Flare Generated Global Blast Waves, Solar Cycle 24

Long, et al. (2015) investigated the energetics of a global shock wave associated with an M 2.2 flare that occurred on February 15, 2011(NOAA 1158), concluding that the wave dynamics could be modeled as a self-similar wave propagating in a radial direction from the originating active region. This paper adds two observations to their work. These are shown in Figure 1. A self-similar analysis for supernova events given by Shu (1961), shows a characteristic evolution for blast waves: (1) the production of an initial fireball, (2) an expanding super-Alfvenic hydromagnetic shock wave, and (3) a subsequent snow plow configuration resulting from acceleration of material in the neighborhood of the impulse The first two features are seen in image differences generated at t= 1.66 and t =15.6 minutes from flare initiation. Three frames from the l195 (Fe XII and Fe XXIV) running difference sequence given by Nitta (https://www.lmsal.com/~nitta/movies/AIA_Waves/index.html) are seen in Figure 1 (upper). ACE and Wind data from Feb 15 - Feb19, 2011 show (Figure 1, lower) a major solar wind disturbance at L1 about 71 hours post-flare, and a pulse of protons passing the L1 point. No other solar candidates for blast wave generation were detected. The solar wind shock occurred about 71 hours post-flare implying a nominal velocity from the low corona to L1 of ~580 km/sec.

23 of 32 X and M class flares observed during solar cycle 24, 2010-2017 have identical EUV difference image features, and each is associated with similar solar wind shock characteristics detected at L1. This pattern of EUV and solar wind features was a sufficient condition for inference of global blast wave generation by a flare and propagation of a global heliospheric wave traveling between the Sun and Earth. It is not known if this is a general or specific pattern only for this portion of cycle 24. If it is generally true, it is an observation that has utility in the field of Space Weather for the detection of blast wave generation at the sun and subsequent global shock wave flow through the solar system.

References:

Long, D. M., Baker, D., Williams, D.R., Carley, E. P. Gallager, P.T., Zuccz, P. (2015) Ap. J., 799, 224, (2015) February 1.