Probing the CME Core--Prominence Relation Using Inner Coronal Observations

TL;DR

This study tests whether CME cores in prominence-associated events are realmente prominence material by combining inner-corona white-light (K-Cor), H$$ (GONG), and 304 Å (AIA) observations with outer-corona LASCO/C2 data. The authors analyze 38 limb CMEs, of which 39 show prominence signatures in the inner corona, and identify 15 Category-A events whose three-part structure persists into LASCO/C2, demonstrating a strong (average $r\approx$0.70) correspondence between CME cores and H$$ prominences, with weaker correlations to 304 Å ($r\approx$0.40). They trace core evolution beyond the inner FOV, showing continuity up to $\sim$6 $R_$ and quantify backtracking uncertainties when relying solely on outer-corona data (average $\Delta\theta\approx 17.5^\u00b0$, average $\Delta T\approx 49$ min; maxima up to $40^$ and $138$ min). The results support the prominence-origin interpretation for the CME core in prominence-associated events and highlight the necessity of inner-coronal observations for accurate CME source associations and kinematic inferences, with implications for space-weather forecasting.

Abstract

Coronal mass ejections (CMEs) often exhibit a three-part structure consisting of a bright inner core, an outer leading edge, and an intervening dark cavity. While the core has traditionally been attributed to prominence material, an alternative interpretation suggests it may arise from the projection effects of a twisted flux rope. We focused on limb CME events to reassess the connection between CME cores and their associated prominences in the inner corona. The CME cores were analyzed using white-light observations from the Mauna Loa Solar Observatory (MLSO) K-Coronagraph (K-Cor), while the corresponding prominence eruptions were examined using H$α$ data from the Global Oscillation Network Group (GONG) and 304 Å images from the Atmospheric Imaging Assembly (AIA). Our results show a strong spatial correspondence between H$α$ prominences and CME cores in white light, with an average image correlation of $\sim$0.7, while correlations between white light and AIA 304 Å are comparatively weaker ($\sim$0.5). Several events could be continuously traced into the Large Angle and Spectrometric Coronagraph Experiment (LASCO/C2) field of view, confirming the persistence of prominence material into the outer corona. We find back-extrapolating LASCO/C2 CME cores under constant-velocity, linear-trajectory assumptions can introduce large errors -- up to 40$^\circ$ in inferred position angle and $\sim$140 minutes in eruption time relative to their true values -- underscoring the importance of inner-coronal observations for accurately constraining CME dynamics. Overall, our findings suggest that in prominence-associated CMEs, the bright cores are predominantly composed of prominence material.

Figures (10)

• Figure 1: Comparison of the structural evolution of CME cores in K-Cor white-light images with their associated prominences in GONG H$\alpha$ and AIA 304 Å is presented for Category-A CMEs, which preserve their three-part structure into the LASCO/C2 FOV. Panel (a) corresponds to the event on 2015 July 02, while panel (b) shows the event on 2015 September 23. For each event, images from all instruments at four selected time steps are presented to illustrate the evolution of the eruption. Red contours, outlining features from H$\alpha$ observations, are projected onto both K-Cor and AIA 304 Å images to assess morphological correspondence. Blue contours, extracted from K-Cor structures, are overlaid on the AIA 304 Å images to facilitate further structural comparison. Yellow boxes in the images indicate ROIs selected for detailed analysis and are shown only for timestamps in which the prominence is the most prominent in H$\alpha$. A gray area with a solid white outline denotes the solar disk and the limb, respectively. A dashed white arc in all images marks 1.05 $R_\odot$, the inner edge of the K-Cor FOV. In the first K-Cor frame of panel (a), a white dot-dashed curve indicates the inner boundary of the CME leading edge. The arrows mark regions where a feature seen in white-light and 304 Å is absent in H$\alpha$, which is discussed in detail in Section \ref{['sec:res1']}. An animation of this figure is available https://drive.google.com/file/d/1b9A55YyB5nHH3rBnGO941-MuenO235IP/view?usp=sharing.
• Figure 2: Same as Figure \ref{['2july15sept']}, with panels (a) and (b) showing structural analysis of two consecutive Category-A CME events on 2022 October 26. An animation of this figure is available https://drive.google.com/file/d/1jlqaYhYeLJS4_LzJnHbHs66Zd2eaVkQi/view?usp=sharing.
• Figure 3: Structural comparison of Category-B CMEs that fail to maintain their three-part structure into the LASCO/C2 FOV is shown at a single representative time step for four distinct events, dated 2015 February 4, 2022 July 10, 2016 February 9, and 2015 April 25, in panels (a)–(d), respectively. The representation of the observational images follows the same format as in Figure \ref{['2july15sept']}. An animation of this figure is available https://drive.google.com/file/d/1chP144_UOntUvH3w-zt0g2CbDGqRxQ_H/view?usp=sharing.
• Figure 4: Cutout images of the yellow-box ROIs from GONG H$\alpha$, K-Cor, and AIA 304 Å observations, as shown in Figures \ref{['2july15sept']}, \ref{['26oct']}, and \ref{['4x4prominence']}. Panels (a)–(d) represent four Category-A CME events, and panels (e)–(h) represent four Category-B CME events. These zoomed-in views highlight the fine-scale structural correspondence between prominence and CME core features across different wavelengths. In each panel, the first image corresponds to GONG H$\alpha$, the second to the K-Cor and the third to the AIA 304 Å. Red contours, extracted from H$\alpha$ images, are overlaid on the 304 Å and K-Cor images. Blue arrows indicate corresponding discernible features observed across images from different instruments.
• Figure 5: Quantitative comparison of CME core and prominence intensities using a combination of scatter plot and density distribution for three pairwise combinations: K-Cor vs. GONG H$\alpha$, K-Cor vs. AIA 304 Å, and H$\alpha$ vs. AIA 304 Å. Intensities (pixel values) from all three observations are shown in arbitrary units. The intensity comparisons are restricted to the ROIs shown in Figure \ref{['subimage']}. The darker shade of black indicates a higher density of occurrence, whereas the lighter gray represents a low density distribution. For each of the eight events (four Category-A and four Category-B CMEs), the Pearson correlation coefficient ($r$) is calculated from the corresponding ROIs, with the values displayed in the bottom-right corner of each plot.