Formation of a Magnetic Cloud from the Merging of Two Successive Coronal Mass Ejections
The Astrophysical Journal Letters(2024)
Abstract
On 2022 March 28 two successive coronal mass ejections (CMEs) were observed
by multiple spacecraft and resulted in a magnetic cloud (MC) at 1 AU. We
investigate the propagation and interaction properties of the two CMEs
correlated with the MC using coordinated multi-point remote sensing and in situ
observations from Solar Orbiter, STEREO A, SOHO, and Wind. The first CME was
triggered by a filament eruption with a high inclination angle. Roughly 9 hr
later, the second CME originating from the same active region erupted with a
smaller tilt angle and faster speed compared to the first one. The second CME
overtook the preceding CME and formed a merged front at approximately 75
, which developed into a complex ejecta at 1 AU. The descending speed
and low proton temperature inside the complex ejecta suggest that the two CMEs
have fully merged before reaching 1 AU, leading them to begin expanding rather
than compressing against each other. The complex ejecta appears to have the
magnetic field and plasma signatures of an MC, although there is a
discontinuity in the magnetic field implying previous interactions. The cross
section of the complex ejecta, reconstructed from in situ data using a
Grad-Shafranov technique, exhibits a right–handed flux rope structure. These
results highlight that an MC–like complex ejecta lacking interaction features
could arise from the complete merging of two CMEs.
MoreTranslated text
Key words
Solar coronal mass ejections,Solar-terrestrial interactions,Solar wind
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