G4 - Severe geomagnetic storming observed as CME from X9.3 flare impacts Earth

A Coronal Mass Ejection (CME) produced by the X9.3 solar flare on September 6, 2017, reached our planet at 23:04 UTC on September 7, 2017, a full day earlier than it was expected. G3 - Strong geomagnetic storming started 23:25 and increased to G4 - Severe at 23:50 UTC.

Over the past 24 hours, solar wind parameters, as measured by the DSCOVR satellite indicated continued influence from the September 4th CME followed by a CME arrival from the September 6th CME at 22:29 UTC. The shock then increased to a peak of 34 nT observed at 22:55 UTC. Bz reached a maximum southward value of -33 nT at 22:57. Solar wind speeds were between 500 - 600 km/s before shock arrival and increased to 623 km/s, further increasing to a peak speed of 751 km/s by 22:45 UTC.

The solar wind environment is expected to remain enhanced for the next two days due to anticipated effects from the September 4th CME and September 6th. CME enhancements are expected to subside by September 10, with possible weak positive polarity influence by late in the day.

Geomagnetic K-index of 7 (G3 - Strong geomagnetic storm) threshold was reached just 21 minutes after the CME arrival, at 23:25 UTC. Under G3 conditions, power system voltage irregularities are 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. Intermittent satellite navigation (GPS) problems, including loss-of-lock and increased range error may occur. HF (high frequency) radio may be intermittent and aurora seen as low as Pennsylvania to Iowa to Oregon.

G4 - Severe geomagnetic storm threshold (geomagnetic K-index of 8) was reached at 23:50 UTC.

Potential Impacts: Area of impact primarily poleward of 45 degrees Geomagnetic Latitude. Induced currents - Possible widespread voltage control problems and some protective systems may mistakenly trip out key assets from the power grid. Induced pipeline currents intensify. Spacecraft - Systems may experience surface charging; increased drag on low earth orbit satellites, and tracking and orientation problems may occur. Navigation - Satellite navigation (GPS) degraded or inoperable for hours. Radio - HF (high frequency) radio propagation sporadic or blacked out. Aurora - Aurora may be seen as low as Alabama and northern California.

G4 - Severe geomagnetic storm levels are expected to continue on September 8 due to CME influence. G3 - Strong geomagnetic storm levels, with G4 - Severe conditions possible, are likely on September 9 under the influence of the September 6th CME. Conditions are expected to decrease to G1 - Minor by September 10 as CME effects subside.

There are, in average, 100 G4 - Severe storms per solar cycle, lasting in total some 60 days. NOAA's Geomagnetic Storm scale has just one more level, G5 - Extreme. Such (Extreme) storms happen about 4 times per cycle and last, in total, about 4 days.

Meanwhile, the greater than 2 MeV electron flux reached high levels with a maximum flux of 7,220 pfu observed at 17:05 UTC on September 6. The greater than 10 MeV proton flux reached S2 - Moderate levels with a peak flux of 355 pfu at 21:50 UTC on September 7.

The greater than 2 MeV electron flux is expected to decrease to normal to moderate levels late Septembre 8 due to the anticipated arrival of the September 6th CME. The 2 MeV electron flux is likely to return to high levels by September 9.

The greater than 10 MeV proton flux is expected to continue at S1 - S2 (Minor - Moderate) levels on September 8 and 9. Flux values are expected to slowly decline but remain above S1 threshold into September 10.

SWPC alerts, watches and warnings

Space Weather Message Code: WARK06 Serial Number: 396 Issue Time: 2017 Sep 08 0537 UTC

EXTENDED WARNING: Geomagnetic K-Index of 6 expected Extension to Serial Number: 395 Valid From: 2017 Sep 07 2255 UTC Now Valid Until: 2017 Sep 08 1500 UTC Warning Condition: Persistence

NOAA Space Weather Scale descriptions can be found at www.swpc.noaa.gov/noaa-scales-explanation

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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Space Weather Message Code: WARK05 Serial Number: 1395 Issue Time: 2017 Sep 08 0537 UTC

EXTENDED WARNING: Geomagnetic K-index of 5 expected Extension to Serial Number: 1394 Valid From: 2017 Sep 07 0003 UTC Now Valid Until: 2017 Sep 08 2359 UTC Warning Condition: Persistence

NOAA Space Weather Scale descriptions can be found at www.swpc.noaa.gov/noaa-scales-explanation

Potential Impacts: Area of impact primarily poleward of 60 degrees Geomagnetic Latitude. Induced Currents - Weak power grid fluctuations can occur. Spacecraft - Minor impact on satellite operations possible. Aurora - Aurora may be visible at high latitudes, i.e., northern tier of the U.S. such as northern Michigan and Maine.

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Space Weather Message Code: WARK07 Serial Number: 71 Issue Time: 2017 Sep 08 0537 UTC

EXTENDED WARNING: Geomagnetic K-index of 7 or greater expected Extension to Serial Number: 70 Valid From: 2017 Sep 07 2300 UTC Now Valid Until: 2017 Sep 08 1500 UTC Warning Condition: Persistence

NOAA Space Weather Scale descriptions can be found at www.swpc.noaa.gov/noaa-scales-explanation

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: WARPX1 Serial Number: 466 Issue Time: 2017 Sep 08 0537 UTC

EXTENDED WARNING: Proton 10MeV Integral Flux above 10pfu expected Extension to Serial Number: 465 Valid From: 2017 Sep 05 0030 UTC Now Valid Until: 2017 Sep 08 2359 UTC Warning Condition: persistence Predicted NOAA Scale: S2 - Moderate

NOAA Space Weather Scale descriptions can be found at www.swpc.noaa.gov/noaa-scales-explanation

Potential Impacts: Radio - Minor impacts on polar HF (high frequency) radio propagation resulting in fades at lower frequencies.

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Space Weather Message Code: WARK04 Serial Number: 3310 Issue Time: 2017 Sep 08 0533 UTC

EXTENDED WARNING: Geomagnetic K-index of 4 expected Extension to Serial Number: 3309 Valid From: 2017 Sep 06 2330 UTC Now Valid Until: 2017 Sep 08 2359 UTC Warning Condition: persistence

NOAA Space Weather Scale descriptions can be found at www.swpc.noaa.gov/noaa-scales-explanation

Potential Impacts: Area of impact primarily poleward of 65 degrees Geomagnetic Latitude. Induced Currents - Weak power grid fluctuations can occur. Aurora - Aurora may be visible at high latitudes such as Canada and Alaska.

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Space Weather Message Code: ALTK05 Serial Number: 1149 Issue Time: 2017 Sep 08 0452 UTC

ALERT: Geomagnetic K-index of 5 Threshold Reached: 2017 Sep 08 0452 UTC Synoptic Period: 0300-0600 UTC

Active Warning: Yes NOAA Scale: G1 - Minor

NOAA Space Weather Scale descriptions can be found at www.swpc.noaa.gov/noaa-scales-explanation

Potential Impacts: Area of impact primarily poleward of 60 degrees Geomagnetic Latitude. Induced Currents - Weak power grid fluctuations can occur. Spacecraft - Minor impact on satellite operations possible. Aurora - Aurora may be visible at high latitudes, i.e., northern tier of the U.S. such as northern Michigan and Maine.

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Space Weather Message Code: ALTK08 Serial Number: 24 Issue Time: 2017 Sep 08 0151 UTC

ALERT: Geomagnetic K-index of 8 Threshold Reached: 2017 Sep 08 0151 UTC Synoptic Period: 0000-0300 UTC

Active Warning: Yes NOAA Scale: G4 - Severe

NOAA Space Weather Scale descriptions can be found at www.swpc.noaa.gov/noaa-scales-explanation

Potential Impacts: Area of impact primarily poleward of 45 degrees Geomagnetic Latitude. Induced Currents - Possible widespread voltage control problems and some protective systems may mistakenly trip out key assets from the power grid. Induced pipeline currents intensify. Spacecraft - Systems may experience surface charging; increased drag on low earth orbit satellites, and tracking and orientation problems may occur. Navigation - Satellite navigation (GPS) degraded or inoperable for hours. Radio - HF (high frequency) radio propagation sporadic or blacked out. Aurora - Aurora may be seen as low as Alabama and northern California.

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Space Weather Message Code: ALTK07 Serial Number: 107 Issue Time: 2017 Sep 08 0116 UTC

ALERT: Geomagnetic K-index of 7 Threshold Reached: 2017 Sep 08 0116 UTC Synoptic Period: 0000-0300 UTC

Active Warning: Yes NOAA Scale: G3 - Strong

NOAA Space Weather Scale descriptions can be found at www.swpc.noaa.gov/noaa-scales-explanation

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: 441 Issue Time: 2017 Sep 08 0028 UTC

ALERT: Geomagnetic K-index of 6 Threshold Reached: 2017 Sep 08 0027 UTC Synoptic Period: 0000-0300 UTC

Active Warning: Yes NOAA Scale: G2 - Moderate

NOAA Space Weather Scale descriptions can be found at www.swpc.noaa.gov/noaa-scales-explanation

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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Space Weather Message Code: ALTK05 Serial Number: 1148 Issue Time: 2017 Sep 08 0022 UTC

ALERT: Geomagnetic K-index of 5 Threshold Reached: 2017 Sep 08 0022 UTC Synoptic Period: 0000-0300 UTC

Active Warning: Yes NOAA Scale: G1 - Minor

NOAA Space Weather Scale descriptions can be found at www.swpc.noaa.gov/noaa-scales-explanation

Potential Impacts: Area of impact primarily poleward of 60 degrees Geomagnetic Latitude. Induced Currents - Weak power grid fluctuations can occur. Spacecraft - Minor impact on satellite operations possible. Aurora - Aurora may be visible at high latitudes, i.e., northern tier of the U.S. such as northern Michigan and Maine.

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Space Weather Message Code: ALTK08 Serial Number: 23 Issue Time: 2017 Sep 07 2350 UTC

ALERT: Geomagnetic K-index of 8 Threshold Reached: 2017 Sep 07 2350 UTC Synoptic Period: 2100-2400 UTC

Active Warning: Yes NOAA Scale: G4 - Severe

NOAA Space Weather Scale descriptions can be found at www.swpc.noaa.gov/noaa-scales-explanation

Potential Impacts: Area of impact primarily poleward of 45 degrees Geomagnetic Latitude. Induced Currents - Possible widespread voltage control problems and some protective systems may mistakenly trip out key assets from the power grid. Induced pipeline currents intensify. Spacecraft - Systems may experience surface charging; increased drag on low earth orbit satellites, and tracking and orientation problems may occur. Navigation - Satellite navigation (GPS) degraded or inoperable for hours. Radio - HF (high frequency) radio propagation sporadic or blacked out. Aurora - Aurora may be seen as low as Alabama and northern California.

***

Space Weather Message Code: ALTK07 Serial Number: 106 Issue Time: 2017 Sep 07 2325 UTC

ALERT: Geomagnetic K-index of 7 Threshold Reached: 2017 Sep 07 2325 UTC Synoptic Period: 2100-2400 UTC

Active Warning: Yes NOAA Scale: G3 - Strong

NOAA Space Weather Scale descriptions can be found at www.swpc.noaa.gov/noaa-scales-explanation

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: SUMSUD Serial Number: 224 Issue Time: 2017 Sep 07 2309 UTC

SUMMARY: Geomagnetic Sudden Impulse Observed: 2017 Sep 07 2304 UTC Deviation: 70 nT Station: FRD

NOAA Space Weather Scale descriptions can be found at www.swpc.noaa.gov/noaa-scales-explanation

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Space Weather Message Code: ALTK06 Serial Number: 440 Issue Time: 2017 Sep 07 2306 UTC

ALERT: Geomagnetic K-index of 6 Threshold Reached: 2017 Sep 07 2302 UTC Synoptic Period: 2100-2400 UTC

Active Warning: Yes NOAA Scale: G2 - Moderate

NOAA Space Weather Scale descriptions can be found at www.swpc.noaa.gov/noaa-scales-explanation

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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Space Weather Message Code: ALTK05 Serial Number: 1147 Issue Time: 2017 Sep 07 2257 UTC

ALERT: Geomagnetic K-index of 5 Threshold Reached: 2017 Sep 07 2256 UTC Synoptic Period: 2100-2400 UTC

Active Warning: Yes NOAA Scale: G1 - Minor

NOAA Space Weather Scale descriptions can be found at www.swpc.noaa.gov/noaa-scales-explanation

Potential Impacts: Area of impact primarily poleward of 60 degrees Geomagnetic Latitude. Induced Currents - Weak power grid fluctuations can occur. Spacecraft - Minor impact on satellite operations possible. Aurora - Aurora may be visible at high latitudes, i.e., northern tier of the U.S. such as northern Michigan and Maine.

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Space Weather Message Code: WARK07 Serial Number: 70 Issue Time: 2017 Sep 07 2257 UTC

WARNING: Geomagnetic K-index of 7 or greater expected Valid From: 2017 Sep 07 2300 UTC Valid To: 2017 Sep 08 0600 UTC Warning Condition: Onset NOAA Scale: G3 or greater - Strong to Extreme

NOAA Space Weather Scale descriptions can be found at www.swpc.noaa.gov/noaa-scales-explanation

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: WARK06 Serial Number: 395 Issue Time: 2017 Sep 07 2244 UTC

WARNING: Geomagnetic K-Index of 6 expected Valid From: 2017 Sep 07 2255 UTC Valid To: 2017 Sep 08 0600 UTC Warning Condition: Onset NOAA Scale: G2 - Moderate

NOAA Space Weather Scale descriptions can be found at www.swpc.noaa.gov/noaa-scales-explanation

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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Space Weather Message Code: WARSUD Serial Number: 178 Issue Time: 2017 Sep 07 2242 UTC

WARNING: Geomagnetic Sudden Impulse expected Valid From: 2017 Sep 07 2255 UTC Valid To: 2017 Sep 07 2330 UTC IP Shock Passage Observed: 2017 Sep 07 2229 UTC

NOAA Space Weather Scale descriptions can be found at www.swpc.noaa.gov/noaa-scales-explanation

Featured image: Taken by Jani Ylinampa on September 8, 2017 at Rovaniemi, Lapland, Finland via SpaceWeather