According to Geosphere Austria, the strongest geomagnetic storm since June 2015 occurred on Friday night. Intense Northern Lights have been observed across northern Europe, the UK, Canada and the US, in the US as far south as Arizona. In Austria, “just following midnight on March 24, a faint glow might be seen on several webcams.”
The solar storm responsible for this was ejected from the sun on March 20 in a relatively unspectacular flare and also traveled to Earth at a comparatively slow speed, which the storm reached at noon on March 23, Geosphere (formerly ZAMG) reported. Whether solar storms cause a so-called geomagnetic storm when they hit the earth’s magnetic field depends primarily on the structure of the internal magnetic field.
Although the magnetic field of this solar storm was rather weak, according to the experts “it had exactly the right orientation to transfer a lot of energy into the earth’s magnetic field and thus cause the northern lights”. The magnetic variations were measured at the Conrad Observatory of Geosphere Austria and reached a high level of activity typical of a solar storm over a period of more than 15 hours. A slight increase in direct currents in the Austrian power grid might also be observed.
The storm had “already almost completely passed the earth” by midday on Friday. However, a second solar storm is expected, which might cause further geomagnetic activity in the coming days. Northern lights in Austria are rather unlikely.
Shortly before the arrival of the solar storm, Emma Davies and Christian Möstl from the Austrian Space Weather Office of Geosphere Austria were able to show that the magnetic field of the storm had the right configuration for a strong geomagnetic storm. Such rare tests are important in order to understand how the space weather can be predicted much more precisely with space probes that might possibly be built in the next ten to 20 years.
