Finite Element Based Comparative Analysis of Positive Streamers in Multi Dispersed Nanoparticle Based Transformer Oil

The dispersion of dissimilar nanoparticles (NPs) in transformer oil (TO) has a major impact on fast propagating positive streamers. This work investigates the positive streamer dynamics in TO modified by dispersing both Fe3O4 and Al2O3 NPs at a homogenous concentration. The hydrodynamic drift diffusion model of positive streamer evolution and propagation are solved using the commercial software package COMSOL Multiphysics. The impact of multiple NPs (MNPs) has been analysed for streamer propagation, electric field intensity, electron density, and space charge density of modified TO. MNPs successfully reduce streamer propagation velocity by 50%, 17%, and 37.5% comparing to pure oil, Fe3O4 based nanodielectric fluids (NDFs), and Al2O3 based NDFs, respectively. The spatial distribution of electron density reveals the loss of electrons from the ionization region until the saturation of NPs. A comparative study demonstrates that MNPs significantly alter the streamer dynamics and augment the dielectric strength of TO compared to individual NPs.

Initial Calibration Results of the NIM Flight Spare Mass spectrometer for Exploration of Jupiter’s Icy Moons Exospheres

<p>The search for life is one of the key topics in modern space science. The JUICE mission of the European Space Agency ESA will investigate Jupiter and its icy moons Ganymede, Callisto and Europa, with Europa being an example of a potentially habitable world around a giant gas planet. The Particle and Environment Package, PEP, on board of the JUICE spacecraft will investigate Jupiter’s icy moons and their environment. The Neutral gas and Ion Mass spectrometer NIM will investigate the icy moon’s exospheres to investigate their formation and the interaction processes of the exospheres with the moons’ surface and Jupiter’s strong magnetic field. It will enhance our understanding of the processes involved in the interactions of ion bombardment on the icy moons' surfaces. From these measurements, we will derive the moons’ surface composition and their formation processes.</p><p>NIM is a time-of-flight mass spectrometer with two particle entrances: an open-source entrance to measure neutral particles and ions directly and a close source entrance where neutral particles get thermalized before entering the sensor’s ionization region. This allows detecting of particles with high speeds. NIM has a specially designed ion storage source and an ion-mirror to double the flight distance of the produced ions by keeping the sensor at a minimal size.</p><p>In this contribution, we show calibration results of the NIM flight spare instrument on one hand operated with laboratory and on the other operated with flight electronics. We demonstrate the performance of NIMs ion-source, verify the performance of the closed-source antechamber. NIM has a demonstrated mass resolution of m/Δm 800.</p>

Исследование динамики формирования плазмоидов в гатчинском разряде

The results of studies of the Gatchina discharge carried out at the Harbin Technological University (China) are presented. The Gatchina discharge is mainly used to create an analogue of ball lightning in the ordinary atmosphere of a laboratory. Most of the research on this discharge by various groups of scientists is devoted to the study of the first phase of the discharge, when an electric discharge is galvanically coupled to an electrode. This is due to the fact that many researchers consider this phase of the discharge to be decisive for the subsequent long-term existence of an autonomous luminous formation - the second phase of the discharge. In this paper, in comparison with similar works, the leader-streamer process on the water surface was demonstrated more fully and with a better resolution. The use of the filter made it possible to better show the role of leaders, streamers, and the ionization region in the immediate vicinity of the water surface and to clarify some of the processes occurring in the autonomous phase of the discharge. In the wavelength range of 400-500 nm, the autonomous luminous formation showed a longer lifetime in the form of a spherical shape than when observed in "white" light. With a sharp increase in the amount of substance introduced to the cathode, a new physical effect was recorded, which consists in the fact that in the medium of an ordinary atmosphere, a complex formation of a white color is formed without losing contact with the electrode (cathode). By varying the electrical conductivity and initial voltage, an unexpectedly small luminous formation with a diameter of 15-17 mm was obtained for the first time, which was not previously observed in a Gatchina discharge. Key words: Gatchina discharge, plasmoid, long-lived luminous formations, plasma sheet, space charge, virtual cathode, ball lightning. By varying the electrical conductivity and the initial voltage, an unexpectedly small luminous formation with a diameter of 15-17 mm was obtained for the first time, which was not previously observed in the Gatchina discharge.

The partial ionization zone of heavy elements in F-stars: a study on how it correlates with rotation

ABSTRACT We study the relation between the internal structures of 10 benchmark main-sequence F-stars and their rotational properties. Stellar rotation of main-sequence F-type stars can be characterized by two distinct rotational regimes. Early-type F-stars are usually rapid rotators with periods typically below 10 d, whereas later-type F-stars have longer rotation periods. Specifically, and since the two rotational regimes are tightly connected to the effective temperatures of the stars, we investigate in detail the characteristics of the partial ionization zones in the outer convective envelopes of these stars, which in turn, depend on the internal temperature profiles. Our study shows that the two rotational regimes might be distinguished by the relative locations of the partial ionization region of heavy elements and the base of the convective zone. Since in all these stars is expected a dynamo-driven magnetic field where the shear layer between convective and radiative zones (tachocline) plays an important role, this result suggests that the magnetic field may be related to the combined properties of convection and ionization.

New insights into atmospherically relevant reaction systems using direct analysis in real-time mass spectrometry (DART-MS)

The application of direct analysis in real-time mass spectrometry (DART-MS), which is finding increasing use in atmospheric chemistry, to two different laboratory model systems for airborne particles is investigated: (1) submicron C3–C7 dicarboxylic acid (diacid) particles reacted with gas-phase trimethylamine (TMA) or butylamine (BA) and (2) secondary organic aerosol (SOA) particles from the ozonolysis of α-cedrene. The diacid particles exhibit a clear odd–even pattern in their chemical reactivity toward TMA and BA, with the odd-carbon diacid particles being substantially more reactive than even ones. The ratio of base to diacid in reacted particles, determined using known diacid–base mixtures, was compared to that measured by high-resolution time-of-flight aerosol mass spectrometry (HR-ToF-AMS), which vaporizes the whole particle. Results show that DART-MS probes ∼ 30 nm of the surface layer, consistent with other studies on different systems. For α-cedrene SOA particles, it is shown that varying the temperature of the particle stream as it enters the DART-MS ionization region can distinguish between specific components with the same molecular mass but different vapor pressures. These results demonstrate the utility of DART-MS for (1) examining reactivity of heterogeneous model systems for atmospheric particles and (2) probing components of SOA particles based on volatility.