North-south asymmetry of the location of the heliospheric currentsheet revisited

摘要

1 The possible latitudinal offset of the location of the heliospheric current sheet (HCS)is an important question, since it has impact on the understanding of various phenomenaincluding the solar dynamo and the modulation of cosmic rays. In the declining phaseof the previous, 22nd solar cycle, in 1993, a southward displacement of the HCS by 10°was proposed to explain the north-south asymmetry of energetic charged-particlefluxes measured by Ulysses. Other observations supported the north-south asymmetryas well, and it is now widely accepted by the scientific community that in 1993, the HCSwas displaced 10° southward. However, in reality, the Ulysses magnetic fieldmeasurements did not give direct evidence for such a large displacement of the HCS. Herewe revisit the question and extend our previous study for the declining phase of solar cycle23 as well. Careful analysis of the HCS crossings observed by Ulysses during the fastlatitude scans shows that a southward displacement of the HCS by 2°-3° is possible andconsistent with the data for cycles 22 and 23. The impact of the HCS location on thelatitudinal gradients of energetic particle fluxes is discussed.