Multiple magnetic flux ropes within reconnection exhausts close to the centers of heliospheric current sheets near the Sun

¹ Department of Astronomy and Space Science, Chungbuk National University, Chungbuk 28644, Korea
² Space Sciences Laboratory, University of California, Berkeley, CA, USA
³ ISR-1: Space Science and Applications, Los Alamos National Laboratory; New Mexico Consortium, Los Alamos, NM, USA

^★ Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Received: 31 January 2026
Accepted: 28 March 2026

Abstract

Context. Magnetic flux ropes are frequently observed in association with magnetic reconnection in space plasmas, yet their formation, evolution, and observational visibility are not fully understood, particularly with respect to the near-Sun heliosphere.

Aims. We investigate the properties and origin of magnetic flux ropes embedded within reconnection exhausts during heliospheric current sheet (HCS) crossings close to the Sun. We assess the conditions under which such structures are most readily identifiable in in situ measurements.

Methods. We analyzed high-resolution magnetic field and plasma observations from Parker Solar Probe (PSP) during two consecutive HCS crossings, separated by ∼10.5 hours, at a heliocentric distance of ∼12 R_⊙. Flux ropes were identified, with particular attention paid to intervals when PSP traversed the HCS central regions.

Results. For each crossing, we identified a series of flux ropes embedded within reconnection exhausts. Their passage durations are below 20 seconds, corresponding to spatial scales of a few thousands kilometers. This result is still greater by three orders of magnitude than the ion inertial length. This identification was possible particularly during intervals when PSP was closest to the central region of HCS. These flux ropes can be distinguished from the background exhausts by enhancements in magnetic field strength, which are shown to be particularly significant in the guide field component. In addition, they travel at speeds that diverge slightly (typically by < 10 km/s) from the speeds of the surrounding outflows, along with the possibility of increased density and reduced temperatures.

Conclusions. We attributed the origin of magnetic flux ropes to a secondary reconnection within the exhausts and subsequent merging of smaller flux ropes into larger structures, consistent with predictions by various simulations. We stress that such flux ropes are most readily identifiable at the HCS center, where the background magnetic field is weakest, so that the relative enhancement in flux rope field becomes most prominent. This observational advantage is particularly notable closer to the Sun, where the high ambient magnetic field strength can otherwise obscure such structures, unless the spacecraft trajectory remains within the HCS central region for a sufficient duration.