Dayside magnetopause reconnection and flux transfer events under radial interplanetary magnetic field (IMF): BepiColombo Earth-flyby observations

• Published in: Annales geophysicae (1988) 2022-04, Vol.40 (2), p.217-229
• Main Authors: Sun, Weijie, Slavin, James A., Nakamura, Rumi, Heyner, Daniel, Trattner, Karlheinz J., Mieth, Johannes Z. D., Zhao, Jiutong, Zong, Qiu-Gang, Aizawa, Sae, Andre, Nicolas, Saito, Yoshifumi
• Format: Article
• Language: English
• Subjects: Analysis; Bepi Colombo (ESA); Coalescence; Coalescing; Equator; Fluctuations; Flux transfer events; Flyby missions; Interplanetary magnetic field; Magnetic equator; Magnetic field; Magnetic fields; Magnetic flux; Magnetic reconnection; Magnetism; Magnetopause; Magnetopause reconnection; Magnetosheath; Magnetosphere; Ropes; Voyager 1 spacecraft
• ISSN: 1432-0576; 0992-7689; 1432-0576
• DOI: 10.5194/angeo-40-217-2022

This study analyzes the flux transfer event (FTE)-type flux ropes and magnetic reconnection around the dayside magnetopause during BepiColombo's Earth flyby. The magnetosheath has a high plasma β (∼ 8), and the interplanetary magnetic field (IMF) has a significant radial component. Six flux ropes are identified around the magnetopause. The motion of flux ropes together with the maximum magnetic shear model suggests that the reconnection X-line possibly swipes BepiColombo near the magnetic equator due to an increase in the radial component of the IMF. The flux rope with the highest flux content contains a clear coalescence signature, i.e., two smaller flux ropes merge, supporting theoretical predictions that the flux contents of flux ropes can grow through coalescence. The coalescence of the two FTE-type flux ropes takes place through secondary reconnection at the point of contact between the two flux ropes. The BepiColombo measurements indicate a large normalized guide field and a reconnection rate comparable to that measured at the magnetopause (∼ 0.1).