Ground-based measurements of turbulence in electrified clouds

2020 ◽  
Author(s):  
Evgeny Mareev ◽  
Vladimir Klimenko ◽  
Lev Lubyako ◽  
Mariya Shatalina ◽  
Svetlana Dementyeva ◽  
...  
Keyword(s):  
Electric Field ◽  
Brightness Temperature ◽  
Large Scale ◽  
High Energy ◽  
Passive Microwave ◽  
Theoretical Studies ◽  
Turbulence Characteristics ◽  
Electrical Structure ◽  
Convective Clouds

<p>A problem of the electric field dynamics in turbulent electro-active clouds (Cumulus, Stratus, Cumulonimbus) is one of the most relevant and complex problems of dynamical meteorology and atmospheric electricity. This problem is important for the study of intense large-scale electric field and its fluctuations that may lead to high-energy particle flows and lightning discharges, for electric current parameterization. Direct field measurements in convective clouds with a developed electrical structure are very difficult; so one of urgent tasks is the development of remote sensing methods for turbulence characteristics in electro-active clouds.</p><p>The growth of a large-scale electric field in a turbulent atmosphere is caused by the generation of an electric charge on colliding particles (hydrometeors and dust). Meanwhile, observations (including preliminary observations of the authors) and theoretical studies (Mareev and Dementyeva, 2017) show that intensification of thunderstorm activity can be associated with increased turbulence in the cloud. This paper presents new ideas and results of experimental and theoretical studies of the role of turbulence in electro-active clouds.</p><p>The main attention is paid to complex remote observations of different types of clouds with an experimental set-up including the microwave radiometers of 3 cm and 8 mm wavelengths (with a time resolution of order of one second), the network of electrostatic fluxmeters spaced by several kilometers each from another, and the meteorological radar. The data of recent several years were used for analysis. Note that recently space-borne passive microwave radiometry of intense convective clouds (see, for example, Peterson et al., 2017) attracted more attention compared to ground-based microwave observations. A principal idea of our approach is to use the wave-length channels allowing us to reveal both optically thick and optically transparent cloud events from the data on fluctuations in the brightness temperature of the atmosphere.</p><p>A special attention was paid to comparative analysis of the turbulence characteristics in thunderclouds and in clouds that do not have a developed electrical structure. The spectral characteristics of electric field and brightness fluctuations were found to be associated with atmospheric air turbulence and mostly are quantitatively described by Kolmogorov-type spectra. Compared with ordinary Cumulus and Stratus clouds, a limited band near a frequency of ~ 0.01 Hz with a higher level of fluctuations is distinguished in the spectral density of fluctuations in the brightness temperature of thunderclouds. The spectra of fluctuations of the electric field caused by thunderclouds, as well as turbulence interior thundercloud, are significantly different from the spectra caused by ordinary Cumulus and layered clouds.</p><p>The work was supported by the Russian Foundation for Basic Research (projects no. 19-05-00975 and 18-45-520010).</p><p>References</p><p>Mareev E.A., Dementyeva S.O. (2017), The role of turbulence in thunderstorm, snowstorm, and dust storm electrification. Journal of Geophysical Research: Atmospheres, V. 122, No. 13, P. 6976-6988. doi: 10.1002/2016JD026150.</p><p>Peterson M., Liu C., Mach D., Deierling W., Kalb C. (2015), A method of estimating electric fields above electrifi_ed clouds from passive microwave observations. J. Atmos. Ocean. Tech., V.32 (8), P.1429-1446. doi: 10.1175/ JTECH-D-14-00119.1.</p>

Dynamics of ionospheric ions in the magnetospheric tail: Role of the large-scale electric field

Radio Science ◽  
1996 ◽  
Vol 31 (3) ◽  
pp. 655-665
Author(s):  
Eugene V. Voronov ◽  
Igor A. Krinberg
Keyword(s):  
Electric Field ◽  
Large Scale ◽  
Magnetospheric Tail

FEATURES OF PHOTOCONDUCTIVITY OF Ge AND Si WITH DISORDERED REGIONS

2010 ◽  
Vol 24 (31) ◽  
pp. 2985-2996 ◽  
Author(s):  
V. YEVSEYEV
Keyword(s):  
Large Scale ◽  
High Energy ◽  
Fast Neutrons ◽  
Potential Relief ◽  
Photoelectrical Properties ◽  
Recombination Centers ◽  
First Time ◽  
High Energy Particles ◽  
Disordered Regions

Influence of large radiation defects — disordered regions on photoconductivity of semiconductors Ge and Si , compensated as a result of an irradiation with fast neutrons and 1 GeV protons, is investigated. For the first time, the combined role of disordered regions and a large-scale potential relief in photoelectrical properties of Ge and Si , irradiated by high energy particles is defined. The model of photoconductivity that takes into consideration disordered regions as specific sensitizing recombination centers and allows formation of the spatial potential relief is developed.

scholarly journals Role of substorm-associated impulsive electric fields in the ring current development during storms

2005 ◽  
Vol 23 (2) ◽  
pp. 579-591 ◽  
Author(s):  
N. Yu. Ganushkina ◽  
T. I. Pulkkinen ◽  
T. Fritz
Keyword(s):  
Energy Density ◽  
Electric Field ◽  
Total Energy ◽  
Large Scale ◽  
Ring Current ◽  
High Energy ◽  
Time Dependent ◽  
Small Scale ◽  
Total Energy Density ◽  
Current Energy

Abstract. Particles with different energies produce varying contributions to the total ring current energy density as the storm progresses. Ring current energy densities and total ring current energies were obtained using particle data from the Polar CAMMICE/MICS instrument during several storms observed during the years 1996-1998. Four different energy ranges for particles are considered: total (1-200keV), low (1-20keV), medium (20-80keV) and high (80-200keV). Evolution of contributions from particles with different energy ranges to the total energy density of the ring current during all storm phases is followed. To model this evolution we trace protons with arbitrary pitch angles numerically in the drift approximation. Tracing is performed in the large-scale and small-scale stationary and time-dependent magnetic and electric field models. Small-scale time-dependent electric field is given by a Gaussian electric field pulse with an azimuthal field component propagating inward with a velocity dependent on radial distance. We model particle inward motion and energization by a series of electric field pulses representing substorm activations during storm events. We demonstrate that such fluctuating fields in the form of localized electromagnetic pulses can effectively energize the plasma sheet particles to higher energies (>80keV) and transport them inward to closed drift shells. The contribution from these high energy particles dominates the total ring current energy during storm recovery phase. We analyse the model contributions from particles with different energy ranges to the total energy density of the ring current during all storm phases. By comparing these results with observations we show that the formation of the ring current is a combination of large-scale convection and pulsed inward shift and consequent energization of the ring current particles.

scholarly journals Synthesized Cluster Head Selection and Routing for Two Tier Wireless Sensor Network

2013 ◽  
Vol 2013 ◽  
pp. 1-11 ◽  
Author(s):  
Keyur Rana ◽  
Mukesh Zaveri
Keyword(s):  
Wireless Sensor Network ◽  
Sensor Network ◽  
Large Scale ◽  
Cluster Head ◽  
Integrated Approach ◽  
High Energy ◽  
Wireless Sensor ◽  
Cluster Head Selection ◽  
Cluster Heads

Large scale sensor networks can be efficiently managed by dividing them into several clusters. With the help of cluster heads, each cluster communicates using some routing schedule. It is essential to rotate the role of cluster heads in a cluster to distribute energy consumption if we do not have dedicated high energy cluster heads. Usually routing and cluster head selection for such networks have been separately solved. If cluster heads are selected with the consideration of routing and routing schedule is prepared with the consideration of selected cluster heads, it can help each other. We have proposed an integrated approach of cluster head selection and routing in two tier wireless sensor network (WSN) using Genetic Algorithm based cluster head selection with A-Star algorithm based routing method to extend life of WSN. This approach can lead to significant improvements in the network lifetime over other techniques.

scholarly journals Photocatalytic Degradation of Pharmaceuticals Carbamazepine, Diclofenac, and Sulfamethoxazole by Semiconductor and Carbon Materials: A Review

Molecules ◽  
2019 ◽  
Vol 24 (20) ◽  
pp. 3702 ◽  
Author(s):  
Ana S. Mestre ◽  
Ana P. Carvalho
Keyword(s):  
Large Scale ◽  
Carbon Materials ◽  
High Energy ◽  
Carbon Quantum Dots ◽  
Solar Irradiation ◽  
Nanoporous Carbons ◽  
Promising Strategy ◽  
Photocatalytic Removal ◽  
Treatment Technologies

The presence of pharmaceutical compounds in the environment is a reality that calls for more efficient water treatment technologies. Photocatalysis is a powerful technology available but the high energy costs associated with the use of UV irradiation hinder its large scale implementation. More sustainable and cheaper photocatalytic processes can be achieved by improving the sunlight harvesting and the synthesis of semiconductor/carbon composites has proved to be a promising strategy. Carbamazepine, diclofenac, and sulfamethoxazole were selected as target pharmaceuticals due to their recalcitrant behavior during conventional wastewater treatment and persistence in the environment, as properly reviewed. The literature data on the photocatalytic removal of carbamazepine, diclofenac, and sulfamethoxazole by semiconductor/carbon materials was critically revised to highlight the role of the carbon in the enhanced semiconductor performance under solar irradiation. Generally it was demonstrated that carbon materials induce red-shift absorption and they contribute to more effective charge separation, thus improving the composite photoactivity. Carbon was added as a dopant (C-doping) or as support or doping materials (i.e., nanoporous carbons, carbon nanotubes (CNTs), graphene, and derived materials, carbon quantum dots (CQDs), and biochars) and in the large majority of the cases, TiO2 was the semiconductor tested. The specific role of carbon materials is dependent on their properties but even the more amorphous forms, like nanoporous carbons or biochars, allow to prepare composites with improved properties compared to the bare semiconductor. The self-photocatalytic activity of the carbon materials was also reported and should be further explored. The removal and mineralization rates, as well as degradation pathways and toxicity of the treated solutions were also critically analyzed.

scholarly journals Blazar Optical Polarimetry: Current Progress in Observations and Theories

Galaxies ◽  
2019 ◽  
Vol 7 (4) ◽  
pp. 85 ◽  
Author(s):  
Haocheng Zhang
Keyword(s):  
Magnetic Field ◽  
High Energy ◽  
Theoretical Studies ◽  
First Principle ◽  
Standard Tool ◽  
Multi Wavelength ◽  
Radiation Processes ◽  
The Magnetic Field ◽  
Shed Light

Polarimetry has been a standard tool to probe the active galactic nucleus (AGN) jet magnetic field. In recent years, several optical polarization monitoring programs have been carried out, bringing in many exciting new results and insights into jet dynamics and emission. This article discusses current progress in blazar optical polarimetry. The main focus is the variability of polarization signatures, which has spurred a lot of theoretical studies. These novel developments have provided unique constraints on the blazar flares and emphasized the role of the magnetic field in jet evolution. Optical polarimetry will continue to act as an essential component in the multi-messenger study of AGN jets, in particular with the upcoming high-energy polarimetry. Comparing to first-principle numerical simulations, future multi-wavelength polarimetry can shed light on jet dynamics, particle acceleration, and radiation processes.

scholarly journals Long-Lived Banana Orbit Formation of Suprathermal Electrons During MHD Spikes in Runaway Tokamak Discharges

2019 ◽  
Keyword(s):  
Magnetic Field ◽  
Electric Field ◽  
Thermal Plasma ◽  
Large Scale ◽  
High Energy ◽  
Runaway Electrons ◽  
Trapped Electrons ◽  
Knock Out ◽  
Coulomb Collisions ◽  
Suprathermal Electrons

The secondary runaway electrons generation is the process in which already existing high energy runaway electrons knock out thermal plasma electrons directly into the runaway region by close Coulomb collisions. Such knocked-on electrons are immediately accelerated to ultrarelativistic velocities, since in the runaway region the toroidal electric field force overcomes the collisional friction force with thermal plasma particles. The avalanche of runaway electrons with mega-electron-volt energy emerges, hit of which with the construction elements of large-scale tokamaks and future international tokamak ITER can lead to catastrophic consequences. Due to its importance, this phenomenon is being actively studied both theoretically and experimentally in leading thermonuclear fusion centers. It is known that during secondary generation, the value of the transversal component of knocked-on electrons momentum with respect to the confining magnetic field may be significantly higher than the longitudinal one: p⊥ >> p∥. Thus, conditions for knocked-on electron trapping in a non-uniform tokamak magnetic field occur (banana orbits). Such electrons can no longer be accelerated by the inducted toroidal electric field to high energies, avalanche formation is partially suppressed. The question is how long this population of knocked-on and trapped electrons exists. In the presented paper, it is shown the additional possibility of formation and existence of such long-lived banana orbits of suprathermal electrons under conditions of plasma MHD activity when MHD instability spikes induced the strong burst of the toroidal electric field that results in the abrupt growth in these knocked-on and trapped electrons. This phenomenon is considered for the recent low-density EAST (Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, China) tokamak quasistationary runaway discharges. Long-lived trapped electrons (p⊥ >> p∥) also have an influence on the intensity of ECE emission. The considered phenomenon is important for correct interpretation of the runaway experiments on present-day tokamaks.

A Method of Estimating Electric Fields above Electrified Clouds from Passive Microwave Observations

2015 ◽  
Vol 32 (8) ◽  
pp. 1429-1446 ◽  
Author(s):  
Michael Peterson ◽  
Chuntao Liu ◽  
Douglas Mach ◽  
Wiebke Deierling ◽  
Christina Kalb
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Electric Circuit ◽  
Passive Microwave ◽  
Field Observations ◽  
Global Electric Circuit ◽  
Convective Clouds ◽  
Unique Approach ◽  
Future Utility ◽  
Unique Dataset

AbstractA unique dataset of coincident high-altitude passive microwave and electric field observations taken by the NASA ER-2 aircraft is used to assess the feasibility of estimating electric fields above electrified clouds using ubiquitous global and multidecadal satellite products. Once applied to a global dataset, such a product would provide a unique approach for diagnosing and monitoring the current sources of the global electric circuit (GEC).In this study an algorithm has been developed that employs ice scattering signals from 37- and 85-GHz passive microwave observations to characterize the electric fields above clouds overflown by the ER-2 aircraft at nearly 20-km altitude. Electric field estimates produced by this passive microwave algorithm are then compared to electric field observations also taken by the aircraft to assess its potential future utility with satellite datasets. The algorithm is shown to estimate observed electric field strengths over intense convective clouds at least 71% (58%) of the time over land and 43% (40%) of the time over the ocean to within a factor of 2 from 85-GHz (37 GHz) passive microwave observations. Electric fields over weaker clouds can be estimated 58% (41%) of the time over land and 22% (8%) of the time over the ocean from 85-GHz (37 GHz) passive microwave observations. The accuracy of these estimates is limited by systematic errors in the observations along with other factors. Despite these sources of error, the algorithm can produce reasonable estimates of electric fields over carefully selected individual electrified clouds that differ from observations by less than 20 V m−1 for clouds that produce 200–400 V m−1 electric fields at 20 km.

scholarly journals How Do Ocean Warm Anomalies Favor the Aggregation of Deep Convective Clouds?

2020 ◽  
Vol 77 (11) ◽  
pp. 3733-3745
Author(s):  
Sara Shamekh ◽  
Caroline Muller ◽  
Jean-Philippe Duvel ◽  
Fabio D’Andrea
Keyword(s):  
Hot Spots ◽  
Large Scale ◽  
Hot Spot ◽  
Spot Size ◽  
Large Scale Circulation ◽  
Convective Clouds ◽  
Sst Anomaly ◽  
Radiative Feedbacks ◽  
Self Aggregation

AbstractWe investigate the role of a warm sea surface temperature (SST) anomaly (hot spot of typically 3 to 5 K) on the aggregation of convection using cloud-resolving simulations in a nonrotating framework. It is well known that SST gradients can spatially organize convection. Even with uniform SST, the spontaneous self-aggregation of convection is possible above a critical SST (here 295 K), arising mainly from radiative feedbacks. We investigate how a circular hot spot helps organize convection, and how self-aggregation feedbacks modulate this organization. The hot spot significantly accelerates aggregation, particularly for warmer/larger hot spots, and extends the range of SSTs for which aggregation occurs; however, at cold SST (290 K) the aggregated cluster disaggregates if we remove the hot spot. A large convective instability over the hot spot leads to stronger convection and generates a large-scale circulation which forces the subsidence drying outside the hot spot. Indeed, convection over the hot spot brings the atmosphere toward a warmer temperature. The warmer temperatures are imprinted over the whole domain by gravity waves and subsidence warming. The initial transient warming and concomitant subsidence drying suppress convection outside the hot spot, thus driving the aggregation. The hot-spot-induced large-scale circulation can enforce the aggregation even without radiative feedbacks for hot spots sufficiently large/warm. The strength of the large-scale circulation, which defines the speed of aggregation, is a function of the hot spot fractional area. At equilibrium, once the aggregation is well established, the moist convective region with upward midtropospheric motion, centered over the hot spot, has an area surprisingly independent of the hot spot size.

The Role of Sense of Direction and Other Factors During Navigation in a Large-Scale, Unconstrained Environment

2013 ◽  
Author(s):  
Elisabeth J. Ploran ◽  
Ericka Rovira ◽  
James C. Thompson ◽  
Raja Parasuraman
Keyword(s):  
Large Scale ◽  
Sense Of Direction
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