Solar wind energy transfer regions inside the dayside magnetopause—I. Evidence for magnetosheath plasma penetration

PROGNOZ-7 high temporal resolution measurements of the ion composition and hot plasma distribution in the dayside high latitude boundary layer near noon have revealed that magnetosheath plasma may penetrate the dayside magnetopause and form high density, high β, magnetosheath-like regions inside the magnetopause. We will from these measurements demonstrate that the magnetosheath injection regions most probably play an important role in transferring solar wind energy into the magnetosphere. The transfer regions are characterized by a strong perpendicular flow towards dawn or dusk (depending on local time) but are also observed to expand rapidly along the boundary layer field lines. This increased flow component transverse to the local magnetic field corresponds to a predominantly radial electric field of up to several mV m^?1, which indicates that the injected magnetosheath plasma causes an enhanced polarization of the boundary layer. Polarization of the boundary layer can therefore be considered a result of a local MHD-process where magnetosheath plasma excess momentum is converted into electromagnetic energy (electric field), i.e. we have primarily an MHD-generator there. We state primarily because we also observe acceleration of “cold” ions inside the magnetopause as a result of this radial electric field. A few cases of polarity reversals suggest that the polarization is sometimes quite localized.The perhaps most significant finding is that the boundary layer is observed to be charged up to tens of kilovolts, a potential which may be highly variable depending on e.g. the presence of a momentum exchange by the energy transfer regions.     

Solar wind plasma protrusion into the martian magnetosphere: ASPERA-3 observations

The ASPERA-3 experiment onboard the Mars Express spacecraft revealed, near the wake boundary of Mars, a spatially narrow, strip-like plasma structure composed of magnetosheath-like electrons and planetary ions. The peak electron energy often exceeds the peak energy at the bow shock that indicates a significant heating (acceleration) during the structure formation. It is shown that this structure is formed during efficient plasma penetration into the martian magnetosphere in the region near the terminator. The penetration of sheath electrons and their gradual heating (acceleration) is accompanied by a change of the ion composition from a solar wind plasma to a planetary plasma dominated by oxygen ions. A possible mechanism of plasma inflow to the magnetosphere is discussed.     

Asymmetry of plasma fluxes at Mars. ASPERA-3 observations and hybrid simulations

The asymmetry of fluxes of solar wind and planetary ions is studied by using the ASPERA-3 observations onboard the Mars Express spacecraft in February 2004 to March 2006. Due to the small scale of the Martian magnetosphere and its induced origin, the flow pattern near Mars is sensitive to the directions of the interplanetary magnetic and electric (-V×B) fields. Asymmetry of the magnetic field draping produces an asymmetry in plasma flows in the plane containing the IMF. The crustal magnetic fields on Mars also influence the flow pattern. Scavenging of planetary ions is less efficient in the regions of strong crustal magnetization and therefore the escape fluxes of planetary ions in the southern hemisphere are smaller. The results of the observations are compared to simulations based on a 3D hybrid model with several ion species.     

Tectonics and magmatism of ultraslow spreading ridges

The tectonics, structure-forming processes, and magmatism in rift zones of ultraslow spreading ridges are exemplified in the Reykjanes, Kolbeinsey, Mohns, Knipovich, Gakkel, and Southwest Indian ridges. The thermal state of the mantle, the thickness of the brittle lithospheric layer, and spreading obliquety are the most important factors that control the structural pattern of rift zones. For the Reykjanes and Kolbeinsey ridges, the following are crucial factors: variations in the crust thickness; relationships between the thicknesses of its brittle and ductile layers; width of the rift zone; increase in intensity of magma supply approaching the Iceland thermal anomaly; and spreading obliquety. For the Knipovich Ridge, these are its localization in the transitional zone between the Gakkel and Mohns ridges under conditions of shear and tensile stresses and multiple rearrangements of spreading; nonorthogonal spreading; and structural and compositional barrier of thick continental lithosphere at the Barents Sea shelf and Spitsbergen. The Mohns Ridge is characterized by oblique spreading under conditions of a thick cold lithosphere and narrow stable rift zone. The Gakkel and the Southwest Indian ridges are distinguished by the lowest spreading rate under the settings of the along-strike variations in heating of the mantle and of a variable spreading geometry. The intensity of endogenic structure-forming varies along the strike of the ridges. In addition to the prevalence of tectonic factors in the formation of the topography, magmatism and metamorphism locally play an important role.     

First results from the hot plasma instrument PROMICS-3 on Interball-2

The PROMICS-3 instrument on Interball-2 is nominally identical to the PROMICS-3 instrument on Interball-1. It performs three-dimensional measurements of ions in the energy range 4 eV–70 keV with mass separation and of electrons in the energy range 300 eV–35 keV. Interball-2 was launched on August 29, 1996, into an orbit with the same inclination as that of Interball-1, 63°, but with apogee at 20 000 km. In this study the PROMICS-3 instrument on Interball-2 is briefly described and examples of the first results are presented. Firstly, we report observations of upward moving molecular ions with energies of up to 700 eV at the poleward edge of the auroral oval. Previous observations of outflowing molecular ions have been at lower altitudes and lower energies. Secondly, we show observations of dawnside magnetosheath plasma injections. Using conjugate data from both PROMICS-3 instruments we have found dispersion structures above the morningside auroral oval, which occurred simultaneously with isolated “pockets” of magnetosheath plasma at a distance of X_GSM = −14 to −12 R_E, which had been injected into the inner part of the low-latitude boundary layer. These isolated plasma structures were sites of strong field-aligned currents and are proposed to be the magnetospheric counterparts of the dispersion structures.     

Localized auroral disturbance in the morning sector of topside ionosphere as a standing electromagnetic wave

An intense, localized auroral disturbance observed by Intercosmos-Bulgaria-1300 satellite in the morning sector at the altitude 850 km is analyzed in detail. The disturbance is characterized by strong “jumps” of electric and magnetic fields reaching ～ 80 mV/m and ～ 100 nT, fluctuations of ion density (Δn/n ～ 70%) and bursts of downward and upward energetic electron fluxes. Electric and magnetic disturbances display a distinct spatial-temporal relationship typical for the standing quasi-monochromatic wave ($\text{? ～ 1}\text{Hz}\text{, λ}{}_{\mathrm{x}}\text{～ 10}\text{km}$). The ratio of amplitudes of electric and magnetic fluctuations is equal to Alfvén velocity (ΔE/ΔB ～ v_A/c). However, a strong parallel component of the electric field (～ 30 mV/m) and large ion density fluctuations indicate significant changes of plasma properties (the effects of anomalous resistivity are possible).     

Simulation of cometary magnetic tails

In order to simulate a cometary tail in a laboratory the flow of hydrogen collisionless supersonic plasma with the magnetic field frozen in was used. The wax ball served as a model of the cometary nucleus. The experimental conditions met the principle of limiting simulation. Field lines enveloped the nucleus at the day side and stretched along the flow at the night side. Tension of field lines in the magnetic tail provided the acceleration of ionized products of wax evaporation up to about 10⁶ cm s^–1. The control experiments showed that the magnetic tail is caused by currents due to the Lorentz electric field.     

Geochemistry of rare earth elements in micro-and macronodules from the pacific bioproductive zone

Concentrations and compositions of rare earth elements (REE) in three micronodule fractions (50–250, 250–500, and >500 μm), coexisting macronodules, and host sediments are examined. The samples were collected from three sites (Guatemala Basin, Peru Basin, and northern equatorial Pacific) located in elevated bioproductivity zones of the surficial water. The influence of micronodule size is dominant for REE compositions and subordinate for REE concentrations. For example, the Ce concentration inversely correlates with the micronodule fraction dimension and drops to the lowest value in macronodules and host sediments. The Ce decrease is generally accompanied by the Mn/Fe increase in micro- and macronodules. Hence, the role of diagenetic source of material directly correlates with the micronodule dimension. The contribution of diagenetic source is maximal for macronodules. The REE signature distinctions of micronodules and macronodules can be attributed to variations of hydrogenic iron oxyhydroxides and diagenetic (hydrothermal) iron hydroxophosphates that are the major REE carriers in ferromanganese ore deposits. The relationship and general trend in the chemistry of coexisting macronodules suggest that they can represent products of the initial stage of nodule formation.     

Dynamics of forest fires and climate in Ilmen nature reserve, 1948–2013

This paper considers the impact of climatic factors on the forest fire rate in Ilmen State Reserve based on 66 years of direct observation data for 1948–2013. This period was marked by a gradual annual increase in the number of recorded fires in the reserve. The higher fire rate is generally related to lengthening of the fire season and more frequent fires in the spring and summer–early autumn periods. We did not obtain sufficient evidence to verify a relation of the higher fire rate to climate changes. The average monthly and seasonal weather conditions can be involved to explain only some causes of the interannual fire rate variability. The observed changes in some climatic characteristics could have contributed to an increase in the fire rate, while others could have reduced it.