Large Solar Flare Reaches Earth - Severe Space Weather Expected

Large Solar Flare Reaches Earth - Severe Space Weather Expected

Keith Cowing
Wednesday, March 28, 2001

Updated 3 April 2001 9:00 PM EDT

The sun continues to release massive amounts of energy in a display whose magnitude has not seen in decades. Last week's solar flare caused effects that are still being felt - according to the SEC "A storm of this magnitude normally causes adverse effects on a number of systems including public power, gas and oil pipelines, satellite operations, high-frequency radio communications, and low-frequency radio navigation."

According to NASA: "the Sun blasted one of its largest flares in 25 years from the same region harboring the largest sunspot of the current solar cycle Monday evening. The region, designated active region 9393, has continued to rotate with the Sun and is no longer in line with the Earth, so most of the flare's energy was directed away from our planet. However, radiation from the flare temporarily disrupted radio communications, and flare-related events generated a storm of high-velocity particles that, in greater numbers and energies, can affect sensitive electronic equipment in space.

"This explosion was estimated as an X-20 flare, and was as strong as the record X-20 flare on August 16, 1989, " said Dr. Paal Brekke, the European Space Agency Deputy Project Scientist for the Solar and Heliospheric Observatory (SOHO), one of a fleet of spacecraft monitoring solar activity and its effects on the Earth. "It was more powerful that the famous March 6, 1989 flare which was related to the disruption of the power grids in Canada." A large eruption on the surface of the sun near a rather large sunspot (9393) has sent a Coronal Mass Ejection (CME) outwards into space. This flare and its stream of charged particles is now arriving at Earth. Auroras are likely to result as are interuptions in radio communication.

The flare erupted at 4:51 p.m. EDT Monday, and produced an R4 radio blackout on the sunlit side of the Earth. An R4 blackout, rated by the NOAA SEC, is second to the most severe R5 classification. The classification measures the disruption in radio communications. X-ray and ultraviolet light from the flare changed the structure ofthe Earth's electrically charged upper atmosphere (ionosphere). This affected radio communication frequencies that either pass through the ionosphere to satellites or are reflected by it to traverse the globe.

The explosion, near the Sun's northwest limb (the upper right in SOHO images), was associated with an eruption of a cloud of electrified gas, called a coronal mass ejection, or CME, into space, but apparently not directed towards Earth."

1.0 MB animated GIF of SOHO Imagery 27-29 March showing CME
3 April 2001 NOAA SEC update:

"Analysis of Solar Active Regions and Activity from 02/2100Z to 03/2100Z: Solar activity has been high. Region 9393 (N18W82) produced a spectacular flare beginning at 02/2132Z, reaching maximum at 02/2151Z and ending at 02/2203Z: the peak of the event saturated the GOES-XRS sensors, but was estimated to be X20, the largest observed so far this solar cycle. A fast coronal mass ejection (CME) was observed in association with this event. The CME appeared to be primarily headed off the west limb, but there was a deflection of material near the north polar region, suggesting that the event trajectory might have some earthward component. In the LASCO-C3 coronagraph images, this CME was overtaking the previous CME associated with yesterday's X-class event from the same region. Region 9393 also produced an M2/2f flare at 1234Z. The leading spots of 9393 are currently rotating off the solar disk."

Forescast For April 4-10:

"Space weather is expected to be at moderate to strong levels. Region 9393 may produce another category R3 (strong) radio blackout before crossing the west limb on or about April 5. Region 9415, which recently rotated onto the face of the Sun, may also produce isolated category R2 (moderate) to R3 (strong) radio blackouts during the period. Category G2 (moderate) to G3 (strong) geomagnetic storm conditions will be possible during April 4 - 5 due to recent CME activity. Category S2 (moderate) to S3 (strong) solar radiation storms will be possible during the period."

Last week's story:

According to NOAA's Space Environment Center on 29 March 2001, "A very large, complex sunspot group is currently crossing the face of the Sun. This sunspot group, designated by NOAA space weather forecasters as Region 9393, has been growing at a rapid rate since rotating into view on March 22. Forecasters expect Region 9393 to produce intermittent radio blackouts as high as the category R3 (strong) level before it rotates to the back side of the Sun on April 5. This region also appears capable of producing a category S1 (minor) to S2 (moderate) space radiation storm. Earlier today, Region 9393 produced an R1 (minor) radio blackout followed by an Earth-directed coronal mass ejection (CME). This CME is expected to cause category G1 (minor) to G2 (moderate) geomagnetic storm conditions on March 30 - 31."

31 March 2001 NOAA SEC update:

"The geomagnetic field has been at severe storm levels. A shock passed the ACE spacecraft at 31/0023 UT and subsequently reached Earth's magnetic field at 31/0051. The storm developed after that time and reached maximum intensity after 31/0900 UT. It has continued into the later hours of the UT days. Dynamic auroral displays were reported across the United States with especially dynamic displays reported in Arizona, west Texas and California. The solar proton event that began at 29/1000 UT was declared over at 01/0600 UT."

30 March 2001 NOAA SEC update:

"Effects from CME's from the events on 29 March are expected to begin early on 31 March. Model runs predict an earlier arrival at Earth late on 30 March. ACE energetic protons are rising slowly indicating the disturbance is still some distance away at 30/2100 UT. Any geomagnetic storm that results is expected to range from minor to major. The small >30 MeV proton event in progress is expected to continue its slow decline with a chance of an enhancement with the passage of the interplanetary shock. Major activity from Region 9393 may well produce additional proton events and geomagnetic activity at Earth."

29 March 2001 NOAA SEC Update:

"Forecasters also expect geomagnetic storms reaching category G1 (minor) to G2 (moderate) to occur during March 30 - April 1 as a result of recent Earth-directed coronal mass ejections. Power systems, spacecraft operations, and high-frequency radio communications are adversely affected by geomagnetic storms. In addition, aurora may be visible along the northern tier of the U.S. this weekend."

28 March 2001 NOAA SEC Update:

"A major class X1.71/1N solar flare erupted at 10:15 UTC from Region 9393. This major flare was associated with a Type IV radio sweep and other radio emissions (data still incoming). A confirmed full halo CME is in-progress at the time of this alert. No velocity estimates are currently available. An Earth-directed CME impact from this disturbance is expected (based on VERY preliminary data) to occur sometime on 31 March or 01 April. A more refined estimate will be possible later. We expect to see protons begin increasing from this event over the next 12 hours. Protons at greater than 10 MeV are expected to reach or exceed event levels of 10 pfu during the interval."