Yet there are longstanding major unsolved questions. These observations and simulations have yielded an increasingly improved knowledge of fundamental physics and have delivered a remarkable understanding of the solar wind and its complexity. In situ measurements of the solar wind have been available for almost 60 years, and in that time plasma physics simulation capabilities have commenced and ground‐based solar observations have expanded into space‐based solar observations. In this scenario, magnetic reconnection is continuous and the wind is driven by both the resulting plasma pressure and the radial Alfvénic flow bursts. Important characteristics of interchange reconnection in the low corona are inferred from the data, including that the reconnection is collisionless and that the energy release rate is sufficient to power the fast wind. Computer simulations of interchange reconnection support key features of the observations, including the ion spectra. We show that the supergranulation structure at the coronal base remains imprinted in the near-Sun solar wind, resulting in asymmetric patches of magnetic ‘switchbacks’ 7,8 and bursty wind streams with power-law-like energetic ion spectra to beyond 100 keV. Here we report measurements of fast solar wind streams from the Parker Solar Probe (PSP) spacecraft 6 that provide strong evidence for the interchange reconnection mechanism. The energy density in these ‘network’ magnetic field bundles is a candidate energy source for the wind. The coronal magnetic field near the solar surface is structured on scales associated with ‘supergranulation’ convection cells, whereby descending flows create intense fields. ![]() The energy source responsible for accelerating the plasma is widely debated however, there is evidence that it is ultimately magnetic in nature, with candidate mechanisms including wave heating 1,2 and interchange reconnection 3–5. more » « lessĪbstract The fast solar wind that fills the heliosphere originates from deep within regions of open magnetic field on the Sun called ‘coronal holes’. ![]() The careful determination of heavy ion and elemental composition of several particle populations, matched at the Sun and in the heliosphere, will permit for a comprehensive examination of fractionation processes, wave-particle interactions, coronal heating, and solar wind release and energization that are key to understanding how the Sun forms and influences the heliosphere. The paper recommends complementary heavy ion measurements that can be traced from the Sun to the heliosphere to properly connect and study these regions to address these topics. ![]() 3) Determining the principal mechanisms driving solar wind evolution from the Sun by identifying the importance and interplay of reconnection, waves, and/or turbulence in driving the extended acceleration and heating of solar wind and transient plasma. 2) Disentangling the solar wind birthplace and drivers of release by determining the relative contributions of active regions (ARs), quiet Sun, and coronal hole plasma to the solar wind. ![]() The key objectives include, 1) understanding the Sun’s chemical composition by identifying specific mechanisms driving elemental variation in the corona. This paper outlines key scientific topics that are important for the development of solar system physics and how observations of heavy ion composition can address them.
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