| Halloween solar storms, 2003 | |
| G-Impacts: | Electrical faults and wear to various satellites; satellite communications blackouts; localized power outage in Sweden |
| Solar-Cycle: | 23 |
| Dst: | −383 nT |
| K-Index: | 9 |
| A-Index: | 204 |
| Ar-Sxr-Flares: | X40+ |
| G-Scale: | 5 |
| Noaa: | 10486 |
The Halloween solar storms were a series of solar storms involving solar flares and coronal mass ejections that occurred from mid-October to early November 2003, peaking around October 28–29.[1] [2] [3] This series of storms generated the largest solar flare ever recorded by the GOES system, modeled as strong as X45 (initially estimated at X28 due to saturation of GOES' detectors).[4] [5]
Satellite-based systems and communications were affected, aircraft were advised to avoid high altitudes near the polar regions,[6] and a one-hour-long power outage occurred in Sweden as a result of the solar activity.[2] Aurorae were observed at latitudes as far south as Texas[2] and the Mediterranean countries of Europe.[6] Twelve transformers in South Africa were disabled and had to be replaced, despite the country's low geomagnetic latitude.[7]
The SOHO satellite failed temporarily and the Advanced Composition Explorer (ACE) was damaged by the solar activity.[2] Numerous other spacecraft were damaged or experienced downtime due to various issues. Some of them were intentionally put into safe mode in order to protect sensitive equipment.[6] Astronauts aboard the International Space Station (ISS) had to stay inside the more shielded parts of the Russian Orbital Segment to protect themselves against the increased radiation levels.[8]
Emissions from the CME were later observed by the Mars Odyssey spacecraft orbiting Mars, Ulysses spacecraft near Jupiter, and the Cassini spacecraft en route to Saturn. In April 2004, Voyager 2 was also able to detect them as they reached the spacecraft.[8]
One of the solar storms was compared by some scientists in its intensity to the Carrington Event of 1859.[9]
These events occurred during solar cycle 23, approximately three years after its peak in 2000, which was marked by another occurrence of solar activity known as the Bastille Day event.