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May 18, 2013 – Solar & Terrestrial News [Space Weather and Earthquakes]

May 18, 2013

The geomagnetic field was quiet to unsettled on May 17. Solar wind speed at SOHO ranged between 346 and 476 km/s. A CME, probably associated with the X1 event on May 15, was observed arriving at SOHO at 00:23 UTC on May 18. This is causing active to major geomagnetic storm conditions.
Solar flux measured at 20h UTC on 2.8 GHz was 136.4 (increasing 31.5 over the last solar rotation).
The background x-ray flux was at the class B6 level.

At midnight UTC the visible solar disk had 13 spotted active regions (in 2K resolution SDO images):
Region 11743 [N21W53] decayed slowly and quietly.
Region 11744 [N05W38] decayed slowly losing spots and penumbral area. The region still has minor polarity intermixing. C5+ flares: C5.0 at 04:41 UTC.
Region 11745 [N12W12] decayed slowly and quietly.
Region 11746 [S29W12] decayed slowly and was quiet.
Region 11747 [S19W16] decayed slowly and quietly.

Region 11748 [N10E25] has a magnetic delta structure in the leading penumbral structure and could produce further M class events, an X class event may still be possible. The positive polarity area in the leading penumbra is moving slowly southwards as compared to the negative polarity area in the eastern part of the penumbra. If this development continues the delta could disappear within a couple of days. The region has decayed losing both spots and penumbral area. C5+ flares: M3.2/2B at 08:57 UTC. This event was associated with a fast asymmetric full halo CME.

Region 11749 [S23W64] decayed slowly and quietly.
Region 11750 [S10W41] developed slowly and quietly. The region has slight polarity intermixing and C flares are possible.
Region 11751 [S25W00] decayed and could soon become spotless.
Region 11752 [N17W37] added penumbral area with a minor reduction in spot number.

Spotted regions not numbered by SWPC:
S2420 [S13W25] was quiet and stable.
S2424 [S29E14] was quiet and stable.
New region S2425 [S14W14] emerged with one spot.

Coronal mass ejections (CMEs)
May 15: A wide CME was observed after the X1 event in AR 11748.
May 16: No obviously Earth directed CMEs were observed in LASCO and STEREO imagery.
May 17: A halo CME was observed after an M3 event in AR 11748. The CME was fast and will likely reach Earth on May 19.
The TEC/density is moderately high over the west pacific and Asia. The electron density GDGPS and NASA’s maps are updated every five minutes. The IPS TEC and f0F2 maps are updated hourly. Elevations in total election count/density & proton density are often associated with major instability in upper atmosphere/ionosphere. In such case, the conditions would be optimal for the presentation of sizable seismic events

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