X1.7 and long duration M6.6 solar flares erupt from Region 3664, solar radiation storm in progress

Active Region 3664 — the source of numerous Earth-directed coronal mass ejections (CMEs) over the past 7 days — began its transit of the western limb on May 13, 2024. The region remains very active, producing a long-duration M6.6 flare on May 13, associated with an Earth-directed CME, and an X1.7 at 02:09 UTC on May 14. Meanwhile, a solar radiation storm is in progress due to activity associated with the same region.

A powerful solar flare measuring X1.7 erupted from Active Region 3664 at 02:09 UTC on May 14, 2024. The event started at 02:03 and ended at 02:19 UTC.

A Type II (estimated velocity 447 km/s) and Type IV radio emissions were associated with this flare — suggesting a strong CME was produced. However, it seems it’s not heading toward Earth.

Radio frequencies were forecast to be most degraded over East Asia, Australia, and the Pacific Ocean at the time of the flare.

At 09:44 UTC on May 13, the same region produced a long-duration M6.6 solar flare, associated with a Type II (estimated velocity of 683 km/s) and Type IV radio sweeps as well as a 1 200 sfu Tenflare.

“This event resulted in an asymmetric halo CME with a southwesterly bias, first seen in SOHO C2 coronagraph imagery beginning at approximately 09:12 UTC on May 13,” SWPC forecasters said.

“While a majority of the bulk material is expected to miss well ahead of Earth’s orbit, shock arrival followed by possible glancing effects can not be ruled out for May 14 -15 as this particular CME is relatively fast and expansive.”

Due to the high activity associated with Region 3664, an S2 – Moderate solar radiation storm threshold was reached at 01:10 UTC on May 14 and dropped below S2 levels at around 06:50 UTC.

S2 radiation storms occur approximately 25 times per cycle. The effects include various impacts across different domains. Biologically, passengers and crew in high-flying aircraft at high latitudes may be exposed to elevated radiation risk. In terms of satellite operations, infrequent single-event upsets are possible. Other systems may experience small effects on HF propagation through the polar regions, and navigation at polar cap locations could potentially be affected.

With Region 3664 now on the west limb — where eruptions can easily trigger solar radiation storms on Earth –, we’ll likely see prolonged S1 or S2 periods over the next couple of days.

Solar wind parameters in 24 hours to 00:30 UTC on May 14 were indicative of weakening CME influences from all the preceding transients.

The total field decreased to 5 nT, and the Bz component was mostly northward during the latter half of the period. Solar wind speeds decreased from near 800 km/s to just under 600 km/s by the end of the period. Phi became negative at approximately 15:00 UTC on May 13.

An enhanced solar wind environment with CME influences from a filament eruption and M6.6 flare on May 12 coupled with weak positive polarity coronal hole high speed stream (CH HSS) is anticipated for May 14 – 15, followed by a more ambient-like environment on May 16.

The geomagnetic field reached G2 – Moderate geomagnetic storm levels on May 13 due to continued CME activity, followed by unsettled to active conditions after 06:00 UTC.

G1 – Minor to G2 – Moderate geomagnetic storming is likely on May 14 due to positive polarity CH HSS and possible CME effects. G1 – Minor geomagnetic storming is likely with any glancing effects from the filament eruption and CME from AR 3664 on May 12.

The Sun has been extremely active since the beginning of the month, producing about 100 M-class and 14 X-class flares from May 1 to 14.

The strongest was X5.8 on May 11, followed by X4.5 on May 6, and X3.9 on May 10.

This activity resulted in G5 – Extreme geomagnetic storming for the first time since 2003.

References:

¹ Forecast Discussion – Issued: 2024 May 14 0030 UTC – Prepared by the U.S. Dept. of Commerce, NOAA, Space Weather Prediction Center

Featured image: X1.7 solar flare on May 14, 2024. Credit: NASA/SDO AIA 304, Helioviewer, The Watchers