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The Magnetospheric Multiscale (MMS) mission has probed Earth's magnetosphere, magnetosheath, and near‐Earth solar wind for over 8 years. We utilize an unsupervised learning algorithm, Gaussian mixture model clustering, along with feature generation and simple post‐cleaning methods to automatically classify 8 years of MMS dayside observations into four plasma regions (magnetosphere, magnetosheath, solar wind, and ion foreshock) at 1‐min resolution. With these plasma regions distinguished, we have also identified boundary surfaces (e.g., magnetopause, bow shock). We validate our results on manually generated and rule based region labels described in the literature. We report overlap rates in our cluster determined magnetopauses and bow shocks against Scientist‐in‐the Loop (SITL) identified transitions and published databases. Our features are general and our model is extensible, potentially making it applicable to observational data from multiple other missions. Key Points: We use an extensible unsupervised Gaussian mixture model (GMM) algorithm to automatically classify 8 years of dayside magnetospheric multiscale (MMS) plasma dataOur model distinguishes between solar wind, ion foreshock, magnetosheath, and magnetosphere with 97.8% accuracy compared to manual labelsWe provide classified labels and transitions at 1‐min resolution and stable region specific lists for all 8 years of dayside MMS data [ABSTRACT FROM AUTHOR]

The occurrence and impacts of magnetopause processes at outer planets, particularly magnetic reconnection and the Kelvin‐Helmholtz instability (KHI), remains unresolved. From a list of 2,114 magnetopause crossings at Saturn spanning the full duration of the Cassini mission, magnetic field and low‐energy plasma properties are analyzed for each crossing to determine the likelihood of particular dynamical processes at Saturn's magnetopause. Using Cassini magnetic field data, crossings are categorized as (a) those with signatures of possible magnetic reconnection, (b) those near/inside a magnetopause surface wave or vortex arising from KHI, and (c) those during quiescent conditions (i.e., lacking signatures indicative of magnetic reconnection or KH waves). Of magnetopause crossings with valid intervals on both sides of the boundary, nearly half of the crossings met criteria for signatures of reconnection, with little dependence on local time or latitude of the magnetopause crossing location. Crossings identified as associated with KHI are found to more likely occur toward the dawn sector as compared to other local times, but with both flanks likely being quasi‐unstable to the instability. Magnetopause properties for crossings with available low‐energy electron data from Cassini are further explored to provide insight into the local plasma conditions that may be conducive to magnetic reconnection and/or KH waves. This investigation reveals that certain dynamics along the magnetopause of Saturn may be more prevalent than previously considered, and provides a basis for a more comprehensive understanding of magnetopause dynamics and plasma transport at the outer planets. Key Points: We analyze Cassini data encompassing 2,114 magnetopause crossings to determine the occurrence of dynamical processes at Saturn's magnetopauseThe occurrence of reconnection is prevalent at Saturn's magnetopause and is independent of Saturn local time and latitudeObservationally, we find more Kelvin‐Helmholtz signatures at dawn, but both dawn and dusk can be conducive to Kelvin‐Helmholtz instability [ABSTRACT FROM AUTHOR]

The Whole Heliosphere and Planetary Interactions initiative was established to leverage relatively quiet intervals during solar minimum to better understand the interconnectedness of the various domains in the heliosphere. This study provides an expansive mosaic of observations spanning from the Sun, through interplanetary space, to the magnetospheric response and subsequent effects on the ionosphere‐thermosphere‐mesosphere (ITM) system. To accomplish this, a diverse set of observational datasets are utilized from 2019 July 26 to October 16 (i.e., over three Carrington rotations, CR2220, CR2221, and CR2222) with connections of these observations to the more focused studies submitted to this special issue. Particularly, this study focuses on two long‐lived coronal holes and their varying impact in sculpting the heliosphere and driving of the magnetospheric system. As a result, the evolution of coronal holes, impacts on the inner heliosphere solar wind, glimpses at mesoscale solar wind variability, magnetospheric response to these evolving solar wind drivers, and resulting ITM phenomena are captured to reveal the interconnectedness of this system‐of‐systems. Plain Language Summary: The field of Heliophysics research spans a large range of plasma regimes and disciplines that are all linked through the complex interactions each system has with one another. To better explore the interconnected nature of the heliosphere, this study combines observations from across the sub‐domains of Heliophysics to construct snapshots of the Sun, solar wind, and the magnetospheric and ionospheric systems at Earth over three revolutions of the Sun. This allows for a unique vantage point to put these systems in perspective of one another and understand how they impact one another. Key Points: The evolution and impacts of two coronal holes are investigated over three Carrington rotationsThe evolution of the coronal hole led to changes in the solar wind throughout the inner solar systemSubsequent geospace response differed with each passage due to both changes in the solar wind and preconditioning within the systems [ABSTRACT FROM AUTHOR]