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From: Cary Oler Message-Id: <> Subject: AstroAlert: Potential Major Auroral/Geomagnetic Storm Warning - 06-07Apr To: Date: Thu, 6 Apr 2000 14:11:45 -0600 (MDT) Sender:

------------------------------------ | | MIDDLE LATITUDE | A s t r o A l e r t | 06 and 07 April AURORA WARNING | | ----------------- Sun-Earth Alert -------------------

** Potential category G3 Geomagnetic Storm **

One of the most vigorous interplanetary disturbances to impact the Earth so far this solar cycle collided with the Earth's magnetosphere near 16:40 UTC on 06 April. The disturbance was preceded by one of the strongest shock fronts yet observed this solar cycle. Solar wind velocities almost instantaneously increased by almost 200 kilometers per second within a minute or two from a background quiet-time value of 380 km/sec to a value exceeding 570 km/sec. The strength of the magnetic fields in space (which originate from the Sun and are dragged outward by the solar wind) also increased dramatically in magnitude by a factor of almost 4 times the normal quiet-time background value.

The sudden increase in solar wind pressure against the Earth's magnetosphere, combined with the favorable southward orientation of the solar wind magnetic fields resulted in increased erosion and compression of the sunward side of the Earth's magnetic field. This has caused the GOES-8 and GOES-10 geosynchronously orbiting spacecraft (and all other geosynchronously orbiting spacecraft near the "noon sector" of the Earth) to pass through the protective barrier that separates the quiet and stable magnetic field of the Earth from the more turbulent and hazardous environment inside what is known as the magnetosheath which is the transition region between the solar wind and the Earth's magnetic field. Passage of spacecraft through these regions can affect satellite health and can make it difficult for satellite operators to maintain spacecraft pointing stability.

The effects of this disturbance are also being strongly felt in the Earth's ionosphere. This is producing heavy degradation in the quality of radio signals that rely on the ionosphere to propagate to distant locations around the world. Communications with spacecraft may also be affected. The disturbed ionosphere can cause spacecraft signals to begin to scintillate, which can affect communications with spacecraft.

Another adverse effect of this storm will be to increase the atmospheric drag on satellites. This effect is expected to begin within the next 3 hours (anytime after about 23:00 UTC on 06 April) and is caused in-part by the heating and expansion of the Earth's upper atmospheric envelope. This increased drag can change the orbital elements of lower orbiting spacecraft, particularly those spacecraft with perigees below about 500 kilometers.

Intensely varying magnetic fields can also cause problems for electrical power generating companies, particularly those whose power-generating grids are located in the upper-middle and high latitude regions. The problems manifest themselves as induced electrical currents that are superimposed upon the existing electrically generated power flowing through power lines. These induced currents can damage (and in rare cases even destroy) expensive equipment such as electrical power transformers. In most cases, the general public will not notice the effects of these induced currents. The equipment that brings power to your house are well regulated against such events. The worst that can happen is the complete loss of electrical power if damage should occur to the large transformers and other susceptible equipment maintained by the power companies. An extreme example of such an event occurred in Quebec in March 1989, where power was lost to more than 6 million people. Since then, power companies such as Hydro Quebec have expended considerable sums of money to help protect against recurrences of geomagnetically induced power outages.

A strong geomagnetic and auroral storm is currently brewing over the northern Russian and European regions, based on the latest spacecraft imagery. There is uncertainty whether this storm will persist into the night hours for North American observers. If the disturbed conditions persist, observations well into the central U.S. states should be possible under dark skies. If the disturbance decays before then, activity may be limited to the southern Canadian provinces and/or the northern tier of the U.S. states. In either case, observers over North America may wish to take special note of this disturbance, which is occurring during the near-new phase of the moon. Thus, optimal observing conditions and dark skies should provide a maximal unimpeded view of possible auroral activity.

Observers who successfully spot auroral activity are asked to report their findings to: so others may see the observations. All reports are permanently archived for potential future scientific use. Space weather forecasters at the Space Environment Center and elsewhere also make use of the reports submitted by amateurs to this site.

We are also interested in receiving digitized (scanned) photographs of auroral activity that amateurs make during this storm. Later, we will release a compiled list of the images we receive on a web page with appropriate credits to those who provided them to us. We will also provide any links to the images that are included with the images. Imagery can be e-mailed to: STD@Solar.Spacew.Com. Please include appropriate wording for credits and links to any of your web pages for further information.

The current estimated visible limits of auroral activity may be seen from the map provided at: Spacecraft derived imagery and products are also available within that page.

The duration of this disturbance will probably continue through the mid UTC hours of 07 April. The intensity of the storm could change rapidly if the magnetic fields within the solar wind do not maintain their current southward orientation. Such shifts in the orientation of the solar wind magnetic fields can occur very rapidly. Within as little as 2 hours, a very strong auroral storm can diminish to insignificant levels during such rapid swings in solar wind magnetic field direction. As a result, for near-realtime information concerning the state of auroral activity, rely on the sites above. Serious users, media, and other organizations requiring immediate notification of the arrival and current status of disturbances such as this one should consider purchasing software such as SWARM ( for staying on top of these (and future) conditions.

This storm has the potential of being one of the largest events observed so far this solar cycle.

** End of AstroAlert **

-- Flash (flash@flash.hq), April 07, 2000



SEC Space Weather Advisory

Official Space Weather Advisory issued by NOAA Space Environment Center Boulder, Colorado, USA SPACE WEATHER BULLETIN #00- 2 2000 April 06 at 02:50 p.m. MDT (2000 April 06 2050 UT)


The ACE spacecraft, located approximately one million miles towards the Sun, detected a fast-moving ejection in the solar wind at approximately 10:00 AM MDT today (1600 UT on April 6). This structure is believed to have been launched from the Sun late on April 4. The Earth's magnetic field responded shortly thereafter, and major storm conditions are now occurring at all latitudes.

It is expected that this storm will continue for the next 24-36 hours. Significant impacts on terrestrial systems include some electrical power systems, spacecraft operations, and communications and navigation systems.

In terms of the New NOAA Space Weather Scales, this storm may reach category G3 (strong)level.

-- viewer (, April 07, 2000.


Expect to see EZboard regulars sporting double thickness tinfoil hats.

First person to post a photo of a SLEZboarder wearing his/her hat wins todays major prize.


-- w0lv3r1n3 (, April 07, 2000.


Thanks for the great NOAA site URL. Nothing better than getting it "straight from the horses mouth".

Now that I think of it, there's a horse about 100 feet from my bedroom window. Maybe I should go ask him ...

-- Flash (flash@flash.hq), April 07, 2000.

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