scholarly journals Subpacket Structure in Strong VLF Chorus Rising Tones: Characteristics and Consequences for Radiation Belt Acceleration

2021 ◽  
Author(s):  
John C. Foster ◽  
Philip J. Erickson ◽  
Yoshiharu Omura
Keyword(s):  
Low Frequency ◽  
Phase Variation ◽  
Continuous Phase ◽  
Inner Magnetosphere ◽  
Equatorial Wave ◽  
Generation Region ◽  
Electron Gyrofrequency ◽  
Wave Normal ◽  
Local Value

Abstract Van Allen Probes in situ observations are used to examine detailed subpacket structure observed in strong VLF (very low frequency) rising tone chorus elements observed at the time of a rapid MeV electron energization in the inner magnetosphere. Analysis of the frequency gap between lower and upper chorus-band waves identifies fceEQ, the electron gyrofrequency in the equatorial wave generation region. Initial subpackets in these strong chorus rising-tone elements begin at a frequency near 1/4 fceEQ, exhibit smooth gradual frequency increase across their > 10 ms temporal duration. A second much stronger subpacket is seen at frequencies around the local value of 1/4 fce with small wave normal angle (< 10 deg) and steeply rising df/dt. Smooth frequency and phase variation across and between the initial subpackets supports continuous phase trapping of resonant electrons and increased potential for MeV electron acceleration. The total energy gain for seed electrons with energies between 100 keV and 3 MeV ranges between 2 % and 15 %, in their nonlinear interaction with a single chorus element.

scholarly journals Subpacket structure in strong VLF chorus rising tones: characteristics and consequences for relativistic electron acceleration

2021 ◽  
Vol 73 (1) ◽  
Author(s):  
John C. Foster ◽  
Philip J. Erickson ◽  
Yoshiharu Omura
Keyword(s):  
Low Frequency ◽  
Phase Variation ◽  
Electron Acceleration ◽  
Continuous Phase ◽  
Equatorial Wave ◽  
Generation Region ◽  
Electron Gyrofrequency ◽  
Wave Normal ◽  
Relativistic Electron Acceleration

AbstractVan Allen Probes in situ observations are used to examine detailed subpacket structure observed in strong VLF (very low frequency) rising-tone chorus elements observed at the time of a rapid MeV electron energization in the inner magnetosphere. Analysis of the frequency gap between lower and upper chorus-band waves identifies fceEQ, the electron gyrofrequency in the equatorial wave generation region. Initial subpackets in these strong chorus rising-tone elements begin at a frequency near 1/4 fceEQ and exhibit smooth gradual frequency increase across their > 10 ms temporal duration. A second much stronger subpacket is seen at frequencies around the local value of 1/4 fce with small wave normal angle (< 10°) and steeply rising df/dt. Smooth frequency and phase variation across and between the initial subpackets support continuous phase trapping of resonant electrons and increased potential for MeV electron acceleration. The total energy gain for individual seed electrons with energies between 100 keV and 3 MeV ranges between 2 and 15%, in their nonlinear interaction with a single chorus element.

scholarly journals Magion 5 observations of chorus-like emissions and their propagation features as inferred from ray-tracing simulation

2003 ◽  
Vol 21 (12) ◽  
pp. 2293-2302 ◽  
Author(s):  
J. Chum ◽  
F. Jiříček ◽  
J. Šmilauer ◽  
D. Shklyar
Keyword(s):  
Wave Propagation ◽  
Satellite Observation ◽  
Particle Interactions ◽  
Discrete Elements ◽  
Inner Magnetosphere ◽  
Different Types ◽  
Generation Region ◽  
Electron Gyrofrequency ◽  
Wave Normal ◽  
Ray Tracing Simulation

Abstract. After reviewing briefly the present state of knowledge about chorus-like emissions, we present an overview of Magion 5 satellite observations of these emissions in the inner magnetosphere of the Earth. From the extensive VLF data recorded on board the Magion 5 satellite, we show examples of different types of discrete elements, representing rising and falling tones, and discuss their spectral properties, such as the bandwidth and the characteristic frequency as compared to the equatorial electron gyrofrequency. We analyse the possibility of satellite observation of discrete elements, assuming nonducted wave propagation from the source. As for the characteristic dimension of the generation region, we apply the figures obtained from the recently published correlation analysis of chorus emission recorded by four satellites in the Cluster experiment. We conclude that different frequencies in the chorus element should be emitted in a certain span of wave normal angles, so that the whole element could be observed far from the generation region.Key words. Magnetospheric physics (plasmasphere; plasma waves and instabilities) – Space plasma physics (wave-particle interactions) – Ionosphere (wave propagation)

Theory of the reflexion of low-frequency radio waves obliquely incident on the ionosphere

1974 ◽  
Vol 336 (1607) ◽  
pp. 525-542 ◽  
Keyword(s):  
Low Frequency ◽  
Extraordinary Wave ◽  
Meridian Plane ◽  
Radio Waves ◽  
Quartic Equation ◽  
Obliquely Incident ◽  
Full Wave ◽  
Magnetic Meridian ◽  
Electron Gyrofrequency ◽  
Wave Normal

The properties of the two principal reflexions for radio waves obliquely incident on a horizontally stratified ionosphere in and near the magnetic meridian plane, for frequencies less than the electron gyrofrequency, are investigated using 'full wave’ numerical methods. When the wave normal of the incident wave is close to either of two directions, which are in the magnetic meridian plane, at particular angles θ b and θ e to the vertical, then for propagation from south to north (northern hemisphere), the polarizations of the two reflexions are found to take anomalous values. This behaviour is related to the properties of the Booker quartic equation. An extraordinary wave incident at an angle near θ e in the N–S direction generates some of the upgoing ‘whistler’ mode, an d this process is also investigated.

Negative Permittivity Behavior in Silver/Polyaniline Metacomposites Induced by the Low-Frequency Plasmonic Oscillation

2021 ◽  
Author(s):  
Jiahong Tian ◽  
Runhua Fan ◽  
Zongxiang Wang ◽  
Jiahao Xin ◽  
Zhongyang Wang
Keyword(s):  
Synthesis Method ◽  
Low Frequency ◽  
In Situ Synthesis ◽  
Negative Permittivity ◽  
Free Electrons ◽  
Dominant Effect ◽  
Equivalent Circuit Analysis ◽  
Inductive Character ◽  
Percolation Network

Abstract Silver/polyaniline (Ag/PANI) composites were prepared by an in-situ synthesis method. Interestingly, the permittivity changed from positive to negative along with the formation of percolation network. The plasma oscillations of free electrons from the network made a dominant effect on the negative permittivity behavior. Further investigation based on equivalent circuit analysis revealed that the composites with negative permittivity presented inductive character. The epsilon-negative composites can be applied to electromagnetic shielding, absorbing and attenuation.

scholarly journals How Do Ultra‐Low Frequency Waves Access the Inner Magnetosphere During Geomagnetic Storms?

2019 ◽  
Vol 46 (19) ◽  
pp. 10699-10709 ◽  
Author(s):  
I. Jonathan Rae ◽  
Kyle R. Murphy ◽  
Clare E.J. Watt ◽  
Jasmine K. Sandhu ◽  
Marina Georgiou ◽  
...  
Keyword(s):  
Geomagnetic Storms ◽  
Low Frequency ◽  
Inner Magnetosphere ◽  
Low Frequency Waves

Research on the dynamic characteristic of semi-active hydraulic damping strut

2019 ◽  
Vol 234 (6) ◽  
pp. 1779-1791 ◽  
Author(s):  
Daoyong Wang ◽  
Wencan Zhang ◽  
Mu Chai ◽  
Xiaguang Zeng
Keyword(s):  
Degrees Of Freedom ◽  
Dynamic Stiffness ◽  
Low Frequency ◽  
Maxwell Model ◽  
Friction Model ◽  
Damping Capacity ◽  
Frequency Range ◽  
Stiffness Model ◽  
Rubber Bushing

To reduce the vibration and shock of powertrain in the process of engine key on/off and vehicle in situ shift, a novel semi-active hydraulic damping strut is developed. The purpose of this paper is to study and discuss the dynamic stiffness model of the semi-active hydraulic damping strut. In this study, the dynamic characteristics of semi-active hydraulic damping strut were analyzed based on MTS 831 test rig first. Then, the dynamic stiffness model of semi-active hydraulic damping strut was established based on 2 degrees of freedom vibration system. In this research, a linear, fractional derivative and friction model was used to represent the nonlinear rubber bushing characteristic; the Maxwell model was used to describe the semi-active hydraulic damping strut body model; and the parameters of rubber bushing and semi-active hydraulic damping strut body were identified. The dynamic stiffness values were calculated with solenoid valve energized and not energized at amplitudes of 1 mm and 4 mm, which were consistent with experimental results in low-frequency range. Furthermore, the simplified dynamic stiffness model of the semi-active hydraulic damping strut was discussed, which showed that bushing can be ignored in low-frequency range. Then, the influence of equivalent spring stiffness, damping constant, and rubber bushing stiffness on the stiffness and damping capacity of the semi-active hydraulic damping strut were analyzed. Finally, the prototype of the semi-active hydraulic damping strut was developed and designed based on the vehicle in situ shift and engine key on/off situations, and experiments of the vehicle with and without semi-active hydraulic damping strut were carried out to verify its function.

Early Detection of Relapse by Hypermetaphase Fluorescence In Situ Hybridization After Allogeneic Bone Marrow Transplantation for Chronic Myeloid Leukemia

2000 ◽  
Vol 18 (9) ◽  
pp. 1831-1836 ◽  
Author(s):  
Chy-Myong Seong ◽  
Sergio Giralt ◽  
Hagop Kantarjian ◽  
Jingping Xu ◽  
Jolynn Swantkowski ◽  
...  
Keyword(s):  
Bone Marrow ◽  
In Situ Hybridization ◽  
Fluorescence In Situ Hybridization ◽  
Low Frequency ◽  
Allogeneic Bone Marrow ◽  
Myelogenous Leukemia ◽  
Mixed Chimerism ◽  
Allogeneic Bone ◽  
Time Points

PURPOSE: Standard G-band cytogenetic analysis (CG) provides information on approximately 25 metaphases for monitoring the presence of Philadelphia chromosome positive (Ph+) cells in chronic myelogenous leukemia (CML) patients, making the detection of a low frequency of Ph+ cells problematic. The purpose of this study was to improve the detection of a low frequency of Ph+ cells. PATIENTS AND METHODS: We combined fluorescence in situ hybridization (FISH) with long-term colcemid exposure, capturing several hundred metaphases in bone marrow cultures (hypermetaphase FISH [HMF]). Using probes that identify Ph+ cells, HMF was compared with CG analysis in the follow-up evaluations of 51 patients with CML at various time points after allogeneic bone marrow transplant (BMT). RESULTS: Thirty-five patients never showed the presence of Ph+ cells by either method. In four patients, high frequencies of Ph+ cells were detected by both methods. In the remaining 12 patients, Ph+ cells were detected by HMF at time points after BMT when they were not detected by CG. In seven of the 12 patients, low but statistically significant frequencies of Ph+ cells (0.37% to 5.20%) were detected 3 months or later after BMT, and when no intervention was initiated, all seven patients later relapsed. Based on those data, an eighth patient with mixed chimerism and a similar HMF-detected Ph+ frequency (1.8% at 27 months after BMT) was reinfused with donor lymphocytes and achieved remission with 0% Ph+ cells studied by HMF (up to 50 months after BMT). Ph+ cells detected by HMF but not by CG less than 3 months after BMT disappeared on later examination in two of four patients. After detection of Ph+ cells by HMF only, the median time to cytogenetic progression (detection of Ph+ cells by CG) was 101 days. CONCLUSION: The results demonstrate the ability of HMF to detect low but clinically relevant levels of leukemic cells not detected by CG in transplant patients. The data indicate that HMF can detect low levels of Ph+ cells before standard cytogenetics at a time that may be useful in monitoring disease status and planning clinical interventions.

scholarly journals Properties of the singing comet waves in the 67P/Churyumov-Gerasimenko plasma environment as observed by the Rosetta mission

2019 ◽  
Vol 630 ◽  
pp. A39 ◽  
Author(s):  
H. Breuillard ◽  
P. Henri ◽  
L. Bucciantini ◽  
M. Volwerk ◽  
T. Karlsson ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Low Frequency ◽  
Compressional Waves ◽  
Weibel Instability ◽  
Plasma Environment ◽  
Background Magnetic Field ◽  
Rosetta Mission ◽  
Ion Waves ◽  
Plasma Coupling

Using in situ measurements from different instruments on board the Rosetta spacecraft, we investigate the properties of the newly discovered low-frequency oscillations, known as singing comet waves, that sometimes dominate the close plasma environment of comet 67P/Churyumov-Gerasimenko. These waves are thought to be generated by a modified ion-Weibel instability that grows due to a beam of water ions created by water molecules that outgass from the comet. We take advantage of a cometary outburst event that occurred on 2016 February 19 to probe this generation mechanism. We analyze the 3D magnetic field waveforms to infer the properties of the magnetic oscillations of the cometary ion waves. They are observed in the typical frequency range (~50 mHz) before the cometary outburst, but at ~20 mHz during the outburst. They are also observed to be elliptically right-hand polarized and to propagate rather closely (~0−50°) to the background magnetic field. We also construct a density dataset with a high enough time resolution that allows us to study the plasma contribution to the ion cometary waves. The correlation between plasma and magnetic field variations associated with the waves indicates that they are mostly in phase before and during the outburst, which means that they are compressional waves. We therefore show that the measurements from multiple instruments are consistent with the modified ion-Weibel instability as the source of the singing comet wave activity. We also argue that the observed frequency of the singing comet waves could be a way to indirectly probe the strength of neutral plasma coupling in the 67P environment.

scholarly journals Propagation properties of Rossby waves for latitudinal β-plane variations of <I>f</I> and zonal variations of the shallow water speed

2012 ◽  
Vol 30 (5) ◽  
pp. 849-855 ◽  
Author(s):  
C. T. Duba ◽  
J. F. McKenzie
Keyword(s):  
Shallow Water ◽  
Group Velocity ◽  
Rossby Wave ◽  
Rossby Waves ◽  
Low Frequency ◽  
Wave Number ◽  
Coriolis Parameter ◽  
Propagation Properties ◽  
Wave Normal ◽  
Water Speed

Abstract. Using the shallow water equations for a rotating layer of fluid, the wave and dispersion equations for Rossby waves are developed for the cases of both the standard β-plane approximation for the latitudinal variation of the Coriolis parameter f and a zonal variation of the shallow water speed. It is well known that the wave normal diagram for the standard (mid-latitude) Rossby wave on a β-plane is a circle in wave number (ky,kx) space, whose centre is displaced −β/2 ω units along the negative kx axis, and whose radius is less than this displacement, which means that phase propagation is entirely westward. This form of anisotropy (arising from the latitudinal y variation of f), combined with the highly dispersive nature of the wave, gives rise to a group velocity diagram which permits eastward as well as westward propagation. It is shown that the group velocity diagram is an ellipse, whose centre is displaced westward, and whose major and minor axes give the maximum westward, eastward and northward (southward) group speeds as functions of the frequency and a parameter m which measures the ratio of the low frequency-long wavelength Rossby wave speed to the shallow water speed. We believe these properties of group velocity diagram have not been elucidated in this way before. We present a similar derivation of the wave normal diagram and its associated group velocity curve for the case of a zonal (x) variation of the shallow water speed, which may arise when the depth of an ocean varies zonally from a continental shelf.

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