Radiation storms at low altitudes

The dynamics of energetic radiation, i.e., particles of radiation belts and galactic and solar cosmic rays in Earth’s environment during solar and geomagnetic disturbances, is analyzed in a review based on the CORONAS-F experimental data.     

The first uranium-thorium dating of the Middle Neopleistocene peat in West Siberia

For a sample from the roof of peat (0–2 cm) located in a reference section for the Middle Neopleistocene in West Siberia near the village of Krivosheino, we obtained an exorbitant value of ¹⁴C date ≥53.9 ka B.P. (LU-6024). In the peat proper, the ²³⁰Th/U dates obtained by the isochronous method are 195.2 ± 10.8/9.1 ka B.P. for the L/L model and 204.1 ± 17/13 ka B.P. for the TSD model. The palynospectra of the peat characterize, from the bottom up, birch forests with fir and spruce participation; then spruce forests with fir; next spruce-cedar forests, similar to the middle taiga subzone. In the clay, the following palynospectra have been examined: forb-gramineous grasslands and light forests with spruce and Betula fruticosa. In the upper part of clays, the palynospectra reflect the evolution of swampy, birch, light forests with spruce participation. The conclusion is made that the studied part of the section formed at the end of the Samarovo Ice Age and in the last third of the Taz Ice Age. The break in sedimentation related to the erosion contact covers a part of the Samarovo Ice Age and the first two-thirds of the Taz Ice Age.     

Stability of planetary systems with respect to masses

The stability in the sense of Lagrange of the Sun–Jupiter–Saturn system and 47 UMa system with respect to masses on a time scale of 10⁶ years was studied using the method of averaging and numerical methods. When the masses of Jupiter and Saturn increase by 20 times (approximately, more accurate value depends on a time-scale of stable motion), these planets can have close approaches. Close approaches appear when analyzing osculating elements; they are absent in the mean elements. A similar situation takes place in the case of 47 UMa and other exoplanetary systems. The study of Lagrange stability with respect to masses allows us to obtain upper limits for masses of extrasolar planets.     

Generation of Intermediate Drift Bursts by Magnetohydrodynamic Waves in the Solar Corona

The plasma mechanism of radio emission generation in an inhomogeneous medium is investigated. In the model under study, the electron beam with loss-cone distribution generates upper-hybrid waves that, in turn, are transformed into radio emission. It is shown that the influence of the plasma density inhomogeneity limits the plasma waves’ intensity considerably due to variation in their wave vector. The results are used to interpret the intermediate drift (IMD) bursts. A model is proposed in which these bursts are reflections of propagating small-scale (with amplitudes of about 1% and sizes of hundreds of kilometers) magnetohydrodynamic (MHD) disturbances of magnetic tubes. It is shown that this model allows us to explain the spectral parameters of the bursts in question. At present, the lack of precise and independent data about the magnetic field does not allow us to decide definitively between the existing models (whistler or MHD waves) of the IMD bursts; nevertheless, if the proposed model is correct, it can be used to determine the characteristics of the coronal MHD waves.     

Polar cap magnetic activity as a signature of substorm development

On the basis of the 5.46 min IMF data and the 3-min data on magnetic field at polar cap station Alert, various characteristics of the interplanetary magnetic field and polar cap magnetic activity are examined for the purpose of separating the substorm precursors. It is shown that the most suitable characteristics toward this aim are the following: 1.σ(B_Z)-index, defined as the 15-min sum of values of the southward (B_ZS) components of the IMF with an account of the negative gradient of the IMF vertical (B_Z) component; and 2.PC(B_Z)-index, defined as the 15-min sum of values of the polar cap magnetic disturbances, concerned with southward component B_ZS, with an account of variability of these disturbances. Every intense peak in the substorm activity is preceded by a corresponding increase in σ(B_Z) and PC(B_Z) indices. Thus, the conclusion is made that moderate and large substorms have a growth phase and as a result such substorms may be forecasted using the above indices.     

‘DEOS_CHAMP-01C_70’: a model of the Earth’s gravity field computed from accelerations of the CHAMP satellite

Performance of a recently proposed technique for gravity field modeling has been assessed with data from the CHAMP satellite. The modeling technique is a variant of the acceleration approach. It makes use of the satellite accelerations that are derived from the kinematic orbit with the 3-point numerical differentiation scheme. A 322-day data set with 30-s sampling has been used. Based on this, a new gravity field model – DEOS_CHAMP-01C_70 - is derived. The model is complete up to degree and order 70. The geoid height difference between the DEOS_CHAMP-01C_70 and EIGEN-GRACE01S models is 14 cm. This is less than for two other recently published models EIGEN-CHAMP03Sp and ITG-CHAMP01E. Furthermore, we analyze the sensitivity of the model to some empirically determined parameters (regularization parameter and the parameter that controls the frequency-dependent data weighting). We also show that inaccuracies related to non-gravitational accelerations, which are measured by the on-board accelerometer, have a minor influence on the computed gravity field model.     

Studying the solar corona above active regions from microwave observations during solar flares recorded by CORONAS-F satellite

In 2001–2003, 45 flares of hard X ray (HXR) and gamma ray radiation, identified with a particular active region (AR) that produced each event, were recorded during the experiments onboard the Russian Solar Observatory CORONAS-F using the SONG (solar neutrons and gamma ray quanta) instrument. The solar corona structure and dynamics above these ARs is studied on the basis of the microwave observations with two Russian radio telescopes RATAN-600 and Siberian Solar Radio Telescope (SSRT). The results are illustrated using the active region NOAA 9601 and flare of September 5, 2001 (～ 1430 UT) as an example. The flare is interesting because the energy of its gamma radiation exceeded 1 MeV, while its power was only M6.0 in soft X rays. Such a combination of the event characteristics is not too frequent, which indicates that the spectrum of the studied event was rather hard. The type of the source of microwave radiation above NOAA 9601 has been determined. Some properties of this-type sources of a diagnostic value for detecting ARs capable of producing HXR and gamma radiation are indicated.