NOAA SEC Space Weather Outlook 07-18-2000
SPACE WEATHER OUTLOOK #00- 33
2000 July 18 at 02:46 p.m. MDT (2000 July 18 2046 UT)
**** SPACE WEATHER OUTLOOK ****
Summary For July 10-16
Space weather reached extreme levels during the period. A large and
extremely complex sunspot group produced four major flares during July
10 – 14, the largest of which produced a category R3 (strong) radio
blackout at 4:24 a.m. (1024 UTC) on July 14. This radio blackout likely
caused the following effects on the sunlit side of Earth: a wide-area
blackout of HF radio communication signals resulting in loss of radio
contact for mariners an en route aviators for an hour or more, and
degradation of low-frequency navigation signals for about an hour
affecting maritime and general aviation positioning. This flare also
produced a category S4 (severe) solar radiation storm which was the
largest radiation event observed since 1991. Severe solar radiation
storms may result in some or all of the following effects: satellite
operations experience memory device problems, noise on imaging systems,
star trackers cause orientation problems, and solar panels degraded;
blackout of HF radio communications throughout the polar regions; and
increased navigation errors for several days. A fast-moving, halo-type
coronal mass ejection (CME) also followed the major flare of July 14.
The CME impacted Earth’s magnetic field on July 15 and caused a
geomagnetic storm that reached category G5 (extreme) levels. This storm
was the largest recorded since 1989. Category G5 (extreme) geomagnetic
storms may cause some or all of the following system effects: power
grids may collapse and transformers experience damage; and spacecraft
operations experience extensive surface charging on spacecraft and
problems with orientation, uplink/downlink and tracking satellites.
Other G5 geomagnetic storm effects include pipeline currents reaching
hundreds of amps, HF radio propagation impossible in many areas for one
or two days, satellite navigation degraded for days, low-frequency
radio navigation out for hours, and the aurora seen as low as the
equator.
Outlook For July 19-25
Space weather is expected to be at minor to moderate levels. There will
be a chance for an isolated category R2 (moderate) radio blackout
during the period. There will also be a chance for a category S1
(minor) solar radiation storm.
Data used to provide space weather services are contributed by NOAA,
USAF, NASA, NSF, USGS, the International Space Environment Services
and other observatories, universities, and institutions. More
information is available at SEC’s Web site http://sec.noaa.gov or
(303) 497-5127. The NOAA Public Affairs contact is Barbara McGehan
at bmcgehan@boulder.noaa.gov or (303) 497-6288.