scholarly journals Small-scale Magnetic Flux Ropes with Field-aligned Flows via the PSP In-situ Observations

2021 ◽  
Author(s):  
Yu Chen ◽  
Qiang Hu ◽  
Lingling Zhao
Keyword(s):  
Magnetic Field ◽  
Magnetic Flux ◽  
Flux Rope ◽  
Local Magnetic Field ◽  
Small Scale ◽  
Magnetic Flux Rope ◽  
Magnetic Flux Ropes ◽  
Flux Ropes ◽  
Field Lines

<p>Magnetic flux rope, formed by the helical magnetic field lines, can sometimes remain its shape while carrying significant plasma flow that is aligned with the local magnetic field. We report the existence of such structures and static flux ropes by applying the Grad-Shafranov-based algorithm to the Parker Solar Probe (PSP) in-situ measurements in the first five encounters. These structures are detected at heliocentric distances, ranging from 0.13 to 0.66 au, in a total of 4-month time period. We find that flux ropes with field-aligned flows have certain properties similar to those of static flux ropes, such as the decaying relations of the magnetic fields within structures with respect to heliocentric distances. Moreover, these events are more likely with magnetic pressure dominating over the thermal pressure and occurring more frequently in the relatively fast-speed solar wind. Taking into account the high Alfvenicity, we also compare these events with switchbacks and present the cross-section maps via the new Grad-Shafranov type reconstruction. Finally, the possible evolution and relaxation of the magnetic flux rope structures are discussed.</p>

scholarly journals Small-scale Magnetic Flux Ropes and Their Properties Based on In Situ Measurements from the Parker Solar Probe

2022 ◽  
Vol 924 (2) ◽  
pp. 43
Author(s):  
Yu Chen ◽  
Qiang Hu
Keyword(s):  
Magnetic Flux ◽  
Flux Rope ◽  
Residual Energy ◽  
In Situ Measurements ◽  
Small Scale ◽  
Flux Function ◽  
Magnetic Flux Ropes ◽  
Flux Ropes ◽  
Field Lines

Abstract We report small-scale magnetic flux ropes via the in situ measurements from the Parker Solar Probe during the first six encounters, and present additional analyses to supplement our prior work in Chen et al. These flux ropes are detected by the Grad–Shafranov-based algorithm, with their durations and scale sizes ranging from 10 s to ≲1 hr and from a few hundred kilometers to 10−3 au, respectively. They include both static structures and those with significant field-aligned plasma flows. Most structures tend to possess large cross helicity, while the residual energy is distributed over wide ranges. We find that these dynamic flux ropes mostly propagate in the antisunward direction relative to the background solar wind, with no preferential signs of magnetic helicity. The magnetic flux function follows a power law and is proportional to scale size. We also present case studies showing reconstructed two-dimensional (2D) configurations, which confirm that both the static and dynamic flux ropes have a common configuration of spiral magnetic field lines (also streamlines). Moreover, the existence of such events hints at interchange reconnection as a possible mechanism for generating flux rope-like structures near the Sun. Lastly, we summarize the major findings, and discuss the possible correlation between these flux rope-like structures and turbulence due to the process of local Alfvénic alignment.

scholarly journals Comparison of counterstreaming suprathermal electron signatures of ICMEs with and without magnetic cloud: are all ICMEs flux ropes?

2019 ◽  
Vol 632 ◽  
pp. A129 ◽  
Author(s):  
Jiemin Wang ◽  
Yan Zhao ◽  
Hengqiang Feng ◽  
Qiang Liu ◽  
Zhanjun Tian ◽  
...  
Keyword(s):  
Magnetic Fields ◽  
Magnetic Flux ◽  
Flux Rope ◽  
The Sun ◽  
Magnetic Flux Rope ◽  
Suprathermal Electron ◽  
Magnetic Flux Ropes ◽  
Flux Ropes ◽  
Field Lines ◽  
Disordered Magnetic

Context. Magnetic clouds (MCs), as in large-scale interplanetary magnetic flux ropes, are usually still connected to the Sun at both ends near 1 AU. Many researchers believe that all nonMC interplanetary coronal mass ejections (ICMEs) also have magnetic flux rope structures, which are inconspicuous because the observing spacecraft crosses the flanks of the rope structures. If so, the field lines of nonMC ICMEs should also usually be connected to the Sun at both ends. Aims. We want to know whether or not the field lines of most nonMC ICMEs are still connected to the Sun at both ends. Methods. This study examined the counterstreaming suprathermal electron (CSE) signatures of 272 ICMEs observed by the Advanced Composition Explorer (ACE) spacecraft from 1998 to 2008 and compared the CSE signatures of MCs and nonMC ICMEs. Results. Results show that only 10 of the 101 MC events (9.9% ) and 75 of the 171 nonMC events (43.9%) have no CSEs. Moreover, 21 of the nonMC ICMEs have high CSE percentages (more than 70%) and show relatively stable magnetic field components with slight rotations, which are in line with the expectations that the observing spacecraft passes through the flank of magnetic flux ropes. Therefore, the 21 events may be magnetic flux ropes but the ACE spacecraft passes through their flanks of magnetic flux ropes. Conclusions. Considering that most other nonMC events have disordered magnetic fields, we suggest that some nonMC ICMEs inherently have disordered magnetic fields, and therefore no magnetic flux rope structures.

scholarly journals Small-scale Magnetic Flux Ropes with Field-aligned Flows via the PSP In Situ Observations

2021 ◽  
Vol 914 (2) ◽  
pp. 108
Author(s):  
Yu Chen ◽  
Qiang Hu ◽  
Lingling Zhao ◽  
Justin C. Kasper ◽  
Jia Huang
Keyword(s):  
Magnetic Flux ◽  
Small Scale ◽  
Magnetic Flux Ropes ◽  
Flux Ropes ◽  
In Situ Observations

scholarly journals Microwave indicator of potential geoeffectiveness and magnetic flux-rope structure of a solar active region

2021 ◽  
Vol 7 (1) ◽  
pp. 3-12
Author(s):  
Anastasiia Kudriavtseva ◽  
Ivan Myshyakov ◽  
Arkadiy Uralov ◽  
Victor Grechnev
Keyword(s):  
Magnetic Field ◽  
Active Region ◽  
Magnetic Flux ◽  
Neutral Line ◽  
Flux Rope ◽  
Coronal Magnetic Field ◽  
Horizontal Magnetic Field ◽  
Magnetic Flux Rope ◽  
Magnetic Flux Ropes ◽  
Class Flare

We analyze the presence of a microwave neutral-line-associated source (NLS) in a super-active region NOAA 12673, which produced a number of geo-effective events in September 2017. To estimate the NLS position, we use data from the Siberian Radioheliograph in a range 4–8 GHz and from the Nobeyama Radioheliograph at 17 GHz. Calculation of the coronal magnetic field in a non-linear force-free approximation has revealed an extended structure consisting of interconnected magnetic flux ropes, located practically along the entire length of the main polarity separation line of the photospheric magnetic field. NLS is projected into the region of the strongest horizontal magnetic field, where the main energy of this structure is concentrated. During each X-class flare, the active region lost magnetic helicity and became a CME source.

The evolution of magnetic flux ropes in sheared plasma flows

2000 ◽  
Vol 64 (1) ◽  
pp. 41-55 ◽  
Author(s):  
J. M. SCHMIDT ◽  
P. J. CARGILL
Keyword(s):  
Magnetic Field ◽  
Magnetic Flux ◽  
Shear Layer ◽  
Cross Section ◽  
Circular Cross Section ◽  
Flux Rope ◽  
Plasma Pressure ◽  
Magnetic Flux Ropes ◽  
Flux Ropes ◽  
The Magnetic Field

The evolution of magnetic flux ropes in a sheared plasma flow is investigated. When the magnetic field outside the flux rope lies parallel to the axis of the flux rope, a flux rope of circular cross-section, whose centre is located at the midpoint of the shear layer, has its shape distorted, but remains in the shear layer. Small displacements of the flux-rope centre above or below the midpoint of the shear layer lead to the flux-rope being expelled from the shear layer. This motion arises because small asymmetries in the plasma pressure around the flux-rope boundary leads to a force that forces the flux rope into a region of uniform flow. When the magnetic field outside the flux rope lies in a plane perpendicular to the flux-rope axis, the flux rope and external magnetic field reconnect with each other, leading to the destruction of the flux rope.

scholarly journals Non-Gaussianity and cross-scale coupling in interplanetary magnetic field turbulence during a rope–rope magnetic reconnection event

2018 ◽  
Vol 36 (2) ◽  
pp. 497-507 ◽  
Author(s):  
Rodrigo A. Miranda ◽  
Adriane B. Schelin ◽  
Abraham C.-L. Chian ◽  
José L. Ferreira
Keyword(s):  
Magnetic Field ◽  
Magnetic Flux ◽  
Magnetic Reconnection ◽  
Coherent Structures ◽  
Flux Rope ◽  
Inertial Subrange ◽  
Order Moment ◽  
Magnetic Flux Ropes ◽  
Flux Ropes ◽  
Non Gaussian

Abstract. In a recent paper (Chian et al., 2016) it was shown that magnetic reconnection at the interface region between two magnetic flux ropes is responsible for the genesis of interplanetary intermittent turbulence. The normalized third-order moment (skewness) and the normalized fourth-order moment (kurtosis) display a quadratic relation with a parabolic shape that is commonly observed in observational data from turbulence in fluids and plasmas, and is linked to non-Gaussian fluctuations due to coherent structures. In this paper we perform a detailed study of the relation between the skewness and the kurtosis of the modulus of the magnetic field |B| during a triple interplanetary magnetic flux rope event. In addition, we investigate the skewness–kurtosis relation of two-point differences of |B| for the same event. The parabolic relation displays scale dependence and is found to be enhanced during magnetic reconnection, rendering support for the generation of non-Gaussian coherent structures via rope–rope magnetic reconnection. Our results also indicate that a direct coupling between the scales of magnetic flux ropes and the scales within the inertial subrange occurs in the solar wind. Keywords. Space plasma physics (turbulence)

scholarly journals The structure of flux transfer events recovered from Cluster data

2006 ◽  
Vol 24 (2) ◽  
pp. 603-618 ◽  
Author(s):  
H. Hasegawa ◽  
B. U. Ö. Sonnerup ◽  
C. J. Owen ◽  
B. Klecker ◽  
G. Paschmann ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetic Flux ◽  
Flux Rope ◽  
Time Interval ◽  
Reconstruction Technique ◽  
Magnetic Flux Ropes ◽  
Flux Transfer Events ◽  
Cluster Data ◽  
Flux Ropes ◽  
Flux Transfer

Abstract. The structure and formation mechanism of a total of five Flux Transfer Events (FTEs), encountered on the equatorward side of the northern cusp by the Cluster spacecraft, with separation of ~5000 km, are studied by applying the Grad-Shafranov (GS) reconstruction technique to the events. The technique generates a magnetic field/plasma map of the FTE cross section, using combined magnetic field and plasma data from all four spacecraft, under the assumption that the structure is two-dimensional (2-D) and time-independent. The reconstructed FTEs consist of one or more magnetic flux ropes embedded in the magnetopause, suggesting that multiple X-line reconnection was involved in generating the observed FTEs. The dimension of the flux ropes in the direction normal to the magnetopause ranges from about 2000 km to more than 1 RE. The orientation of the flux rope axis can be determined through optimization of the GS map, the result being consistent with those from various single-spacecraft methods. Thanks to this, the unambiguous presence of a strong core field is confirmed, providing evidence for component merging. The amount of magnetic flux contained within each flux rope is calculated from the map and, by dividing it by the time interval between the preceding FTE and the one reconstructed, a lower limit of the reconnection electric field during the creation of the flux rope can be estimated; the estimated value ranges from ~0.11 to ~0.26 mV m-1, with an average of 0.19 mV m-1. This can be translated to the reconnection rate of 0.038 to 0.074, with an average of 0.056. Based on the success of the 2-D model in recovering the observed FTEs, the length of the X-lines is estimated to be at least a few RE.

scholarly journals Observations of Magnetic Flux Ropes Opened or Disconnected From the Sun by Magnetic Reconnection in Interplanetary Space

2021 ◽  
Vol 9 ◽  
Author(s):  
Hengqiang Feng ◽  
Yan Zhao ◽  
Jiemin Wang ◽  
Qiang Liu ◽  
Guoqing Zhao
Keyword(s):  
Magnetic Field ◽  
Magnetic Flux ◽  
Magnetic Reconnection ◽  
Interplanetary Space ◽  
Closed Field ◽  
Magnetic Flux Ropes ◽  
Flux Ropes ◽  
Solar Eruptions ◽  
Wind Spacecraft ◽  
Field Lines

During solar eruptions, many closed magnetic flux ropes are ejected into interplanetary space, which contribute to the heliospheric magnetic field and have important space weather effect because of their coherent magnetic field. Therefore, understanding the evolution of these closed flux ropes in the interplanetary space is important. In this paper, we examined all the magnetic and plasma data measured in 1997 by the Wind spacecraft and identified 621 reconnection exhausts. Of the 621 reconnection events, 31 were observed at the boundaries of magnetic flux ropes and were thought to cause the opening or disconnection magnetic field lines of the adjacent ropes. Of the 31 magnetic reconnection events, 29 were interchange reconnections and the closed field lines of these related flux ropes were opened by them. Only 2 of the 31 magnetic reconnection events disconnected the opened field lines of the original flux ropes. These observations indicate that interchange reconnection and disconnection may be two important mechanisms changing the magnetic topology of the magnetic flux ropes during their propagation during the interplanetary space.

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