Investigating plasma motion of magnetic clouds at 1 AU through a velocity‐modified cylindrical force‐free flux rope model

Wang, Yuming; Zhou, Zhenjun; Shen, Chenglong; Liu, Rui; Wang, S.

doi:10.1002/2014ja020494

Cited by 67 publications

(72 citation statements)

References 74 publications

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“…This fact provides a further justification of the force-free expression for B e.g. in [14]; now, however, it is not an ansatz anymore, as it follows from (11).…”

Section: Double Beltramimentioning

confidence: 97%

“…Examples of such force-free configurations for B are the spheromak-like structure in eq. 8 of [13] and the cylindrical solution of equations (1)-(3) of [14]. Simulations show that the evolution of B is self-similar -see 2…”

Section: ≈ 10mentioning

confidence: 99%

“…This equation is often invoked when describing plasmas both in lab (reversed field pinches [34], spheromaks [35]) and in space (CMEs [14] [36], jets like in NGC6251 [37]). Remarkably, both Turner's and Taylor's principle neglect internal energy; this is reasonable in the initial, low-β period of plasmoid lifetime at least.…”

Section: Double Beltramimentioning

confidence: 99%

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On super-elastic collisions between magnetized plasmoids in the heliosphere

Vita

2018

Eur. Phys. J. D

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Recently, a unique collision between two large-scale magnetized plasmoids produced by coronal mass ejections in the heliosphere has been observed [C. Shen et al., Nature Physics 8, 923-928 (2012)]. Results suggest that the collision is super-elastic, i.e. the total linear kinetic energy of the two plasmoids after the collision is larger than before the collision, and that an anti-correlation exists, i.e. the lower the initial relative velocity of the plasmoids, the larger the relative increase in total kinetic energy. The problemCoronal mass ejections (CMEs) give birth to large-scale plasmoids, originating from the solar atmosphere and expanding and propagating into the heliosphere [1] [2]. The occurrence rate of CMEs is about 4-5 CMEs per day at solar maximum [3], so that encounters and interactions between plasmoids are unavoidable. Nevertheless, inter-plasmoid collisions are far from understood. While collisions between blobs of ordinary gases are heavily affected by mixing, cross-field diffusion is effectively prohibited by sufficiently strong magnetic field.Experiments show that initially well-distinct plasmoids preserve their identity after a collision; historically, these experiments led to the very definition of 'plasmoid' as a 'plasma magnetic entity' with well-distinguished identity and geometrical structure [4]. In the lab, conventional magnetohydrodynamics fails to provide adequate macroscopic description of isolated plasmoids [5] -let alone their mutual interaction. In space, such description requires detailed knowledge of energy balance and state equation [2].Recent observation of a collision between plasmoids [1] suggests that such collisions may be superelastic, i.e. the total linear kinetic energy of the colliding plasmoids after the collision is larger than before the collision. A similar phenomenon is observed in collisions of spheres with elastoplastic plates, where rotational kinetic energy may be transferred into linear kinetic energy [6]. This analogy suggests that the linear kinetic energy in collisions between plasmoids may increase at the expense of the energy of some other degree of freedom, and magnetic energy is an obvious candidate. A preliminary investigation of energy balance supports this point of view; moreover, it has been suggested that the lower the impact velocity, the larger the relative increase of the linear kinetic energy [1]; in contrast, if the relative velocity of colliding plasmoids is too large, then no elastic scattering occurs [7], and the plasmoids may merge into each other.The aim of this work is to investigate this suggestion. We invoke the analogy [8] between plasmoids in the lab and space plasmoids and show how recent progress [5] [9] in the analytical description of the former provide information on the latter. In particular, we show that quantities usually invoked in Hall MHD [10] lead to a simple macroscopic description of interacting plasmoids. Some relevant properties of our plasmoids are discussed in Sec. 2. Secs. 3 and 4 discuss the structure...

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“…This fact provides a further justification of the force-free expression for B e.g. in [14]; now, however, it is not an ansatz anymore, as it follows from (11).…”

Section: Double Beltramimentioning

confidence: 97%

Section: ≈ 10mentioning

confidence: 99%

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On super-elastic collisions between magnetized plasmoids in the heliosphere

Vita

2018

Eur. Phys. J. D

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“…Many MC or flux-rope fitting models are available in the science community (e.g., Hua and Sonnerup 1999;Marubashi and Cho 2015;Möstl et al 2009;Lepping et al 1990;Wang et al 2015). It would be useful to know whether and/or how they perform differently.…”

Section: How Many Mcs Were Associated With the Super-storm Of 17 Marcmentioning

confidence: 99%

The first super geomagnetic storm of solar cycle 24: “The St. Patrick’s day event (17 March 2015)”

Liou

Lepping³

et al. 2016

Earth Planet Sp

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The first super geomagnetic storm (Dst < −200 nT) of solar cycle 24 occurred on "St. Patrick's day" (17 March 2015). Notably, it was a two-step storm. The source of the storm can be traced back to the solar event on 15 March 2015. At ~2:10 UT on that day, SOHO/LASCO C3 recorded a partial halo coronal mass ejection (CME), which was associated with a C9.1/1F flare (S22W25) and a series of type II/IV radio bursts. The initial propagation speed of this CME is estimated to be ~668 km/s. An interplanetary (IP) shock, likely driven by a magnetic cloud (MC), arrived at the Wind spacecraft at 03:59 UT on 17 March and caused a sudden storm commencement. The storm intensified during the Earth's crossing of the ICME/shock sheath and then recovered slightly after the interplanetary magnetic field (IMF) turned northward. The IMF started turning southward again due to a large MC field itself, which caused the second storm intensification, reaching a minimum value (Dst = −223 nT). It is found that the first step is caused by a southward IMF component in the sheath (between the upstream shock and the front of the MC), whereas the second step is associated with the passage of the MC. The CME that erupted on 15 March is the sole solar source of the MC. We also discuss the CME/ storm event with detailed data from observations (Wind and SOHO) and our algorithm for predicting the intensity of a geomagnetic storm (Dst min ) from known IP parameter values. We found that choosing the correct Dst min estimating formula for predicting the intensity of MC-associated geomagnetic storms is crucial for space weather predictions.

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“…In addition to these motions, the "poloidal plasma motion" here refers to the motion of a velocity component along the poloidal direction, i.e., around the MC axis, that has recently been found in the moving MC frame for many MCs by Wang et al (2015). For this motion, the authors raised three possible explanations: i) it might be locally generated through the interaction with the solar wind; ii) it might be internally generated by the expansion of MCs, during which magnetic energy is converted into kinetic energy, including the rotational component; and iii) it might be initially generated at the eruption of the corresponding CME, and carried all the way to 1 AU.…”

Section: Introductionmentioning

confidence: 99%

Main Cause of the Poloidal Plasma Motion Inside a Magnetic Cloud Inferred from Multiple-Spacecraft Observations

et al. 2017

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Although the dynamical evolution of magnetic clouds (MCs) has been one of the foci of interplanetary physics for decades, only few studies focus on the internal properties of large-scale MCs. Recent work by Wang et al. (J. Geophys. Res. 120, 1543 suggested the existence of the poloidal plasma motion in MCs. However, the main cause of this motion is not clear. In order to find it, we identify and reconstruct the MC observed by the Solar Terrestrial Relations Observatory (STEREO)-A, Wind, and STEREO-B spacecraft during 19 -20 November 2007 with the aid of the velocity-modified cylindrical force-free fluxrope model. We analyze the plasma velocity in the plane perpendicular to the MC axis. It is found that there was evident poloidal motion at Wind and STEREO-B, but this was not clear at STEREO-A, which suggests a local cause rather than a global cause for the poloidal plasma motion inside the MC. The rotational directions of the solar wind and MC plasma at the two sides of the MC boundary are found to be consistent, and the values of the rotational speeds of the solar wind and MC plasma at the three spacecraft show a rough correlation. All of these results illustrate that the interaction with ambient solar wind through viscosity might be one of the local causes of the poloidal motion. Additionally, we propose another possible local cause: the existence of a pressure gradient in the MC. The significant difference in the total pressure at the three spacecraft suggests that this speculation is perhaps correct.

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Investigating plasma motion of magnetic clouds at 1 AU through a velocity‐modified cylindrical force‐free flux rope model

Cited by 67 publications

References 74 publications

On super-elastic collisions between magnetized plasmoids in the heliosphere

On super-elastic collisions between magnetized plasmoids in the heliosphere

The first super geomagnetic storm of solar cycle 24: “The St. Patrick’s day event (17 March 2015)”

Main Cause of the Poloidal Plasma Motion Inside a Magnetic Cloud Inferred from Multiple-Spacecraft Observations

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