Explicit IMF $B_y$-effect maximizes at subauroral latitudes (Dedicated to the memory of Eigil Friis-Christensen). (arXiv:1904.04568v1 [physics.space-ph])
<a href="http://arxiv.org/find/physics/1/au:+Holappa_L/0/1/0/all/0/1">Lauri Holappa</a>, <a href="http://arxiv.org/find/physics/1/au:+Gopalswamy_N/0/1/0/all/0/1">Nat Gopalswamy</a>, <a href="http://arxiv.org/find/physics/1/au:+Mursula_K/0/1/0/all/0/1">Kalevi Mursula</a>
The most important parameter in the coupling between solar wind and
geomagnetic activity is the $B_z$-component of the interplanetary magnetic
field (IMF). However, recent studies have shown that IMF $B_y$ is an
additional, independent driver of geomagnetic activity. We use here local
geomagnetic indices from a large network of magnetic stations to study how IMF
$B_y$ affects geomagnetic activity at different latitudes for all solar wind
and, separately during coronal mass ejections (CMEs). We show that geomagnetic
activity, for all solar wind, is 20% stronger for $B_y>0$ than for $B_y<0$ at
subauroral latitudes of about $60^{circ}$ corrected geomagnetic (CGM)
latitude. During CMEs, the $B_y$-effect is larger, about 40%, at slightly lower
latitudes of about $57^{circ}$ (CGM) latitude. These results highlight the
importance of the IMF $B_y$-component for space weather at different latitudes
and must be taken into account in space weather modeling.
The most important parameter in the coupling between solar wind and
geomagnetic activity is the $B_z$-component of the interplanetary magnetic
field (IMF). However, recent studies have shown that IMF $B_y$ is an
additional, independent driver of geomagnetic activity. We use here local
geomagnetic indices from a large network of magnetic stations to study how IMF
$B_y$ affects geomagnetic activity at different latitudes for all solar wind
and, separately during coronal mass ejections (CMEs). We show that geomagnetic
activity, for all solar wind, is 20% stronger for $B_y>0$ than for $B_y<0$ at
subauroral latitudes of about $60^{circ}$ corrected geomagnetic (CGM)
latitude. During CMEs, the $B_y$-effect is larger, about 40%, at slightly lower
latitudes of about $57^{circ}$ (CGM) latitude. These results highlight the
importance of the IMF $B_y$-component for space weather at different latitudes
and must be taken into account in space weather modeling.
http://arxiv.org/icons/sfx.gif
