ASPI experiment: measurements of fields and waves on board the INTERBALL-1 spacecraft

The plasma-wave experiment ASPI (analysis of spectra of plasma waves and instabilities) on board the INTERBALL spacecraft is a combined wave diagnostics experiment. It performs measurements of the DC and AC magnetic field vector by flux-gate and searchcoil sensors, the DC and AC electric field vector by Langmuir double probes and the plasma current by Langmuir split probe. Preliminary data analysis shows the low noise levels of the sensors and the compatibility of new data with the results of previous missions. During several months of in-orbit operation a rich collection of data was acquired, examples of which at the magnetopause and plasma sheet are presented in second part of the paper.     

The first data on U–Pb (SHRIMP) dating of zircon from metamorphic rocks of the crystalline base of the Taigonos-Paren Uplift (southern margins of the Omolon Massif)

U–Pb SHRIMP dating of zircons from metamorphic rocks of the crystalline basement of the Omolon-Taigonos area (northeastern margins of Asia) has been used to determine the periods of early endogenic activity of the crust. These periods correlate to the time of formation of the magmatic rock protolith (3.2–3.3 Ga), the stage of regional metamorphism (2.6–2.8 Ga), and the superimposed granitization. The resulting data can be used to reconstruct the history of development of the crust in the Precambrian.     

Composition and origin of metamorphosed ferromanganese rocks in metavolcanics of Eastern Kamchatka

This paper presents detailed mineralogical and geochemical data on the metamorphosed ferromanganese rocks observed as rare lenticular bodies among the metavolcanics of the Khavyven Highland and Ganal Ridge in Eastern Kamchatka. They are specific porphyry-type banded Mn-garnet and amphibole rocks with large (up to 1–5 mm) magnetite porphyroblasts. In the Khavyven Highland, ilmenohematite is associated with magnetite in the metamorphosed ferromanganese rocks of the greenschist facies. In the Ganal Ridge, magnetite in metamorphosed ferromanganese rocks of the amphibolite facies shows decay structures and contains Mn-ilmenite lamellae surrounded by tiny crystals of ferroaluminous Zn-spinel. Comparison of Fe-Ti oxides in the ferromanganese rocks of the Khavyven Highland and Ganal Ridge shows that metamorphism of these structures differed not only in temperature and pressure levels but also in the oxygen fugacity. The rocks of the Khavyven Highland were metamorphosed under greater oxidizing conditions relative to the analogous rocks of the Ganal Ridge. The garnets in the studied rocks demonstrate progressive zonality from the center to the rims of crystals: the Fe, Mg, and Ca concentrations are increased, while the Mn concentration is decreased. Amphibolites in the ferromanganese rocks of the Khavyven Highland are also characterized by progressive zonality: the crystal cores are composed of Mn-actinolite, whereas the marginal zones consist of Ca-Na amphibole (winchite and less common barroisite), testifying to an increase of temperature, pressure, and oxygen fugacity during metamorphism. The higher-temperature rocks of the Ganal Ridge usually contain Mg-hornblende and tschermakitic hornblende.     

ULF/ELF monochromatic oscillations observed by Prognoz-8 and -10 spacecrafts during quasiperpendicular supercritical shock crossings

The present paper analyses electromagnetic turbulence in the frequency range 0.1-75 Hz, associated with the supercritical quasiperpendicular crossings of the Earth’s bow shock recorded by the Prognoz-8 and -10 satellites. The quasimonochromatic waves are identified in the shock transition region. Their frequencies, lying in the range 2–5 Hz upstream from the shock ramp, shift to a value less than 1 Hz in the downstream region. The amplitudes of these narrow emissions are great enough to provide the primary dissipation in the flow of the solar wind plasma. Electromagnetic oscillations with such properties are likely to be generated during non-linear evolution of the shock front, rather than by the instabilities driven by ion and electron drifts. Emissions with frequencies higher than 5 Hz have much smaller amplitudes and may be driven by lower hybrid-like instabilities.     

Geochemistry of obsidian from Krasnoe Lake on the Chukchi Peninsula (Northeastern Siberia)

Doklady Earth Sciences - This report considers features of the geochemical composition of obsidian from beach sediments of Krasnoe Lake along the lower course of the Anadyr River, as well as from...