphere

We compared fluxes of the 1–100 MeV solar energetic particles (SEP) measured in the interplanetary medium (ACE) and in the magnetosphere (Universitetsky-Tatiana, POES—in polar caps, and GOES-11—at geosynchronous orbit) during several SEP events of 2005–2006. Peak intensities of the SEP fluxes inside and outside the magnetosphere were compared for each event. It is shown that observed inside-outside difference depends mainly on direction of interplanetary magnetic field (IMF), on degree of the SEP anisotropy (pitch-angle distribution) in IMF, and on distance of the dayside magnetopause from the Earth.     

Algebra and statistics of the solar wind

Statistical studies of properties of the solar wind and interplanetary magnetic field, based on an extended database for the period 1963–2007 including four solar cycles, show that the Gaussian approximation well suites for some parameters as the probability distribution of their numerical values, while for others the lognormal law is preferred. This paper gives an interpretation of these results as associated with predominance of linear or nonlinear processes in composition and interaction of various disturbances and irregularities propagating and originating in the interior of the Sun and its atmosphere, including the solar corona and the solar wind running away from it. Summation of independent random components of disturbances leads, according to the central limit theorem of the probability theory, to the normal (Gaussian) distributions of quantities proper, while their multiplication leads to the normal distributions of logarithms. Thus, one can discuss the algebra of events and associate observed statistical distinctions with one or another process of formation of irregularities in the solar wind. Among them there are impossible events (having null probability) and reliable events (occurring with 100% probability). For better understanding of the relationship between algebra and statistics of events in the solar wind further investigations are necessary.     

太阳高能粒子在行星际中的扩散过程

当太阳活动频繁,特别是有耀斑爆发或者日冕物质抛射驱动的激波时,经常能够观察到高能粒子(能量从几十keV到几十MeV)通量突然增加,这种由太阳活动产生的高能粒子事件被称为太阳高能粒子事件。文章研究了耀斑和日冕物质抛射产生的两类高能粒子事件,重点讨论了高能粒子横越磁力线的扩散对粒子在行星际空间传播过程中所起到的作用,给出了对于不同扩散系数条件的数值模拟结果。     

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.     

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

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

Fluxes of low-energy particles in quiet periods of solar activity and the <Emphasis Type="Italic">MgII</Emphasis> index

Low fluxes of protons with energies 0.3–10 MeV were studied during 21–23 solar cycles as a function of the MgII index using the data of the instruments CPME, EIS (IMP8), and EPHIN (SOHO). It has been shown that a) during quiet time of solar activity the fluxes of protons (background protons) have a positive correlation with the MgII index value throughout the solar cycle, b) specific features of variations of the MgII index during the solar minima of 1986–1987 and 1996–1997 can be considered, as well as variations of background fluxes of low energy charged particles, to be manifestations of the 22-year magnetic cycle of the Sun, and c) periods of the lowest value of the MgII index are also characterized by the smaller values of the ratio of intensities of protons and helium nuclei than in other quiet periods. A hypothesis is put forward that acceleration in a multitude of weak solar flares is one of the sources of background fluxes of low energy particles in the interplanetary space.     

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.     

Specific features of solar cosmic ray fluxes and geomagnetic conditions on December 5–18, 2006

Results of the analysis of specific features of solar activity, dynamics of solar cosmic ray fluxes, and state of the interplanetary medium are presented for the period December 5–18, 2006. The data analysis is based on new model concepts on coronal and interplanetary propagation of solar cosmic rays: partial capture into the magnetic field traps and oscillations at reflections from magnetic mirrors. Some new hypotheses about possible relations of the features of the interplanetary medium with processes in the Earth’s magnetosphere are put forward: the influence of the discrete interplanetary medium on processes in the Earth’s magnetosphere does exist always and, in this sense, it is a fundamental phenomenon; the discreteness of the inter-planetary medium can be one of the causes of geomagnetic substorms.     

Penetration of solar cosmic rays into the Earth’s magnetosphere on January 28, 2012

Results of the comparative analysis of the dynamics of SCR fluxes with energies of 1–100 MeV in the interplanetary environment according to the data of the ACE and Wind spacecraft and within the Earth’s magnetosphere according to the data of the GOES-15 and Electro-L satellites in the region of geostationary orbits, and POES-19 and Meteor-M1 in the region of polar caps during two increases in SCR of January 19–31, 2012, are presented. It is shown that the decrease in the efficiency of SCR penetration into the Earth’s magnetosphere in the region of the orbits under study on January 28, 2012, is related to the passage of the Earth’s magnetosphere through the interplanetary environment structure with a quasi-radial interplanetary magnetic field and a small pressure of the solar wind.     

不同内边界条件下SEP事件实例的集合数值模拟及其在SEP事件预报中的应用

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

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

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

MHD Simulations of the Dynamics of Sharp Disturbances of the Interplanetary Medium and Comparison with Spacecraft Observations

One-dimensional MHD simulations of solitary sharp and strong disturbances (impulses) of the interplanetary magnetic field and plasma of the homogeneous solar wind were performed. The characteristics of a disturbance of this type, recorded onboard the WIND spacecraft (SC) rather far from the Earth, were taken as initial conditions. The results of numerical experiments simulating the evolution of this disturbance in the moving interplanetary plasma, whose parameters correspond to observations of the WIND and INTERBALL-1 SC, show the efficiency of the computer code developed with the special purpose of investigating low-frequency wave events in the space environment. The calculated characteristics of the impulse resulting from the evolution are in good agreement with parameters of the disturbance recorded by the INTERBALL-1 SC closer to the Earth. In particular, the impulse expands due to imbalance of thermal and magnetic pressures, but keeps its abrupt boundaries. It was demonstrated that stable plasma objects, corresponding to stationary MHD solutions, could really exist in the solar wind plasma for a long time.