Locating the solar source of 13 April 2006 magnetic cloud

Steed, K.; Owen, C. J.; Harra, L. K.; Green, L. M.; Dasso, S.; Walsh, A. P.; Démoulin, P.; Driel‐Gesztelyi, L. van

doi:10.5194/angeo-26-3159-2008

Cited by 5 publications

(7 citation statements)

References 56 publications

(48 reference statements)

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“…[8] Vertical dot-dashed black lines indicate the boundaries of the magnetic cloud at WIND, which are found to be very similar to those determined by Steed et al [2008], using data from the ACE spacecraft. Unusual magnetic field and plasma observations persist beyond the identified rear boundary of this magnetic cloud and we suggest that this may be the result of interaction between the magnetic cloud flux rope and the solar wind.…”

Section: Overview Of the Eventsupporting

confidence: 48%

“…We have shown that the rate of radial expansion of the 13 April 2006 magnetic cloud is small at 1 AU. However, unlike the examples studied by Owens [2009], the angular width of this magnetic cloud is believed to be quite small, because despite originating close to disk center, this CME is not observed by the Large Angle Spectroscopic Coronagraph (LASCO) [Brueckner et al, 1995] onboard the SoHO spacecraft [Steed et al, 2008]. Owens [2009] also hypothesise that magnetic reconnection occurring across such current sheets in magnetic clouds may result in a single flux rope being fragmented into multiple, smaller flux ropes.…”

Section: Discussionmentioning

confidence: 99%

“…This MC displays many of the typical characteristics used to identify a magnetic cloud [Steed et al, 2008] and also exhibits the clearest example of substructure toward its center that we have found. Magnetic field data from the Magnetic Field Investigation [MFI, Lepping et al, 1995] and plasma data from the 3-D Plasma and Energetic Particle Experiment [3DP, Lin et al, 1995] on the WIND spacecraft, located upstream of Earth, are shown at 3 s resolution.…”

Section: Overview Of the Eventmentioning

confidence: 96%

“…This "back" region is expected to exhibit different behavior to both the main body of the ejecta and the solar wind. Steed et al [2008] investigated several locations for the rear boundary of this MC and, despite the complexity of the observations toward the rear of the ejecta, they found that changes in the rear boundary location over a time interval spanning almost 10 h did not result in major changes in the orientation of the MC axis. Within this magnetic cloud the rotation of the magnetic field evident in B y is not smooth, and vertical dashed red lines bound the region where the B y magnetic field observations deviate from the larger scale trend bipolar signature, exhibiting multiple reversals of the gradient of this magnetic field component toward the center of the cloud.…”

Section: Overview Of the Eventmentioning

confidence: 99%

“…The MV analysis gives a ratio between the intermediate and the minimum eigenvalues of ∼12, which implies that the minimum variance direction is well defined [Siscoe and Suey, 1972]. The MC axis orientation was also determined using MVA by Steed et al [2008] and is described by and , where is the angle between the ecliptic plane and the MC axis and is the angle between x GSE and the projection of the MC axis on the ecliptic plane (measured positive when anticlockwise). They found that ∼ 68°and ∼ 294°.…”

Section: Overview Of the Eventmentioning

confidence: 99%

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Investigating the observational signatures of magnetic cloud substructure

et al. 2011

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[1] Magnetic clouds (MCs) represent a subset of interplanetary coronal mass ejections (ICMEs) that exhibit a magnetic flux rope structure. They are primarily identified by smooth, large-scale rotations of the magnetic field. However, both small-and large-scale fluctuations of the magnetic field are observed within some magnetic clouds. We analyzed the magnetic field in the frames of the flux ropes, approximated using a minimum variance analysis (MVA), and have identified a small number of MCs within which multiple reversals of the gradient of the azimuthal magnetic field are observed. We herein use the term "substructure" to refer to regions that exhibit this signature. We examine, in detail, one such MC observed on 13 April 2006 by the ACE and WIND spacecraft and show that substructure has distinct signatures in both the magnetic field and plasma observations. We identify two thin current sheets within the substructure and find that they bound the region in which the observations deviate most significantly from those typically expected in MCs. The majority of these clouds are followed by fast solar wind streams, and a comparison of the properties of this magnetic cloud with five similar events reveals that they have lower nondimensional expansion rates than nonovertaken magnetic clouds. We discuss and evaluate several possible explanations for this type of substructure, including the presence of multiple flux ropes and warping of the MC structure, but we conclude that none of these scenarios is able to fully explain all of the aspects of the substructure observations.

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Section: Overview Of the Eventsupporting

confidence: 48%

Section: Discussionmentioning

confidence: 99%

Section: Overview Of the Eventmentioning

confidence: 96%

Section: Overview Of the Eventmentioning

confidence: 99%

Section: Overview Of the Eventmentioning

confidence: 99%

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Investigating the observational signatures of magnetic cloud substructure

et al. 2011

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Tracking the momentum flux of a CME and quantifying its influence on geomagnetically induced currents at Earth

et al. 2013

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[1] We investigate a coronal mass ejection (CME) propagating toward Earth on 29 March 2011. This event is specifically chosen for its predominately northward directed magnetic field, so that the influence from the momentum flux onto Earth can be isolated. We focus our study on understanding how a small Earth-directed segment propagates. Mass images are created from the white-light cameras onboard STEREO which are also converted into mass height-time maps (mass J-maps). The mass tracks on these J-maps correspond to the sheath region between the CME and its associated shock front as detected by in situ measurements at L1. A time series of mass measurements from the STEREO COR-2A instrument is made along the Earth propagation direction. Qualitatively, this mass time series shows a remarkable resemblance to the L1 in situ density series. The in situ measurements are used as inputs into a three-dimensional (3-D) magnetospheric space weather simulation from the Community Coordinated Modeling Center. These simulations display a sudden compression of the magnetosphere from the large momentum flux at the leading edge of the CME, and predictions are made for the time derivative of the magnetic field (dB/dt) on the ground. The predicted dB/dt values were then compared with the observations from specific equatorially located ground stations and showed notable similarity. This study of the momentum of a CME from the Sun down to its influence on magnetic ground stations on Earth is presented as a preliminary proof of concept, such that future attempts may try to use remote sensing to create density and velocity time series as inputs to magnetospheric simulations.

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Automatic Detection and Extraction of Coronal Dimmings from SDO/AIA Data

Attrill

Wills-Davey

2009

Sol Phys

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The volume of data anticipated from the Solar Dynamics Observatory/Atmospheric Imaging Assembly (SDO/AIA) highlights the necessity for the development of automatic-detection methods for various types of solar activity. Initially recognized in the 1970s, it is now well established that coronal dimmings are closely associated with coronal mass ejections (CMEs), and they are particularly noted as a reliable indicator of front-side (halo) CMEs, which can be difficult to detect in white-light coronagraph data.Existing work clearly demonstrates that several properties derived from the analysis of coronal dimmings can give useful information about the associated CME. The development and implementation of an automated coronal-dimming region detection and extraction algorithm removes visual observer bias, however unintentional, from the determination of physical quantities such as spatial location, area, and volume. This allows for reproducible, quantifiable results to be mined from very large data sets. The information derived may facilitate more reliable early space-weather detection, as well as offering the potential for conducting large-sample studies focused on determining the geo-effectiveness of CMEs, coupled with analysis of their associated coronal dimming signatures.In this paper we present examples of both simple and complex dimming events extracted using our algorithm, which will be run as a module for the SDO/Computer Vision Centre. Contrasting and well-studied events at both the minimum and maximum of solar cycle 23 are identified in Solar and Heliospheric Observatory/Extreme ultra-violet Imaging Telescope (SOHO/EIT) data. A more recent example extracted from Solar and Terrestrial Relations Observatory/Extreme Ultra-Violet Imager (STEREO/EUVI) data is also presented, demonstrating the potential for the anticipated application to SDO/AIA data. The detection part of our algorithm is based largely on the principle of operation of the NEMO software, namely the detection of significant variation in the statistics of the EUV image pixels (Podladchikova and Berghmans in Solar Phys. 228, 265 -284, 2005). As well as running on historic data Solar Image Processing and Analysis

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Locating the solar source of 13 April 2006 magnetic cloud

Cited by 5 publications

References 56 publications

Investigating the observational signatures of magnetic cloud substructure

Investigating the observational signatures of magnetic cloud substructure

Tracking the momentum flux of a CME and quantifying its influence on geomagnetically induced currents at Earth

Automatic Detection and Extraction of Coronal Dimmings from SDO/AIA Data

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