Propagation Characteristics of the April 21, 2023 CME

Abstract

Accurate estimation of propagation characteristics of coronal mass ejections (CMEs) is crucial for predicting their geoeffectiveness. Stereoscopic techniques to study the kinematics of CMEs generally have been carried out using remote sensing observations from three viewpoints, i.e. STEREO-A, STEREO-B, and SOHO. Since the loss of STEREO-B in 2014, stereoscopic reconstruction of CMEs has been restricted to the observations from only two viewpoints, i.e., STEREO-A and SOHO. When the angle of separation between STEREO-A and SOHO is small, it leads to larger uncertainties in the CME kinematics derived using stereoscopic techniques. In this paper, we demonstrate how this limitation can be addressed and how uncertainties in the estimation of CME kinematics and propagation direction can be reduced. For this purpose, we selected the CME of April 21, 2023, which was observed by two spacecraft, i.e. STEREO-A and SOHO, separated by a small 10 degree angle. Using the Graduated Cylindrical Shell (GCS) model on the remote-sensing observations near the Sun and the Advanced Drag-Based Model (ADBM) in the heliosphere, we estimated the arrival time of the CME at different locations in the heliosphere and compared it with the actual arrival time obtained from the in-situ measurements taken by three spacecraft, BepiColombo, STEREO-A and Wind. Our analysis reveals a directional uncertainty of approx 20 degree from observations from two viewpoints. These uncertainties significantly affect the arrival-time prediction of the CME. We consider the actual chronology of CME arrival times at STEREO-A and Wind as critical parameters to constrain the direction of propagation, which serves as a key input in the ADBM. The chronology of arrival of the CME ejecta at STEREO-A, which is 4.5 hrs earlier than at Wind, proved essential for resolving directional ambiguities in the GCS reconstruction model

Figures (6)

• Figure 1: The relative orientation and location of different spacecraft, i.e., STEREO-A (red), BepiColombo (orange), and Earth/Wind (green) on 23 April 2023. The angular separation between Wind and STEREO-A is nearly -10°, and between Wind and BepiColombo is nearly +22°. The image was generated by the online tool of Stereo Science Center .
• Figure 2: GCS reconstruction of the 21 April 2023 CME using observations from two viewpoints of STEREO-A/HI1 and SOHO LASCO-C3. The top panel shows the CME overplotted with GCS reconstructed mesh. The bottom panel shows a CME without GCS mesh at 21 April 2023 22:30 UT.
• Figure 3: In-situ observations by the STEREO-A spacecraft from 23 to 26 April 2023 showing, from top to bottom: the IMF vectors, solar wind flow speed, proton density, and proton temperature in RTN coordinate. The first vertical dashed black line marks the arrival of the CME-driven shock, while the second and third lines indicate the start and end times of the associated magnetic cloud, respectively.
• Figure 4: In-situ parameters at L1 observed by the Wind spacecraft from 23 to 26 April 2023. IMF vectors, total magnetic field, plasma flow speed and temperature are plotted with time from top to bottom, respectively in GSE coordinate. The first vertical black line marks the arrival of the shock of the CME, and the second and third dashed lines represent the start and end of the magnetic cloud, respectively.
• Figure 5: Scatter plot of ToA of MC versus heliocentric distances(AU) of different spacecraft, i.e, BepiColombo, STEREO-A, and Wind, respectively. The blue star represents the observed ToA of the MC at each spacecraft. The red crosses represent the ToA of MC estimated considering the case of eastward propagation where the final longitude reaches -10$^\circ$. The yellow crosses represent the case where the CME is considered to propagate along the Sun-Earth line. The green crosses are the ToA estimated by considering the westward propagation of the CME.