Bibcode
Moreno-Insertis, F.; Vazquez, M.
Referencia bibliográfica
Astronomy and Astrophysics (ISSN 0004-6361), vol. 205, no. 1-2, Oct. 1988, p. 289-296.
Fecha de publicación:
10
1988
Número de citas
36
Número de citas referidas
32
Descripción
A statistical study of the decay of sunspots and sunspot groups is
carried out using data contained in the Greenwich Photoheliographic
Results. The period studied spans more than six decades, namely from
1874 to 1939. The adequacy of exponential, quadratic and linear decay
laws to the area decay data is considered. The dependence, or otherwise,
of the mean area decay rate for each single spot, D, on its maximum
area, A0, is studied; no relationship of the form
D(A0) can be ascertained. In fact, when plotted on a D vs.
A0 diagram, the couples (A0, D) cluster in two
pencils issuing from the origin of coordinates. These two clusters can
be seen to correspond with the families of the recurrent and
non-recurrent spot groups. The adequacy of a quadratic law to the decay
data is considered. A most probable parabolic decay law is obtained;
this law corresponds to the case in which the decay rate is proportional
to the spot perimeter. Finally, the variation of the decay rates in
successive activity cycles is also discussed.