FG: Multiscale Dayside Transients and their Effect on Earth’s Magnetosphere

Dates: 2025 – 2029
Leaders: Savvas Raptis, Ivan Vasko, Yuxi Chen, Gonzalo Cucho-Padin, Imogen Gingell, Terry Z. Liu, Ying Zou, Runyi Liu, David Tonoian
Research Areas: Primary – SWMI

Topic

A variety of transient phenomena occurs within Earth’s dayside plasma environment, spanning a wide range of spatial and temporal scales. These include localized shock processes both upstream at the foreshock and downstream at the magnetosheath, such as Hot Flow Anomalies (HFAs), Spontaneous Hot Flow Anomalies (SHFAs), Foreshock Bubbles (FBs), High-Speed Jets (HSJs), and non-linearly evolved Ultra Low Frequency (ULF) waves (e.g., shocklets and SLAMS). Collectively referred to as shock-generated transients, these processes may be either intrinsic or driven by variable upstream solar wind conditions. While large-scale solar transients are established drivers of geomagnetic storms, mesoscale shock-generated transients play a critical role in solar wind-magnetosphere-ionosphere coupling, contributing to significant magnetopause deformation, the generation of field-aligned currents (FACs), and auroral activity. Furthermore, dayside processes include phenomena such as magnetopause reconnection, driven by strong magnetic field shear, and the Kelvin-Helmholtz Instability (KHI), triggered by velocity shear in plasma flows that can be initiated or influenced by interactions between shock-generated transients and the magnetopause. Kinetic processes occurring at ion and electron scales within the foreshock, bow shock, and magnetosheath can evolve into larger structures or interact with existing transients. SLAMS evolve from ULF waves, while the Kelvin-Helmholtz Instability—an MHD-scale convective instability—cascades down to kinetic scales, involving secondary processes such as reconnection and plasma turbulence. Disentangling these complex, multiscale processes is crucial for assessing their contributions to energy transfer across the magnetosphere, which, in turn, impacts space weather dynamics.

Our proposed Focus Group (FG) will investigate the multiscale nature of these transients, their variability in response to solar transients, and their overall effects on the magnetosphere-ionosphere system. Key questions include:

How do transients affect magnetopause reconnection in terms of onset and rate? What is the interplay between KHI, shock localized processes and magnetic reconnection?

How do CMEs and HSSs interact with Earth’s bow shock and influence the generation and evolution of shock-generated transients? How do they modify plasma transport across the magnetopause through magnetopause reconnection and KH instability?

How do shock-generated transients affect the magnetosphere, such as the magnetopause, ULF waves, particle precipitation, aurora, and geomagnetic field perturbation? How do these effects compare to those of solar transients, both individually and cumulatively?

What role do shock-generated transients play in wave transmission, particle energization, and turbulence generation between the magnetosheath and magnetosphere?

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