Ion Plasma Composition Research Articles

Wave Effects Related to Altitude Variations in the Ion Composition of the Ionosphere

Properties of the waves, which can propagate in a magnetized plasma in the frequency range below the proton gyrofrequency, depend strongly on the ion composition of the plasma. Addition of a new sort of ions leads to the appearance of a new resonance frequency, at which the refractive index becomes infinite, and a new cutoff frequency, at which the refractive index becomes zero. In this case, the topology of frequency dependence of the squared refractive index changes. Specifically, a new oscillation branch appears, which is located above the cutoff frequency. A question arises whether these oscillations are excited if radiation with the corresponding frequency, which propagates in a different mode, is present in the plasma. A linear transformation of the waves is another important effect, which is related to variations in the ion plasma composition. These two issues, which are directly related to the theory of formation of proton whistlers in the ionosphere, where the ion composition varies with altitude, are considered in this work.

Ion–plasma composition for brazing of titanium alloys

The results of development of a Mo–Ni layered composition, based on OT4 titanium alloys, using the ecologically efficient magnetron methods, are presented. The mechanism of formation of the joint in the OT4–Mo contact pair in the coating deposition stage are described. It is shown that in the thermal conditions of brazing the layer composition (850°C) mutual diffusion penetration of the material takes place ensuring the high quality of bonding in the OT4–Mo and Mo–Ni contact pairs.

The cleft ion plasma environment at low solar activity

Low energy (0.3–25 eV) ion plasma composition and three‐dimensional differential velocity distribution measurements have been made from the Sounding of the Cleft Ion Fountain Energization Region (SCIFER) mission. SCIFER traveled poleward into the dayside prenoon cleft region under conditions of low solar activity. Upleg measurements show that the subcleft topside had a rapid density fall‐off with altitude (ne ≤ 300 cm−3 at 1400 km altitude), and that the payload floating potential changed from typical ionospheric negative values of about a volt, to zero or positive values consistent with ne ≤ 1000 cm−3 in sunlight. As the payload moved poleward and approached apogee, the ion plasma flux abruptly increased. Observations of Langmuir waves at the electron plasma frequency show the plasma density increased by a factor of 6 over a scale length of ∼1 km. The plasma density boundary coincided with passage into the cleft region, as judged from the appearance of field‐perpendicular ion heating to T⟂∼1 eV, with upward bulk flows of several km/s for H+, and 1–2 km/s for O+, and warm superthermal tails in the core H+ with characteristic energy ∼4 eV. An inverse association was observed between ion temperature and plasma density, consistent with heating by current‐driven waves. The heated cleft plasma was H+‐dominated in this region, in stark contrast to the O+ domination observed from 3000–6000 km altitude by DE‐1 and Akebono near solar maximum.