A comparative analysis of the properties of the magnetic fields in leading and trailing sunspots

Pairs of leading and trailing sunspots whose umbrae are joined by magnetic-field lines have been selected based on calculations using SOLIS magnetic-field data in a potential approximation and the Bd technique of Rudenko, together with SDO data for 2010–2013. The shape of the field lines reflects to some extent the shape of the magnetic tube connecting the leading and trailing spots. The minimum angle between the field lines and the radial direction amin, the maximum magnetic field Bmax, the length of the field line from the leading spot to the apex, where the radial component of the field is zero, Ll, and the length of the field line from the apex to its eastern base Lf are determined in the umbrae of all the selected sunspots. In ∼81% of cases, amin is smaller in the leading spot than in the trailing spot. For such sunspots, there is a positive correlation between these angles in the leading and trailing spots. The dependences of amin on the areas of the umbrae in the leading and trailing spots are different. There is a weak negative correlation between amin and Bmax. In other words, on average, the field lines are closer to radial in magnetic tubes forming the umbrae of both leading and trailing spots with stronger fields at the photospheric level. In ∼60–65% of cases, the section of the field adjacent to the leading spot Ll is shorter than Lf. Similar results are obtained for large single spots.