Evidence for Plasma Heating at Thin Current Sheets in the Solar Wind

Plasma heating at thin current sheets in the solar wind is examined using magnetic field and plasma data obtained by the WIND spacecraft in the past 17 years from 2004 to 2019. In this study, a thin current sheet is defined by an abrupt rotation (larger than 45°) of the magnetic field direction in 3 s. A total of 57,814 current sheets have been identified, among which 25,018 current sheets are located in the slow wind and 19,842 current sheets are located in the fast wind. Significant plasma heating is found at current sheets in both slow and fast wind. Proton temperature increases more significantly at current sheets in the fast wind than in the slow wind, while the enhancement in electron temperature is less remarkable at current sheets in the fast wind. The results reveal that plasma heating commonly exists at thin current sheets in the solar wind regardless of the wind speed, but the underlying heating mechanisms might be different.

Probing Protoplanetary Disk Winds with C ii Absorption

We present an analysis of wind absorption in the C ii λ1335 doublet toward 40 classical T Tauri stars with archival far-ultraviolet (FUV) spectra obtained by the Hubble Space Telescope. Absorption features produced by fast or slow winds are commonly detected (36 out of 40 targets) in our sample. The wind velocity of the fast wind decreases with disk inclination, which is consistent with expectations for a collimated jet. Slow wind absorption is mostly detected in disks with intermediate or high inclination, without a significant dependence of wind velocity on disk inclination. Both the fast and slow wind absorption are preferentially detected in FUV lines of neutral or singly ionized atoms. The Mg ii λ λ2796, 2804 lines show wind absorption consistent with the absorption in the C ii lines. We develop simplified semi-analytical disk/wind models to interpret the observational disk wind absorption. Both fast and slow winds are consistent with expectations from a thermal-magnetized disk wind model and are generally inconsistent with a purely thermal wind. Both the models and the observational analysis indicate that wind absorption occurs preferentially from the inner disk, which offers a wind diagnostic in complement to optical forbidden line emission that traces the wind in larger volumes.

Nozzle Type and Driving Speed Effects on Spray Density of Aerial Application According to the Wind Tunnel Measurements

Spray density (Number of droplets/cm2) is an important component of agricultural spraying processes. In the field, assessment of the spray density under effect of a number of variables such as nozzle type and driving speed without take in account the effect of cross wind speed is insufficient. In this study, to simulate field spray operation, tests were carried out in wind tunnel using automatic spraying mechanism to investigate and to clarify effect of three types of flat fan nozzle tip spray at three driving speeds under effect three cross wind speeds on spray density. Water sensitive papers (WSPs) were used to collect spray density data. Spray density was calculated through image processing program software. Performance of spray nozzles was validated relative to experimental data of a TP11003 reference nozzle. Results indicated that XR11003 nozzle behavior was to some extent similar to that TP11003 nozzle under effect slow wind speed. It is also noticed that the spray density value decreased with increasing driving speed and wind speed, the spray density value with driving speed of 2.2 m/s and wind speed of 1 m/s was the best, reaching 64.3 droplet /cm2. While the spray density value with driving speed of 5.5 m/s and wind speed of 3 m/s was the least, reaching 3.8 droplet /cm2. The current study presents that the use of DG11003 nozzle gives the best control spray density data under effect very windy conditions to the reference nozzle.

Design and Fabrication of Low Speed Wind Tunnel

A slow wind tunnel should be designed and built. This project involved the design and construction of the small wind tunnel. During this project, a computer aided design (CAD) called ANSYS will be used to design the wind tunnel.

Alfvénic versus non-Alfvénic turbulence in the inner heliosphere as observed by Parker Solar Probe

<p>Parker Solar Probe (PSP) measures the magnetic field and plasma parameters of the solar wind at unprecedentedly close distances to the Sun, providing a great opportunity to study the early-stage evolution of magnetohydrodynamic (MHD) turbulence in the solar wind. Here we use PSP data to explore the nature of solar wind turbulence focusing on the Alfvénic character and power spectra of the fluctuations and their dependence on heliocentric distance and context (i.e., large-scale solar wind properties), aiming to understand the role that different effects such as source properties, solar wind expansion, and stream interaction might play in determining the turbulent state. We carried out a statistical survey of the data from the first five orbits of PSP with a focus on how the fluctuation properties at the large MHD scales vary with different solar wind streams and the distance from the Sun. A more in-depth analysis from several selected periods is also presented. Our results show that as fluctuations are transported outward by the solar wind, the magnetic field spectrum steepens while the shape of the velocity spectrum remains unchanged. The steepening process is controlled by the age of the turbulence, which is determined by the wind speed together with the radial distance. Statistically, faster solar wind has higher Alfvénicity with a more dominant outward propagating wave component and more balanced magnetic and kinetic energies. The outward wave dominance gradually weakens with radial distance, while the excess of magnetic energy is found to be stronger as we move closer toward the Sun. We show that the turbulence properties can significantly vary from stream to stream even if these streams are of a similar speed, indicating very different origins of these streams. Especially, the slow wind that originates near the polar coronal holes has much lower Alfvénicity compared with the slow wind that originates from the active regions and pseudostreamers. We show that structures such as the heliospheric current sheet and wind stream velocity shears can play an important role in modifying the properties of the turbulence.</p><p>*The PSP Team: Stuart D.Bale,  Justin Kasper, Kelly Korreck, J. W. Bonnell, Thierry Dudok de Wit, Keith Goetz, Peter R. Harvey, Robert J. MacDowall, David Malaspina, Marc Pulupa, Anthony W.Case, Davin Larson,  Jenny Verniero, Roberto Livi, Michael Stevens, PhyllisWhittlesey, Milan Maksimovic, and Michel Moncuquet</p>

Implementation of PSO MPPT Technique for Wind Energy Conversion Systems

One major advantage of renewable energy is that it is sustainable and will never run out. They provide clean energy because they are non-pollutant and non-contributor to greenhouse effects and global warming. Renewable energy facilities generally require less maintenance than traditional generators. Their fuel being derived from natural and available resources reduces the costs of operation. The proposed PSO algorithm uses the dc current as the perturbing variable. The algorithm detects sudden wind speed changes indirectly through the dc-link voltage slope. The voltage slope is also used to enhance the tracking speed of the algorithm and to prevent the generator from stalling under rapid wind speed slow down conditions. The proposed method uses two modes of operation: A PSO mode with adaptive step size under slow wind speed fluctuation conditions, and a prediction mode employed under fast wind speed change conditions. The dc-link capacitor voltage slope reflects the acceleration information of the generator, which is then used to predict the next step size and direction of the current command.

Long-term properties of the solar wind and their relation to solar cycles

<p>The solar wind variations during particular solar cycles have been described in many previous studies including the solar cycle 23 that was characterized by a long, deep, and very complex solar minimum with very low values of many solar wind parameters.</p><p>Using statistical methods, we analyzed 25 years of Wind spacecraft measurements with motivation to reveal differences and similarities in magnetic field components and solar wind plasma parameters in individual solar cycles. We tracked the changes of the solar magnetic field strength, and components, solar wind speed, density, dynamic pressure, temperature, and composition). Except quiet solar wind conditions during solar minima and maxima, we also selected significant discontinuities (ICME and CIRs) and investigated their influence on profiles of average parameters. For this, we followed other quantities connected with their presence as their average front normals, regions of transitions between high and slow wind streams, special interplanetary magnetic field orientations, etc.). We discuss a behavior of investigated parameters over solar cycles as well as on shorter time scales (in the order of days and hours).</p>

Modeling and forecasting the background solar wind with data-driven physics-based models

<p>The quasi-steady solar wind flow is a key component of space weather, being the source of corotating density structures that perturb planetary atmospheres and affect the propagation of impulsive perturbations (such as CME). Fast and slow wind streams develop at different places in the solar atmosphere, reflecting the global distribution of the coronal magnetic field during solar cycle and its consequences for heat and mass transport across the corona. I will present recent advances on global solar wind simulations that provides robust and fully physics-based predictions of the structure and physical parameters of the solar wind based on a multi-1D approach (MULTI-VP, ISAM). Such advances relate to the driving the models with time-dependant magnetogram data, to the inclusion of transient heating phenomena, and to switching from a fluid to a multi-species description of the solar wind. The model was also driven by daily synchronic magnetograms (ADAPT) for a full solar rotation and the simulation results were compared to UVCS plane-of-sky data.The simulations produce a large range of synthetic observables (e.g multi-spacecraft in-situ measurements, white-light and EUV imagery) meant to be compared to data from current and future missions (e.g Solar Orbiter and Parker Solar Probe), and to establish physiccal connections between remote observation of the solar surface and corona and the interplanetary medium.</p>