[10] It saturated the Solrad 9 X-ray sensor at approximately X5.3 but was estimated to be in the vicinity of X20,[11] the threshold of the very rarely reached R5 on the NOAA radio blackout space weather scale.

[25] The 4 August flare and ejecta caused significant to extreme effects on the Earth's magnetosphere, which responded in an unusually complex manner.

Initially an exceptional geomagnetic response occurred and some extreme storming occurred locally later (some of these possibly within substorms), but arrival of subsequent CMEs with northward oriented magnetic fields is thought to have shifted the interplanetary magnetic field (IMF) from an initial southward to northward orientation, thus substantially suppressing geomagnetic activity as the solar blast was largely deflected away from rather than toward Earth.

[26] A 2006 study found that if a favorable IMF southward orientation were present that the Dst may have surpassed −1,600 nT, comparable to the 1859 Carrington Event.

[29] Estimated AE index peaked at over 3,000 nT and Kp reached 9 at several hourly intervals[30] (corresponding to NOAA G5 level).

[35] The Intelsat IV F-2 communications satellite solar panel arrays power generation was degraded by 5%, about 2 years worth of wear.

[37] Disruptions of Defense Meteorological Satellite Program (DMSP) scanner electronics caused anomalous dots of light in the southern polar cap imagery.

[1] On 4 August, an aurora shone so luminously that shadows were cast on the southern coast of the United Kingdom[1] and shortly later as far south as Bilbao, Spain at magnetic latitude 46°.

[38] Extending to 5 August, intense geomagnetic storming continued with bright red (a relatively rare color associated with extreme events) and fast-moving aurora visible at midday from dark regions of the Southern Hemisphere.

The voltage collapse of 64% on the North Dakota to Manitoba interconnection would have been sufficient to cause a system breakup if occurring during high export conditions on the line, which would have precipitated a large power outage.

Many U.S. utilities in these regions reported no disturbances, with the presence of igneous rock geology a suspected factor, as well as geomagnetic latitude and differences in operational characteristics of respective electrical grids.

[1] The U.S. Air Force's Vela nuclear detonation detection satellites mistook that an explosion occurred, but this was quickly dealt with by personnel monitoring the data in real-time.

[1] The U.S. Navy concluded, as shown in declassified documents,[43] that the seemingly spontaneous detonation of dozens of Destructor magnetic-influence sea mines (DSTs) within about 30 seconds in the Hon La area (magnetic latitude ≈9°) was highly likely the result of an intense solar storm.

However, this reduced dose could still have caused acute radiation sickness if the astronauts were located outside the protective magnetic field of Earth, which was the case for much of a lunar mission.

An astronaut engaged in EVA in orbit or on a moonwalk could have experienced severe radiation poisoning, or even absorbed a potentially lethal dose.

[45] Had the most intense solar activity of early August occurred during a mission, it would have forced the crew to abort the flight and resort to contingency measures, including an emergency return and landing for medical treatment.

Almost fifty years after the fact, the storm was reexamined in an October 2018 article published in the American Geophysical Union (AGU) journal Space Weather.

That initial terrestrial data from ground stations and balloons was later combined with spaceborne observatories to form far more complete information than had been previously possible, with this storm being one of the first widely documented of the then young Space Age.