Novel forecasting of solar eruptions

Published: Wednesday, 15 May 2019


Dr. Marianna Korsós, from Eötvös Loránd University (Budapest, Hungary), writes on current efforts to develop a solar flare prediction method that can also lead to more reliable forecasts of solar flares and massive coronal mass ejections.

Figure (a) shows the highly twisted and sheared delta-spots, which are very often sources of massive solar eruptions. Figure (b) displays a model of how the twisted and complex magnetic field lines may be manifested in the chromosphere. Finally, figure (c) shows the "converging-diverging motion" of the barycenters of the opposite polarities in a delta-spot just before an intensive flare occurrence.

 

Predicting solar eruptions, like energetic flares and massive coronal mass ejections (CMEs), has become of paramount importance for our modern technology-based society. Intense flare eruptions can cause long-lasting radiation storms in the Earth's upper atmosphere and trigger serious radio blackouts in our communication systems. CMEs are potentially even more hazardous than flares. When a CME impinges upon the Earth's upper atmosphere, the interaction could result in rather dramatic consequences in the functioning of a number of vital ground-based (e.g. oil or gas pipelines, power lines) and space-based (satellites, telecommunication, GPS) infrastructures as they may be seriously damaged.

Scientists from Eötvös University have developed a new flare prediction algorithm, called the "WG_M" method. This method aims to analyse the dynamic evolution of the highly twisted and sheared delta-spots (see Figure a), which are very often sources of massive solar eruptions. A delta-spot is part of a magnetically complex active region visible in the solar surface. There, two small opposite polarity sunspots become close to each other, but still remain separated by the polarity inversion line (PIL, see the red lines separating the black and white patches that refer to the opposite polarities).

Two new characteristic pre-flare behaviours have been discovered with the WG_M method. Such flare-precursors can provide important diagnostic information about the intensity and estimated onset time preceding the expected flare eruptions by many hours. The most scientifically interesting but not yet well-understood pre-flare behaviour is the "converging-diverging motion" of the barycenters of the opposite polarities in a delta-spot, just before an intensive flare occurrence (see Figure c).

The concept of the WG_M method has recently been further explored, by applying it not only to magnetic measurements of sunspots that are present in the photosphere but also to the magnetic fields in higher regions above it, e.g. in the chromosphere. This has revealed that the characteristic "converging-diverging motion" of the pre-flare behaviour shows in fact its earliest signs in the chromosphere, exactly at the heights where flares usually occur. Therefore this latter discovery enables to estimate the flare onset time much earlier once information about the magnetic field is available in the solar chromosphere. A model of how the twisted and complex magnetic field lines may be manifested in the chromosphere can be seen in the example of Figure b. There is now a crucial need to measure the magnetic fields in the chromosphere, which is precisely one of the central aims of the European Solar Telescope.

Applying the WG_M method in 3D to the high spatial and temporal resolution observations that will be available from EST will allow us to not just better understand the physics of the "converging-diverging motion" prior to flares, but will also eventually lead to more reliable forecasts of those hazardous flares and CMEs.



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