Origin and Ion Charge State Evolution of Solar Wind Transients during 4 -- 7 August 2011

Abstract

We present study of the complex event consisting of several solar wind transients detected by Advanced Composition Explorer (ACE) on 4 -- 7 August 2011, that caused a geomagnetic storm with Dst$=-$110 nT. The supposed coronal sources -- three flares and coronal mass ejections (CMEs) occurred on 2 -- 4 August 2011 in the active region (AR) 11261. To investigate the solar origin and formation of these transients we studied kinematic and thermodynamic properties of the expanding coronal structures using the Solar Dynamics Observatory/Atmospheric Imaging Assembly (SDO/AIA) EUV images and the differential emission measure (DEM) diagnostics. The Helioseismic and Magnetic Imager (HMI) magnetic field maps were used as the input data for the 3D magnetohydrodynamic (MHD) model to describe the flux rope ejection. We characterize the early phase of the flux rope ejection in the corona, where the usual three-component CME structure formed. The flux rope ejected with a speed of about 200~km~s${}^{-1}$ to the height of 0.25~R${}_{\odot }$. The kinematics of the modeled CME front agrees well with the Solar Terrestrial Relations Observatory (STEREO) EUV measurements. Using the results of the plasma diagnostics and MHD modeling, we calculated the ion charge ratios of carbon and oxygen as well as the mean charge state of iron ions of the 2 August 2011 CME, taking into account the processes of heating, cooling, expansion, ionization, and recombination of the moving plasma in the corona up to the frozen-in region. We estimated a probable heating rate of the CME plasma in the low corona by matching the calculated ion composition parameters of the CME with those measured in situ for the solar wind transients. We also consider the similarities and discrepancies between the results of the MHD simulation and the observations.

Title and abstract changed, figure 4c modified, figures' and tables' captions changed, Equations 5-7 modified, proofread was made, text revised (p.2,3,4,5,7,8,24,26). The final publication is available at Springer

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Cited by in corpus (11)

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• Simulating the Coronal Evolution of Bipolar Active Regions to Investigate the Formation of Flux Ropes
• Determining the source and eruption dynamics of a stealth CME using NLFFF modelling and MHD simulations
• A Prospective New Diagnostic Technique for Distinguishing Eruptive and Non-Eruptive Active Regions
• Hydrogen Non-Equilibrium Ionisation Effects in Coronal Mass Ejections
• A New Space Weather Tool for Identifying Eruptive Active Regions
• Tracking Filament Evolution in the Low Solar Corona using Remote-Sensing and In-situ Observations
• Understanding the Origins of Problem Geomagnetic Storms Associated With "Stealth" Coronal Mass Ejections
• Formation of Coronal Mass Ejection and Post-eruption Flow of Solar Wind on 2010 August 18 event