Which Bow Shock Theory, Gasdynamic or Magnetohydrodynamic, Better Explains CME Stand-off Distance Ratios from LASCO-C2 Observations ?

Lee, Jae‐Ok; Moon, Yong‐Jae; Lee, Jinyi; Kim, Rok‐Soon; Cho, Kyung-Suk

doi:10.3847/1538-4357/aa656f

Cited by 7 publications

(4 citation statements)

References 41 publications

(60 reference statements)

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“…The CME front of this three-part structure corresponds to the HCB, shown in Figures 5 and 6. These features in the synthetic image agree nicely with observations of CME by white-light coronagraph (such as Vourlidas et al 2013;Lee et al 2017). The CME front is the dominant feature in the white line observations, and the FS is a relatively faint feature immediately ahead of the CME front.…”

Section: Resultssupporting

confidence: 80%

“…However, the researcher realized the difference between the fast shock and the CME front because the legs of the CME front do not expand laterally (Howard et al 1982;Sime et al 1984) and some CMEs are too slow to drive a fast shock. Furthermore, the fast shock can be observed as faint features ahead of the CME in white-light coronagraphs (Gopalswamy et al 2009;Vourlidas et al 2013;Lee et al 2014), and some researchers have used the stand-off distance between the fast shock and the CME front to develop technology to deduce coronal magnetic field parameters (Gopalswamy & Yashiro 2011;Lee et al 2017;Ying et al 2022). It is widely known that the CME front is the density enhancement of ambient plasma caused by the eruptive magnetic structures (Forbes 2000;Ciaravella et al 2005;Cheng et al 2012).…”

Section: Introductionmentioning

confidence: 99%

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Numerical Simulation on the Leading Edge of Coronal Mass Ejection in the Near-Sun Region

Mei,

Ye,

et al. 2023

ApJ

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The coronal mass ejections (CMEs) observed by white-light coronagraphs, such as the Large Angle and Spectrometric Coronagraph (LASCO) C2/C3, commonly exhibit the three-part structure, with the bright leading edge as the outermost part. In this work, we extend previous work on the leading edge by performing a large-scale 3D magnetohydrodynamic numerical simulation on the evolution of an eruptive magnetic flux rope (MFR) in a near-Sun region based on a radially stretched calculation grid in spherical coordination and the incorporation of solar wind. In the early stage, the new simulation almost repeats the previous results, i.e., the expanding eruptive MFR and associated CME bubble interact with the ambient magnetic field, which leads to the appearance of the helical current ribbon/boundary (HCB) wrapping around the MFR. The HCB can be interpreted as a possible mechanism of the CME leading edge. Later, the CME bubble propagates self-consistently to a larger region beyond a few solar radii from the solar center, similar to the early stage of evolution. The continuous growth and propagation of the CME bubbles leading to the HCB can be traced across the entire near-Sun region. Furthermore, we can observe the HCB in the white-light synthetic images as a bright front feature in the large field of view of LASCO C2 and C3.

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Section: Resultssupporting

confidence: 80%

Section: Introductionmentioning

confidence: 99%

Numerical Simulation on the Leading Edge of Coronal Mass Ejection in the Near-Sun Region

Mei,

Ye,

et al. 2023

ApJ

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“…The diffuse region has often been identified as the CME-driven shock front; see Schmidt et al (2016b) and the references therein. Usually, the shock is more visible toward the flank regions of the CME, and the stand off distance between the shock and the CME leading edge is not more than 1 -2 R in this height range (Schmidt et al, 2016a), and often much less (Lee et al, 2017).…”

Section: Events With Large Height Difference Between the Cme Leading Front And The Type II Burst Sourcementioning

confidence: 99%

Formation of Isolated Radio Type II Bursts at Low Frequencies

Pohjolainen

Sheshvan

2021

Sol Phys

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The first appearance of radio type II burst emission at decameter-hectometer (DH) waves typically occurs in connection, and often simultaneously, with other types of radio emissions. As type II bursts are signatures of propagating shock waves that are associated with flares and coronal mass ejections (CMEs), a rich variety of radio emissions can be expected. However, sometimes DH type II bursts appear in the dynamic spectra without other or earlier radio signatures. One explanation for them could be that the flare-CME launch happens on the far side of the Sun, and the emission is observed only when the source gets high enough in the solar atmosphere. In this study we have analysed 26 radio type II bursts that started at DH waves and were well-separated (‘isolated’) from other radio emission features. These bursts were identified from all DH type II bursts observed in 1998 – 2016, and for 12 events we had observations from at least two different viewing angles with the instruments on board Wind and the Solar Terrestrial Relations Observatory (STEREO) satellites. We found that only 30% of the type II bursts had their source origin on the far side of the Sun, but also that no bursts originated from the central region of the Sun (longitudes E30 – W40). Almost all of the isolated DH type II bursts could be associated with a shock near the CME leading front, and only few were determined to be shocks near the CME flank regions. In this respect our result differs from earlier findings. Our analysis, which included inspection of various CME and radio emission characteristics, suggests that the isolated DH type II bursts could be a special subgroup within DH type II bursts, where the radio emission requires particular coronal conditions to form and to die out.

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“…The difference in the shape of the obstacle can be accounted for to improve the applicability of equation (e.g., Farris & Russell, ; Russell & Mulligan, ; Merka et al, ; Savani et al, ). Lee et al () compare the different standoff relations for 18 CMEs and find that in general, the observations are well described using MHD theory for quasi‐parallel shocks with an adiabatic index,

γ

, of 5/3.…”

Section: Introductionmentioning

confidence: 99%

FIDO‐SIT: The First Forward Model for the In Situ Magnetic Field of CME‐Driven Sheaths

2020

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We have shown previously that the in situ magnetic field of coronal mass ejections (CMEs) can be well reproduced by simple, physics‐driven flux rope models using the ForeCAT In situ Data Observer (FIDO, Kay et al., 2017). Here, we show that a similar approach can be taken to forward model the shock and sheath of a CME (Sheath Induced by Transient [SIT]). We develop a relation between the downstream density and magnetic field strength that only depends on the upstream properties and downstream speed. Next, we establish a set of well‐observed CME‐driven shocks combining results from several online catalogs. We establish a baseline using the observed downstream speed and show that the mean absolute errors only increase slightly to 3.4 cm −3 and 3.8 nT when using a predicted downstream velocity. We also develop a model for the sheath duration or the standoff distance of the CME‐driven shock. While there is certainly room for improvement, our model does perform better than those currently available, reducing the error from 7.0 to 4.6 hr. We couple our flux rope and sheath models as FIDO‐SIT and present results for four observed cases. For three of the four cases, FIDO‐SIT reproduces the sheath magnetic field with an error of one third the total magnitude for each individual vector component.

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Which Bow Shock Theory, Gasdynamic or Magnetohydrodynamic, Better Explains CME Stand-off Distance Ratios from LASCO-C2 Observations ?

Cited by 7 publications

References 41 publications

Numerical Simulation on the Leading Edge of Coronal Mass Ejection in the Near-Sun Region

Numerical Simulation on the Leading Edge of Coronal Mass Ejection in the Near-Sun Region

Formation of Isolated Radio Type II Bursts at Low Frequencies

FIDO‐SIT: The First Forward Model for the In Situ Magnetic Field of CME‐Driven Sheaths

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