IMF By dependence of ionospheric currents and particle precipitation during non-zero dipole tilt

Auroral currents are important manifestations of solar wind-magnetosphere interaction, which is strongly controlled by the direction of the interplanetary magnetic field (IMF). While the dawn-dusk (By) component of the IMF is known to play an important role in this interaction, its effects on geomagnetic activity are usually assumed to be independent of its sign. However, several recent studies have shown evidence that especially the westward auroral electrojet is significantly stronger for By > 0 (By < 0) in Northern Hemisphere winter (summer). The physical mechanism of the By effect is still not fully understood, but significant progress has been achieved in recent years. Here we review how IMF By modulates auroral electrojets, field-aligned currents and ionospheric particle precipitation. These results are based on various datasets, including geomagnetic indices, AMPERE, POES and DMSP satellites. Our results highlight the importance of the IMF By component for space weather and must be taken into account in the future space weather modeling.