Can MHD Oscillations Modulate Quasi-Periodic Plasma Release from Coronal Streamers?

Abstract

Periodic density structures in the slow solar wind are associated with quasi-periodic plasma release from coronal streamer and open-closed boundary regions, but the origin of their organization remains uncertain. We distinguish the process that releases plasma from the process that sets or modifies its cadence. In the proposed source-modulator framework, S-Web, interchange, cusp, or current-sheet reconnection releases the plasma, while structured MHD responses may modulate density or release rate. An observation-informed parameter-space analysis gives compact slow-mode periods of about 22-231 min; reproducing 80-130 min requires an effective path length of 0.35-1.20 solar radii. In a classical top-hat cylinder with L/a = 5-50 and rho_i/rho_e = 1.6-2.5, the fundamental fast sausage mode is not trapped and the minimum trapped harmonic is approximately n = 4-50. A transverse fast-timescale benchmark based on a = 0.10-0.45 solar radii and outer-coronal fast speeds of 250-530 km/s gives 5.7-55 min. A corresponding fast-interface proxy gives 4.4-93 min, but is not a current-sheet eigenmode solution. Kink responses are constrained empirically rather than by inserting observer-frame propagation speeds into a standing-mode formula: one COR1 event showed an approximately 25 min pulse, whereas a LASCO/COR2 survey found global streamer-wave periods of 2-8 hr, observer-frame speeds of 360-740 km/s, and typically only one or two visible cycles. Among the candidates considered here, compact slow modes are the best-constrained stable compressive modulators; confirming their role requires constraints on longitudinal reflection and damping. Surface/current-sheet responses remain high-priority coupling candidates but require a sheet-specific dispersion relation; kink responses are transient geometric candidates; and tearing/plasmoid formation remains a strong intrinsic reconnection-driven alternative.