Global Spatial Distribution of Dipolarization Fronts in the Saturn's Magnetosphere: Cassini Observations

Xu, S. B.; Huang, Suming; Yuan, Zhigang; Deng, Xiaohua; Jiang, K.; Wei, Yong; Zhang, J.; Zhang, Z. H.; Xiong, Qian; Yu, Lei; Lin, R. T.; Waite, J. H.

doi:10.1029/2021gl092701

Cited by 13 publications

(13 citation statements)

References 43 publications

(59 reference statements)

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“…In Earth's magnetotail, the energy in the jet is ultimately injected into the inner magnetosphere where it can greatly impact magnetospheric dynamics and has important space weather implications (McPherron, 1979; Pulkkinen, 2007). Analogous dynamics takes place in magnetospheres of other planets (Smith et al., 2018; S. B. Xu et al., 2021) and in sunward jets that occur during solar flares (Reeves et al., 2008).…”

Section: Introductionmentioning

confidence: 93%

Scaling of Electron Heating by Magnetization During Reconnection and Applications to Dipolarization Fronts and Super‐Hot Solar Flares

et al. 2022

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We predict major and minor radii of ring distributions during reconnection in terms of upstream parameters and confirm with PIC simulations • We find that ring distributions occur at a shoulder (plateau) in the reconnected magnetic field in the simulations • The predicted temperatures are comparable to observed values in dipolarization fronts in Earth's magnetotail and in super-hot solar flares

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Section: Introductionmentioning

confidence: 93%

Scaling of Electron Heating by Magnetization During Reconnection and Applications to Dipolarization Fronts and Super‐Hot Solar Flares

et al. 2022

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“…At the expansion phase of a substorm, the dipolarization front (DF) is one of the most prominent structures for magnetosphere substorm dynamics (Fu et al., 2012b; Vogiatzis et al., 2015). The dipolarization front (DF) is identified by the sharp increase in the normal (usually south‐north) component of the magnetic field in the magnetotail, usually accompanied by a decrease in the plasma density and an increase in the plasma temperature (Fu et al., 2012b; S. Y. Huang et al., 2012; S. Y. Huang, Fu, Yuan, et al., 2015; S. Y. Huang, Fu, Vaivads, et al., 2015; Liu et al., 2014; Nakamura & Baumjohann, 2002; Wei et al., 2021; Xu et al., 2021). DFs in planetary plasma environments have been reported and investigated for the past two decades.…”

Section: Introductionmentioning

confidence: 99%

“…Huang et al, 2012;S. Y. Huang, Fu, Vaivads, et al, 2015;Liu et al, 2014;Nakamura & Baumjohann, 2002;Wei et al, 2021;Xu et al, 2021). DFs in planetary plasma environments have been reported and investigated for the past two decades.…”

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confidence: 99%

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Successive Dipolarization Fronts With a Stepwise Electron Acceleration During a Substorm in Saturn's Magnetotail

Huang

Yuan

et al. 2022

Geophysical Research Letters

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Studies on substorms originated from the discovery of consistent patterns of auroral activity in Earth's ionosphere (Akasofu, 1964). After decades of intense studies, several features of Earth's substorms have become well known (e.g., Haerendel, 2015). At the beginning of a substorm, dayside magnetopause reconnection occurs, and the corresponding magnetic flux is transported to the lobes and loaded into the magnetotail (Dungey, 1961). Then, the increased magnetic pressure within the lobes thins the central current sheet and promotes magnetic reconnection in the magnetotail (Coroniti & Kennel, 1972). Moreover, a pair of connected X-and O-lines form in the plasma sheet (Russell & McPherron, 1973). As the rate of magnetotail reconnection increases, the O-line evolves to the plasmoid and will be released from the central magnetotail. Magnetic dipolarization is generated near the earthward X-line, and then transports the energetic particles into the inner magnetosphere (Russell & McPherron, 1973). Saturn's space environment is different from Earth's, suggesting that Saturn has a different substorm driving mechanism. Compared with Earth (1 AU), Saturn is farther away from the Sun (9.58 AU), and the solar wind near Saturn is relatively weak, with a dynamic pressure of 0.015 nPa (1.7 nPa for Earth). Although magnetopause reconnections occasionally occur at Saturn's magnetopause (Desroche et al., 2013;Masters et al., 2014;Fuselier et al., 2014), the solar wind is not the most important driver of magnetopause reconnection at Saturn. The water-group neutrals released from Enceladus are ionized and serve as the internal plasma source in Saturn's inner magnetosphere (Bagenal & Delamere, 2011). Moreover, due to Saturn's rapid rotation, the magnetic field configuration and the plasmas in Saturn's magnetosphere present the characteristic of rotation. The rotational energy arises from the corotational kinetic energy that planetary rotation exerts on magnetospheric plasma (Ge Abstract Substorms are a fundamental phenomenon in planetary magnetospheric systems. Using Cassini measurements, we report a typical event in which four successive dipolarization fronts (DFs) were observed within 1 hour during the substorm in Saturn's magnetotail. The last three DFs caused a type of stepwise electron acceleration and generated energetic electrons. The pitch angle distributions of the electrons show evidence of the Fermi acceleration mechanism behind these DFs. Therefore, we infer the magnetotail dynamics process during Saturn's substorm: The stepwise acceleration by successive DFs powerfully accelerates the field-aligned electrons and generates field-aligned energetic electrons. These high-energy electrons are injected into the inner magnetosphere and become an important trigger of Saturn's aurora. Our results show an efficient acceleration mechanism for the electrons caused by successive DFs and confirm an important source of energetic particles during the substorm in Saturn, and these findings improve our understanding of Saturn's substorm ...

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“…The BBF plays a vital role in the mass and magnetic ﬂuxes transport during the active period in the Earth's magnetosphere (Angelopoulos et al., 2013; Cao et al., 2006; Huang, Fu, et al., 2015; Huang, Jiang, Yuan, et al., 2019), such as during the substorm (Angelopoulos et al., 1992, 2008; Cao et al., 2006). Previous studies have proposed that BBF is a product of magnetic reconnection (Birn et al., 2011; Fu, Cao, et al., 2013; Huang, Zhou, et al., 2015; Huang et al., 2018; Xu, Fu et al., 2018, 2021), which is closely related to the acceleration process of the particles (Fu et al., 2011; Fu, Khotyaintsev, et al., 2013, 2019; Fu, Grigorenko, et al., 2020; Duan et al., 2014; Huang, Vaivads, et al., 2012; Liu et al., 2019; Xu, Fu et al., 2018). It is also highly related to the wave activities (Fu et al., 2014, Fu, Zhao, et al., 2020; Huang et al., 2010, 2016, 2017; Huang, Zhou, et al., 2012; Zhou et al., 2009, 2014).…”

Section: Introductionmentioning

confidence: 99%

Observations of Pitch Angle Changes of Electrons and High‐Frequency Wave Activities in the Magnetotail Plasma Bubble

et al. 2022

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Plasma bubble, a low‐entropy flux tube, is usually regarded as the bearer of plasma flux transport in the magnetotail. In this study, we perform a complete analysis of electron dynamics in a plasma bubble in the Earth's magnetotail based on the high time‐resolution data from the Magnetospheric Multiscale (MMS) mission. An electron jet is observed at the center of this plasma bubble. Simultaneously, intense electric field and significant current density, as well as the strong energy dissipation are detected associated with this electron jet. The pitch angle distributions (PADs) of high‐energy electrons exhibit different features at different substructures in this plasma bubble. In Region‐1 and Region‐3, pancake‐type PAD is formed; the PAD becomes isotropic type in Region‐2. The electrons pitch angle changes to field‐aligned distribution in Region‐4. All these changes of electron PADs in substructures can be interpreted mainly by the capture of magnetic mirror and betatron cooling. High‐frequency waves, including whistler waves and electrostatic waves, are detected in several parts of the plasma bubble. The observations of abundant electron‐scale phenomena or processes reveal that the electrons are very dynamic in the large‐scale plasma bubble.

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Global Spatial Distribution of Dipolarization Fronts in the Saturn's Magnetosphere: Cassini Observations

Cited by 13 publications

References 43 publications

Scaling of Electron Heating by Magnetization During Reconnection and Applications to Dipolarization Fronts and Super‐Hot Solar Flares

Scaling of Electron Heating by Magnetization During Reconnection and Applications to Dipolarization Fronts and Super‐Hot Solar Flares

Successive Dipolarization Fronts With a Stepwise Electron Acceleration During a Substorm in Saturn's Magnetotail

Observations of Pitch Angle Changes of Electrons and High‐Frequency Wave Activities in the Magnetotail Plasma Bubble

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