Environment

Moderate geomagnetic storm in progress


A G2 – Moderate geomagnetic storm threshold was reached at 08:25 UTC on April 20, 2018 and G2 warning is in now in effect until 12:00 UTC.

An interplanetary shock wave hit Earth’s magnetic field around 23:50 UTC on April 19, Dr. Tony Phillips of SpaceWeather.com said.

“When the shock arrived, the density of the solar wind flowing around our planet abruptly quadrupled. Moreover, magnetic fields in the solar wind near Earth have since intensified 10-fold.” 

An interplanetary shock wave is a supersonic disturbance in the gaseous material of the solar wind. These waves are frequently delivered by Coronal Mass Ejections (CMEs).

“Indeed, this one might have been a minor CME that left the Sun unrecognized earlier this week. Or it might be an unusually sharp co-rotating interaction region (CIR). CIRs are transition zones between slow- and fast-moving streams of solar wind. They contain plasma density gradients that often do a good job of sparking auroras,” Phillips concludes.

Solar wind parameters were at background levels under a nominal solar wind regime over the past 24 hours, SWPC reported 00:30 UTC today, adding that weak enhancement was observed by the end of the UTC day.

Solar wind speeds were steady in the high 200s to low 300s km/s range throughout the period with anomalous solar wind speed/temp/density observed between 00:00 and 01:30 UTC on April 19, their forecasters said.

Total field strength values varied between 1-7 nT and Bz reached a maximum southward value of -5 nT.

Solar wind parameters are expected to become enhanced on April 20 through midday April 22 due to the influence of a negative polarity CH HSS. 

Geoeffective coronal hole on April 16 and 17, 2018

SWPC alerts, warnings and watches

Space Weather Message Code: ALTK06
Serial Number: 460
Issue Time: 2018 Apr 20 0825 UTC

ALERT: Geomagnetic K-index of 6
Threshold Reached: 2018 Apr 20 0825 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.

***

Space Weather Message Code: WARK06
Serial Number: 416
Issue Time: 2018 Apr 20 0714 UTC

WARNING: Geomagnetic K-Index of 6 expected
Valid From: 2018 Apr 20 0714 UTC
Valid To: 2018 Apr 20 1200 UTC
Warning Condition: Onset
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.

***

Space Weather Message Code: ALTK05
Serial Number: 1214
Issue Time: 2018 Apr 20 0651 UTC

ALERT: Geomagnetic K-index of 5
Threshold Reached: 2018 Apr 20 0650 UTC
Synoptic Period: 0600-0900 UTC

Active Warning: Yes
NOAA Scale: G1 – Minor

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.

***

Space Weather Message Code: ALTK05
Serial Number: 1213
Issue Time: 2018 Apr 20 0558 UTC

ALERT: Geomagnetic K-index of 5
Threshold Reached: 2018 Apr 20 0558 UTC
Synoptic Period: 0300-0600 UTC

Active Warning: Yes
NOAA Scale: G1 – Minor

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.

***

Space Weather Message Code: WARK04
Serial Number: 3463
Issue Time: 2018 Apr 20 0512 UTC

EXTENDED WARNING: Geomagnetic K-index of 4 expected
Extension to Serial Number: 3462
Valid From: 2018 Apr 20 0032 UTC
Now Valid Until: 2018 Apr 20 1500 UTC
Warning Condition: Onset

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.

***

Space Weather Message Code: WARK05
Serial Number: 1468
Issue Time: 2018 Apr 20 0511 UTC

WARNING: Geomagnetic K-index of 5 expected
Valid From: 2018 Apr 20 0510 UTC
Valid To: 2018 Apr 20 1200 UTC
Warning Condition: Onset
NOAA Scale: G1 – Minor

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.

***

Space Weather Message Code: ALTK04
Serial Number: 2050
Issue Time: 2018 Apr 20 0300 UTC

ALERT: Geomagnetic K-index of 4
Threshold Reached: 2018 Apr 20 0259 UTC
Synoptic Period: 0000-0300 UTC

Active Warning: Yes

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.

***

Space Weather Message Code: WARK04
Serial Number: 3462
Issue Time: 2018 Apr 20 0033 UTC

WARNING: Geomagnetic K-index of 4 expected
Valid From: 2018 Apr 20 0032 UTC
Valid To: 2018 Apr 20 0900 UTC
Warning Condition: Onset

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.

***

Space Weather Message Code: ALTEF3
Serial Number: 2767
Issue Time: 2018 Apr 19 1816 UTC

CONTINUED ALERT: Electron 2MeV Integral Flux exceeded 1000pfu
Continuation of Serial Number: 2766
Begin Time: 2018 Apr 10 1830 UTC
Yesterday Maximum 2MeV Flux: 3739 pfu

Potential Impacts: Satellite systems may experience significant charging resulting in increased risk to satellite systems.

***

Space Weather Message Code: ALTEF3
Serial Number: 2766
Issue Time: 2018 Apr 18 1430 UTC

CONTINUED ALERT: Electron 2MeV Integral Flux exceeded 1000pfu
Continuation of Serial Number: 2765
Begin Time: 2018 Apr 10 1830 UTC
Yesterday Maximum 2MeV Flux: 4586 pfu

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

Potential Impacts: Satellite systems may experience significant charging resulting in increased risk to satellite systems.

Featured image: Aurora from Lake Rice, Minnesota on April 20, 2018. CreditL Matthew Sunderman (via SpaceWeather)



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