  Rieger-type periodicity has been detected in different activity indices over
many solar cycles. It was recently shown that the periodicity correlates with
solar activity having a shorter period during stronger cycles. Solar activity
level is generally asymmetric between northern and southern hemispheres, which
could suggest the presence of a similar behavior in the Rieger-type
periodicity. We analyse the sunspot area/number and the total magnetic flux
data for northern and southern hemispheres during solar cycles 19-23 which had
remarkable north-south asymmetry. Using wavelet analysis of sunspot area and
number during the north-dominated cycles (19-20) we obtained the periodicity of
160-165 days in the stronger northern hemisphere and 180-190 days in the weaker
southern hemisphere. On the other hand, south-dominated cycles (21-23) display
the periodicity of 155-160 days in the stronger southern hemisphere and 175-188
days in the weaker northern hemisphere. Therefore, the Rieger-type periodicity
has the north-south asymmetry in sunspot area/number data during solar cycles
with strong hemispheric asymmetry. We suggest that the periodicity is caused by
magnetic Rossby waves in the internal dynamo layer. Using the dispersion
relation of magnetic Rossby waves and observed Rieger periodicity we estimated
the magnetic field strength in the layer as 45-49 kG in more active hemispheres
(north during the cycles 19-20 and south during the cycles 21-23) and 33-40 kG
in weaker hemispheres. The estimated difference in the hemispheric field
strength is around 10 kG, which provides a challenge for dynamo models. Total
magnetic flux data during the cycle 20-23 reveals no clear north-south
asymmetry which needs to be explained in the future.
