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 www.swpc.noaa.gov/noaa-scales-explanation
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]cfa.harvard.edu: 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