Search

Your search keyword '"Fu, H. S."' showing total 407 results
Start Over Author "Fu, H. S."
407 results on '"Fu, H. S."'

1. Observational Evidence of Magnetic Reconnection in the Terrestrial Foreshock Region

Author

Jiang, K., Huang, S. Y., Fu, H. S., Yuan, Z. G., Deng, X. H., Wang, Z., Guo, Z. Z., Xu, S. B., Wei, Y. Y., Zhang, J., Zhang, Z. H., Xiong, Q. Y., and Yu, L.

Subjects
Physics - Plasma Physics, Astrophysics - Earth and Planetary Astrophysics, Physics - Space Physics
Abstract

Electron heating/acceleration in the foreshock, by which electrons may be energized beyond thermal energies prior to encountering the bow shock, is very important for the bow shock dynamics. And then these electrons would be more easily injected into a process like diffusive shock acceleration. Many mechanisms have been proposed to explain electrons heating/acceleration in the foreshock. Magnetic reconnection is one possible candidate. Taking advantage of the Magnetospheric Multiscale mission, we present two magnetic reconnection events in the dawn-side and dusk-side ion foreshock region, respectively. Super-Alfv\'enic electron outflow, demagnetization of the electrons and the ions, and crescent electron distributions in the plane perpendicular to the magnetic field are observed in the sub-ion-scale current sheets. Moreover, strong energy conversion from the fields to the plasmas and significant electron temperature enhancement are observed. Our observations provide direct evidence that magnetic reconnection could occur in the foreshock region and heat/accelerate the electrons therein., Comment: 17 pages, 4 figures, accepted by ApJ

Published
2021
Full Text
View/download PDF

2. Characteristics of Interplanetary Discontinuities in the Inner Heliosphere Revealed by Parker Solar Probe

Author

Liu, Y. Y., Fu, H. S., Cao, J. B., Liu, C. M., Wang, Z., Guo, Z. Z., Xu, Y., Bale, S. D., and Kasper, J. C.

Subjects
Astrophysics - Solar and Stellar Astrophysics, Physics - Space Physics
Abstract

We present a statistical analysis for the characteristics and spatial evolution of the interplanetary discontinuities (IDs) in the solar wind, from 0.13 to 0.9 au, by using the Parker Solar Probe measurements on Orbits 4 and 5. 3948 IDs have been collected, including 2511 rotational discontinuities (RDs) and 557 tangential discontinuities (TDs), with the remnant unidentified. The statistical results show that (1) the ID occurrence rate decreases from 200 events/day at 0.13 au to 1 events/day at 0.9 au, following a spatial scaling r-2.00, (2) the RD to TD ratio decreases quickly with the heliocentric distance, from 8 at r<0.3 au to 1 at r>0.4 au, (3) the magnetic field tends to rotate across the IDs, 45{\deg} for TDs and 30{\deg} for RDs in the pristine solar wind within 0.3 au, (4) a special subgroup of RDs exist within 0.3 au, characterized by small field rotation angles and parallel or antiparallel propagations to the background magnetic fields, (5) the TD thicknesses normalized by local ion inertial lengths (di) show no clear spatial scaling and generally range from 5 to 35 di, and the normalized RD thicknesses follow r-1.09 spatial scaling, (6) the outward (anti-sunward) propagating RDs predominate in all RDs, with the propagation speeds in the plasma rest frame proportional to r-1.03. This work could improve our understandings for the ID characteristics and evolutions and shed light on the study of the turbulent environment in the pristine solar wind., Comment: Accepted by ApJS

Published
2021
Full Text
View/download PDF

3. First observation of magnetic flux rope inside electron diffusion region

Author

Chen, Z. Z., Fu, H. S., Wang, Z., Guo, Z. Z., Xu, Y., and Liu, C. M.

Subjects
Physics - Space Physics, Physics - Plasma Physics
Abstract

Magnrtic flux ropes (MFRs) play a crucial role during magnetic reconnection. They are believed to be primarily generated by tearing mode instabilities in the electron diffusion region (EDR). However, they have never been observed inside the EDR. Here, we present the first observation of an MFR inside an EDR. The bifurcated non-force-free MFR, with a width of 27.5de in the L direction and 4.8de in the N direction, was moving away from the X-line. Inside the MFR, strong energy dissipation was detected. The MFR can modulate the electric field in the EDR. We reconstructed magnetic topology of the electron-scale MFR. Our study promotes understanding of MRFs' initial state and its role in electron-scale processes during magnetic reconnection., Comment: 27 pages, 4 figures

Published
2020
Full Text
View/download PDF

4. Electron Heating by Debye-Scale Turbulence in Guide-Field Reconnection

Author

Khotyaintsev, Yu. V., Graham, D. B., Steinvall, K., Alm, L., Vaivads, A., Johlander, A., Norgren, C., Li, W., Divin, A., Fu, H. S., Hwang, K. -J., Ahmadi, N., Contel, O. Le, Gershman, D. J., Russell, C. T., Torbert, R. B., and Burch, J. L.

Subjects
Physics - Space Physics, Physics - Plasma Physics
Abstract

We report electrostatic Debye-scale turbulence developing within the diffusion region of asymmetric magnetopause reconnection with moderate guide field using observations by the Magnetospheric Multiscale (MMS) mission. We show that Buneman waves and beam modes cause efficient and fast thermalization of the reconnection electron jet by irreversible phase mixing, during which the jet kinetic energy is transferred into thermal energy. Our results show that the reconnection diffusion region in the presence of a moderate guide field is highly turbulent, and that electrostatic turbulence plays an important role in electron heating., Comment: 5 pages, 4 figures

Published
2019
Full Text
View/download PDF

6. Strong Field‐Aligned Current and Its Driven Energy Conversion at Anti‐Dipolarization Front.

Author

Du, C. X., Wang, Z., Fu, H. S., Fu, W. D., Cao, J. B., Grigorenko, E., and Yu, Y.

Subjects
ENERGY conversion, ELECTRIC fields, MAGNETIC fields, DISTRIBUTION (Probability theory), ELECTRONS
Abstract

Anti‐dipolarization fronts (ADFs), characterized by the rapid increase of the negative magnetic field Bz component, are typically formed at the leading edge of the tailward reconnection jets in the Earth's magnetotail. To date, the electron‐scale current structures, which govern the energy conversion at ADFs, are still barely understood due to the lack of high‐resolution measurements. Here, using Magnetospheric Multiscale mission, we for the first time report a tailward ADF associated with strong field‐aligned current (FAC). The FAC appears at the leading part of the ADF and its densities can reach about 200 nA/m2, which is significantly larger than those reported before. Such current is primarily contributed by the electron flow, which also forms electron beam distribution in the anti‐parallel direction. Significant energy conversion (E⋅ J, E is electric field and J is current density) is also observed at the ADF, which is mainly contributed by the FAC and the fluctuating electric fields. This study makes essential steps toward understanding the current system and the energy conversion at the ADF in the Earth's magnetotail. Plain Language Summary: Dipolarization fronts (DFs) and anti‐dipolarization fronts (ADFs) are the leading edge of the reconfigured magnetic field after reconnection, expanding earthward and tailward from the reconnection site respectively. The field‐aligned current (FAC) at DFs play crucial roles in global mass transport and energy conversion during substorm and they have been widely studied by in situ observation and simulation. However, the FAC at ADFs and the corresponding energy conversion have not been studied so for. Here, for the first time, we report an ADF associated with strong FAC using high‐resolution data from the MMS mission. We investigate the detailed features of the currents, electron distribution functions, electric fields and energy conversion at the ADF. This study shed light on how strong FAC drive energy conversion at ADFs. Key Points: We for the first time report a tailward anti‐dipolarization front (ADF) associated with strong field‐aligned current (FAC)The FAC is primarily carried by electrons and can reach ∼200 nA/m2, which is even stronger than the FACs reported in earthward Dipolarization frontsThe strong FAC and fluctuating electric fields can drive significant energy conversion at the ADF [ABSTRACT FROM AUTHOR]

Published
2024
Full Text
View/download PDF

7. Magnetospheric Multiscale Observations of Electron Vortex Magnetic Hole in the Magnetosheath Turbulent Plasma

Author

Huang, S. Y., Sahraoui, F., Yuan, Z. G., He, J. S., Zhao, J. S., Contel, O. Le, Deng, X. H., Zhou, M., Fu, H. S., Pang, Y., Shi, Q. Q., Lavraud, B., Yang, J., Wang, D. D., Yu, X. D., Pollock, C. J., Giles, B. L., Torbert, R. B., Russell, C. T., Goodrich, K. A., Gershman, D. J., Moore, T. E., Ergun, R. E., Khotyaintsev, Y. V., Lindqvist, P. -A., Strangeway, R. J., Magnes, W., Bromund, K., Leinweber, H., Plaschke, F., Anderson, B. J., and Burch, J. L.

Subjects
Physics - Space Physics, Astrophysics - Solar and Stellar Astrophysics, Physics - Plasma Physics
Abstract

We report the observations of an electron vortex magnetic hole corresponding to a new type of coherent structures in the magnetosheath turbulent plasma using the Magnetospheric Multiscale (MMS) mission data. The magnetic hole is characterized by a magnetic depression, a density peak, a total electron temperature increase (with a parallel temperature decrease but a perpendicular temperature increase), and strong currents carried by the electrons. The current has a dip in the center of the magnetic hole and a peak in the outer region of the magnetic hole. The estimated size of the magnetic hole is about 0.23 \r{ho}i (~ 30 \r{ho}e) in the circular cross-section perpendicular to its axis, where \r{ho}i and \r{ho}e are respectively the proton and electron gyroradius. There are no clear enhancement seen in high energy electron fluxes, but an enhancement in the perpendicular electron fluxes at ~ 90{\deg} pitch angles inside the magnetic hole is seen, implying that the electron are trapped within it. The variations of the electron velocity components Vem and Ven suggest that an electron vortex is formed by trapping electrons inside the magnetic hole in the circular cross-section (in the M-N plane). These observations demonstrate the existence of a new type of coherent structures behaving as an electron vortex magnetic hole in turbulent space plasmas as predicted by recent kinetic simulations., Comment: 19 pages, 4 figures

Published
2016
Full Text
View/download PDF

10. Intense Electric Currents and Energy Conversion Observed at Electron Scales in the Plasma Sheet During Propagation of High‐Speed Ion Bulk Flows.

Author

Grigorenko, E. E., Leonenko, M. V., Malykhin, A. Y., Zelenyi, L. M., and Fu, H. S.

Subjects
ELECTRIC currents, ENERGY conversion, ELECTRON plasma, THERMAL electrons, ELECTRON beams, PLASMA turbulence, ELECTRON diffusion
Abstract

The intense electron‐scale current structures (ECSs) with the current density J ≥ 30 nA/m2 are often observed in the Plasma Sheet (PS) during high‐speed bulk flows. Using MMS observations we have analyzed 41 earthward and 37 tailward flow intervals and found 452 and 754 ECSs distributed over the PS region, respectively. Almost all ECSs are generated by high‐speed electron beams. The duration of ECSs is ≤1 s, and many of them have a half‐thickness L ≤ a few ρe (ρe is the gyroradius of thermal electrons). In such thin ECSs electrons become demagnetized and experience the dynamics like that observed in the electron diffusion region. Strong nonideal electric fields (E') associated with violation of frozen‐in condition for electrons are observed in the ECSs. This results in the intense energy conversion with J·E' up to hundreds pW/m3. The major part of the dissipating energy is transferred to electron heating and acceleration. We suggest that the ECSs are manifestations of kinetic‐scale turbulence driven by the high‐speed ion bulk flows. The inductive electric fields generated by the growing magnetic fluctuations accelerate electron beams which, in turn, generate the ECSs. The ECSs thinning during their evolution, probably, stops for L ≤ a few ρe. Further thinning leads to development of kinetic instability causing the current disruption and strong electric field generation. The last accelerates new electron beams which generate new ECSs in other locations. Thus, the life cycles of the ECSs contribute to energy cascade in turbulent plasma at electron kinetic scales. Key Points: Electron‐scale current structures (ECSs) with a few L/ρe thickness are observed in the plasma sheet during fast ion bulk flowsThe ECSs are mostly generated by demagnetized electrons experiencing the dynamics similar to that observed in electron diffusion regionIn the ECSs J·E' reaches the values typical for EDR, thus, they significantly contribute to the turbulent energy cascade at electron scales [ABSTRACT FROM AUTHOR]

Published
2024
Full Text
View/download PDF

11. Statistical Observations of Proton‐Band Electromagnetic Ion Cyclotron Waves in the Outer Magnetosphere: Full Wavevector Determination.

Author

Toledo‐Redondo, S., Lee, J. H., Vines, S. K., Albert, I. F., André, M., Castilla, A., Dargent, J. P., Fu, H. S., Fuselier, S. A., Genot, V., Graham, D. B., Kitamura, N., Khotyaintsev, Yu. V., Lavraud, B., Montagud‐Camps, V., Navarro, E. A., Norgren, C., Perrone, D., Phan, T. D., and Portí, J.

Subjects
ION acoustic waves, MAGNETOSPHERE, RELATIVISTIC electrons, SOLAR wind, DECOMPOSITION method, CYCLOTRONS
Abstract

Electromagnetic Ion Cyclotron (EMIC) waves mediate energy transfer from the solar wind to the magnetosphere, relativistic electron precipitation, or thermalization of the ring current population, to name a few. How these processes take place depends on the wave properties, such as the wavevector and polarization. However, inferring the wavevector from in‐situ measurements is problematic since one needs to disentangle spatial and time variations. Using 8 years of Magnetospheric Multiscale (MMS) mission observations in the dayside magnetosphere, we present an algorithm to detect proton‐band EMIC waves in the Earth's dayside magnetosphere, and find that they are present roughly 15% of the time. Their normalized frequency presents a dawn‐dusk asymmetry, with waves in the dawn flank magnetosphere having larger frequency than in the dusk, subsolar, and dawn near subsolar region. It is shown that the observations are unstable to the ion cyclotron instability. We obtain the wave polarization and wavevector by comparing Single Value Decomposition and Ampere methods. We observe that for most waves the perpendicular wavenumber (k⊥) is larger than the inverse of the proton gyroradius (ρi), that is, k⊥ρi > 1, while the parallel wavenumber is smaller than the inverse of the ion gyroradius, that is, k‖ρi < 1. Left‐hand polarized waves are associated with small wave normal angles (θBk < 30°), while linearly polarized waves are associated with large wave normal angles (θBk > 30°). This work constitutes, to our knowledge, the first attempt to statistically infer the full wavevector of proton‐band EMIC waves observed in the outer magnetosphere. Key Points: We conduct a statistical analysis of proton‐band Electromagnetic Ion Cyclotron (EMIC) waves in dayside magnetosphere using 8 years of Magnetospheric Multiscale data and measure full wavevectorsThe normalized frequency of EMIC waves presents a dawn‐dusk asymmetryThe perpendicular wavevector is, for most of the waves, larger than the inverse of proton gyroradius and ion inertial lengths [ABSTRACT FROM AUTHOR]

Published
2024
Full Text
View/download PDF

15. Kinetic Turbulence in the Terrestrial Magnetosheath: Cluster Observations

Author

Huang, S. Y., Sahraoui, F., Deng, X. H., He, J. S., Yuan, Z. G., Zhou, M., Pang, Y., and Fu, H. S.

Subjects
Astrophysics - Solar and Stellar Astrophysics, Physics - Space Physics
Abstract

We present a first statistical study of subproton and electron scales turbulence in the terrestrial magnetosheath using the Cluster Search Coil Magnetometer (SCM) waveforms of the STAFF instrument measured in the frequency range [1,180] Hz. It is found that clear spectral breaks exist near the electron scale, which separate two power-law like frequency bands referred to as the dispersive and the electron dissipation ranges. The frequencies of the breaks f_b are shown to be well correlated with the electron gyroscale \rho_e rather than with the electron inertial length de. The distribution of the slopes below fb was found to be narrow and peaks near -2.9, while that of the slopes above fb was found broader, peaks near -5.2 and has values as low as -7.5. This is the first time that such steep power-law spectra are reported in space plasma turbulence. These observations provide strong constraints on theoretical modeling of kinetic turbulence and dissipation in collisionless magnetized plasmas., Comment: 13 pages, 6 figures, submitted

Published
2013
Full Text
View/download PDF

26. Two-step Acceleration of Energetic Electrons at Magnetic Flux Ropes during Turbulent Reconnection.

Author

Wang, Z., Vaivads, A., Fu, H. S., Cao, J. B., Lindberg, M., Turner, D. L., Ergun, R. E., and Liu, Y. Y.

Subjects
MAGNETIC flux, THERMAL electrons, ELECTRONS, MAGNETIC reconnection, PARTICLE acceleration, CORONAL mass ejections
Abstract

Energetic electrons have been frequently observed during magnetic reconnection in the magnetotail. The acceleration process of the energetic electrons is not fully understood. In this paper, we select for a detailed study a case of energetic electron acceleration from the earlier reported interval of turbulent magnetic reconnection in Earth's magnetotail observed by the Magnetospheric Multiscale mission. We use the first-order Taylor expansion method to reconstruct the magnetic topology of electron acceleration sites from the data. We find that the energetic electron fluxes increase inside the flux rope forming in front of the magnetic pileup region. We show that the energetic electrons are produced by a two-step process where two different acceleration mechanisms are successively operating outside and inside the flux rope. First, the thermal electrons are energized in the field-aligned direction inside the magnetic pileup region owing to the Fermi mechanism forming a cigar-like distribution. Second, those energized electrons are further accelerated predominately antiparallel to the magnetic field direction by a parallel electric field inside the flux rope. Our findings provide information for a better understanding of the generation of energetic electrons during turbulent reconnection process. [ABSTRACT FROM AUTHOR]

Published
2023
Full Text
View/download PDF

27. In Situ Observation of Magnetic Reconnection Between an Earthward Propagating Flux Rope and the Geomagnetic Field

Author

Man, H. Y, Zhou, M, Deng, X. H, Fu, H. S, Zhong, Z. H, Chen, Z. Z, Russell, C. T, Strangeway, R. J, Paterson, W. R, Giles, B. L, Lindqvist, P.-A, Ergun, R. E, and Burch, J. L

Subjects
Plasma Physics
Abstract

It has been proposed that, in the near-Earth magnetotail, earthward propagating flux ropes can merge with the Earth's dipole magnetic field and dissipate its magnetic energy. However, the reconnection diffusion region related to this process has not been identified. Here we report the first in situ observation of magnetic reconnection between an earthward propagating flux rope and the closed magnetic field lines connecting to Earth. Magnetospheric Multiscale (MMS) spacecraft crossed a vertical current sheet between the leading edge of the flux rope (negative B(sub z)) and the geomagnetic field (positive B(sub z)). The subion-scale current sheet, super-Alfvénic electron outflow, Hall magnetic and electric field, conversion of magnetic energy to plasma energy (J·E > 0), and magnetic null were observed during the crossing. All the above signatures indicate that MMS detected the reconnection diffusion region. This result is also relevant to other planets with intrinsic magnetosphere.

Published
2018
Full Text
View/download PDF

38. Low-frequency Whistler Waves Modulate Electrons and Generate Higher-frequency Whistler Waves in the Solar Wind

Author

Yao, S. T., primary, Shi, Q. Q., additional, Zong, Q. G., additional, Degeling, A. W., additional, Guo, R. L., additional, Li, L., additional, Li, J. X., additional, Tian, A. M., additional, Zhang, H., additional, Yao, Z. H., additional, Fu, H. S., additional, Liu, C. M., additional, Sun, W. J., additional, Niu, Z., additional, Li, W. Y., additional, Liu, Z. Y., additional, Le Contel, O., additional, Zhang, S., additional, Xiao, C., additional, Shang, W. S., additional, Torbert, R. B., additional, Ergun, R. E., additional, Lindqvist, P.-A., additional, and Pollock, C. J., additional

Published
2021
Full Text
View/download PDF

41. Curlometer Technique and Applications

Author

Dunlop, M. W., primary, Dong, X.‐C., additional, Wang, T.‐Y., additional, Eastwood, J. P., additional, Robert, P., additional, Haaland, S., additional, Yang, Y.‐Y., additional, Escoubet, P., additional, Rong, Z.‐J., additional, Shen, C., additional, Fu, H.‐S., additional, and De Keyser, J., additional

Published
2021
Full Text
View/download PDF

42. Solar Wind—Magnetosphere Coupling During Radial Interplanetary Magnetic Field Conditions: Simultaneous Multi‐Point Observations

Author

Toledo‐Redondo, S., primary, Hwang, K.‐J., additional, Escoubet, C. P., additional, Lavraud, B., additional, Fornieles, J., additional, Aunai, N., additional, Fear, R. C., additional, Dargent, J., additional, Fu, H. S., additional, Fuselier, S. A., additional, Genestreti, K. J., additional, Khotyaintsev, Yu V., additional, Li, W. Y., additional, Norgren, C., additional, and Phan, T. D., additional

Published
2021
Full Text
View/download PDF

46. Betatron Cooling of Electrons in Martian Magnetotail

Author

Guo, Z. Z., primary, Fu, H. S., additional, Cao, J. B., additional, Fan, K., additional, Yao, Z. H., additional, Liu, Y. Y., additional, Chen, Z. Z., additional, Wang, Z., additional, Liu, X. Y., additional, Xu, Y., additional, Mazelle, C., additional, and Mitchell, D. L., additional

Published
2021
Full Text
View/download PDF

49. Kinetic Interaction of Cold and Hot Protons With an Oblique EMIC Wave Near the Dayside Reconnecting Magnetopause

Author

Toledo‐Redondo, S., primary, Lee, J. H., additional, Vines, S. K., additional, Turner, D. L., additional, Allen, R. C., additional, André, M., additional, Boardsen, S. A., additional, Burch, J. L., additional, Denton, R. E., additional, Fu, H. S., additional, Fuselier, S. A., additional, Gershman, D. J., additional, Giles, B., additional, Graham, D. B., additional, Kitamura, N., additional, Khotyaintsev, Yu. V., additional, Lavraud, B., additional, Le Contel, O., additional, Li, W. Y., additional, Moore, T. E., additional, Navarro, E. A., additional, Portí, J., additional, Salinas, A., additional, and Vinas, A., additional

Published
2021
Full Text
View/download PDF

Catalog

Books, media, physical & digital resources
See catalog results