Timeliness of the ISSI meetings

Swings of a millisecond pulsar between regimes powered by accretion and by the rotation of their magnetic field were sought for during the last three decades, and were finally first observed in 2013 (Papitto et al. 2013, Nature, 501, 517). Soon afterwards, state transitions were caught from two more systems, showing how they might be much more common than expected. The close multi-wavelength coverage of these events already unveiled a complex phenomenology, and we are now in the position of exploiting it in order to test theoretical predictions and simulations of the disk-field interaction. At the same time, the discussions between observers and theoreticians during the meetings will devise new observing strategies to identify other similar systems, and to observe them in the best conditions to constrain models. This is fundamental considering that the X-ray observatories involved in similar studies (XMM-Newton, Chandra, Swift, INTEGRAL) are in the last years of their operations and no replacement is planned for the recent future. Optimal observational strategies are then crucial to obtain data of unprecedented quality which would be used for the decade to come as a benchmark of theories and models of disk accretion onto magnetized fast rotators