September 2, 2019, 7:30 UTC

Second strongest magnetic storm of this year is occurring at present

Magnetic storm August 31 - September 1, 2019 Magnetic storm on August 31 - September 1, 2019

Quite a noticeable increase in geomagnetic activity is being simultaneously recorded at almost every tracking station on our planet nowadays. The beginning of the magnetic field oscillations was noted as early as on 31 August (last Saturday), moreover, in the afternoon their amplitude reached the level of Kp = 6 which corresponds to a second level on a five-point scale of the magnetic storms. The started on Saturday magnetic storm lasted almost all of Sunday and have continued till Monday morning. Herewith, the level of the magnetic storm on Sunday had risen again to 2 scores. According to the forecast, by mid-Monday on 2 September, the amplitude of field oscillations should decline and on no later than Tuesday morning the geomagnetic situation promises to stabilize completely.

Occurring growth of perturbations in the magnetic field was predicted in advance in connection to the stream of fast solar wind approaching the Earth. However, to some surprise was the early start of the storm, which was expected no earlier than on Sunday, as well as its strength - the forecast was only made for the storm with its usual for this year minimal first level. In reality, the Earth entered a stream of fast solar wind earlier than expected, already by the evening of August 30th, besides, the increase in the wind velocity had also exceeded the forecast - from an entry-level at about 400 km/s (the usual value for the stream of solar wind on the level of the Earth’s orbit), by Sunday the speed of the wind had risen to 600 km/s and then to 800 km/s and is remaining in the range of 600-800 km/s to date. This, presumably, was the main reason for the higher level of the storm than originally expected. Noticeable that the temperature of the cosmic plasma simultaneously had increased almost 10 times - from the initial 100 thousand to about 1 million degrees. As mentioned already, the situation is currently stabilizing and the velocity of the wind and its temperature are gradually decreasing to their original values.

Currently occurring magnetic storm became the second most powerful storm this year. Larger event over the past 8 months has been recorded only once — in May of this year when the storm had reached level 3 of the 5.

Because of the streams of the solar wind are ‘tied’ to the Sun and rotate with it, they, like the Sun, make their rotations in 27 days. Given quite a high speed of the current stream, as well as the stable situation on the Sun, it is very likely that it will come back to Earth at the end of September, on the 27th -28th . It is difficult to say right now if the storm will repeat in these days with the same strength or will the velocity of the plasma decrease in this period. So far for the corresponding dates the storm of a lower first level being cautiously forecasted, but what will happen in reality, it will become completely clear only after 4 weeks.

Laboratory of X-ray astronomy of the Sun, Lebedev Institute, Russia