SOLSTICE

Space storms: Solar and stellar variability, seasonal pattern predictability and societal consequences

Consortium project funded by the Research Council of Finland 2020-3, decision No. 324161.

Consortium PI: Eija Tanskanen, Sodankylä observatory

Co-PI: Thomas Hackman, Department of Physics, University of Helsinki

Description of project: The goal of the project is to examine space storms and the magnetic disturbances caused by them. Ground magnetic data will be used from 1844 onwards and thus the changes in the near-Earth magnetic environment can be studied for over 16 solar cycles. One of the goals is to find out how the Sun has varied in different time-scales and how the variability has affected to the near-Earth magnetic climate in different latitudes, and how strong space storms the Sun is capable of producing. We will investigate the predictability of the auroral substorms and other geomagnetic disturbances based on the solar and solar wind data, separately in auroral zone, sub-oval and polar cap. Stellar measurements will be used for examining the link between active regions and super-flares and estimate the occurrence rates for extreme events.

The University of Helsinki research group focused on observations of stellar magnetic activity and radiocarbon measurements from historical solar particle events. Results from this research include (links to papers are on the parent page):

• New magnetic field maps retrieved with Zeeman-Doppler imaging (see Figure below).
• Study on shape of stellar activity cycles.
• Study on connection between strong magnetic fields and dark starspots.
• Study on biases related to Zeeman-Doppler inaging.
• New methods on analysing high precision stellar light curves of late-type stars.
• New methods for estimating stellar surface differential rotation from ground and satellite based photometry.
• Transient radiocarbon excess after the Carrington event in 1859.

Fig. 1. ZDI images of the young solar-type star LQ Hya taken at the epochs  January 2010, February 2011, January 2016, and December 2017. The images show that a polarity reversal occurred in 2016-7 (Lehtinen et al. 2022).