5 Earth-directed CMEs, G3 – Strong geomagnetic storm

A several degree long solar filament south of the Region 2741 disappeared by approximately 15:14 UTC on May 13, 2019. Initial analysis suggests an Earth-directed component is likely with this Coronal Mass Ejection (CME). This is the fifth Earth-directed CME since May 6 (May 6 1x, May 10 x 2, May 12 1x, May 13 1x).

Solar wind parameters were indicative of a slow, but mildly enhanced regime on May 13. A transient feature in the solar wind was captured by the DSCOVR spacecraft at approximately 22:30 UTC. Total field increased to 12 nT, and the Bz component underwent a southward deflection of -10 nT. Wind speeds also increased during this time to a peak of 481 km/s at 23:18 UTC.

At approximately 03:01 UTC on May 14, the DSCOVR spacecraft observed the likely arrival of a CME that departed the Sun on May 10. In reaction to the CME arrival, the Bz component began a period of sustained southward deflection near -15 nT, total field strength increased slightly to 15 nT, and wind speeds increased further to nearly 550 km/s. 

Geomagnetic K-index of 6 threshold (G2 – Moderate geomagnetic storm) was reached at 05:45 UTC on May 14 followed by K-index of 7 (G3 – Strong geomagnetic storm) at 08:59 UTC.

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Space Weather Message Code: ALTK07
Serial Number: 114
Issue Time: 2019 May 14 0901 UTC

ALERT: Geomagnetic K-index of 7
Threshold Reached: 2019 May 14 0859 UTC
Synoptic Period: 0600-0900 UTC

Active Warning: Yes
NOAA Scale: G3 – Strong

Potential Impacts: Area of impact primarily poleward of 50 degrees Geomagnetic Latitude.
Induced Currents – Power system voltage irregularities possible, false alarms may be triggered on some protection devices.
Spacecraft – Systems may experience surface charging; increased drag on low Earth-orbit satellites and orientation problems may occur.
Navigation – Intermittent satellite navigation (GPS) problems, including loss-of-lock and increased range error may occur.
Radio – HF (high frequency) radio may be intermittent.
Aurora – Aurora may be seen as low as Pennsylvania to Iowa to Oregon.

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Space Weather Message Code: ALTK06
Serial Number: 472
Issue Time: 2019 May 14 0736 UTC

ALERT: Geomagnetic K-index of 6
Threshold Reached: 2019 May 14 0736 UTC
Synoptic Period: 0600-0900 UTC

Active Warning: Yes
NOAA Scale: G2 – Moderate

Potential Impacts: Area of impact primarily poleward of 55 degrees Geomagnetic Latitude.
Induced Currents – Power grid fluctuations can occur. High-latitude power systems may experience voltage alarms.
Spacecraft – Satellite orientation irregularities may occur; increased drag on low Earth-orbit satellites is possible.
Radio – HF (high frequency) radio propagation can fade at higher latitudes.
Aurora – Aurora may be seen as low as New York to Wisconsin to Washington state.

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The arrival of a pair of CMEs from May 10 is anticipated on May 15, SWPC forecasters said 00:30 UTC, May 14.

WSA-Enlil modeling suggests slow propagation; therefore, while an IMF enhancement is likely, a modest increase is solar wind is expected.

The arrival of a third CME, partial halo from May 12, is expected on May 16 – leading to an additional enhancement and disturbance in the IMF. Based off modeled radial velocity, this third CME could lead to an additional increase in solar wind speed.

The May 13 CME is likely to reach Earth at roughly the same time as May 12^th – mid to late in the day on May 16 (UTC).

Featured image: NASA SDO/AIA 304 at 21:12 UTC on May 13, 2019