Regular Article

Magnetic field sector structure and origins of solar wind streams in 2012

¹ Skobeltsyn Institute of Nuclear Physics, Lomonosov Moscow State University, Moscow 119991, Russia
² Lebedev Physical Institute, Russian Academy of Sciences, Moscow 119991, Russia
³ Space Research Institute (IKI), Russian Academy of Sciences, Moscow 117997, Russia

^* Corresponding author: jshugai@srd.sinp.msu.ru

Received: 4 December 2013
Accepted: 26 June 2014

Abstract

The origins of the solar wind and the interplanetary magnetic field sector structure in the beginning of the magnetic polarity reversal of 24th solar cycle were investigated using the Wilcox Solar Observatory magnetic field measurements and their products as well as the solar wind data from ACE and the SDO/AIA EUV images. The dominance of the quadrupole harmonics in the solar magnetic field in this period resulted in a four-sector structure of the interplanetary magnetic field. The dominating source of recurrent high-speed solar wind stream was a large trans-equatorial coronal hole of negative polarity evolving in the course of the polarity reversal process. The contribution of ICMEs to the high-speed solar wind did not exceed 17% of the total flux. The solar wind density flux averaged over the year amounted to 1 × 10⁸ cm⁻² s⁻¹ which is considerably lower than the typical long-term value (2–4 × 10⁸ cm⁻² s⁻¹). The slow-speed component of solar wind density flux constituted in average more than 68% of the total flux, the high-speed component was about 10%, reaching the maximum of 32% in some Carrington rotations.