| Summary: | On 4th September 2017, the largest solar flare ever recorded this year saturated the GOES satellite X-ray detectors, making an assessment of its size difficult. We report a large solar flare that produces a hydrodynamic blast wave, moving out through interplanetary space with velocities of 573.6 km/sec and densities 18.1 protons/cm3 of protons. The type III burst with split band and herring bones has been recorded from the Kangarlussuaq, Greenland site. It shows a signature of propagating beams of nonthermal electrons with a large and complex structure. During that time, R1-R2 (Minor-Moderate) radio blackouts have occurred on 4 September, 2017; with sunspot number and radio flux is 96 and 120 respectively. The active region, RGN 2673 is a magnetically complex and compact sunspot group that has produced numerous C-class flares and occasional M-class flares on 4 September; the largest thus far was an M5 (R2-Moderate) event at 2033 UTC (1633 ET). Meanwhile, the active region, RGN 2674 is not as magnetically complex and has been relatively inactive. However, due to the development of mixed polarities within RGN 2673, its continued growth, and activity trends, the forecast now calls for expected R1-R2 events the remainder of 4th September on into 5 September. © Published under licence by IOP Publishing Ltd.
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