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Your search keyword '"Azadifar, Mohammad"' showing total 155 results
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155 results on '"Azadifar, Mohammad"'

10. Laser lightning rod and artificial fog dissipation

Author

Wolf, Jean-Pierre, primary, Produit, Thomas, additional, Schroder, Malte C., additional, Walch, Pierre, additional, Herkommer, Clemens, additional, Mostajabi, Amirhossein, additional, Moret, Michel, additional, Andral, Ugo, additional, Moreno, Victor, additional, Sunjerga, Antonio, additional, Azadifar, Mohammad, additional, Andre, Yves-Bernard, additional, Mahieu, Benoit, additional, Krotz, Peter, additional, Metzger, Thomas, additional, Michel, Knut, additional, Mysyrowicz, Andre, additional, Rubinstein, Marcos, additional, Rachidi, Farhad, additional, Kasparian, Jerome, additional, and Houard, Aurelien, additional

Published
2021
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11. Measured data for the M-component

Author

Quanxin Li, Rachidi, Farhad, Rubinstein, Marcos, Jianguo Wang, Cai, Li, Azadifar, Mohammad, Amirhossein Mostajabi, Zhou, Mi, and Yadong Fan

Subjects
GeneralLiterature_REFERENCE(e.g.,dictionaries,encyclopedias,glossaries)
Abstract

Measured data published in the paper.

Published
2020
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13. The laser lightning rod project

Author

Produit, Thomas, primary, Walch, Pierre, additional, Herkommer, Clemens, additional, Mostajabi, Amirhossein, additional, Moret, Michel, additional, Andral, Ugo, additional, Sunjerga, Antonio, additional, Azadifar, Mohammad, additional, André, Yves-Bernard, additional, Mahieu, Benoît, additional, Haas, Walter, additional, Esmiller, Bruno, additional, Fournier, Gilles, additional, Krötz, Peter, additional, Metzger, Thomas, additional, Michel, Knut, additional, Mysyrowicz, André, additional, Rubinstein, Marcos, additional, Rachidi, Farhad, additional, Kasparian, Jérôme, additional, Wolf, Jean-Pierre, additional, and Houard, Aurélien, additional

Published
2021
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23. LMA observations of upward lightning flashes at the Säntis Tower initiated by nearby lightning activity

Author

Sunjerga, Antonio, primary, Rubinstein, Marcos, additional, Pineda, Nicolau, additional, Mostajabi, Amirhossein, additional, Azadifar, Mohammad, additional, Romero, David, additional, Van der Velde, Oscar, additional, Montanya, Joan, additional, Figueras i Ventura, Jordi, additional, Besic, Nikola, additional, Grazioli, Jacopo, additional, Hering, Alessandro, additional, Germann, Urs, additional, Diendorfer, Gerhard, additional, and Rachidi, Farhad, additional

Published
2020
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29. Meteorological Aspects of Self‐Initiated Upward Lightning at the Säntis Tower (Switzerland)

Author

Pineda, Nicolau, primary, Figueras i Ventura, Jordi, additional, Romero, David, additional, Mostajabi, Amirhossein, additional, Azadifar, Mohammad, additional, Sunjerga, Antonio, additional, Rachidi, Farhad, additional, Rubinstein, Marcos, additional, Montanyà, Joan, additional, van der Velde, Oscar, additional, Altube, Patricia, additional, Besic, Nikola, additional, Grazioli, Jacopo, additional, Germann, Urs, additional, and Williams, Earle R., additional

Published
2019
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31. Analysis of the lightning production of convective cells

Author

Figueras i Ventura, Jordi, primary, Pineda, Nicolau, additional, Besic, Nikola, additional, Grazioli, Jacopo, additional, Hering, Alessandro, additional, van der Velde, Oscar A., additional, Romero, David, additional, Sunjerga, Antonio, additional, Mostajabi, Amirhossein, additional, Azadifar, Mohammad, additional, Rubinstein, Marcos, additional, Montanyà, Joan, additional, Germann, Urs, additional, and Rachidi, Farhad, additional

Published
2019
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38. Polarimetric radar characteristics of lightning initiation and propagating channels

Author

Figueras i Ventura, Jordi, primary, Pineda, Nicolau, additional, Besic, Nikola, additional, Grazioli, Jacopo, additional, Hering, Alessandro, additional, van der Velde, Oscar A., additional, Romero, David, additional, Sunjerga, Antonio, additional, Mostajabi, Amirhossein, additional, Azadifar, Mohammad, additional, Rubinstein, Marcos, additional, Montanyà, Joan, additional, Germann, Urs, additional, and Rachidi, Farhad, additional

Published
2019
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39. Electromagnetic Fields Associated With the M-Component Mode of Charge Transfer

Author

He, Lixia, Rachidi, Farhad, Azadifar, Mohammad, Rubinstein, Marcos, Rakov, Vladimir A., Cooray, Vernon, Pavanello, Davide, Xing, Hongyan, He, Lixia, Rachidi, Farhad, Azadifar, Mohammad, Rubinstein, Marcos, Rakov, Vladimir A., Cooray, Vernon, Pavanello, Davide, and Xing, Hongyan

Abstract

In upward flashes, charge transfer to ground largely takes place during the initial continuous current (ICC) and its superimposed pulses (ICC pulses). ICC pulses can be associated with either M-component or leader/return-stroke-like modes of charge transfer to ground. In the latter case, the downward leader/return stroke process is believed to take place in a decayed branch or a newly created channel connected to the ICC-carrying channel at relatively short distance from the tower top, resulting in the so-called mixed mode of charge transfer to ground. In this paper, we study the electromagnetic fields associated with the M-component charge transfer mode using simultaneous records of electric fields and currents associated with upward flashes initiated from the Santis Tower. The effect of the mountainous terrain on the propagation of electromagnetic fields associated with the M-component charge transfer mode (including classical M-component pulses and M-component-type pulses superimposed on the initial continuous current) is analyzed and compared with its effect on the fields associated with the return stroke (occurring after the extinction of the ICC) and mixed charge transfer modes. For the analysis, we use a 2-Dimentional Finite-Difference Time Domain method, in which the M-component is modeled by the superposition of a downward current wave and an upward current wave resulting from the reflection at the bottom of the lightning channel (Rakov et al., 1995, model) and the return stroke and mixed mode are modeled adopting the MTLE (Modified Transmission Line with Exponential Current Decay with Height) model. The finite ground conductivity and the mountainous propagation terrain between the Santis Tower and the field sensor located 15 km away at Herisau are taken into account. The effects of the mountainous path on the electromagnetic fields are examined for classical M-component and M-component-type ICC pulses. Use is made of the propagation factors defined as the

Published
2019
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40. Characteristics of Upward Lightning Flashes

Author

Azadifar, Mohammad, Rachidi-Haeri, Farhad, and Paolone, Mario

Subjects
Tall Towers, Ray Tracing, Electromagnetic Fields, Upward Lightning Flash, Lightning Location Systems, Snell's Law, Earth-Ionosphere Waveguide, Finite Difference Time Domain, Upward Leaders, Numerical Simulation
Abstract

In addition to the general aims of lightning research such as lightning physics and meteorology, the study of upward lightning is of particular importance in protection of tall objects such as wind turbines and telecommunication towers. It also helps us in better understanding the lightning initiation process and its role in the earth- atmosphere electrical balance. Within this context, this thesis presents an analysis on various aspects of upward lightning discharge (negative, positive, bipolar) using experimental observation and theoretical modeling for better understanding of its initial stage, the propagation of its electromagnetic field along irregular terrain and its interaction with the ionosphere. Our investigation on the superimposed impulsive components of the initial stage of upward negative flashes revealed that they can transfer net negative charges to ground by both M-component and return stroke modes of charge transfer, which can be distinguished by their associated electric field signature. Moreover, we investigated the ability of Lightning Location Systems (LLSs) to locate and detect upward negative flashes. Different aspects of upward negative flashes which might affect the evaluation performance of LLSs were discussed. It is found that LLSs tend to overestimate the peak current values of RS pulses of upward negative flashes. Using full-wave numerical simulation, it is demonstrated that this overestimation is mainly due to electric field enhancement by wave propagation along mountainous terrain around Säntis Tower. Using simultaneous channel-base current and electric field records of upward positive flashes, we observed that two types of pulsations can be distinguished during the course of progression of upward negative leaders which are very similar to ¿Classical PBPs¿ and ¿Narrow PBPs¿ of the initial stage of downward negative leaders suggesting a general similarity between upward and downward negative leaders. We present and discuss current waveforms associated with 13 bipolar flashes recorded at the Säntis Tower during the period from June 2010 to January 2015. We have found two flashes of our data base each characterized by a sequence of two upward leaders of opposite polarity within the same flash, a scenario that has never been reported from previous observations at instrumented towers. The obtained results suggest that the traditional classification of bipolar flashes should be revisited. We present simultaneous channel-base current and wideband electric field waveforms at 380 km distance from the strike point associated with upward flashes initiated from the Säntis Tower. The dataset presented in this study represents, to the best of the Author¿s knowledge, the first simultaneous records of lightning currents and distant fields associated with natural upward flashes featuring ionospheric reflections. The data are used to infer the characteristics of the ionospheric layers. We present a full-wave 2D FDTD analysis of the field propagation including the effect of the ionospheric reflections and the results are compared with the experimental data. Furthermore, we present a novel semi-analytical simplified approach based on the ray tracing concept to estimate radiated electric fields associated with lightning return strokes, taking into account ionospheric reflections.

Published
2018
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46. An Analysis of Current and Electric Field Pulses Associated With Upward Negative Lightning Flashes Initiated from the Santis Tower

Author

He, Lixia, Azadifar, Mohammad, Rachidi, Farhad, Rubinstein, Marcos, Rakov, Vladimir A., Cooray, Vernon, Pavanello, Davide, Xing, Hongyan, He, Lixia, Azadifar, Mohammad, Rachidi, Farhad, Rubinstein, Marcos, Rakov, Vladimir A., Cooray, Vernon, Pavanello, Davide, and Xing, Hongyan

Abstract

We present a study on the characteristics of current and electric field pulses associated with upward lightning flashes initiated from the instrumented Santis Tower in Switzerland. The electric field was measured 15km from the tower. Upward flashes always begin with the initial stage composed of the upward-leader phase and the initial-continuous-current (ICC) phase. Four types of current pulses are identified and analyzed in the paper: (1) return-stroke pulses, which occur after the extinction of the ICC and are preceded by essentially no-current time intervals; (2) mixed-mode ICC pulses, defined as fast pulses superimposed on the ICC, which have characteristics very similar to those of return strokes and are believed to be associated with the reactivation of a decayed branch or the connection of a newly created channel to the ICC-carrying channel at relatively small junction heights; (3) classical M-component pulses superimposed on the continuing current following some return strokes; and (4) M-component-type ICC pulses, presumably associated with the reactivation of a decayed branch or the connection of a newly created channel to the ICC-carrying channel at relatively large junction heights. We consider a data set consisting of 9 return-stroke pulses, 70 mixed-mode ICC pulses, 11 classical M-component pulses, and 19 M-component-type ICC pulses (a total of 109 pulses). The salient characteristics of the current and field waveforms are analyzed. A new criterion is proposed to distinguish between mixed-mode and M-component-type pulses, which is based on the current waveform features. The characteristics of M-component-type pulses during the initial stage are found to be similar to those of classical M-component pulses occurring during the continuing current after some return strokes. It is also found that about 41% of mixed-mode ICC pulses were preceded by microsecond-scale pulses occurring in electric field records some hundreds of microseconds prior to the onset of

Published
2018
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49. Electromagnetic Fields Associated With the M‐Component Mode of Charge Transfer.

Author

Xing, Hongyan, He, Lixia, Rachidi, Farhad, Azadifar, Mohammad, Rubinstein, Marcos, Rakov, Vladimir A., Cooray, Vernon, and Pavanello, Davide

Subjects
ELECTROMAGNETIC fields, ATMOSPHERIC electricity, ELECTRIC charge, CHARGE transfer, FINITE difference time domain method
Abstract

Copyright of Journal of Geophysical Research. Atmospheres is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Published
2019
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50. Analysis of the lightning production of convective cells.

Author

i Ventura, Jordi Figueras, Pineda, Nicolau, Besic, Nikola, Grazioli, Jacopo, Hering, Alessandro, van der Velde, Oscar A., Romero, David, Antonio Sunjerga, Mostajabi, Amirhossein, Azadifar, Mohammad, Rubinstein, Marcos, Montanyà, Joan, Germann, Urs, and Rachidi-Haeri, Farhad

Subjects
LIGHTNING, TRACKING radar, CELLS, THUNDERSTORMS
Abstract

This paper presents an analysis of the lightning production of convective cells. The cells were detected by the MeteoSwiss Thunderstorms Radar Tracking (TRT) algorithm in the course of a lightning measurement campaign that took place in the summer of 2017 in the area surrounding the Säntis mountain, in the northeastern part of Switzerland. For this campaign, and for the first time in the Alps, a Lightning Mapping Array (LMA) was deployed. In the first part of the paper, we examine the relationship between the intra-cloud (IC) and cloud-to-ground (CG) activity and the cell severity as derived by the TRT algorithm of a large dataset of cells gathered during the campaign. We also propose and analyze the performance of a new metric to quantify lightning intensity, the rimed particles column (RPC) height and base altitude. In the second part, we focus on two of the most severe cells detected during the campaign that produced significantly different outcomes in terms of the lightning activity. The paper shows that the newly proposed metric (RPC) seems to be a very promising predictor of lightning activity, particularly for IC flashes. Future lightning nowcasting algorithms in any case should be probabilistic in nature and incorporate the polarimetric properties of the convective cells as well as the lightning climatology. [ABSTRACT FROM AUTHOR]

Published
2019
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