The Substorm Current Wedge at Earth and Mercury
Location
Yosemite National Park
Start Date
2-13-2014 9:40 AM
End Date
2-13-2014 9:55 AM
Description
Magnetospheric substorms occur within the magnetospheres of both Earth and Mercury in response to unsteady energy transfer from the solar wind. Substorms at Mercury occur on a much more rapid timescale and with higher relative amplitudes, but phenomenologically, the characteristic features of substorms at both planets are quite similar. An important element of substorms at Earth is the Substorm Current Wedge (SCW). The SCW is created by the braking, pile-up, and diversion of high speed plasma flows that propagate earthward from the reconnection site. The SCW consists of a set of field-aligned and ionospheric closure currents that serves to separate the near-Earth dipolarization and increased pressure gradient from the surrounding plasma, while also communicating the new plasma convection pattern to the ionosphere. Because of its importance in terrestrial substorms researchers have questioned whether a SCW exists at Mercury. Recent MESSENGER observations of dipolarizations during Hermean substorms that are phenomenologically similar to terrestrial dipolarizations has led to renewed interest in the SCW at Mercury, especially considering that Mercury has a low conductivity regolith and does not contain an ionosphere. In this paper, we review observations of substorms and dipolarizations at both Mercury and Earth, and discuss how the different magnetospheres can lead to greater understanding of substorm dynamics.
The Substorm Current Wedge at Earth and Mercury
Yosemite National Park
Magnetospheric substorms occur within the magnetospheres of both Earth and Mercury in response to unsteady energy transfer from the solar wind. Substorms at Mercury occur on a much more rapid timescale and with higher relative amplitudes, but phenomenologically, the characteristic features of substorms at both planets are quite similar. An important element of substorms at Earth is the Substorm Current Wedge (SCW). The SCW is created by the braking, pile-up, and diversion of high speed plasma flows that propagate earthward from the reconnection site. The SCW consists of a set of field-aligned and ionospheric closure currents that serves to separate the near-Earth dipolarization and increased pressure gradient from the surrounding plasma, while also communicating the new plasma convection pattern to the ionosphere. Because of its importance in terrestrial substorms researchers have questioned whether a SCW exists at Mercury. Recent MESSENGER observations of dipolarizations during Hermean substorms that are phenomenologically similar to terrestrial dipolarizations has led to renewed interest in the SCW at Mercury, especially considering that Mercury has a low conductivity regolith and does not contain an ionosphere. In this paper, we review observations of substorms and dipolarizations at both Mercury and Earth, and discuss how the different magnetospheres can lead to greater understanding of substorm dynamics.