A major X-class solar flare erupted from geoeffective Active Region 2673 peaking as X9.3 at 12:02 UTC on September 6, 2017. The event started at 11:53, peaked at 12:02 and ended at 12:10 UTC. This is the second X-class solar flare of the day. It comes just hours after a long-duration X2.2 at 09:33 UTC. It is also the strongest solar flare of the current solar cycle (Solar Cycle 24).

Radio signatures suggest a strong Coronal Mass Ejection (CME) was produced during this event. The location of this region favors Earth-directed CMEs.

The event was associated with a Type IV and Type II (estimated velocity 1969 km/s) radio emission. Type II emissions occur in association with eruptions on the sun and typically indicate a coronal mass ejection is associated with a flare event. Type IV emissions occur in association with major eruptions on the sun and are typically associated with strong coronal mass ejections and solar radiation storms.

In addition, this impressive event was associated with a 10cm Radio Burst lasting 3 minutes with peak flux of 12000 sfu.

Today's X9.3 is the strongest solar flare of Solar Cycle 24. Although X-class solar flares were expected (25% chance) since Region 2673 rapidly grew into a monster region and attained 'beta-gamma-delta' magnetic configuration, such powerful flare comes as a huge surprise, as our star is heading toward Solar Minimum. The previous record for the strongest flare of the cycle was X6.9 of August 9, 2011.

The cycle has so far had 47 X-class flares, including today's X2.2 and X9.3.

The last time our star erupted with an X-class flare was on May 5, 2015 - X2.7. CME was produced, but the location didn't favor Earth-directed CMEs.

The location of Active Region 2673 favors Earth-directed CMEs. However, analysis of the event is still in progress.

CME produced by M5.5 solar flare on September 4, 2017 is heading toward Earth and is expected to arrive later today (September 6). A G3 - Strong geomagnetic storm watch is in effect for September 6 and 7.

WSA-Enlil model below shows both CMEs (September 4th and 6th). The September 6th CME is expected to arrive late September 8.

SWPC alerts

Space Weather Message Code: ALTTP2

Serial Number: 1058

Issue Time: 2017 Sep 06 1212 UTC

ALERT: Type II Radio Emission

Begin Time: 2017 Sep 06 1202 UTC

Estimated Velocity: 1969 km/s

Description: Type II emissions occur in association with eruptions on the sun and typically indicate a coronal mass ejection is associated with a flare event.

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Space Weather Message Code: ALTTP4

Serial Number: 540

Issue Time: 2017 Sep 06 1210 UTC

ALERT: Type IV Radio Emission

Begin Time: 2017 Sep 06 1201 UTC

Description: Type IV emissions occur in association with major eruptions on the sun and are typically associated with strong coronal mass ejections and solar radiation storms.

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Space Weather Message Code: SUM10R

Serial Number: 697

Issue Time: 2017 Sep 06 1209 UTC

SUMMARY: 10cm Radio Burst

Begin Time: 2017 Sep 06 1154 UTC

Maximum Time: 2017 Sep 06 1156 UTC

End Time: 2017 Sep 06 1157 UTC

Duration: 3 minutes

Peak Flux: 12000sfu

Latest Penticton Noon Flux: 121 sfu

Description: A 10cm radio burst indicates that the electromagnetic burst associated with a solar flare at the 10cm wavelength was double or greater than the initial 10cm radio background. This can be indicative of significant radio noise in association with a solar flare. This noise is generally short-lived but can cause interference for sensitive receivers including radar, GPS, and satellite communications.

Featured image: X9.3 solar flare erupts from AR 2673 - 12:13 UTC. Credit: NASA/SDO AIA 131