Comparison of the properties of leading and trailing sunspots

Abstract

The magnetic properties of leading and trailing sunspots were compared based on SDO/HMI and SDO/AIA data with a high spatial resolution for the growth phase and maximum of cycle 24. The properties of the solar atmosphere above sunspots are also discussed independently for both of these sunspot types. It was shown that the contrast in the He II 304 (C ₃₀₄) line above the umbra of leading and single sunspots is on average smaller than such a contrast above the umbra of trailing sunspots and on average weakly depends on the umbra area for both C ₃₀₄ sunspot types. It was established that the minimal angle between the field direction and the normal to the solar surface at the field measurement site is smaller in leading sunspots than in trailing ones (α_{min − ls} < α_{min − fs} ) in 84% of the considered magnetically connected “leading-trailing” sunspot pairs, and a positive correlation exists between angles α_{min − ls} and α_{min − fs} . It was found that the C ₃₀₄ contrast increases with decreasing α_{min − ls, fs} for leading and trailing sunspots, and the C _{304 − ls} /C _{304 − fs} ratio on average decreases with increasing α_{min − ls} /α_{min − fs} ratio. The dependences of the maximal and average magnetic induction values in an umbra on the umbra area were constructed for the first time and compared independently for leading and trailing sunspots. It was concluded that the maximal and average magnetic field values do not vanish when the umbra area decreases to very small values. In all cases the magnetic field in leading and single sunspots is larger than in trailing ones.