University of Oulu

Space Research Group Kalevi Mursula

I am working as professor of space physics in the Space Research Group of the Department of Physical Sciences in the University of Oulu, Finland.

I conduct research in space physics, in particular in heliospheric and magnetospheric physics.

Most of my research deals with Space Climate, i.e., the study of long-term changes in the Sun and its effects in the heliosphere (solar wind and heliospheric magnetic field), and in the near-Earth space (magnetosphere, ionosphere, atmosphere) and climate.

Some highlights: Bashful Ballerina

We have made interesting new findings about the solar/heliospheric structure. The heliospheric current sheet (HCS) which separates the two magnetic hemispheres has a wavy structure and is therefore often called the ballerina skirt. Interestingly, HCS is systematically shifted or displaced southwards from the solar heliographic equator during the declining to minimum phase of the solar cycle.

We have amused ourselves with the following analogy: It seems that, whenever her activity is fading, the solar Ballerina becomes aware of her high flaring skirt and she tries to push it downward. The Sun is therefore a Bashful Ballerina.

We have also found that the dominance of either of the two magnetic hemispheres alternates with a period of about 3.2 years. This implies that two subsequent tilts (deflections with respect ot the rotation axis) of the heliospheric magnetic field (HMF) and are, on an average, roughly directed in opposite longitudes. Thus, the solar magnetic field has two active longitudes whose activity alternates ("flip-flops") three times in an 10-year solar activity cycle. (Nowadays cycles are slightly shorter and higher than, say 100 years ago).

Thinking these activations as "steps" of the Bashful Ballerina, we can say that she is dancing in waltz tempo !

In fact, recent studies have shown that this ratio of 3 between the activity cycle and the flip-flop cycle is common for cool, sun-like stars. Accordingly, there is a lot of waltzing in the Heavens by all those Bashful Ballerinas!

You can read about this more, e.g., in the following publications:

K. Mursula, and T. Hiltula, Bashful ballerina: Southward shifted heliospheric current sheet, Geophys. Res. Lett. 30 (22), p. SSC 2--1-4, doi: 10.1029/2003GL018201, 2003.

K. Mursula, and T. Hiltula, Systematically asymmetric heliospheric magnetic field: Evidence for a quadrupole mode and non-axisymmetry with polarity flip-flops, Sol. Phys., 224, 133-143, 2004.

J. Takalo, and K. Mursula, Annual and solar rotation periodicities in IMF components: Evidence for phase/frequency modulation, Geophys. Res. Lett., 29(9), p. 31--1-4, doi: 10.1029/2002GL014658, 2002.

T. Hiltula, and K. Mursula, The long dance of the bashful ballerina, Geophys. Res. Lett. , 2006, in print.

Space Physics Textbook