Low‐latitude ionospheric electric and magnetic field disturbances in response to solar wind pressure enhancements

Abstract

[1] We study the characteristics of the low-latitude ionospheric electric field and geomagnetic field in response to a sudden enhancement of the solar wind pressure. When the magnetosphere is compressed by an interplanetary shock, a significant enhancement in the dayside equatorial ionospheric ion vertical velocity occurs over 30-40 min and is measured by the Jicamarca incoherent scatter radar. A similar enhancement occurs in the high-latitude ionospheric convection and is detected by the SuperDRAN HF radars. The simultaneous enhancements of the ionospheric ion velocity at high and low latitudes provide strong evidence of the occurrence of penetration electric fields produced by solar wind pressure enhancements. The geomagnetic field first increases rapidly over 2-3 min and then falls over 30-40 min to an asymptotic value. The enhanced magnetic field occurs from the subauroral region to the equator at all local times. The time scale of 30-40 min is much longer than the conventional preliminary and main impulses of geomagnetic response to interplanetary shocks. There are two possible mechanisms that may be responsible for the generation of the enhanced ionospheric electric and magnetic fields. One mechanism is that the solar wind shock causes an over-compression of the magnetosphere, and the other is that the field-aligned and ionospheric currents driven by the solar wind shock cause the enhancements of the ionospheric electric and magnetic fields. However, neither of the mechanisms appears to be able to provide a complete explanation of all observed features.Citation: Huang, C.-S., K. Yumoto, S. Abe, and G. Sofko (2008), Low-latitude ionospheric electric and magnetic field disturbances in response to solar wind pressure enhancements,

IMF-By dependence of transient ionospheric flow perturbation associated with sudden impulses: SuperDARN observations

“…Besides the geomagnetic field observations, the Super Dual Auroral Radar Network (SuperDARN) (Greenwald et al 1995) has played an important role in the measurement of the two-dimensional structure of ionospheric convection associated with SIs (Lyatsky et al 1999;Thorolfsson et al 2001;Vontrat-Reberac et al 2002;Coco et al 2008;Huang et al 2008;Kane and Makarevich 2010;Liu et al 2011;Gillies et al 2012;Hori et al 2012). A conclusion from these studies with the radar observations is that changes in flow direction and the polarity of flow shear are consistent with a PI-MI sequence on ground magnetograms described by the SC model proposed by Araki (1977Araki ( , 1994.…”

Studies of ionospheric F-region response in the Latin American sector during the geomagnetic storm of 21–22 January 2005

“…5, the dayside ionospheric electric field was eastward during 17:23-20:00 UT on 21 January and became westward during 20:00-24:00 UT. The eastward electric field was the penetration electric field driven by the large solar wind pressure (Huang et al, 2008) and caused enhanced equatorial fountain effect.…”

“…The eastward electrojet/electric field lasts until about 20:00 UT, covering most of the storm main phase. In addition as described by Huang et al (2008), solar wind pressure enhancements, without geomagnetic storms, can cause an eastward penetration electric field in the dayside equatorial ionosphere (see hpF2/hmF2 at JIC and MAN in Fig. 4).…”

Ionospheric current contribution to the main impulse of a negative sudden impulse

“…Over the past six decades, several studies have been dedicated to understanding the characteristics of SIs (Sugiura 1953;Nagata and Abe 1955;Matsushita 1962;Sano 1962;Tamao 1964;Nishida et al 1966;Rastogi and Sastri 1974;Araki et al 1985Araki et al , 2006Araki and Nagano 1988;Araki 1994;Sastri et al 1995;Yamada et al 1997;Takeuchi et al 2000Takeuchi et al , 2002aVillante and Di Giuseppe 2004;Huang et al 2008;Shinbori et al 2009;Wang et al 2009). Based on the magnetic field observations on ground, an equivalent ionospheric current system for the PI has been deduced (Araki et al 1985;Araki 1994), which is similar to the DP2 current system .…”