Bastille Day solar storm

The Bastille Day solar storm was a powerful solar storm on 14–16 July 2000 during the solar maximum of solar cycle 23. The storm began on the national day of France, Bastille Day. It involved a solar flare, a solar particle event, and a coronal mass ejection which caused a severe geomagnetic storm.^[1][2]

Bastille Day solar storm

IMAGE ultraviolet image of the Aurora Borealis on 15 July 2000
Associated solar active region
NOAA region no.	9077
Largest SXR flares	X5.7
G5 "Extreme" geomagnetic storm
G-scale (NOAA/SWPC)
Initial onset	14 July 2000 (2000-07-14)
Dissipated	16 July 2000 (2000-07-16)
Peak Kp-index	9
Peak Ap-index	164
Peak Dst	−301 nT
Impacts	Minor satellite and terrestrial power transformer damage
Part of solar cycle 23

Overview

Solar flare and particle event

On 14 July 2000 from about 10:03 to 10:43 UTC, GOES satellites detected a very strong, X5.7-class solar flare^{[note 1]} which peaked in soft X-ray intensity at around 10:24 UTC. This flare originated from the solar active region AR9077 which was located near the center of the Sun's disk (N22 W02) at the time of the flare.^[3][4]

Starting at around 10:41 UTC, GOES satellites began detecting a strong, S3, solar particle event^{[note 2]} associated with the ongoing X5.7-class flare.^[1] This resulted in high energy protons penetrating and ionizing parts of the Earth's ionosphere and creating noise in various satellite imaging systems such as in the EIT and LASCO instruments.^[7] Some of these particles had sufficient energy to generate effects measured on Earth's surface, an event referred to as a ground level enhancement. Although the flare was not extremely large, the associated solar particle event was the fourth largest since 1967.^[4]

Geomagnetic storm

The detection of the solar flare was also followed by the detection of a halo, or Earth-directed, coronal mass ejection (CME) in coronagraph data starting at 10:54 UTC.^[7] This CME reached Earth on 15 July causing a geomagnetic storm on 15–16 July which would reach a peak Kp index of 9+ in the late hours of 15 July corresponding to an extreme-level, or G5, geomagnetic storm^{[note 3]} and register a peak Dst of −301 nT. The storm caused minor damage to power transformers and satellites.^[8] It was also one of only three solar storms having registered a maximum Kp of 9+ since the March 1989 geomagnetic storm, the others being the 2003 Halloween solar storms and the May 2024 solar storms.^[9]

Aftermath

Due to being the first major solar storm since the launch of various solar-monitoring satellites, the Bastille Day event proved important towards helping scientists piece together a general theory of how eruptions on the sun occur as well as protecting the Earth from a larger event, such as a Carrington-class event, some day in the future.^[10]

Despite their great distance from the Sun, the Bastille Day event was observed by Voyager 1 and Voyager 2.^[11]

See also

• List of solar storms

Notes

1. The label X5.7-class implies that the solar flare had a peak soft X-ray flux of 5.7×10⁻³ W/m² in the 0.1 to 0.8 nm (1 to 8 Å) passband. (See Solar flare § Soft X-ray classification.)
2. The label S3 is assigned to solar particle events which have a flux of protons with energies ≥10 MeV peaking between 10³ and 10⁴ proton flux units (or particle cm⁻² s⁻¹ sr⁻¹).^[5][6]
3. The label G5 is assigned to geomagnetic storms which reach a peak Kp index of 9 or more.^[5] (See K-index § G-scale.)

References

1. "Space Radiation Storm". NASA. 2004-07-14. Archived from the original on 2000-08-15. Retrieved 2007-03-09.
2. "NASA Says Solar Flare Caused Radio Blackouts". The New York Times. Associated Press. 2000-07-14. Retrieved 2007-03-09.
3. Reiner, M.J.; Kaiser, M.L.; Karlický, M.; Jiřička, K.; Bougeret, J.-L. (2001). "Bastille Day Event: A Radio Perspective". Solar Physics. 204: 121–137. Bibcode:2001SoPh..204..121R. doi:10.1023/A:1014225323289. S2CID 133879595.
4. Watari, Shinichi; Kunitake, Manabu; Watanabe, Takashi (January 2001). "The Bastille Day (14 July 2000) event in historical large sun-earth connection events". Solar Physics. 204: 425–438. Bibcode:2001SoPh..204..425W. doi:10.1023/A:1014273227639. S2CID 117394988. Retrieved 2 January 2021.
5. "NOAA Space Weather Scales | NOAA / NWS Space Weather Prediction Center". www.swpc.noaa.gov. Archived from the original on 19 August 2024. Retrieved 7 August 2022.
6. "Solar Radiation Storm | NOAA / NWS Space Weather Prediction Center". www.swpc.noaa.gov. Archived from the original on 26 July 2024. Retrieved 7 August 2022.
7. Andrews, M.D. (2001). "Lasco and eit Observations of the Bastille day 2000 Solar Storm". Solar Physics. 204: 179–196. Bibcode:2001SoPh..204..179A. doi:10.1023/A:1014215923912. S2CID 118618198.
8. "Minor Damage Reported from Geomagnetic Storm" (PDF). Archived (PDF) from the original on 14 May 2024. Retrieved 2 January 2021.
9. "Top 50 Geomagnetic Storms". Archived from the original on 21 May 2024. Retrieved 2 January 2021.
10. Moskowitz, Clara (14 July 2011). "Bastille Day Solar Storm: Anatomy of a Gargantuan Sun Tempest". Archived from the original on 12 May 2024. Retrieved 2 January 2021.
11. Webber, W. R.; McDonald, F. B.; Lockwood, J. A.; Heikkila, B. (15 May 2002). "The effect of the July 14, 2000 "Bastille Day" solar flare event on >70 MeV galactic cosmic rays observed at V1 and V2 in the distant heliosphere". Geophysical Research Letters. 29 (10): 15–1–15-3. Bibcode:2002GeoRL..29.1377W. doi:10.1029/2002GL014729. S2CID 115950366.

External links

• 'Bastille Day' Flare Animations Archived 2016-12-10 at the Wayback Machine
• Propagation of Bastille Day Event to Voyagers 1 & 2
• High-Energy Ions Energized by Bastille Day 2000 Shock Bombardment
• Ulysses Observations of Solar Energetic Particles From the Bastille Day Event