The Dynamic Coupling of Streamers and Pseudostreamers to the Heliosphere

Abstract

The slow solar wind is generally believed to result from the interaction of open and closed coronal magnetic flux at streamers and pseudostreamers. We use three-dimensional magnetohydrodynamic simulations to determine the detailed structure and dynamics of open-closed interactions that are driven by photospheric convective flows. The photospheric magnetic field model includes a global dipole giving rise to a streamer together with a large parasitic polarity region giving rise to a pseudostreamer that separates a satellite coronal hole from the main polar hole. Our numerical domain extends out to 30R ⊙ and includes an isothermal solar wind, so that the coupling between the corona and heliosphere can be calculated rigorously. This system is driven by imposing a large set of quasi-random surface flows that capture the driving of coronal flux in the vicinity of streamer and pseudostreamer boundaries by the supergranular motions. We describe the resulting structures and dynamics. Interchange reconnection dominates the evolution at both streamer and pseudostreamer boundaries, but the details of the resulting structures are clearly different from one another. Additionally, we calculate in situ signatures of the reconnection and determine the dynamic mapping from the inner heliosphere back to the Sun for a test spacecraft orbit. We discuss the implications of our results for interpreting observations from inner heliospheric missions, such as Parker Solar Probe and Solar Orbiter, and for space weather modeling of the slow solar wind.

The S-Web Origin of Composition Enhancement in the Slow-to-moderate Speed Solar Wind

“…Since there has been recent progress integrating aspects of heavy ion composition forward modeling into steady-state MHD solar wind calculations (e.g., Oran et al 2015;Shen et al 2017;Lionello et al 2019;Szente et al 2022), it would be extremely interesting to perform these calculations on dynamic, time-dependent MHD modeling of the formation and evolution of coherent magnetic structures generated under different reconnection scenarios. For example, the Aslanyan et al (2022) calculation of the synthetic suprathermal electron PAD "time series" associated with PS interchange reconnection outflows shows excellent qualitative agreement with the observed broadening of the strahl for some of our PS intervals (#4, #6, and #7 in particular). Lynch et al (2014) showed the largest (i.e., low-frequency) δB/〈B〉 signatures resulting from PS reconnection had characteristic length scales of 100-350 Mm (0.14-0.50 R e ) in the corona, which reflected the spatial scale of their PS flux system of origin, and Higginson & Lynch (2018) demonstrated that the MHDsimulation-derived, synthetic in situ magnetic field signatures of a similarly sized, nonlinear torsional Alfvén wave could resemble the coherent magnetic structure of small-scale magnetic flux ropes/streamer blob plasmoids typically associated with HS slow wind in the vicinity of the HCS/HPS.…”

“…With the inclusion of the magnetic field and suprathermal electron PAD, the intervals corresponding to sector boundaries and heliospheric current sheet/plasma sheet (HCS/HPS) crossings are immediately apparent as #8 and #3, both shaded light yellow.Another particularly noteworthy feature of Figure3is that each of the remaining slow-to-moderate speed intervals are coincident with broader suprathermal electron PADs and/or elevated charge states in carbon, oxygen, and iron. While recent analyses byBorovsky (2020Borovsky ( , 2021 have shown that changes in the suprathermal electron strahl intensities often occur with simultaneous changes in other plasma and/or composition properties, here we note that the broader PADs of intervals #7, #6, and #4 exhibit remarkable, qualitative agreement with the synthetic PAD distribution constructed byAslanyan et al (2022) from their MHD simulation of…”

“…In general, energizing surface flows (e.g., translation or rotational shearing flows, flux emergence, and/or flux cancellation/tether cutting) will build up volumetric currents, stress magnetic null points, and develop strong current sheets at topological boundaries, thereby creating favorable conditions for magnetic reconnection (e.g., Antiochos et al 2012;Rappazzo et al 2012;Burkholder et al 2019;Mason et al 2021). Lynch & Edmondson (2013) showed that 2.5D PS interchange reconnection (in the form of pre-eruption breakout reconnection) could result in bursty, quasi-steady signatures in density along the external spine and coronal dimming signatures near the stressed null point and current sheet (see also Kumar et al 2021), while recent simulations from Aslanyan et al (2021Aslanyan et al ( , 2022 have illustrated that the complex 3D interchange reconnection dynamics seen by Higginson et al (2017aHigginson et al ( , 2017b can also be produced at the open-closed boundaries of PS flux systems.…”

“…Figure 1(b) presents simulation results from Higginson & Lynch (2018), who showed that the continual formation of flux rope/plasmoid structures essentially filled the entire HCS. Figure 1(c) shows the simulation results by Aslanyan et al (2022) in which they examined interchange reconnection occurring in a 3D PS configuration and developed a synthetic suprathermal electron pitch-angle proxy based on the simulation's instantaneous magnetic connectivity.…”