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 ◽  
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 Multiple Triangulation Analysis: another approach to determine the orientation of magnetic flux ropes

2006 ◽  
Vol 24 (6) ◽  
pp. 1759-1765 ◽  
Author(s):  
X.-Z. Zhou ◽  
Q.-G. Zong ◽  
Z. Y. Pu ◽  
T. A. Fritz ◽  
M. W. Dunlop ◽  
...  
Keyword(s):  
Magnetic Flux ◽  
Flux Rope ◽  
Magnetic Flux Rope ◽  
Magnetic Flux Ropes ◽  
Error Range ◽  
Cluster Data ◽  
Flux Ropes

Abstract. Another approach (Multiple Triangulation Analysis, MTA) is presented to determine the orientation of magnetic flux rope, based on 4-point measurements. A 2-D flux rope model is used to examine the accuracy of the MTA technique in a theoretical way. It is found that the precision of the estimated orientation is dependent on both the spacecraft separation and the constellation path relative to the flux rope structure. However, the MTA error range can be shown to be smaller than that of the traditional MVA technique. As an application to real Cluster data, several flux rope events on 26 January 2001 are analyzed using MTA, to obtain their orientations. The results are compared with the ones obtained by several other methods which also yield flux rope orientation. The estimated axis orientations are shown to be fairly close, suggesting the reliability of the MTA method.

scholarly journals Formation of Magnetic Flux Rope During Solar Eruption. I. Evolution of Toroidal Flux and Reconnection Flux

2021 ◽  
Vol 9 ◽  
Author(s):  
Chaowei Jiang ◽  
Jun Chen ◽  
Aiying Duan ◽  
Xinkai Bian ◽  
Xinyi Wang ◽  
...  
Keyword(s):  
Magnetic Flux ◽  
Early Phase ◽  
Flux Rope ◽  
Three Dimensions ◽  
Bottom Surface ◽  
Peak Time ◽  
Magnetic Flux Ropes ◽  
Twisted Field ◽  
Solar Eruptions ◽  
Field Lines

Magnetic flux ropes (MFRs) constitute the core structure of coronal mass ejections (CMEs), but hot debates remain on whether the MFR forms before or during solar eruptions. Furthermore, how flare reconnection shapes the erupting MFR is still elusive in three dimensions. Here we studied a new MHD simulation of CME initiation by tether-cutting magnetic reconnection in a single magnetic arcade. The simulation follows the whole life, including the birth and subsequent evolution, of an MFR during eruption. In the early phase, the MFR is partially separated from its ambient field by a magnetic quasi-separatrix layer (QSL) that has a double-J shaped footprint on the bottom surface. With the ongoing of the reconnection, the arms of the two J-shaped footprints continually separate from each other, and the hooks of the J shaped footprints expand and eventually become closed almost at the eruption peak time, and thereafter the MFR is fully separated from the un-reconnected field by the QSL. We further studied the evolution of the toroidal flux in the MFR and compared it with that of the reconnected flux. Our simulation reproduced an evolution pattern of increase-to-decrease of the toroidal flux, which is reported recently in observations of variations in flare ribbons and transient coronal dimming. The increase of toroidal flux is owing to the flare reconnection in the early phase that transforms the sheared arcade to twisted field lines, while its decrease is a result of reconnection between field lines in the interior of the MFR in the later phase.

scholarly journals Observations of flux rope formation prior to coronal mass ejections

2013 ◽  
Vol 8 (S300) ◽  
pp. 209-214 ◽  
Author(s):  
Lucie M. Green ◽  
Bernhard Kliem
Keyword(s):  
Magnetic Flux ◽  
Magnetic Structure ◽  
Solar Atmosphere ◽  
Coronal Mass Ejections ◽  
Flux Rope ◽  
Active Regions ◽  
Magnetic Configuration ◽  
Magnetic Flux Rope ◽  
Source Regions ◽  
Flux Ropes

AbstractUnderstanding the magnetic configuration of the source regions of coronal mass ejections (CMEs) is vital in order to determine the trigger and driver of these events. Observations of four CME productive active regions are presented here, which indicate that the pre-eruption magnetic configuration is that of a magnetic flux rope. The flux ropes are formed in the solar atmosphere by the process known as flux cancellation and are stable for several hours before the eruption. The observations also indicate that the magnetic structure that erupts is not the entire flux rope as initially formed, raising the question of whether the flux rope is able to undergo a partial eruption or whether it undergoes a transition in specific flux rope configuration shortly before the CME.

scholarly journals Editorial: Magnetic Flux Ropes: From the Sun to the Earth and Beyond

2020 ◽  
Vol 7 ◽  
Author(s):  
Rui Liu ◽  
Jie Zhang ◽  
Yuming Wang ◽  
Hongqiang Song
Keyword(s):  
Magnetic Flux ◽  
The Sun ◽  
Magnetic Flux Ropes ◽  
The Earth ◽  
Flux Ropes

scholarly journals Structure and Topology of Magnetic Fields in Solar Prominences

2013 ◽  
Vol 8 (S300) ◽  
pp. 127-134 ◽  
Author(s):  
Adriaan A. van Ballegooijen ◽  
Yingna Su
Keyword(s):  
Magnetic Flux ◽  
Flux Rope ◽  
Time Dependent ◽  
Magnetic Flux Rope ◽  
Magnetic Flux Ropes ◽  
And Topology ◽  
Solar Prominences ◽  
Magnetic Elements ◽  
Dependent Model ◽  
Time Dependent Model

AbstractRecent observations and models of solar prominences are reviewed. The observations suggest that prominences are located in or below magnetic flux ropes that lie horizontally above the PIL. However, the details of the magnetic structure are not yet fully understood. Gravity likely plays an important role in shaping the vertical structures observed in quiescent prominences. Preliminary results from a time-dependent model describing the interaction of a magnetic flux rope with photospheric magnetic elements are presented.

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.

scholarly journals A new trigger mechanism for coronal mass ejections

2020 ◽  
Vol 644 ◽  
pp. A137
Author(s):  
A. W. James ◽  
L. M. Green ◽  
L. van Driel-Gesztelyi ◽  
G. Valori
Keyword(s):  
Magnetic Flux ◽  
Magnetic Reconnection ◽  
Extreme Ultraviolet ◽  
Flux Rope ◽  
Active Regions ◽  
Magnetic Activity ◽  
Trigger Mechanism ◽  
Magnetic Flux Rope ◽  
Left Handed ◽  
Flux Ropes

Context. Many previous studies have shown that the magnetic precursor of a coronal mass ejection (CME) takes the form of a magnetic flux rope, and a subset of them have become known as “hot flux ropes” due to their emission signatures in ∼10 MK plasma. Aims. We seek to identify the processes by which these hot flux ropes form, with a view of developing our understanding of CMEs and thereby improving space weather forecasts. Methods. Extreme-ultraviolet observations were used to identify five pre-eruptive hot flux ropes in the solar corona and study how they evolved. Confined flares were observed in the hours and days before each flux rope erupted, and these were used as indicators of episodic bursts of magnetic reconnection by which each flux rope formed. The evolution of the photospheric magnetic field was observed during each formation period to identify the process(es) that enabled magnetic reconnection to occur in the β <  1 corona and form the flux ropes. Results. The confined flares were found to be homologous events and suggest flux rope formation times that range from 18 hours to 5 days. Throughout these periods, fragments of photospheric magnetic flux were observed to orbit around each other in sunspots where the flux ropes had a footpoint. Active regions with right-handed (left-handed) twisted magnetic flux exhibited clockwise (anticlockwise) orbiting motions, and right-handed (left-handed) flux ropes formed. Conclusions. We infer that the orbital motions of photospheric magnetic flux fragments about each other bring magnetic flux tubes together in the corona, enabling component reconnection that forms a magnetic flux rope above a flaring arcade. This represents a novel trigger mechanism for solar eruptions and should be considered when predicting solar magnetic activity.

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