17:15 〜 18:45
[PEM10-P02] Disturbances of dayside current system near the magnetopause by foreshock or solar wind transients
キーワード：MI coupling, foreshock, current system, aurora
The magnetopause current system is susceptible to disruption caused by magnetic reconnection, compressions, or rarefactions from its upstream region, resulting in the transfer of energy and particles into the magnetosphere and ionosphere. Recent research has highlighted disturbances to this current system induced by large-scale transients in the pristine solar wind and localized structures in the foreshock or magnetosheath, commonly referred to as Magnetic Impulse Events (MIEs) or Traveling Convection Vortices (TCVs) as identified by ground magnetometer observations. However, the limited spatial resolution of ground magnetometers often fails to adequately capture the two dimensional structure of the disturbed current system.
In this study, we investigate the evolution of the system near the dayside magnetopause from a two-dimensional perspective and identify potential upstream sources of these disturbances based on coordinated observations between THEMIS probes and ground-based all-sky imagers at the South Pole during 2008 and 2009. Notably, our analysis reveals a distinctive type of auroral arc, evident in red-emission snapshots, which emerges at the equatorward boundary of the discrete auroral boundary and extends both equatorward and azimuthally, resembling a bifurcation of the auroral oval. A representative case from June 29, 2008, illustrates this phenomenon. We ascertain that this auroral arc is driven by magnetospheric compression induced by a foreshock cavity, rather than magnetic reconnection or field line resonance (FLR). Especially, it exhibits greater brightness and thickness compared to subsequent FLR-induced arcs. Ground-based magnetometer observations detected a TCV near its northern conjugate point, accompanied by an upward field-aligned current (FAC). In total, we identified 64 arcs of this type, with approximately 72% extending eastward, indicative of the generation of R1-sense FACs. Analysis of THEMIS probe data indicates that both solar wind and foreshock transients serve as sources for these auroral arcs, with 10 arcs exhibiting favorable conjunctions with THEMIS probes in the magnetosphere. Importantly, these 10 arcs were consistently associated with a total magnetic field strength increase of at least 1 nT, indicating a close association with TCVs induced by magnetospheric compressions. Furthermore, we observed that the extent of arc extension both equatorward and eastward correlated with the intensity of compressions in the magnetosphere.
In this study, we investigate the evolution of the system near the dayside magnetopause from a two-dimensional perspective and identify potential upstream sources of these disturbances based on coordinated observations between THEMIS probes and ground-based all-sky imagers at the South Pole during 2008 and 2009. Notably, our analysis reveals a distinctive type of auroral arc, evident in red-emission snapshots, which emerges at the equatorward boundary of the discrete auroral boundary and extends both equatorward and azimuthally, resembling a bifurcation of the auroral oval. A representative case from June 29, 2008, illustrates this phenomenon. We ascertain that this auroral arc is driven by magnetospheric compression induced by a foreshock cavity, rather than magnetic reconnection or field line resonance (FLR). Especially, it exhibits greater brightness and thickness compared to subsequent FLR-induced arcs. Ground-based magnetometer observations detected a TCV near its northern conjugate point, accompanied by an upward field-aligned current (FAC). In total, we identified 64 arcs of this type, with approximately 72% extending eastward, indicative of the generation of R1-sense FACs. Analysis of THEMIS probe data indicates that both solar wind and foreshock transients serve as sources for these auroral arcs, with 10 arcs exhibiting favorable conjunctions with THEMIS probes in the magnetosphere. Importantly, these 10 arcs were consistently associated with a total magnetic field strength increase of at least 1 nT, indicating a close association with TCVs induced by magnetospheric compressions. Furthermore, we observed that the extent of arc extension both equatorward and eastward correlated with the intensity of compressions in the magnetosphere.