Traversi, R.
Becagli, S.
Poluianov, S.
Severi, M.
Solanki, S. K.
Usoskin, I. G.
Udisti, R.
Article History
Received: 7 October 2015
Accepted: 23 December 2015
First Online: 28 January 2016
Competing interests
: The authors declare no competing financial interests.