CME Expansion as the Driver of Metric Type II Shock Emission as Revealed by Self-consistent Analysis of High-Cadence EUV Images and Radio Spectrograms

Kouloumvakos, A.; Patsourakos, S.; Hillaris, A.; Vourlidas, A.; Preka‐Papadema, P.; Moussas, X.; Caroubalos, C.; Tsitsipis, P.; Kontogeorgos, A.

doi:10.1007/s11207-013-0460-z

Cited by 35 publications

(39 citation statements)

References 49 publications

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“…The distance between the IL and the OL becomes larger with propagation, implying that the OL moves faster than the IL. These characteristics have been observed in other CME-driven shocks (Ontiveros & Vourlidas 2009;Chen 2011;Gopalswamy et al 2012;Eselevich & Eselevich 2012;Kouloumvakos et al 2014;Lee et al 2014), suggesting that the OL may be the front of a CME-driven shock. The double layers appear at 03:45 UT in 193Å and 211Å, and then propagate outward.…”

Section: Observationssupporting

confidence: 65%

“…Generally, type II radio bursts are believed to originate from the shock front, but it is difficult to determine the exact position along the shock front. Kouloumvakos et al (2014) calculated the compression ratio of the shock, and found that the type II radio burst can originate from the whole sheath region between the CME leading edge (LE) and the shock front. However, most authors considered that the source region of the type II radio burst is at a small region of the shock front (Bain et al 2012;Zimovets et al 2012;Carley et al 2013;Zucca et al 2014b;.…”

Section: Introductionmentioning

confidence: 99%

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Investigating the Conditions of the Formation of a Type Ii Radio Burst on 2014 January 8

Cheng

Ding

et al. 2016

ApJ

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It is believed that type II radio bursts are generated by shock waves. In order to understand the generation conditions of type II radio bursts, in this paper, we analyze the physical parameters of a shock front. The type II radio burst we selected was observed by Siberian Solar Radio Telescope (SSRT) and Learmonth radio station and was associated with a limb CME occurring on 2014 January 8 observed by the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO). The evolution of the CME in the inner corona presents a doublelayered structure that propagates outward. We fit the outer layer of the structure with a partial circle and divide it into 7 directions from -45• to 45• with an angular separation of 15• . We measure the outer layer speed along the 7 directions, and find that the speed in the direction of -15• with respect to the central direction is the fastest. We use the differential emission measure (DEM) method to calculate the physical parameters at the outer layer at the moment when the type II radio burst was initiated, including the temperature (T ), emission measure (EM ), temperature ratio (T d /T u ), compression ratio (X), and Alfvén Mach number (M A ). We compare the quantities X and M A to that obtained from band-splitting in the radio spectrum, and find that this type II radio burst is generated at a small region of the outer layer that is located at the sector in 45• direction. The results suggest that the generation of type II radio bursts (shock) requires larger values of X and M A rather than simply a higher speed of the disturbance.

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Section: Observationssupporting

confidence: 65%

Section: Introductionmentioning

confidence: 99%

Investigating the Conditions of the Formation of a Type Ii Radio Burst on 2014 January 8

Cheng

Ding

et al. 2016

ApJ

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“…They found that the type II burst kinematics were consistent with the wave and that the wave itself was consistent with a weak shock (Kozarev et al, 2011;Ma et al, 2011). The compression ratios derived from the band-split of the type II burst and from the EUV imaging data are actually consistent ( ≈ 1.5) and decline during the wave's propagation (Kouloumvakos et al, 2014). These results point to a freely propagating, shock-like disturbance.…”

Section: Metric Type II Radio Burstsmentioning

confidence: 91%

Large-scale Globally Propagating Coronal Waves

Warmuth

2015

Living Rev. Sol. Phys.

163

140

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Large-scale, globally propagating wave-like disturbances have been observed in the solar chromosphere and by inference in the corona since the 1960s. However, detailed analysis of these phenomena has only been conducted since the late 1990s. This was prompted by the availability of high-cadence coronal imaging data from numerous spaced-based instruments, which routinely show spectacular globally propagating bright fronts. Coronal waves, as these perturbations are usually referred to, have now been observed in a wide range of spectral channels, yielding a wealth of information. Many findings have supported the "classical" interpretation of the disturbances: fast-mode MHD waves or shocks that are propagating in the solar corona. However, observations that seemed inconsistent with this picture have stimulated the development of alternative models in which "pseudo waves" are generated by magnetic reconfiguration in the framework of an expanding coronal mass ejection. This has resulted in a vigorous debate on the physical nature of these disturbances. This review focuses on demonstrating how the numerous observational findings of the last one and a half decades can be used to constrain our models of large-scale coronal waves, and how a coherent physical understanding of these disturbances is finally emerging. Article RevisionsLiving Reviews supports two ways of keeping its articles up-to-date:Fast-track revision. A fast-track revision provides the author with the opportunity to add short notices of current research results, trends and developments, or important publications to the article. A fast-track revision is refereed by the responsible subject editor. If an article has undergone a fast-track revision, a summary of changes will be listed here.Major update. A major update will include substantial changes and additions and is subject to full external refereeing. It is published with a new publication number.For detailed documentation of an article's evolution, please refer to the history document of the article's online version at http://dx

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“…Several attempts have been made in the past literature to determine the density ratios X from white light (Ontiveros and Vourlidas, 2009;Mancuso, 2010, 2011) and EUV (Kozarev et al, 2011;Kouloumvakos et al, 2014;Long et al, 2015), and radio observations (Ma et al, 2011). Ontiveros and Vourlidas (2009) determined X, ranging between 1.2 and 2.8 for 11 CMEs that were faster than 1500 km s À1 observed by LASCO C2 coronagraph.…”

Section: Density Compression Ratiomentioning

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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-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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CME Expansion as the Driver of Metric Type II Shock Emission as Revealed by Self-consistent Analysis of High-Cadence EUV Images and Radio Spectrograms

Cited by 35 publications

References 49 publications

Investigating the Conditions of the Formation of a Type Ii Radio Burst on 2014 January 8

Investigating the Conditions of the Formation of a Type Ii Radio Burst on 2014 January 8

Large-scale Globally Propagating Coronal Waves

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

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