The Beam Plasma Interactions Experiment: An Active Experiment Using Pulsed Electron Beams
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79 ASTRONOMY AND ASTROPHYSICS↗
Engineering topics
Spanswick, Emma
Publications and source records attributed to Spanswick, Emma.
Linking Space-Borne and Ground-Based Observations Observed Around Substorm Onset to Magnetospheric Processes
The combined THEMIS five spacecraft in-situ and ground magnetic and camera arrays have advanced considerably our understanding of the causal relationship between midtail plasma flows, transient ionospheric features, and ground magnetic signatures. In particular, recent work has shown a connection between equatorward moving visible ionospheric transients and substorm onset, in both 6300 nm and white-light emissions. Although both observations detail pre-onset auroral features the interpretations differ substantially. We first provide a brief summary of these observations, highlighting in particular areas where the two observations differ, and suggest reasons for the differences. We then detail how these observations relate to dynamical magnetospheric processes, and show how they constrain models of transient convection. Next, we pull together observations and models of Pi2 generation, substorm current wedge (SCW) initiation and dipolarization to present a self-consistent description of the dynamical processes and communicative pathways that occur just prior to and during substorm expansion onset. Finally, we present a summary of open questions and suggest a roadmap for future work.
Kepko, Larry↗
The Relationship of Magnetotail Flow Bursts and Ground Onset Signatures
It has been known for decades that auroral substorm onset occurs on (or at least near) the most equatorward auroral arc, which is thought to map to the near geosynchronous region. The lack of auroral signatures poleward of this arc prior to onset has been a major criticism of flow-burst driven models of substorm onset. The combined THEMIS 5 spacecraft in-situ and ground array measurements provide an unprecedented opportunity to examine the causal relationship between midtail plasma flows, aurora, and ground magnetic signatures. I first present an event from 2008 using multi-spectral all sky imager data from Gillam and in-situ data from THEMIS. The multispectral data indicate an equatorward moving auroral form prior to substorm onset. When this forms reaches the most equatorward arc, the arc brightens and an auroral substorm begins. The THEMIS data show fast Earthward flows prior to onset as well. I discuss further the association of flow bursts and Pi2 pulsations, in the con text of the directly-driven Pi2 model. This model directly links flows and Pi2 pulsations, providing an important constraint on substorm onset theories.
Kepko, Larry↗