The formation heights of coronal shocks from 2D density and Alfvén speed maps

Zucca, Pietro; Carley, Eoin; Bloomfield, D. Shaun; Gallagher, Peter T.

doi:10.1051/0004-6361/201322650

Cited by 99 publications

(96 citation statements)

References 41 publications

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“…When applying the DEM method to calculate the electron density, the difficulty is how to estimate the effective LOS depth l. Zucca et al (2014a) proposed a method to estimate the effective LOS depth by assuming the EM per unit length along the LOS is the same. But actually, the EM is not uniform, especially in the situation where different structures exist along the LOS.…”

Section: Discussionmentioning

confidence: 99%

“…However, since the contribution per unit length drops significantly when moving away from the Sun, the effective depth that contributes most of the EM is limited. Zucca et al (2014a) gave a formula to estimate the effective LOS depth:…”

Section: Parameters Derived From the Dem Methodsmentioning

confidence: 99%

“…It was found that the temperature does not change obviously before and after the shock passes through the region, and a lower limit of X was obtained for the shock. Zucca et al (2014a) made a density map using extreme ultraviolet (EUV) data from the Atmospheric Imaging Assembly (AIA; Lemen et al 2012) on board the Solar Dynamics Observatory (SDO; Pesnell et al 2012) and polarized brightness data from Large Angle and Spectrometric Coronagraph (LASCO; Brueckner et al 1995) on board the Solar and Heliospheric Observatory (SOHO). Combining with the potential-field source-surface (PFSS) model, they also calculated the Alfvén speed map.…”

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: Discussionmentioning

confidence: 99%

Section: Parameters Derived From the Dem Methodsmentioning

confidence: 99%

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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“…This delay between the start time of the global wave and the associated type II burst is likely due to the time taken for the disturbance to either become superAlfvénic (as modelled by Vršnak and Lulić, 2000), or the time taken for the driver to reach regions of low ambient Alfvén speed in the corona (Mann et al, 2003;Zucca et al, 2014); in some cases this can take up to 30 minutes after detection of the wave. The duration of the radio bursts was also observed to be at most 35 minutes, with most radio bursts lasting less than 20 minutes, consistent with the lifetime of the observed waves.…”

Section: Relationship With Type II Radio Burstsmentioning

confidence: 99%

A Statistical Analysis of the Solar Phenomena Associated with Global EUV Waves

et al. 2017

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Solar eruptions are the most spectacular events in our solar system and are associated with many different signatures of energy release including solar flares, coronal mass ejections, global waves, radio emission and accelerated particles. Here, we apply the Coronal Pulse Identification and Tracking Algorithm (CorPITA) to the high-cadence synoptic data provided by the Solar Dynamics Observatory (SDO) to identify and track global waves observed by SDO. 164 of the 362 solar flare events studied (45%) were found to have associated global waves with no waves found for the remaining 198 (55%). A clear linear relationship was found between the median initial velocity and the acceleration of the waves, with faster waves exhibiting a stronger deceleration (consistent with previous results). No clear relationship was found between global waves and type II radio bursts, electrons or protons detected in situ near Earth. While no relationship was found between the wave properties and the associated flare size (with waves produced by flares from B to X-class), more than a quarter of the active regions studied were found to produce more than one wave event. These results suggest that the presence of a global wave in a solar eruption is most likely determined by the structure and connectivity of the erupting active region and the surrounding quiet solar corona rather than by the amount of free energy available within the active region.

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“…For off-limb locations, we follow the procedure of Zucca et al (2014), and calculate effective column lengths dependent on the radial distance of the points from Sun center. We have further improved the method by using pixel-specific values for the radial locations and the average coronal temperature from our DEM model results, rather than just a single value for the coronal temperature (as described in Zucca et al (2014)). Within the CASHeW framework, the DEM model can be run for every pixel in the field of view, as well as for individual groups of pixels specified by the user (Kozarev et al, 2015), or small groups of pixels (∼25) surrounding the time-dependent locations where PFSS field lines cross the CSGS surface (Kozarev & Schwadron, 2016).…”

Section: Density and Temperature Characterization Modulementioning

confidence: 99%

The Coronal Analysis of SHocks and Waves (CASHeW) framework

Kozarev

Davey

Kendrick

et al. 2017

J. Space Weather Space Clim.

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-Coronal bright fronts (CBF) are large-scale wavelike disturbances in the solar corona, related to solar eruptions. They are observed (mostly in extreme ultraviolet (EUV) light) as transient bright fronts of finite width, propagating away from the eruption source location. Recent studies of individual solar eruptive events have used EUVobservations of CBFs and metric radio type II burst observations to show the intimate connection between waves in the low corona and coronal mass ejection (CME)-driven shocks. EUV imaging with the atmospheric imaging assembly instrument on the solar dynamics observatory has proven particularly useful for detecting large-scale short-lived CBFs, which, combined with radio and in situ observations, holds great promise for early CME-driven shock characterization capability. This characterization can further be automated, and related to models of particle acceleration to produce estimates of particle fluxes in the corona and in the near Earth environment early in events. We present a framework for the coronal analysis of shocks and waves (CASHeW). It combines analysis of NASA Heliophysics System Observatory data products and relevant data-driven models, into an automated system for the characterization of off-limb coronal waves and shocks and the evaluation of their capability to accelerate solar energetic particles (SEPs). The system utilizes EUV observations and models written in the interactive data language. In addition, it leverages analysis tools from the SolarSoft package of libraries, as well as third party libraries. We have tested the CASHeW framework on a representative list of coronal bright front events. Here we present its features, as well as initial results. With this framework, we hope to contribute to the overall understanding of coronal shock waves, their importance for energetic particle acceleration, as well as to the better ability to forecast SEP events fluxes.

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The formation heights of coronal shocks from 2D density and Alfvén speed maps

Cited by 99 publications

References 41 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

A Statistical Analysis of the Solar Phenomena Associated with Global EUV Waves

The Coronal Analysis of SHocks and Waves (CASHeW) framework

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