Stereoscopic Observation of Recurrent Streamer Waves Driven by Successive Slow Coronal Mass Ejections

Abstract

We report the stereoscopic observations of two recurrent streamer waves in a single streamer structure, utilizing coordinated observations from the SOHO, STEREO, and SDO missions. Contrary to the long-held view that fast coronal mass ejections (CMEs) are necessary drivers, we demonstrate that these recurrent waves were excited by two consecutive slow CMEs (<500 km/s} accompanied by only modest flare activity. Three-dimensional reconstruction reveals that the first and second waves propagated with significant decelerations of - 7.93 and - 10.26 m s^-2, respectively. Their average amplitudes were 0.41 and 0.77 solar radii, wavelengths were 4.02 and 6.17, and periods were 2.66 and 2.53 hours, respectively. While the amplitude of the first wave declined with heliocentric distance (consistent with conventional energy convection), the second wave exhibited an intriguing increasing trend in amplitude. Both waves showed a linear increase in wavelength and period with distance, indicating a non-stationary and dispersive medium. Crucially, despite the disparity in driver energy and wave scales, the periods and their change rates remained nearly identical for both events. This provides compelling case-specific evidence that the streamer wave period is primarily determined by the inherent eigenmodes of the streamer plasma slab rather than the specific characteristics of the trigger. We conclude that the generation of observable streamer waves is a combined consequence of the streamer's structural stability and the energy transfer efficiency of the triggering disturbance.

Figures (13)

• Figure 1: The positions of STEREO Ahead and STEREO Behind spacecraft relative to Sun (red) and the orbit of Earth (blue) in the x-y plane of the Heliocentric Earth Ecliptic coordinate system. The green arrow points to the eruption direction of the filaments. The positions and orbits of Venus and Mercury are also plotted. The dotted lines show the angular displacement from the Sun. Units are in astronomical units (au).
• Figure 2: The eruption of the two adjacent filaments. Panels (a) and (e) display STA 304 Å images, while (b) and (f) show STA 195 Å running difference images. Similarly, AIA 304 Å images are presented in (c) and (g), and AIA 193 Å running difference images in (d) and (h). White arrows in panels (a) and (c) indicate the eruption of the first filament, while those in panels (e) and (g) highlight the second filament eruption. Yellow dashed curves in panels (b) and (h) delineate the bright EUV waves associated with these two filament eruptions. The FOV for each panel is 800" × 1130". An accompanying animation (animation1.mp4) is available in the online journal.
• Figure 3: Composite coronagraph images depict the streamer and its associated CMEs. The left and right columns display data from STEREO and SOHO-SDO, respectively. Specifically, for STEREO (SOHO-SDO) composite images, the inner, middle, and outer regions are observed by the STA 195 Å (AIA 193 Å), COR1 (C2), and COR2 (C3) instruments, respectively. Panels (a) and (b) present direct images, with two white arrows indicating the bright streamer structure. Panels (c)--(f) are running difference images. The two CMEs are designated as "CME1" and "CME2", and arrows in the bottom row indicate the wave crest and trough. Green dashed lines indicate the paths used for constructing time-distance diagrams, as illustrated in Figure \ref{['fig4']}. The approximate position angles of these green dashed lines are 285°, 105°, 277°, and 100° for panels (c)--(f), respectively. Each panel has a FOV of ${30}\,R_\odot$ . An accompanying animation (animation2.mp4) for this figure is available in the online journal.
• Figure 4: Time-distance diagrams show the kinematics of the two successive CMEs. Panels (a) and (b) present composite time-distance diagrams, constructed from measurements along the dashed green lines indicated in Figure \ref{['fig3']} (d) and (f). Within these diagrams, the orange and green sections are derived from C2 and C3 running difference images, respectively. Panels (c) and (d) display time-distance diagrams generated from COR2 running difference images, with measurements taken along the green lines depicted in Figure \ref{['fig3']} (c) and (e), respectively. In each panel, the red dashed curve represents a second-order polynomial fit to the trajectory of the prominent emission front, while the yellow dotted curve shows the corresponding GOES soft X-ray 1 -- 8 Å flux. The corresponding derived decelerations and speeds for the two CMEs are also overlaid in each panel.
• Figure 5: Running difference coronagraph images displaying the first streamer wave. The left column contains COR2 running difference images, while the middle and right columns present C2 and C3 running difference images, respectively. In each panel, the inner white circle indicates the solar surface, and the shaded plate represents the occulting disk of the coronagraph. The wave crest and trough are indicated by arrows, the associated dimming regions are labeled Dim.", and the CME is labeled CME1". The FOVs of the three columns are , respectively.