Spectacular double-peaked, long-duration solar flare might result in “glancing blow” on Earth

A solar flare, which peaked in intensity twice within two hours, erupted from the Sun’s Active Region (AR) 3363 yesterday causing a spectacular solar-scape.

For the technically minded here are the details:  the region produced an M2.7 flare at 10:54pm, 17 July UTC (8:54am, 18 July AEST) followed by an M5.7 12:06am, 18 July UTC (10:06am, 18 July AEST).

Both peaks are in the M-class of solar flare, the second highest category behind X-class flares like the X1 flare which caused a 30-minute radio blackout over the Pacific earlier this month.

The event produced an asymmetric halo coronal mass ejection (CME).

CMEs are ejections from the surface of the sun of the solar magnetic field which take with them huge amounts of plasma and ionising matter. They shoot high-energy charged particles into space – CMEs can cause disruption of radio frequencies and satellites on Earth if they come our way.

Though the CME produced from AR 3363 is a “limb event” directed away from Earth, NASA and the US National Oceanic and Atmospheric Administration (NOAA) are predicting a “glancing blow” according to space weather physicist Dr Tamitha Skov.

NOAA’s space weather forecast says G1-class minor geomagnetic storms caused by the CME interacting with the Earth’s magnetic field are expected on 20 July. They write that “numerous model results show a wide and expansive CME front, which is likely to pass close enough to Earth on 20 July to cause minor (G1) geomagnetic storming.”

Australia’s Bureau of Meteorology’s space weather forecast predicts minor R2-level low-frequency radio blackouts in the western Pacific as a result.

The NASA-European Space Agency Solar and Heliospheric Observatory has been tracking sunspot AR 3363 since it became visible on July 6. The sunspot’s area is seven times larger than the area of the Earth’s cross-section across the equator.

As our Sun reaches the peak of Solar Cycle 25, which is set to be at maximum in 2024–25, increased solar activity is expected. While disruptions such as radio blackouts may become more frequent, experts say major impacts from geomagnetic storms and damage to satellites are unlikely during this solar maximum.

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