Observation of the aurorae and SAR arc due to the effect of a solar wind density impulse on the magnetosphere
Abstract
A close connection of geomagnetic and auroral activity with the southward IMF Bz and solar wind (SW) speed is well-known. Recently Boudouridis et al. (2005, 2008) have shown that the increase of dynamic pressure owing to a fast growth of SW density at southward Bz immediately strengthens the convection electric field in the magnetosphere. In this work we analyze the manifestations of impulse increase of SW density during southward IMF in the dynamics of SAR arc and aurorae in 557.7 and 630.0 nm emissions according to the photometric observations at the Yakutsk meridian (130ºE) for the isolated event of December 28, 2010. After a fast southward turn of IMF Bz a slow depression of the Earth’s magnetic field at low latitudes takes place. From 12 UT (~ 21 MLT) the growth of magnetospheric convection is observed in the equatorward extension of diffuse aurora (DA) at the Yakutsk meridian. An impulse of SW high density up to ~70 sm-3 with a duration of ~10 minutes is observed in the sudden impulse (SI) at low latitudes at 1340 UT and causes: 1) the impulse intensification of the westward electrojet at auroral latitudes at midnight sector of MLT with a duration of SI and also the increase of ASY-H index up to ~100 nT; 2) the sharp brightening of auroral arc and DA at lower latitudes; 3) the appearance of intense SAR arc in the equatorial region of DA and its southward movement with velocity of ~70 m/s till 1630 UT. Subsequent sudden changes of the SW density are well manifested in the brightening of auroral arc, DA and SAR arc during ~4 hours of observations. Magnetic and auroral activities promptly damp after the sharp northward turn of IMF Bz. We assume that the observed dynamics of aurorae and SAR arc in this event is caused by the fast intensification of convection and asymmetric ring current in the magnetosphere as consequences of the impulse increase of SW density during southward IMF.
- Publication:
-
40th COSPAR Scientific Assembly
- Pub Date:
- 2014
- Bibcode:
- 2014cosp...40E1262I