Interplanetary shock waves semi-automated identified as seen by Solar Orbiter.

The solar wind and interplanetary magnetic field parameters observed in situ by the SWA and MAG instruments onboard the Solar Orbiter mission provide a unique opportunity to identify interplanetary (IP) shock waves at various distances from the Sun on the rising phase of the 25^th solar activity cycle.

In the frame of this work, to recognize IP shocks, we applied a semi-automated method on the base of quality factors comprising the solar wind velocity, density characteristics, and total interplanetary magnetic field parameters. As an example, we identified a few tens of various IP shocks that occurred in the inner heliosphere, at radial distances of 0.29–0.95 AU from the Sun. Most of them were classified as FF-type shock waves, with only a few events identified as FR-, SF- and SR-type shock waves. The semi-automatic algorithm mentioned was used to determine the time of passage of the shock wave front through the spacecraft’s location.

Moreover, we calculated the typical kinetic and magnetohydrodynamic characteristics of each identified shock wave. In particular, the radial dependences of parameters such as the density ratio (r_N), magnetic field (r_B) ratio, plasma beta (β_us), Alfvén velocity (V_A), the angle between the shock normal and the interplanetary magnetic field (Q_Bn), shock wave front velocity (V_sh), sound speed (V_s) and magnetosonic speed (V_fms) were analyzed. Additionally Alfvén (M_A) and magnetosonic (M_fms) Mach numbers were studied. Finally, the dependence of the number of identified shock waves on radial distance was also examined and compared with solar flares activity.

 

This work is supported by the “Long-term program of support of the Ukrainian research teams at the Polish Academy of Sciences carried out in collaboration with the U.S. National Academy of Sciences with the financial support of external partners”.