Solar Storm Watch: Geomagnetic Sudden Impulse 2-20-23

Solar Storm Watch: Geomagnetic Sudden Impulse 2-20-23
NOAA Space Weather 

NOAA started with a warning then issued a Space Weather observation of a Geomagnetic Sudden Impulse at 10:59 Coordinated Universal Time (UTC) on 2-20-23. 

Space Weather Message Code: SUMSUD
Serial Number: 243
Issue Time: 2023 Feb 20 1059 UTC

SUMMARY: Geomagnetic Sudden Impulse
Observed: 2023 Feb 20 1039 UTC
Deviation: 16 nT
Station: WNG

NOAA Space Weather Scale descriptions can be found at

Geomagnetic Sudden Impulses (SIs)

Geomagnetic sudden impulses (SIs) are sharp changes of the horizontal magnetic field which are caused by sudden increases or decreases of the solar wind dynamic pressure at interplanetary shocks and discontinuities.

adshelp[at] A Statistical Study of Sudden Impulse Characteristics to Understand their Space Weather Importance

Sudden Impulse (SI+ or SI-)

In solar-terrestrial terms, a sudden perturbation of several gammas in the northward component of the low-latitude geomagnetic field, not associated with a following geomagnetic storm. (An SI becomes an SC if a storm follows.)

NOAA forcast weather glossary: Sudden Impulse (SI+ or SI-)

Further Descriptions of SI Related to CMEs by NOAA

A Sudden Impulse (SI) caused by CME and detected by ground magnetometers that measure deviations in the Earth’s natural geomagnetic field in nanoteslas (nT). An SI is an instantaneous deviation in the northward component of the geomagnetic field at mid and low latitudes.

The geoelectric field can be integrated along conducting pathways to infer the induced voltage on power lines which leads to geomagnetically induced currents in the power grid.

SWPC.NOAA.Gov: Geoelectric Field Model Responses to Sudden Impulse

John Mortensen

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