Disturbed Zone and Piston Shock Ahead of Coronal Mass Ejection

Еселевич, В. Г.; Еселевич, М.

doi:10.1088/0004-637x/761/1/68

Cited by 21 publications

(14 citation statements)

References 19 publications

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“…Wood & Howard 2009;Ontiveros & Vourlidas 2009). Second, we notice that values derived in Paper 1 for the projected thicknesses (0.06 R ⊙ at 11:26 UT and 0.09 R ⊙ at 11:50 UT) of the shock shell at different altitudes/times are in good agreement with values given by Eselevich & Eselevich (2012, Figure 5, bottom panel) and identified as representative of the proton mean free paths in the corona below heliocentric distances of 6 R ⊙ . Third, these values for the thicknesses of the shock shell were used (after correction for the shock motion during the LASCO C2 exposure time) to estimate reliable values of the actual shock depth L along the LOS (0.28 R ⊙ at 11:26 UT and 0.61 R ⊙ at 11:50 UT), which is a critical parameter for the derivation of the compression ratios; this estimate was different to previous and successive works (e.g.…”

Section: Previous Results Of Shocks With Uv and Wl Datasupporting

confidence: 79%

Plasma Physical Parameters Along Coronal-Mass-Ejection-Driven Shocks. I. Ultraviolet and White-Light Observations

Бемпорад

Susino

Lapenta

2014

ApJ

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In this work UV and white light (WL) coronagraphic data are combined to derive the full set of plasma physical parameters along the front of a shock driven by a Coronal Mass Ejection. Pre-shock plasma density, shock compression ratio, speed and inclination angle are estimated from WL data, while pre-shock plasma temperature and outflow velocity are derived from UV data. The Rankine-Hugoniot (RH) equations for the general case of an oblique shock are then applied at three points along the front located between 2.2 − 2.6 R ⊙ at the shock nose and at the two flanks. Stronger field deflection (by ∼ 46 • ), plasma compression (factor ∼ 2.7) and heating (factor ∼ 12) occur at the nose, while heating at the flanks is more moderate (factor 1.5 − 3.0). Starting from a pre-shock corona where protons and electrons have about the same temperature (T p ∼ T e ∼ 1.5 · 10 6 K), temperature increases derived with RH equations could better represent the protons heating (by dissipation across the shock), while the temperature increase implied by adiabatic compression (factor ∼ 2 at the nose, ∼ 1.2 − 1.5 at the flanks) could be more representative of electrons heating: the transit of the shock causes a decoupling between electron and proton temperatures. Derived magnetic field vector rotations imply a draping of field lines around the expanding flux rope. The shock turns out to be super-critical (sub-critical) at the nose (at the flanks), where derived post-shock plasma parameters can be very well approximated with those derived by assuming a parallel (perpendicular) shock.

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Section: Previous Results Of Shocks With Uv and Wl Datasupporting

confidence: 79%

Plasma Physical Parameters Along Coronal-Mass-Ejection-Driven Shocks. I. Ultraviolet and White-Light Observations

Бемпорад

Susino

Lapenta

2014

ApJ

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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%

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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“…Moreover, combination of EUV and WL data shows that the shock thickness δ is of the same order as the proton mean free path λ p only for heliocentric distances r < 6 R while higher up in the corona δ << λ p . Hence, during its propagation, the shock regime changes from collisional to collisionless (Eselevich & Eselevich 2012). These information are crucial for our understanding of the physics at the base of the shock.…”

Section: Introductionmentioning

confidence: 99%

Physical Conditions of Coronal Plasma at the Transit of a Shock Driven by a Coronal Mass Ejection

Susino

Бемпорад

Mancuso

2015

ApJ

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We report here on the determination of plasma physical parameters across a shock driven by a Coronal Mass Ejection using White Light (WL) coronagraphic images and Radio Dynamic Spectra (RDS). The event analyzed here is the spectacular eruption that occurred on June 7th 2011, a fast CME followed by the ejection of columns of chromospheric plasma, part of them falling back to the solar surface, associated with a M2.5 flare and a type-II radio burst. Images acquired by the SOHO/LASCO coronagraphs (C2 and C3) were employed to track the CME-driven shock in the corona between 2-12 R in an angular interval of about 110 • . In these intervals we derived 2-Dimensional (2D) maps of electron density, shock velocity and shock compression ratio, and we measured the shock inclination angle with respect to the radial direction. Under plausible assumptions, these quantities were used to infer 2D maps of shock Mach number M A and strength of coronal magnetic fields at the shock's heights. We found that in the early phases (2-4 R ) the whole shock surface is super-Alfvénic, while later on (i.e. higher up) it becomes super-Alfvenic only at the nose. This is in agreement with the location for the source of the observed type-II burst, as inferred from RDS combined with the shock kinematic and coronal densities derived from WL. For the first time, a coronal shock is used to derive a 2D map of the coronal magnetic field strength over a 10 R altitude and ∼ 110 • latitude intervals.

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Disturbed Zone and Piston Shock Ahead of Coronal Mass Ejection

Cited by 21 publications

References 19 publications

Plasma Physical Parameters Along Coronal-Mass-Ejection-Driven Shocks. I. Ultraviolet and White-Light Observations

Plasma Physical Parameters Along Coronal-Mass-Ejection-Driven Shocks. I. Ultraviolet and White-Light Observations

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

Physical Conditions of Coronal Plasma at the Transit of a Shock Driven by a Coronal Mass Ejection

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