On September 29, 2013, a large magnetic filament erupted on the Sun’s northern hemisphere and produced a C1.2 solar flare.
Observation in the EUV (Extreme ultraviolet radiation) showed two elongated ribbon-like structures, symmetrically developing on either side of the active region, along the polarity inversion line (neutral line).
Two-ribbon flares are extremely powerful eruptions; during magnetic reconnection the magnetic energy is converted into radiation across the electromagnetic spectrum – energetic particles are accelerated up to several hundred MeV (1 MeV = 10^6 eV)) or even to GeV (1 GeV = 10^9 eV) range. These high-energy particles (Solar energetic particles or SEPs)- atoms associated with solar flares- are a type of cosmic rays.
In summary, the large flare often shows two bright bands of emission in H alpha. These ribbons appear to move slowly apart as the flare develops. Before the flare a prominence is often observed and this disappears at the onset of the flare. The two ribbons form on either side of the prominence.
As the ribbons move apart loop-like structures are seen connecting one ribbon to the other one. These are post flare loops and are an indication that magnetic reconnection has allowed the coronal magnetic field to relax into a lower energy state (i.e. a simpler configuration).
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