  We analyzed the size, intensity, and magnetic field strength of sunspot
umbrae to compare the present cycle 24 with the previous one. We used data of
the Helioseismic and Magnetic Imager onboard the Solar Dynamics Observatory and
selected all sunspots between May 2010 and October 2012, using one image per
day. We created two subsets of this data with a manual tracking algorithm, both
without duplication. One is containing each sunspot (910 umbrae within 488
spots) and was used to analyze the distribution of umbral areas, selected with
an automated thresholding method. The other one contains 205 fully evolved
sunspots. We find nonlinear relations between umbral minimum intensity and size
and between maximum magnetic field strength and size. The field strength scales
linear with the intensity and the umbral size scales roughly linear with the
total magnetic flux, while the size and field strength level off with stronger
flux. When separated in hemisphere and averaged temporally, the southern umbrae
show a temporal increase in size and the northern umbrae stay constant. There
is no temporal variation in the umbral mean intensity detectable. The
probability density function of the umbral area in the ascending phase of the
current solar cycle is similar to that of the last solar cycle. From our
investigation of umbral area, magnetic field, magnetic flux and umbral
intensity of the sunspots of the rising phase of cycle 24, we do not find a
significant difference to the previous cycle, and hence no indication for a
long-term decline of solar activity.
