New Insights Into the Physical Nature of Coronal Mass Ejections and Associated Shock Waves Within the Framework of the Three-Dimensional Structure

Kwon, Ryun-Young; Zhang, J.; Olmedo, Oscar

doi:10.1088/0004-637x/794/2/148

Cited by 90 publications

(115 citation statements)

References 48 publications

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“…The other source of the error is the 3D geometry of the shock modeled with the ellipsoid. The error of the ellipsoid model has been determined as shown in the Appendix of Kwon et al (2014). The error is ∼4% for all images we have analyzed.…”

Section: Resultsmentioning

confidence: 99%

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The density compression ratio of shock fronts associated with coronal mass ejections

Kwon

Vourlidas

2018

J. Space Weather Space Clim.

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-We present a new method to extract the three-dimensional electron density profile and density compression ratio of shock fronts associated with coronal mass ejections (CMEs) observed in white light coronagraph images. We demonstrate the method with two examples of fast halo CMEs (∼2000 km s À1 ) observed on 2011 March 7 and 2014 February 25. Our method uses the ellipsoid model to derive the threedimensional geometry and kinematics of the fronts. The density profiles of the sheaths are modeled with double-Gaussian functions with four free parameters, and the electrons are distributed within thin shells behind the front. The modeled densities are integrated along the lines of sight to be compared with the observed brightness in COR2-A, and a x 2 approach is used to obtain the optimal parameters for the Gaussian profiles. The upstream densities are obtained from both the inversion of the brightness in a pre-event image and an empirical model. Then the density ratio and Alfvénic Mach number are derived. We find that the density compression peaks around the CME nose, and decreases at larger position angles. The behavior is consistent with a driven shock at the nose and a freely propagating shock wave at the CME flanks. Interestingly, we find that the supercritical region extends over a large area of the shock and lasts longer (several tens of minutes) than past reports. It follows that CME shocks are capable of accelerating energetic particles in the corona over extended spatial and temporal scales and are likely responsible for the wide longitudinal distribution of these particles in the inner heliosphere. Our results also demonstrate the power of multi-viewpoint coronagraphic observations and forward modeling in remotely deriving key shock properties in an otherwise inaccessible regime.

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Section: Resultsmentioning

confidence: 99%

“…We believe that this effect is negligible in the corona. Instead, we determine the error in the ellipsoid model as shown in the Appendix in Kwon et al (2014). This error gives us the difference of the ellipsoid model from the observed front.…”

Section: Error In Electron Density Excessmentioning

confidence: 99%

The density compression ratio of shock fronts associated with coronal mass ejections

Kwon

Vourlidas

2018

J. Space Weather Space Clim.

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“…It can be a reasonable assumption in the low corona since the CME shock expansion is usually dominant in the initial phase of CME eruptions (e.g., Kwon et al 2014). The circular shock front propagates outward, with a constant expansion speed V sh =2000 km s −1 and a compression ratio X=3.…”

Section: Shock and Magnetic Fieldsmentioning

confidence: 99%

The Acceleration of High-energy Protons at Coronal Shocks: The Effect of Large-scale Streamer-like Magnetic Field Structures

Kong

Guo

Giacalone

et al. 2017

ApJ

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Recent observations have shown that coronal shocks driven by coronal mass ejections can develop and accelerate particles within several solar radii in large solar energetic particle (SEP) events. Motivated by this, we present an SEP acceleration study that including the process in which a fast shock propagates through a streamer-like magnetic field with both closed and open field lines in the low corona region. The acceleration of protons is modeled by numerically solving the Parker transport equation with spatial diffusion both along and across the magnetic field. We show that particles can be sufficiently accelerated to up to several hundred MeV within 2-3 solar radii. When the shock propagates through a streamer-like magnetic field, particles are more efficiently accelerated compared to the case with a simple radial magnetic field, mainly due to perpendicular shock geometry and the natural trapping effect of closed magnetic fields. Our results suggest that the coronal magnetic field configuration is an important factor for producing large SEP events. We further show that the coronal magnetic field configuration strongly influences the distribution of energetic particles, leading to different locations of source regions along the shock front where most high-energy particles are concentrated. This work may have strong implications for SEP observations. The upcoming Parker Solar Probe will provide in situ observations for the distribution of energetic particles in the coronal shock region, and test the results of the study.

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“…In particular, here we will use the compound geometric model developed by Kwon et al (2014) to determine the three-dimensional (3D) structure of the CME associated with the 2010 August 14 SEP event using EUV and WL data from STEREO-A, STEREO-B, SDO, and SOHO. An ellipsoid shape centered at a certain altitude h E is used to describe the outermost front driven by the CME.…”

Section: Cme Front Shockmentioning

confidence: 99%

“…The GCS model has seven free parameters: the height, longitude, and latitude of the center of the flux rope, as well as the half angle, aspect ratio, height, and rotation of the flux rope, as described in detail by Thernisien (2011). The ellipsoid model also uses seven free parameters: the height, longitude, and latitude of the center of the ellipsoid; the length of the three semi-principal axes; and rotation angle of the ellipsoid (see details in Kwon et al 2014).…”

Section: Cme Front Shockmentioning

confidence: 99%

The Solar Energetic Particle Event of 2010 August 14: Connectivity with the Solar Source Inferred from Multiple Spacecraft Observations and Modeling

Lario

Kwon

Richardson

et al. 2017

ApJ

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We analyze one of the first solar energetic particle (SEP) events of solar cycle 24 observed at widely separated spacecraft in order to assess the reliability of models currently used to determine the connectivity between the sources of SEPs at the Sun and spacecraft in the inner heliosphere. This SEP event was observed on 2010 August 14 by near-Earth spacecraft, STEREO-A (∼80°west of Earth) and STEREO-B (∼72°east of Earth). In contrast to near-Earth spacecraft, the footpoints of the nominal magnetic field lines connecting STEREO-A and STEREO-B with the Sun were separated from the region where the parent fast halo coronal mass ejection (CME) originated by ∼88°and ∼47°in longitude, respectively. We discuss the properties of the phenomena associated with this solar eruption. Extreme ultraviolet and white-light images are used to specify the extent of the associated CME-driven coronal shock. We then assess whether the SEPs observed at the three heliospheric locations were accelerated by this shock or whether transport mechanisms in the corona and/or interplanetary space provide an alternative explanation for the arrival of particles at the poorly connected spacecraft. A possible scenario consistent with the observations indicates that the observation of SEPs at STEREO-B and near Earth resulted from particle injection by the CME shock onto the field lines connecting to these spacecraft, whereas SEPs reached STEREO-A mostly via cross-field diffusive transport processes. The successes, limitations, and uncertainties of the methods used to resolve the connection between the acceleration sites of SEPs and the spacecraft are evaluated.

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New Insights Into the Physical Nature of Coronal Mass Ejections and Associated Shock Waves Within the Framework of the Three-Dimensional Structure

Cited by 90 publications

References 48 publications

The density compression ratio of shock fronts associated with coronal mass ejections

The density compression ratio of shock fronts associated with coronal mass ejections

The Acceleration of High-energy Protons at Coronal Shocks: The Effect of Large-scale Streamer-like Magnetic Field Structures

The Solar Energetic Particle Event of 2010 August 14: Connectivity with the Solar Source Inferred from Multiple Spacecraft Observations and Modeling

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