Dayside reconnection enhancement resulting from a solar wind dynamic pressure increase

Abstract

It is well known that the Interplanetary Magnetic Field (IMF) is the major contributor to geomagnetic activity on Earth. Recent studies, however, have shown that solar wind dynamic pressure variations also cause global effects when they encounter the terrestrial magnetosphere. In particular, it has been shown that solar wind dynamic pressure enhancements significantly increase particle precipitation and cause global intensification of the aurora. Further studies using Defense Meteorological Satellite Program (DMSP) measurements have demonstrated that solar wind pressure increases also significantly affect the size of the polar cap and the cross‐polar cap potential drop. This implies that the dynamic pressure has an important effect on the coupling efficiency between the solar wind and the Earth’s magnetosphere, which is in addition to that due to the IMF. It was previously suggested, on the basis of the DMSP data, that solar wind dynamic pressure enhancements induce enhanced magnetotail reconnection and magnetospheric convection. We now present Super Dual Auroral Radar Network (SuperDARN) observations for a number of events that demonstrate significantly enhanced ionospheric convection in the dayside ionosphere associated with the impact of solar wind pressure fronts. The enhanced convection extends to the vicinity of the expected location of the dayside separatrix, suggesting that the solar wind dynamic pressure strongly affects dayside reconnection as well as polar‐cap convection.

Repetitive occurrence of explosive events at a coronal hole boundary

“…These oscillations periodically separate and bring together the closed and open field lines on the two sides of the coronal hole boundary. This picture is somewhat similar to what is seen in the magnetosphere: a sudden increase in the solar wind pressure during southward interplanetary magnetic field orientation leads to enhanced magnetic reconnection on the dayside magnetopause (Boudouridis et al 2005). Hence, the proposed mechanism explains the repetitive nature of the observed EEs, however, other possibilities should not be excluded.…”

The effects of an interplanetary shock on the high-latitude ionospheric convection during an IMF <I>B<sub>y</sub></I>-dominated period

“…In particular, Bosqued et al (2005) reported about CLUSTER observations of transient reconnection signatures in the Cusp region, which are often one to one correlated with repeated pressure variations, during a strongly B y dominated period. Further to that, Boudouridis et al (2007) clearly showed that, for B z <0, the pressure variations are often directly related to variations of the dayside reconnection rate. Finally, we recall that Laitinen et al (2007) suggest that higher values of solar wind dynamic pressure yield increased reconnection rates at the magnetopause for B z <0 and that the dominant parameter to account for such increased rates is solar wind velocity rather than density.…”

Transpolar voltage and polar cap flux during the substorm cycle and steady convection events

“…[e.g., Boudouridis et al, 2007]. For a linear system the factor a would be independent of the state of the magnetosphere (and hence the substorm phase); however we note that the theories of voltage saturation predict that a falls with increasing F O [Siscoe et al, 2004] and hence increasing F PC .…”