Влияние параллельного слоям магнитного поля на фототок в GaAs/AlAs p-i-n-структурах

The behavior of the photocurrent in GaAs / AlAs p-i-n heterostructures is studied in a magnetic field parallel to the heterolayers in the wavelength range from 395 to 650 nm. A strong dependence of the non-oscillating component of the photocurrent on the radiation wavelength associated with the suppression of the diffusion current by the magnetic field was found. It is shown that the behavior of the oscillating component of the photocurrent in a magnetic field does not depend on the wavelength of light and is determined by the transfer of electrons through the dimensional quantization level in a triangular near-barrier well. It is shown that the suppression of the oscillating component by the magnetic field is due to the smearing of the level in the triangular well due to the motion of electrons parallel to the walls of the well and perpendicular to the magnetic field.

The Occurrence and Prevalence of Time Domain Structures in the Kelvin-Helmholtz Instability at Different Positions Along the Earth’s Magnetospheric Flanks

The Kelvin-Helmholtz instability (KHI) is thought to be an important driver for mass, momentum, and energy transfer between the solar wind and magnetosphere. This can occur through global-scale “viscous-like” interactions, as well as through local kinetic processes such as magnetic reconnection and turbulence. An important aspect of these kinetic processes for the dynamics of particles is the electric field parallel to the background magnetic field. Parallel electric field structures that can occur in the KHI include the reconnection electric field of high guide field reconnection, large amplitude ion acoustic waves, as well as time domain structures (TDS) such as double layers and electrostatic solitary waves. In this study, we present a survey of parallel electric field structures observed during three Kelvin Helmholtz events observed by NASA’s Magnetospheric Multiscale (MMS), each at different positions along the magnetosphere’s dusk flank. Using data from MMS’s on-board solitary wave detector (SWD) algorithm, we statistically investigate the occurrence of TDS within the KHI events. We find that early in the KHI development, TDS typically occur in regions with strong field-aligned currents (FACs) on the magnetospheric side of the vortices. Further down the flanks, as the vortices become more rolled up, the prevalence of large electric currents decreases, as well as the prevalence of SWDs. These results suggest that as the instability develops and vortices grow in size along the flanks, kinetic-scale activity becomes less prevalent.

Polarimetric and photometric observations of CB54, with analysis of four other dark clouds

ABSTRACT We present the results of our BVR-band photometric and R-band polarimetric observations of ∼40 stars in the periphery of the dark cloud CB54. From different photometric data, we estimate E(B − V) and E(J − H). After involving data from other sources, we discuss the extinction variations towards CB54. We reveal two main dust layers: a foreground, E(B − V) ≈ 0.1 mag, at ∼200 pc and an extended layer, $E(B-V) \gtrsim 0.3$ mag, at ∼1.5 kpc. CB54 belongs to the latter. Based on these results, we consider the reason for the random polarization map that we have observed for CB54. We find that the foreground is characterized by low polarization ($P \lesssim 0.5$ per cent) and a magnetic field parallel to the Galactic plane. The extended layer shows high polarization (P up to 5–7 per cent). We suggest that the field in this layer is nearly perpendicular to the Galactic plane and both layers are essentially inhomogeneous. This allows us to explain the randomness of polarization vectors around CB54 generally. The data – primarily observed by us in this work for CB54, by A. K. Sen and colleagues in previous works for three dark clouds CB3, CB25 and CB39, and by other authors for a region including the B1 cloud – are analysed to explore any correlation between polarization, the near-infrared, E(J − H), and optical, E(B − V), excesses, and the distance to the background stars. If polarization and extinction are caused by the same set of dust particles, we should expect good correlations. However, we find that, for all the clouds, the correlations are not strong.

Investigation on Effect of Solution Temperature on The Structure of Cu/Ni Layer in The Electroplating Assisted withParallel Magnetic Field

Tujuan penelitian ini adalah mengidentifikasi pengaruh variasi suhu larutan terhadap struktur lapisan yang terbentuk melalui metode elektroplating. Larutan elektrolit dibuat dengan campuran NiSO4, NiCL2,H3BO3, dan H2O. Elektroplating dilakukan selama 180 s dengan tegangan 4,5 V dan medan magnet 150 G pada arah sejajar permukaan katoda-anoda. Hasil penelitian menunjukkan suhu mempengaruhi ketebalan lapisan, arus listrik, jumlah zat yang terlepas dan terbentuk dan pH larutan. Lapisan paling tebal adalah sampel hasil deposisi pada suhu 40°C dengan ketebalan [(133,8 ± 0,9745)´ 10-5] cm pada pH 4,21. Kemudian yang paling tipis adalah sampel hasil deposisi pada suhu 60°C dengan ketebalan [(59,83 ± 0,6270) x 10-5] cm pada pH 4,18. Ketebalan lapisan yang terbentuk sebanding dengan jumlah zat terlarut dan jumlah arus yang mengalir selama pelapisan berlangsung. The purpose of this study is to identify the effect of temperature variations on the structure of the layers formed through the electroplating method. Electrolyte solution was made with mixture of NiSO4, NiCL2,H3BO3, and H2O. Electroplating was carried out for 180 s on the voltage of 4.5 V and magnetic field parallel to 150 G. The results showed temperature affects the thickness of the layer, electric current, the amount of released and formed substances and the pH of the solution. The thicknest of layer is according to the sample deposited at a temperature of 40°C with a thickness of [(133,8 ± 0,9745)x 10-5] cm at pH of 4.21. Then the thinnest one was according to the sample which was deposited at 60°C with a thickness of [(59,83 ± 0,6270) x 10-5] cm at pH of 4.18. The thickness of the layer is proportional to the amount of solute and the amount of current flowing during the coating. Keywords: Elektroplating, Flim Tipis, Cu/Ni, Suhu Larutan, Magnet Sejajar.

Anisotropy of Lower Critical Field in Organic Layered Superconductor λ-(BETS)2GaCl4

The lower critical field of type-II organic layered superconductor l-(BETS)2GaCl4 has been estimated by magnetic measurements. The demagnetization factor of a needle-like sample shape has been taken into account for the measurements by applying the external field, parallel and perpendicular to the conducting plane. The lower critical field for the field parallel to the conducting plane is 5.5(2) G, in contrast with the previous studies. This allows us to discuss the anisotropy of lower critical field Hc1 in a quasi-two-dimensional organic layered superconductor l-(BETS)2GaCl4.

Alpha particle thermodynamics in the inner heliosphere fast solar wind

Context. Plasma processes occurring in the corona and solar wind can be probed by studying the thermodynamic properties of different ion species. However, most in situ observations of positive ions in the solar wind are taken at 1 AU, where information on their solar source properties may have been irreversibly erased. Aims. In this study we aim to use the properties of alpha particles at heliocentric distances between 0.3 AU and 1 AU to study plasma processes occurring at the points of observation, and to infer processes occurring inside 0.3 AU by comparing our results to previous remote sensing observations of the plasma closer to the Sun. Methods. We reprocessed the original Helios positive ion distribution functions, isolated the alpha particle population, and computed the alpha particle number density, velocity, and magnetic field perpendicular and parallel temperatures. We then investigated the radial variation of alpha particle temperatures in fast solar wind observed between 0.3 AU and 1 AU. Results. Between 0.3 AU and 1 AU alpha particles are heated in the magnetic field perpendicular direction and cooled in the magnetic field parallel direction. Alpha particle evolution is bounded by the alpha firehose instability threshold, which provides one possible mechanism to explain the observed parallel cooling and perpendicular heating. Closer to the Sun our observations suggest that the alpha particles undergo heating in the perpendicular direction, whilst the large magnetic field parallel temperatures observed at 0.3 AU may be due to the combined effect of double adiabatic expansion and alpha particle deceleration inside 0.3 AU.