Y. H. Wang, W. X. Ding, C. Zhou, A. D. Liu, X. Feng, H. Lian, H. Q. Liu, Y. Q. Chu, D. L. Brower, W. Z. Mao, J. L. Xie, L. T. Gao, R. J. Zhu, X. M. Zhong, H. J. Ren, Z. Chen, W. X. Shi, S. F. Wang
Velocity, density, and magnetic fluctuations of the geodesic acoustic mode (GAM) have been measured using the Doppler backscattering system, Faraday-effect polarimeter-interferometer, and external pick-up coils in the Experimental Advanced Superconducting Tokamak. Simultaneous measurements of density and velocity fluctuations at the midplane and top of plasmas demonstrate that m = 1 density fluctuations are quantitatively balanced by the compression of perpendicular flow fluctuations. Furthermore, internal magnetic fluctuations associated with GAM have now been directly measured by laser-based Faraday-effect polarimetry for the first time. Line-averaged magnetic fluctuations (up to 16 Gauss, B̃¯R,GAMBT∼0.066%) are significantly larger than those extrapolated from edge coils (a few Gauss) and that magnetic fluctuations increase with β. The observed discrepancy between finite β theory and experimental data indicates the need for further theoretical investigations.
{"title":"Internal measurements of electromagnetic geodesic acoustic mode (GAM) in EAST plasmas","authors":"Y. H. Wang, W. X. Ding, C. Zhou, A. D. Liu, X. Feng, H. Lian, H. Q. Liu, Y. Q. Chu, D. L. Brower, W. Z. Mao, J. L. Xie, L. T. Gao, R. J. Zhu, X. M. Zhong, H. J. Ren, Z. Chen, W. X. Shi, S. F. Wang","doi":"10.1063/5.0211489","DOIUrl":"https://doi.org/10.1063/5.0211489","url":null,"abstract":"Velocity, density, and magnetic fluctuations of the geodesic acoustic mode (GAM) have been measured using the Doppler backscattering system, Faraday-effect polarimeter-interferometer, and external pick-up coils in the Experimental Advanced Superconducting Tokamak. Simultaneous measurements of density and velocity fluctuations at the midplane and top of plasmas demonstrate that m = 1 density fluctuations are quantitatively balanced by the compression of perpendicular flow fluctuations. Furthermore, internal magnetic fluctuations associated with GAM have now been directly measured by laser-based Faraday-effect polarimetry for the first time. Line-averaged magnetic fluctuations (up to 16 Gauss, B̃¯R,GAMBT∼0.066%) are significantly larger than those extrapolated from edge coils (a few Gauss) and that magnetic fluctuations increase with β. The observed discrepancy between finite β theory and experimental data indicates the need for further theoretical investigations.","PeriodicalId":20175,"journal":{"name":"Physics of Plasmas","volume":"40 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2024-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142221808","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The drift dynamics of ion-temperature-gradient (ITG) driven fluctuations in the plane perpendicular to a guiding magnetic field is investigated by mapping its governing equation into a Schrödinger-type equation. First, we separate the parallel dynamics and the perpendicular dynamics. The parallel dynamics can coherently couple with the perpendicular dynamics, leading to the growth of a coherent, localized ITG eigenmode. The E × B flow plays a dominant role for the fluctuation propagation dynamics and impact on the radial redistribution of fluctuations. Another attractive finding is that the ITG wave packet can penetrate a strong yet narrow E × B shear layer through “tunneling.” When the parallel dynamics becomes stochastic, non-eigenmode peaks can emerge in the fluctuation power spectrum and an estimate of the saturated spectrum intensity of the ITG fluctuations can be obtained.
通过将离子-温度梯度（ITG）驱动的波动的支配方程映射为薛定谔型方程，研究了离子-温度梯度（ITG）驱动的波动在垂直于引导磁场的平面上的漂移动力学。首先，我们将平行动力学和垂直动力学分开。平行动力学可以与垂直动力学相干耦合，从而产生相干的局部 ITG 特征模式。E × B 流在波动传播动力学中起着主导作用，并对波动的径向再分布产生影响。另一个有吸引力的发现是，ITG 波包可以通过 "隧道 "穿透强而窄的 E × B 剪切层。当平行动力学变得随机时，波动功率谱中就会出现非特征模峰值，并可获得 ITG 波动饱和谱强度的估计值。
{"title":"Propagation and stochastic dynamics of ion-temperature-gradient driven fluctuations","authors":"Yihan Wang, Zhibin Guo","doi":"10.1063/5.0221923","DOIUrl":"https://doi.org/10.1063/5.0221923","url":null,"abstract":"The drift dynamics of ion-temperature-gradient (ITG) driven fluctuations in the plane perpendicular to a guiding magnetic field is investigated by mapping its governing equation into a Schrödinger-type equation. First, we separate the parallel dynamics and the perpendicular dynamics. The parallel dynamics can coherently couple with the perpendicular dynamics, leading to the growth of a coherent, localized ITG eigenmode. The E × B flow plays a dominant role for the fluctuation propagation dynamics and impact on the radial redistribution of fluctuations. Another attractive finding is that the ITG wave packet can penetrate a strong yet narrow E × B shear layer through “tunneling.” When the parallel dynamics becomes stochastic, non-eigenmode peaks can emerge in the fluctuation power spectrum and an estimate of the saturated spectrum intensity of the ITG fluctuations can be obtained.","PeriodicalId":20175,"journal":{"name":"Physics of Plasmas","volume":"39 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2024-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142221815","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
S. Jiang, O. L. Landen, H. D. Whitley, S. Hamel, R. A. London, P. Sterne, S. B. Hansen, S. X. Hu, G. W. Collins, Y. Ping
X-ray refraction-enhanced radiography (RER) or phase contrast imaging is widely used to study internal discontinuities within materials. The resulting radiograph captures both the decrease in intensity caused by material absorption along the x-ray path, as well as the phase shift, which is highly sensitive to gradients in density. A significant challenge lies in effectively analyzing the radiographs to decouple the intensity and phase information and accurately ascertain the density profile. Conventional algorithms often yield ambiguous and unrealistic results due to difficulties in including physical constraints and other relevant information. We have developed an algorithm that uses a deep neural network to address these issues and applied it to extract the detailed density profile from an experimental RER. To generalize the applicability of our algorithm, we have developed a technique that quantitatively evaluates the complexity of the phase retrieval process based on the characteristics of the sample and the configuration of the experiment. Accordingly, this evaluation aids in the selection of the neural network architecture for each specific case. Beyond RER, the model has potential applications for other diagnostics where phase retrieval analysis is required.
X 射线折射增强射线照相术（RER）或相位对比成像被广泛用于研究材料内部的不连续性。由此产生的射线照片既能捕捉到材料沿 X 射线路径吸收所导致的强度下降，也能捕捉到对密度梯度高度敏感的相移。有效分析射线照片，将强度和相位信息解耦，并准确确定密度剖面是一项重大挑战。由于难以纳入物理约束和其他相关信息，传统算法通常会产生模糊和不切实际的结果。我们开发了一种使用深度神经网络来解决这些问题的算法，并将其应用于从实验 RER 中提取详细的密度曲线。为了推广我们算法的适用性，我们开发了一种技术，可根据样本的特征和实验的配置，定量评估相位检索过程的复杂性。因此，这种评估有助于为每种特定情况选择神经网络架构。除 RER 外，该模型还有可能应用于其他需要进行相位检索分析的诊断。
{"title":"Phase retrieval for refraction-enhanced x-ray radiography using a deep neural network","authors":"S. Jiang, O. L. Landen, H. D. Whitley, S. Hamel, R. A. London, P. Sterne, S. B. Hansen, S. X. Hu, G. W. Collins, Y. Ping","doi":"10.1063/5.0211331","DOIUrl":"https://doi.org/10.1063/5.0211331","url":null,"abstract":"X-ray refraction-enhanced radiography (RER) or phase contrast imaging is widely used to study internal discontinuities within materials. The resulting radiograph captures both the decrease in intensity caused by material absorption along the x-ray path, as well as the phase shift, which is highly sensitive to gradients in density. A significant challenge lies in effectively analyzing the radiographs to decouple the intensity and phase information and accurately ascertain the density profile. Conventional algorithms often yield ambiguous and unrealistic results due to difficulties in including physical constraints and other relevant information. We have developed an algorithm that uses a deep neural network to address these issues and applied it to extract the detailed density profile from an experimental RER. To generalize the applicability of our algorithm, we have developed a technique that quantitatively evaluates the complexity of the phase retrieval process based on the characteristics of the sample and the configuration of the experiment. Accordingly, this evaluation aids in the selection of the neural network architecture for each specific case. Beyond RER, the model has potential applications for other diagnostics where phase retrieval analysis is required.","PeriodicalId":20175,"journal":{"name":"Physics of Plasmas","volume":"37 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2024-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142221807","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
An experimental study is conducted on macro- and microscopic characteristics of low to high (LH) transition acquired by electron cyclotron resonance heating (ECRH) in KSTAR. A scan of pre-transition density demonstrates the existence of the characteristic minimum density, which requires minimum power to make LH transition. The minimum density in KSTAR shows a tendency to be lower than that evaluated from an empirical scaling law proposed by Ryter et al. [Nucl. Fusion 54, 083003 (2014)]. A comprehensive study of the evolution of low wavenumber electron temperature fluctuations is carried out using electron cyclotron emission imaging diagnostics. An analysis of the fluctuation amplitude in L-mode in terms of the electron collisionality and the electron temperature scaling length suggests that the dissipative trapped electron mode is likely to be a dominant instability before the LH transition. The fluctuation amplitude reduces first as the transition starts. A coherent mode that chirps down from 60 to 20 kHz emerges when the transition further develops. This coherent mode is then shown to revive turbulence that has been reduced significantly during the initial stage of the LH transition. The revival of turbulence could be a possible origin of the absence of the large edge localized mode when the coherent mode is persistent in ECRH-induced H-mode plasmas.
{"title":"Transition characteristics, fluctuation evolution, and the role of coherent mode in electron cyclotron resonance heated low to high mode transition in KSTAR","authors":"Hogun Jhang, Minjun J Choi, Hyun-Seok Kim","doi":"10.1063/5.0225207","DOIUrl":"https://doi.org/10.1063/5.0225207","url":null,"abstract":"An experimental study is conducted on macro- and microscopic characteristics of low to high (LH) transition acquired by electron cyclotron resonance heating (ECRH) in KSTAR. A scan of pre-transition density demonstrates the existence of the characteristic minimum density, which requires minimum power to make LH transition. The minimum density in KSTAR shows a tendency to be lower than that evaluated from an empirical scaling law proposed by Ryter et al. [Nucl. Fusion 54, 083003 (2014)]. A comprehensive study of the evolution of low wavenumber electron temperature fluctuations is carried out using electron cyclotron emission imaging diagnostics. An analysis of the fluctuation amplitude in L-mode in terms of the electron collisionality and the electron temperature scaling length suggests that the dissipative trapped electron mode is likely to be a dominant instability before the LH transition. The fluctuation amplitude reduces first as the transition starts. A coherent mode that chirps down from 60 to 20 kHz emerges when the transition further develops. This coherent mode is then shown to revive turbulence that has been reduced significantly during the initial stage of the LH transition. The revival of turbulence could be a possible origin of the absence of the large edge localized mode when the coherent mode is persistent in ECRH-induced H-mode plasmas.","PeriodicalId":20175,"journal":{"name":"Physics of Plasmas","volume":"29 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2024-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142221812","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Yaping Hong, Hao Wei, Jiachen Wang, Hanyu Wu, Liangping Wang, Chuangsi Cheng, Mo Li, Aici Qiu
A series of current transport experiments of a conical magnetically insulated transmission line (MITL) and a single post-hole convolute (PHC) had been done on a 12-stage linear transformer driver (LTD). The LTD produced a current with a rise time of about 120 ns and a peak varying from 0.5 to 0.8 MA depending on the terminated connection loads. The conical MITL was designed with a constant gap distance of 8 mm, which was equivalent to the MITL segments that are close to the PHC locations in the multi-level conical MITL in tens of megaampere current drivers. A single PHC was also designed to operate at conditions close to those fielded on tens of MA current drivers such as the Z machine. The experiment results indicated that there was almost no current loss along the constant-gap MITL before the peak current even the MITL figure of merit, i.e., E/cB varied from 0.1 to 1. However, the time when current trails appeared gradually advanced. The effects of the geometric sizes on the current transport efficiency of a single PHC were studied. It was indicated that the current transport efficiency of the single PHC was considerable high while the gap distance is larger than 6 mm. Whereas the PHC current loss was increased to about 30% when the gap is 3 mm. The dynamic impedance of the single PHC was obtained. During the pulse, as the plasma diffused, the convolute shunt impedance rapidly decreased, which was consistent with the known mechanism.
{"title":"Current loss experiments of a conical MITL and PHC system on a megaampere-class LTD module","authors":"Yaping Hong, Hao Wei, Jiachen Wang, Hanyu Wu, Liangping Wang, Chuangsi Cheng, Mo Li, Aici Qiu","doi":"10.1063/5.0220464","DOIUrl":"https://doi.org/10.1063/5.0220464","url":null,"abstract":"A series of current transport experiments of a conical magnetically insulated transmission line (MITL) and a single post-hole convolute (PHC) had been done on a 12-stage linear transformer driver (LTD). The LTD produced a current with a rise time of about 120 ns and a peak varying from 0.5 to 0.8 MA depending on the terminated connection loads. The conical MITL was designed with a constant gap distance of 8 mm, which was equivalent to the MITL segments that are close to the PHC locations in the multi-level conical MITL in tens of megaampere current drivers. A single PHC was also designed to operate at conditions close to those fielded on tens of MA current drivers such as the Z machine. The experiment results indicated that there was almost no current loss along the constant-gap MITL before the peak current even the MITL figure of merit, i.e., E/cB varied from 0.1 to 1. However, the time when current trails appeared gradually advanced. The effects of the geometric sizes on the current transport efficiency of a single PHC were studied. It was indicated that the current transport efficiency of the single PHC was considerable high while the gap distance is larger than 6 mm. Whereas the PHC current loss was increased to about 30% when the gap is 3 mm. The dynamic impedance of the single PHC was obtained. During the pulse, as the plasma diffused, the convolute shunt impedance rapidly decreased, which was consistent with the known mechanism.","PeriodicalId":20175,"journal":{"name":"Physics of Plasmas","volume":"6 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2024-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142221811","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
It has been suggested that under solar coronal conditions, drift waves may contribute to coronal heating. Specific properties of the drift waves to be expected in the solar corona have, however, not yet been determined using more advanced numerical models. We investigate the linear properties of density-gradient-driven drift waves in the solar coronal plasma using gyrokinetic ion–electron simulations with the gyrokinetic code Gene, solving the Vlasov–Maxwell equations in five dimensions assuming a simple slab geometry. We determine the frequencies and growth rates of the coronal density gradient-driven drift waves with changing plasma parameters, such as the electron β, the density gradient, the magnetic shear, and additional temperature gradients. To investigate the influence of the finite Larmor radius effect on the growth and structure of the modes, we also compare the gyrokinetic simulation results to those obtained from drift-kinetics. In most of the investigated conditions, the drift wave has positive growth rates that increase with increasing density gradient and decreasing β. In the case of increasing magnetic shear, we find that from a certain point, the growth rate reaches a plateau. Depending on the considered reference environment, the frequencies and growth rates of these waves lie on the order of 0.1 mHz–1 Hz. These values correspond to the observed solar wind density fluctuations near the Sun detected by WISPR, currently of unexplained origin. As a next step, nonlinear simulations are required to determine the expected fluctuation amplitudes and the plasma heating resulting from this mechanism.
{"title":"Density-gradient-driven drift waves in the solar corona","authors":"M. Brchnelova, M. J. Pueschel, S. Poedts","doi":"10.1063/5.0223417","DOIUrl":"https://doi.org/10.1063/5.0223417","url":null,"abstract":"It has been suggested that under solar coronal conditions, drift waves may contribute to coronal heating. Specific properties of the drift waves to be expected in the solar corona have, however, not yet been determined using more advanced numerical models. We investigate the linear properties of density-gradient-driven drift waves in the solar coronal plasma using gyrokinetic ion–electron simulations with the gyrokinetic code Gene, solving the Vlasov–Maxwell equations in five dimensions assuming a simple slab geometry. We determine the frequencies and growth rates of the coronal density gradient-driven drift waves with changing plasma parameters, such as the electron β, the density gradient, the magnetic shear, and additional temperature gradients. To investigate the influence of the finite Larmor radius effect on the growth and structure of the modes, we also compare the gyrokinetic simulation results to those obtained from drift-kinetics. In most of the investigated conditions, the drift wave has positive growth rates that increase with increasing density gradient and decreasing β. In the case of increasing magnetic shear, we find that from a certain point, the growth rate reaches a plateau. Depending on the considered reference environment, the frequencies and growth rates of these waves lie on the order of 0.1 mHz–1 Hz. These values correspond to the observed solar wind density fluctuations near the Sun detected by WISPR, currently of unexplained origin. As a next step, nonlinear simulations are required to determine the expected fluctuation amplitudes and the plasma heating resulting from this mechanism.","PeriodicalId":20175,"journal":{"name":"Physics of Plasmas","volume":"25 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2024-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142221806","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Andrew T. Walsten, Brian Z. Bentz, Kevin Youngman, Kunning G. Xu
Laser-collisional induced fluorescence is used to study the plasma generated by a split-ring resonator discharge under an external cusp shaped magnetic field created by permanent magnets. The electron density and electron temperature are measured for a helium plasma at different pressures, powers, and magnet field strengths. It is found that the magnetic fields produce higher electron temperatures with peak temperatures of ∼3 eV, while the no magnet case has peak temperatures of ∼0.8 eV. Conversely, the peak electron density is obtained in the no magnet case at a value of ∼1.9 × 1011 cm−3. This indicates that the cusp-field did magnetize the electrons, but contrary to expectations, it resulted in a decrease in electron density. This is believed to be due to the magnetic field having negative effects on the resonance of the plasma source.
{"title":"Spatially resolved measurements of electron density of a magnetically confined split-ring resonator source","authors":"Andrew T. Walsten, Brian Z. Bentz, Kevin Youngman, Kunning G. Xu","doi":"10.1063/5.0215171","DOIUrl":"https://doi.org/10.1063/5.0215171","url":null,"abstract":"Laser-collisional induced fluorescence is used to study the plasma generated by a split-ring resonator discharge under an external cusp shaped magnetic field created by permanent magnets. The electron density and electron temperature are measured for a helium plasma at different pressures, powers, and magnet field strengths. It is found that the magnetic fields produce higher electron temperatures with peak temperatures of ∼3 eV, while the no magnet case has peak temperatures of ∼0.8 eV. Conversely, the peak electron density is obtained in the no magnet case at a value of ∼1.9 × 1011 cm−3. This indicates that the cusp-field did magnetize the electrons, but contrary to expectations, it resulted in a decrease in electron density. This is believed to be due to the magnetic field having negative effects on the resonance of the plasma source.","PeriodicalId":20175,"journal":{"name":"Physics of Plasmas","volume":"20 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2024-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142221814","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This study investigated the relationship between the cosmic ray intensity (CRI) and the horizontal component of Earth's magnetic field (dH) during two intense geomagnetic storms that occurred on September 8, 2017, and August 26, 2018, and a moderate storm on February 18, 2020 over three stations: IRKT, YKTK, and HRMS. The findings of this study indicate that the CRI and dH do not exhibit a simple association over each station. A significant decrease in CRI and dH was seen during the intense geomagnetic storm on September 8, 2017, over all stations as compared to the other two storm events. The decrease was more pronounced over the YKTK station, which has low cutoff rigidity (1.65 GV), than the HRMS (4.58 GV) and IRKT (3.64 GV) stations with high cutoff rigidity. Furthermore, the cross-wavelet analysis reveals that the relationship between CRI and dH varies with the strength of the storm, the location, and the cutoff rigidity of the station.
{"title":"Relationship between cosmic ray intensity and Earth's magnetic field: Cross-wavelet analysis during intense and moderate geomagnetic storms","authors":"Chali Idosa Uga, Sujan Prasad Gautam, Binod Adhikari, Ashok Silwal, Ashutosh Giri","doi":"10.1063/5.0201135","DOIUrl":"https://doi.org/10.1063/5.0201135","url":null,"abstract":"This study investigated the relationship between the cosmic ray intensity (CRI) and the horizontal component of Earth's magnetic field (dH) during two intense geomagnetic storms that occurred on September 8, 2017, and August 26, 2018, and a moderate storm on February 18, 2020 over three stations: IRKT, YKTK, and HRMS. The findings of this study indicate that the CRI and dH do not exhibit a simple association over each station. A significant decrease in CRI and dH was seen during the intense geomagnetic storm on September 8, 2017, over all stations as compared to the other two storm events. The decrease was more pronounced over the YKTK station, which has low cutoff rigidity (1.65 GV), than the HRMS (4.58 GV) and IRKT (3.64 GV) stations with high cutoff rigidity. Furthermore, the cross-wavelet analysis reveals that the relationship between CRI and dH varies with the strength of the storm, the location, and the cutoff rigidity of the station.","PeriodicalId":20175,"journal":{"name":"Physics of Plasmas","volume":"185 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2024-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142227587","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Observation of a dip in plasma density with the rise of ion plasma waves demonstrates the process of detrapping electrons under the double-layer conditions in a DC glow discharge plasma. This study presents an experimental observation of self-excitation and interplay between electron and ion plasma waves when a high positive DC voltage (Vp∼+100 V) is applied to a planar probe immersed in plasma. For lower voltages (Vp∼+5 V), the electron sheath forms on the surface of the probe; however, for sufficiently high applied voltage, plasma could not supply the sufficient number of electrons to shield it from penetrating deep into the plasma. Therefore, the electron-deficient sheath attracts plasma electrons toward the probe, resulting in the excitation of plasma waves and the formation of double layers. Low energy streaming electrons get trapped in the double layers potential step. On ionization of background neutrals, trapped electrons get detrapped. It results in the excitation of ion waves and damping of electron plasma waves. The wavelet analysis of the observed floating potential fluctuations exhibits the interplay between electron and ion plasma waves. The trapping of electrons causes the excitation of electron plasma waves, and detrapping results in the excitation of ion plasma waves as overall electron density dips. It provides new insight into the nonlinear effects of the wave–wave interaction, the onset of Buneman instability, and streaming instability under the double-layer condition.
{"title":"Trapping and detrapping of electrons in a typical DC glow discharge plasma under double layer condition","authors":"Thangjam Rishikanta Singh, Sneha Latha Kommuguri, Suraj Kumar Sinha","doi":"10.1063/5.0222639","DOIUrl":"https://doi.org/10.1063/5.0222639","url":null,"abstract":"Observation of a dip in plasma density with the rise of ion plasma waves demonstrates the process of detrapping electrons under the double-layer conditions in a DC glow discharge plasma. This study presents an experimental observation of self-excitation and interplay between electron and ion plasma waves when a high positive DC voltage (Vp∼+100 V) is applied to a planar probe immersed in plasma. For lower voltages (Vp∼+5 V), the electron sheath forms on the surface of the probe; however, for sufficiently high applied voltage, plasma could not supply the sufficient number of electrons to shield it from penetrating deep into the plasma. Therefore, the electron-deficient sheath attracts plasma electrons toward the probe, resulting in the excitation of plasma waves and the formation of double layers. Low energy streaming electrons get trapped in the double layers potential step. On ionization of background neutrals, trapped electrons get detrapped. It results in the excitation of ion waves and damping of electron plasma waves. The wavelet analysis of the observed floating potential fluctuations exhibits the interplay between electron and ion plasma waves. The trapping of electrons causes the excitation of electron plasma waves, and detrapping results in the excitation of ion plasma waves as overall electron density dips. It provides new insight into the nonlinear effects of the wave–wave interaction, the onset of Buneman instability, and streaming instability under the double-layer condition.","PeriodicalId":20175,"journal":{"name":"Physics of Plasmas","volume":"72 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2024-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142221817","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Modifications to Swisdak's [Phys. Plasmas 20, 062110 (2013)] rejection sampling algorithm for drawing a Maxwell–Jüttner distribution in particle simulations are presented. Handy approximations for e-folding points and a linear slope in the envelope function are proposed, to make the algorithm self-contained and more efficient.
{"title":"Modifications to Swisdak (2013)'s rejection sampling algorithm for a Maxwell–Jüttner distribution in particle simulations","authors":"Seiji Zenitani","doi":"10.1063/5.0226859","DOIUrl":"https://doi.org/10.1063/5.0226859","url":null,"abstract":"Modifications to Swisdak's [Phys. Plasmas 20, 062110 (2013)] rejection sampling algorithm for drawing a Maxwell–Jüttner distribution in particle simulations are presented. Handy approximations for e-folding points and a linear slope in the envelope function are proposed, to make the algorithm self-contained and more efficient.","PeriodicalId":20175,"journal":{"name":"Physics of Plasmas","volume":"5 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2024-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142221860","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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