Conjugate observations of traveling convection vortices associated with transient events at the magnetopause

Abstract

Traveling convection vortices (TCVs) are generally produced by field-aligned currents (FACs) at high latitudes associated with transient changes of the magnetopause. This paper presents multipoint conjugate observations of transient events at the magnetopause measured in space and on the ground. The transient events showing radial fluctuation of the magnetopause in association with sudden increases in solar wind dynamic pressure were detected by both the Time History of Events and Macroscale Interactions during Substorms and the Geostationary Operational Environmental Satellite spacecraft. Geomagnetic signatures seen as TCVs in response to the transient events were observed by the ground magnetometer array in Greenland and Canada and their conjugate locations in Antarctica including recently developed Antarctic magnetometers, mostly located along the 40 • magnetic meridian. This new conjugate network provides a unique opportunity to observe geomagnetic field signatures over a relatively large region in both hemispheres. This study focuses mainly on the spatial and temporal features of the TCVs in the conjugate hemispheres in relation to the transient events at the magnetopause. The TCV events are characterized by their single or twin vortex, of which the centers are located approximately at 72 • -76 • magnetic latitude, propagating either dawnward or duskward away from local noon. While interhemispheric conjugacy is expected with an assumption that TCV signatures are created by FACs directed in both hemispheres, our observations suggest that there might be more complex mechanisms contributing the asymmetrical features, perhaps due to field line mapping and/or conductivity differences.

Modeling Study of the Geospace System Response to the Solar Wind Dynamic Pressure Enhancement on 17 March 2015

“…These perturbation FACs were superimposed on the preexisting NBZ current system due to the northward IMF B Z . The vertical ion convection patterns that formed in association with these perturbation FACs have similar physical properties to those of the TCVs (Clauer et al, ; Engebretson et al, ; Friis‐Christensen et al, ; Glassmeier & Heppner, ; Hönisch & Glassmeier, ; Kim et al, ; Lanzerotti et al, ; Zesta et al, ). They formed on the dayside, near 70° latitude, and propagated toward the nightside.…”

“…The TCVs are pairs of twin vortices that form on the dayside and propagate toward the nightside, together with the PI and MI FAC profiles, as shown in Yu and Ridley (), Fujita, Tanaka, Kikuchi, Fujimoto, and Itonaga (), and Ozturk et al (). Some theoretical and observational studies have also found the links between the TCVs to the twin magnetospheric vortices in the equatorial plane (Glassmeier & Heppner, ; Glassmeier, Hönisch, & Untiedt, ; Keiling et al, ; Kim et al, ; Slinker, Fedder, Hughes, et al, ).…”

Conjugate observations of electromagnetic ion cyclotron waves associated with traveling convection vortex events

“…The companion paper by Kim et al [] reported that the TCV centers during Event 1 and Event 2 were 73.5° MLAT and 72.0° MLAT, respectively, and the latitude of the transient compression events observed by THEMIS coincided approximately with that of the TCV center. These locations are similar to the estimated wave source locations based on the ground data.…”

“…Spacecraft positions in the GSE X ‐ Y plane during Events 1 and 2 are illustrated in Figure [cf. Kim et al , , Figures 6c and 6f], in which the three THEMIS spacecraft were fortuitously located near the magnetopause. The bow shock locations are obtained using the static model by Fairfield [].…”

Space Weather Quarterly Volume 14, Issue 4, 2017

“…g. Global and regional maps and parameterizations of geomagnetic disturbances (and time derivatives) that drive ground-induced currents (e.g., Carter et al, 2016;Woodroffe et al, 2016). h. Interhemispheric comparisons of regional ULF wave activity (e.g., Kim et al, 2013Kim et al, , 2015Zesta et al, 2016), electrojet currents, and cusp and substorm phenomena, in order to understand the way energy from the solar wind is transmitted asymmetrically to Earth's high-latitude regions.…”