First Determination of 2D Speed Distribution within the Bodies of Coronal Mass Ejections with Cross-correlation Analysis

Bao, Ying; Бемпорад, А.; Giordano, S.; Pagano, Paolo; Li, Feng; Lu, Lei; Li, Hui; Gan, Weiqun

doi:10.3847/1538-4357/ab2713

Cited by 19 publications

(25 citation statements)

References 54 publications

(82 reference statements)

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“…These constraints are more accurate when polarised light observations are also available Pagano et al 2015). In addition, it would be possible to constrain the temperature distribution using Lyman-α observations as outlined in Bemporad et al (2018) and the plane-of-the-sky velocity field Ying et al (2019). The present study does however, illustrate the power in using a coupled data-driven NLFFF and MHD approach to model eruptions on the Sun.…”

Section: Discussionmentioning

confidence: 90%

Determining the source and eruption dynamics of a stealth CME using NLFFF modelling and MHD simulations

Yardley

Pagano

Mackay

et al. 2021

A&A

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Context. Coronal mass ejections (CMEs) that exhibit weak or no eruption signatures in the low corona, known as stealth CMEs, are problematic as upon arrival at Earth they can lead to geomagnetic disturbances that were not predicted by space weather forecasters. Aims. We investigate the origin and eruption of a stealth event that occurred on 2015 January 3 that was responsible for a strong geomagnetic storm upon its arrival at Earth. Methods. To simulate the coronal magnetic field and plasma parameters of the eruption we use a coupled approach. This approach combines an evolutionary nonlinear force-free field model of the global corona with a MHD simulation. Results. The combined simulation approach accurately reproduces the stealth event and suggests that sympathetic eruptions occur. In the combined simulation we found that three flux ropes form and then erupt. The first two flux ropes, which are connected to a large AR complex behind the east limb, erupt first producing two near-simultaneous CMEs. These CMEs are closely followed by a third, weaker flux rope eruption in the simulation that originated between the periphery of AR 12252 and the southern polar coronal hole. The third eruption coincides with a faint coronal dimming, which appears in the SDO/AIA 211 Å observations, that is attributed as the source responsible for the stealth event and later the geomagnetic disturbance at 1 AU. The incorrect interpretation of the stealth event being linked to the occurrence of a single partial halo CME observed by LASCO/C2 is mainly due to the lack of STEREO observations being available at the time of the CMEs. The simulation also shows that the LASCO CME is not a single event but rather two near-simultaneous CMEs. Conclusions. These results show the significance of the coupled data-driven simulation approach in interpreting the eruption and that an operational L5 mission is crucial for space weather forecasting.

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Section: Discussionmentioning

confidence: 90%

Determining the source and eruption dynamics of a stealth CME using NLFFF modelling and MHD simulations

Yardley

Pagano

Mackay

et al. 2021

A&A

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“…Similar to Ying et al (2019), we applied these steps to the current and previous images to derive the backward radial velocity (v rB ), and to the current and next images to obtain the forward radial velocity (v rF ). Their average value was assigned as the final radial velocity of the pixel.…”

Section: Procedures: Cross-correlation Trackingmentioning

confidence: 99%

Radial velocity map of solar wind transients in the field of view of STEREO/HI1 on 3 and 4 April 2010

Li,

Wang,

Guo

et al. 2021

Preprint

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Context. The solar wind transients propagating out in the inner heliosphere can be observed in white-light images from Heliospheric Imager-1 (HI1), an instrument of the Sun Earth Connection Coronal and Heliospheric Investigation (SECCHI) on board the Solar Terrestrial Relations Observatory (STEREO), from two perspectives. The spatial velocity distribution inside solar wind transients is key to understanding their dynamic evolution processes.Aims. We generated a velocity map of transients in 3D space based on 2D white-light images and used it to estimate the expansion rate as well as some kinematic properties of solar wind transients.Methods. Based on the recently developed correlation-aided reconstruction (CORAR) method in our previous work, which can recognize and locate 3D solar wind transients from STEREO/HI1 image data, we further developped a new technique for deriving the spatial distribution of the radial velocities of the most pronounced features inside solar wind transients.Results. The technique was applied to events including a coronal mass ejection (CME) and three small-scale transients, so-called blobs, observed by HI1 on 3-4 April 2010 to reconstruct their radial velocity maps. The results match the forward-modeling results, simulations, and in situ observations at 1 AU fairly well. According to the obtained spatial distributions of height and radial velocity of the CME, we analyzed the self-similarity of the radial expansion of the CME ejecta. The dimensionless radial expansion rate of the northern and middle parts of the CME

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“…These techniques will likely provide the first ever 2D maps of plasma temperatures inside CMEs in the intermediate corona, and were also strengthened by the improved methods developed by Bemporad & Pagano (2015) and Pagano et al (2015a) to derive the column density of the CME plasma from polarised VL observations. Moreover, because of the Doppler dimming (Noci et al 1987), the UV Lyman-α emission by coronal atoms also depends on their radial outflow speed, and thus the derivation of temperatures in CMEs also requires the technique recently developed by Ying et al (2019) to reconstruct the 2D distribution of plasma speed in the CME bodies from a sequence of VL images.…”

Section: Introductionmentioning

confidence: 99%

Hydrogen non-equilibrium ionisation effects in coronal mass ejections

Pagano

Бемпорад

Mackay

2020

A&A

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Context.A new generation of coronagraphs to study the solar wind and Coronal Mass Ejections (CMEs) are being developed and launched. These coronagraphs will heavily rely on multi-channel observations where visible light (VL) and UV-EUV observations provide new plasma diagnostics. One of these instruments, Metis on board ESA-Solar Orbiter, will simultaneously observe VL and the UV Lyman-α line. The number of neutral Hydrogen atoms (a small fraction of coronal protons) is a key parameter for deriving plasma properties such as temperature from the observed Lyman-α line intensity. However, these measurements are significantly affected if non-equilibrium ionisation effects occur, which can be relevant during CMEs. Aims. The aim of this work is to determine if non-equilibrium ionisation effects are relevant in CMEs and in particular when and in which regions of the CME plasma ionisation equilibrium can be assumed for data analysis. Methods. We use a magneto-hydrodynamic simulation of a magnetic flux rope ejection to generate a CME. From this we then reconstruct the ionisation state of Hydrogen atoms in the CME by evaluating both the advection of neutral and ionised Hydrogen atoms and the ionisation and recombination rates in the MHD simulation. Results. We find that the equilibrium ionisation assumption holds mostly in the core of the CME, which is represented by a magnetic flux rope. In contrast non-equilibrium ionisation effects are significant at the CME front, where we find about 100 times more neutral Hydrogen atoms than prescribed by ionisation equilibrium conditions, even if this neutral Hydrogen excess might be difficult to identify due to projection effects. Conclusions. This work provides key information for the development of a new generation of diagnostic techniques that aim at combining visible light and Lyman-α line emissions. The results show that non-ionisation equilibrium effects need to be considered when we analyse CME fronts. To incorrectly assume equilibrium ionisation in these regions would lead to a systematic underestimate of plasma temperatures.

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First Determination of 2D Speed Distribution within the Bodies of Coronal Mass Ejections with Cross-correlation Analysis

Cited by 19 publications

References 54 publications

Determining the source and eruption dynamics of a stealth CME using NLFFF modelling and MHD simulations

Determining the source and eruption dynamics of a stealth CME using NLFFF modelling and MHD simulations

Radial velocity map of solar wind transients in the field of view of STEREO/HI1 on 3 and 4 April 2010

Hydrogen non-equilibrium ionisation effects in coronal mass ejections

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