Article
Geosciences, Multidisciplinary
Lei Wang, Can Huang, Aimin Du, Yasong Ge
Summary: In this study, the authors statistically investigate the plasma sheet region ahead of the Dipolarization Front (DF) using data from the Magnetospheric Multiscale (MMS) mission. They observe the presence of bipolar B-y ahead of the DF, and identify thermal electrons and ions above 4 keV as the main carriers of the current system. This research reveals the Hall nature ahead of the DF.
GEOPHYSICAL RESEARCH LETTERS
(2022)
Article
Geosciences, Multidisciplinary
S. B. Xu, S. Y. Huang, Z. G. Yuan, X. H. Deng, K. Jiang, Y. Y. Wei, J. Zhang, Z. H. Zhang, Q. Y. Xiong, L. Yu, R. T. Lin, J. H. Waite
Summary: Through analyzing data from the Cassini spacecraft, researchers have identified and characterized dipolarization fronts (DF) in Saturn's magnetosphere. They found that DFs are not only present in the nightside magnetotail, but also in the dayside magnetosphere, with an asymmetric distribution between the northern and southern hemispheres. The presence of DFs on the dayside suggests that magnetic reconnection may occur in this region as well.
GEOPHYSICAL RESEARCH LETTERS
(2021)
Article
Geosciences, Multidisciplinary
S. B. Xu, S. Y. Huang, Z. G. Yuan, K. Jiang, Y. Y. Wei, J. Zhang, Z. H. Zhang, Q. Y. Xiong, R. T. Lin, L. Yu
Summary: Substorms are fundamental phenomena in planetary magnetospheric systems. This study reports a typical event during a substorm in Saturn's magnetotail, where four successive dipolarization fronts (DFs) were observed within one hour. The last three DFs caused the acceleration of electrons and the generation of energetic electrons through a stepwise process. These findings confirm the efficient acceleration mechanism caused by successive DFs and provide insight into the source of energetic particles during substorms in Saturn.
GEOPHYSICAL RESEARCH LETTERS
(2022)
Article
Astronomy & Astrophysics
M. Hasan Barbhuiya, P. A. Cassak, M. A. Shay, Vadim Roytershteyn, M. Swisdak, Amir Caspi, Andrei Runov, Haoming Liang
Summary: This article presents a theory of electron ring velocity space distributions and validates it using 2.5-dimensional PIC simulations. The study finds that the ring distributions are caused by a plateau in the reconnected magnetic field profile and the predicted temperature matches the observed values. This research may provide an explanation for the generation of high temperature plasma in super-hot solar flares.
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
(2022)
Article
Astronomy & Astrophysics
Y. Y. Wei, S. Y. Huang, K. Jiang, Z. G. Yuan, S. B. Xu, J. Zhang, Q. Y. Xiong, Z. Wang, R. T. Lin, L. Yu, Y. Y. Li, C. M. Wang, G. J. Song
Summary: Our study performs a direct quantitative analysis to reveal the acceleration process of energetic electrons at the dipolarization front (DF) using high-time-resolution data. The analysis shows that these electrons at the front could be locally accelerated to over 100 keV by betatron acceleration. The temperature anisotropy formed via the betatron mechanism provides the free energy to excite whistler waves at the DF. Our study provides strong direct evidence for the local electron acceleration at the DF for the first time.
ASTROPHYSICAL JOURNAL
(2023)
Article
Astronomy & Astrophysics
Kai Huang, Quanming Lu, San Lu, Rongsheng Wang, Shui Wang
Summary: The two-dimensional PIC simulation studied the formation of pitch angle distribution of energetic electrons at dipolarization fronts driven by magnetic reconnection. Energetic electrons at DFs originate from the lobe region and undergo a two-step acceleration process, forming Pancake, Rolling pin, and Cigar distributions in sequence during the propagation of the DFs. The Pancake distribution is formed through betatron acceleration, with Rolling pin and Cigar distributions gradually replacing it in the later stage.
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
(2021)
Article
Astronomy & Astrophysics
Hongtao Huang, Yiqun Yu, Zuzheng Chen, Chengming Liu, Jinbin Cao, Tongpu Yu
Summary: By analyzing spacecraft measurements and conducting kinetic simulations, the presence of a dip ahead of the dipolarization front (DF) is found to be related to the presence of a guide field B-y. The simulations reveal that the dip is generated due to the separation of the gyro-motion between ions and electrons under the influence of the guide field. These findings provide a new perspective on the formation of the dip in single X line reconnection.
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
(2022)
Article
Astronomy & Astrophysics
Kevin J. Genestreti, Charles J. Farrugia, San Lu, Sarah K. Vines, Patricia H. Reiff, Tai Phan, Daniel N. Baker, Trevor W. Leonard, James L. Burch, Samuel T. Bingham, Ian J. Cohen, Jason R. Shuster, Daniel J. Gershman, Christopher G. Mouikis, Anthony J. Rogers, Roy B. Torbert, Karlheinz J. Trattner, James M. Webster, Li-Jen Chen, Barbara L. Giles, Narges Ahmadi, Robert E. Ergun, Christopher T. Russell, Robert J. Strangeway, Rumi Nakamura, Drew L. Turner
Summary: The local dynamics of magnetotail reconnection onset were analyzed using MMS data, revealing features such as cross-tail current sheet thinning, flapping wave growth, and electron tearing. Multiple magnetic islands were detected coincident with the growth of the ion exhaust. Two secondary reconnection sites were found embedded within the primary X-line.
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
(2023)
Article
Astronomy & Astrophysics
A. Bloecker, E. A. Kronberg, E. E. Grigorenko, E. Roussos, G. Clark
Summary: By studying magnetic dipolarization fronts in Jupiter's magnetotail, it is found that some events are accompanied by an increase in high-energetic ion intensities, while others show no significant change. In about 40% of the events located in the dawn sector, a significant decrease in energy spectral index is detected, indicating ion acceleration by the dipolarization fronts.
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
(2023)
Article
Astronomy & Astrophysics
Kun Bai, Yiqun Yu, Hongtao Huang, Xingbin Tian, Jinbin Cao
Summary: This study investigates electron acceleration in RFs and finds that rippled RF surfaces are more conducive to increasing high-energy electron flux compared to smooth RF surfaces. The main acceleration mechanism is electron surfing acceleration.
ASTROPHYSICAL JOURNAL
(2022)
Article
Geosciences, Multidisciplinary
C. M. Liu, J. B. Cao, C. J. Pollock
Summary: Using high-cadence data from NASA's Magnetospheric Multiscale mission, a comprehensive investigation of energy budgets at dipolarization fronts (DFs) was carried out. The study found that energy released at the DFs is predominantly manifested in the form of energy flux, which is primarily influenced by ion and electron enthalpy flux, ion heat flux, and Poynting flux.
GEOPHYSICAL RESEARCH LETTERS
(2022)
Article
Astronomy & Astrophysics
C. M. Liu, H. S. Fu, Y. Y. Liu
Summary: Using magnetospheric multiscale high-resolution measurements, this study presents a comprehensive investigation of electron vorticity at earthward-propagating dipolarization fronts (DFs). The analysis reveals that vorticity is related to Hall dynamics at the DFs and shows clear anisotropy. Additionally, electron vorticity is found to be anticorrelated with electron density.
ASTROPHYSICAL JOURNAL
(2021)
Article
Astronomy & Astrophysics
S. W. Alqeeq, O. Le Contel, P. Canu, A. Retino, T. Chust, L. Mirioni, A. Chuvatin, R. Nakamura, N. Ahmadi, F. D. Wilder, D. J. Gershman, Yu. V. Khotyaintsev, P. -A. Lindqvist, R. E. Ergun, J. L. Burch, R. B. Torbert, S. A. Fuselier, C. T. Russell, H. Y. Wei, R. J. Strangeway, K. R. Bromund, D. Fischer, B. L. Giles, Y. Saito
Summary: In this study, a statistical analysis of equatorial dipolarization fronts (DFs) detected by the Magnetospheric Multiscale mission during the 2017 magnetotail season was conducted. Two distinct classes of DFs were identified: class I, which corresponds to the standard DF properties and energy dissipation, and class II, a new class that features a bump in the magnetic field, a minimum in ion and electron pressures, and a reversal of the energy conversion process. The study also reveals that the energy conversion processes of these two classes of DFs differ in the spacecraft frame and fluid frame, mainly due to variations in the electric fields.
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
(2023)
Article
Geosciences, Multidisciplinary
M. Sitnov, T. Motoba, M. Swisdak
Summary: Mining of substorm magnetic field data reveals the formation of two X-lines preceded by the flux accumulation at the tailward end of a thin current sheet. Three-dimensional particle-in-cell simulations show the formation of stronger magnetic field variations and inhomogeneous electric fields closer to Earth. The appearance of X-lines is followed by the formation of diverging electron outflow regions embedded into a single diverging ion outflow pattern, transforming into faster electron-scale reconnection jets after the onset.
GEOPHYSICAL RESEARCH LETTERS
(2021)
Article
Astronomy & Astrophysics
A. Runov, V. Angelopoulos, M. G. Henderson, C. Gabrielse, A. Artemyev
Summary: The study suggests that dipolarizations in the near-Earth equatorial region may play an important role in enhancing energetic ion fluxes during geomagnetic storms.
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
(2021)
Article
Geosciences, Multidisciplinary
M. Sitnov, T. Motoba, M. Swisdak
Summary: Mining of substorm magnetic field data reveals the formation of two X-lines preceded by the flux accumulation at the tailward end of a thin current sheet. Three-dimensional particle-in-cell simulations show the formation of stronger magnetic field variations and inhomogeneous electric fields closer to Earth. The appearance of X-lines is followed by the formation of diverging electron outflow regions embedded into a single diverging ion outflow pattern, transforming into faster electron-scale reconnection jets after the onset.
GEOPHYSICAL RESEARCH LETTERS
(2021)
Article
Physics, Multidisciplinary
Grant K. Stephens, Mikhail I. Sitnov
Summary: Data mining has led to a new era in magnetic reconstructions of the magnetosphere by utilizing the k-nearest neighbors method. The challenge lies in accounting for substorm contributions to the ring current and describing storm-time substorms. The construction of a hybrid model, fitting virtual magnetic field observations from two existing models, resolves the scale inconsistency and captures spatial scales associated with both storms and substorms.
FRONTIERS IN PHYSICS
(2021)
Article
Astronomy & Astrophysics
V Agapitov, J. F. Drake, M. Swisdak, S. D. Bale, T. S. Horbury, J. C. Kasper, R. J. MacDowall, F. S. Mozer, T. D. Phan, M. Pulupa, E. Raouafi, M. Velli
Summary: A major discovery of Parker Solar Probe is the presence of localized increases in solar wind speed and associated deflections of the magnetic field. This phenomenon is believed to be caused by magnetic reconnection and flux rope ejection. The study examines the role of flux rope merging in controlling the structure of these deflections through observations, analysis, and simulations. The results reveal the importance of merging in reducing the wrapping magnetic field and elongating the deflections. The findings are consistent with recent statistical analysis from PSP.
ASTROPHYSICAL JOURNAL
(2022)
Article
Astronomy & Astrophysics
H. Arnold, J. F. Drake, M. Swisdak, F. Guo, J. T. Dahlin, Q. Zhang
Summary: This study explores the formation, development, and impact of slow shocks in the upstream regions of reconnecting current layers. It investigates their potential role in producing the hot thermal component of electrons in solar flares.
ASTROPHYSICAL JOURNAL
(2022)
Article
Physics, Multidisciplinary
Peiyun Shi, Prabhakar Srivastav, M. Hasan Barbhuiya, Paul A. Cassak, Earl E. Scime, M. Swisdak
Summary: Non-Maxwellian electron velocity distribution functions containing a warm bulk population and a cold beam were measured directly during electron-only reconnection in a laboratory plasma. The experimental results are consistent with recent observations in the magnetosheath and provide further insight.
PHYSICAL REVIEW LETTERS
(2022)
Article
Astronomy & Astrophysics
M. Hubbert, C. T. Russell, Yi Qi, S. Lu, J. L. Burch, B. L. Giles, T. E. Moore
Summary: This study reports three types of current sheets in Earth's magnetotail and conducts event studies on each type. The observations show that electron-only reconnecting current sheets undergo certain changes over time to support traditional reconnection.
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
(2022)
Article
Astronomy & Astrophysics
S. J. Naus, J. Qiu, C. R. DeVore, S. K. Antiochos, J. T. Dahlias, J. F. Drake, M. Swisdak
Summary: We analyzed the structure and evolution of ribbons from the M7.3 flare and found that the ribbon width is highly intermittent and closely related to nonthermal hard X-ray emissions. Our results suggest a strong connection between the production of nonthermal electrons and the locally enhanced perpendicular extent of flare ribbon fronts.
ASTROPHYSICAL JOURNAL
(2022)
Article
Physics, Fluids & Plasmas
Peiyun Shi, Prabhakar Srivastav, M. Hasan Barbhuiya, Paul A. Cassak, Earl E. Scime, M. Swisdak, Cuyler Beatty, Tyler Gilbert, Regis John, Matthew Lazo, Ripudaman Singh Nirwan, Mitchell Paul, Ethan E. Scime, Katey Stevenson, Thomas Steinberger
Summary: In this study, electron heating and acceleration during electron-only reconnection were investigated using the PHAse Space MApping (PHASMA) facility. The results showed that electron heating is localized around the separatrix, and the electron temperature increases continuously along the separatrix with distance from the X-line. Non-Maxwellian electron velocity distribution functions (EVDFs) consisting of a warm bulk population and a cold beam were directly measured, revealing the signature of electron acceleration caused by electron-only reconnection. The laboratory measurements agreed well with the theoretical simulations, and provided insights beyond the magnetosheath observations.
PHYSICS OF PLASMAS
(2022)
Article
Astronomy & Astrophysics
Stefan Eriksson, Marc Swisdak, James M. Weygand, Alfred Mallet, David L. Newman, Giovanni Lapenta, Lynn B. Wilson, Drew L. Turner, Bjorn Larsen
Summary: Wind spacecraft measurements were used to analyze magnetic reconnection exhausts in the ecliptic plane of the solar wind at 1 au. The study found an exponential decay in the distribution of current sheet widths, and a linear increase in the distribution of magnetic field rotation angles. The orientations of wide exhausts were consistent with a dominant Parker-spiral magnetic field, while narrow exhausts were isotropic. These findings suggest that CS bifurcation and turbulence play a role in aligning the exhaust directions with the large-scale heliospheric current sheet.
ASTROPHYSICAL JOURNAL
(2022)
Article
Astronomy & Astrophysics
M. Hasan Barbhuiya, P. A. Cassak, M. A. Shay, Vadim Roytershteyn, M. Swisdak, Amir Caspi, Andrei Runov, Haoming Liang
Summary: This article presents a theory of electron ring velocity space distributions and validates it using 2.5-dimensional PIC simulations. The study finds that the ring distributions are caused by a plateau in the reconnected magnetic field profile and the predicted temperature matches the observed values. This research may provide an explanation for the generation of high temperature plasma in super-hot solar flares.
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
(2022)
Article
Astronomy & Astrophysics
G. K. Stephens, M. I. Sitnov, R. S. Weigel, D. L. Turner, N. A. Tsyganenko, A. J. Rogers, K. J. Genestreti, J. A. Slavin
Summary: Reconnection in the magnetotail occurs along X-lines, where magnetic field lines tear and detach from plasma on microscopic scales. Previous observations were limited to local scales, and the global structure and evolution of X-lines remained unknown. This study analyzed multi-year magnetometer data and reconstructed the global pattern of X-lines, confirming their consistency with direct satellite observations.
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
(2023)
Article
Multidisciplinary Sciences
S. D. Bale, J. F. Drake, M. D. McManus, M. I. Desai, S. T. Badman, D. E. Larson, M. Swisdak, T. S. Horbury, N. E. Raouafi, T. Phan, M. Velli, D. J. McComas, C. M. S. Cohen, D. Mitchell, O. Panasenco, J. C. Kasper
Summary: The fast solar wind that fills the heliosphere originates from coronal holes on the Sun and is believed to be accelerated by magnetic reconnection mechanisms such as wave heating and interchange reconnection. Measurements from the Parker Solar Probe provide strong evidence for the interchange reconnection mechanism, showing imprints of supergranulation structure in the solar wind and the presence of magnetic switchbacks and bursty wind streams. Computer simulations support these observations and suggest that the reconnection is collisionless and drives the fast wind through both plasma pressure and radial Alfvenic flow bursts.
Article
Astronomy & Astrophysics
B. Lavraud, M. Opher, K. Dialynas, D. L. Turner, S. Eriksson, E. Provornikova, M. Z. Kornbleuth, P. Mostafavi, A. Fedorov, J. D. Richardson, S. A. Fuselier, J. Drake, M. Swisdak, M. Eubanks, T. Y. Chen, H. Kucharek, P. Kollmann, M. Blanc, N. Andre, V. Genot, R. F. Wimmer-Schweingruber, S. Barabash, P. Brandt, R. McNutt
Summary: We emphasize the significance of magnetic reconnection at the heliopause, both as a crucial process driving the interaction between the solar and interstellar media and as a defining element of the heliopause itself. We discuss the key observations that have contributed to the ongoing debates regarding the definition, location, and shape of the heliopause. Furthermore, we highlight the need for appropriate measurements in order to differentiate between the current interpretations of plasma and magnetic field structures near the heliopause, particularly due to the lack of data from Voyager 1 and 2, and propose certain requirements for thermal plasma measurements on a future Interstellar Probe.
FRONTIERS IN ASTRONOMY AND SPACE SCIENCES
(2023)
Article
Astronomy & Astrophysics
Hanqing Ma, J. F. Drake, M. Swisdak
Summary: This study investigates the scattering of electron heat flux by self-generated oblique electromagnetic waves using two-dimensional particle-in-cell simulations. The results show that oblique whistler waves and filamentary-like Weibel instabilities inhibit the heat flux and drive the electron velocity distributions toward isotropy. The scattering rate is mainly controlled by the average speed of the heat flux compared with the electron Alfven speed.
ASTROPHYSICAL JOURNAL
(2023)
Article
Astronomy & Astrophysics
M. Swisdak, J. Giacalone, J. F. Drake, M. Opher, G. P. Zank, B. Zieger
Summary: We compare hybrid and particle-in-cell simulations of the solar wind termination shock and find excellent agreement in downstream variations. The quasi-perpendicular shock accelerates interstellar pickup ions to a maximum energy, with higher fluxes and maximal energies observed in the particle-in-cell simulation.
ASTROPHYSICAL JOURNAL
(2023)