Air Force Keeps a Wary Eye on Ferocious Space Storms
HANSCOM AIR FORCE BASE, MA — If you plan to orbit the Earth this week, be sure
to pack plenty of sunscreen. Two whopping solar flares — among recorded
history’s worst 20 — have blasted the Earth’s protective magnetosphere with
potent clouds of solar radiation and energized particles from the sun, leaving
in their wake the potential for fried satellites and scrambled circuits on the
ground. Not good news for electronically-dependant military and civilian
telecommunication operations.
But instead of merely complaining about this "weather" in space, solar
physicists at the Air Force Research Laboratory’s (AFRL) Space Weather Center of
Excellence outside Boston are actually doing something about it. And they rely
on one of their most recent space-based tools, the Solar Mass Ejection Imager
(SMEI), to track the sun’s activity.
Also known as coronal mass ejections, or CMEs, solar eruptions are incompletely
understood yet natural phenomena that occur periodically — often in 11-year
cycles — and with varying levels of intensity. They trigger geomagnetic storms
— this week’s first one rated at G5, the highest possible — harmful to
spacecraft and communications, increase radiation exposure for astronauts and
high-flying aircraft, and damage ground-based power grids and subsystems. Such
storms have impaired U.S. communication satellites in the past and blacked-out
power stations in Canada. This week’s solar assault forced some air traffic
controllers to alter aircraft flight plans due to disrupted radio transmissions
and crippled two Japanese satellites. If CMEs were better understood and more
accurately anticipated, steps might then be taken to mitigate their disruptive
effects, such as temporarily shutting down satellites and switching off power
systems. SMEI is now beginning to help shed some light on the yet hidden
mysteries behind solar storms and their effects on advanced technology.
For its solar reconnaissance mission, SMEI uses first-of-a-kind cameras aboard
Coriolis, a DoD Space Test Program spacecraft. Launched just nine months ago,
SMEI and its highly sensitive cameras reached orbit just in time to study how
such violent storms behave. Built as a proof-of-concept experiment to detect,
track and forecast CMEs, SMEI has now detected many of the sun’s radiation-laden
eruptions.
"An Earth-bound CME looks like a broad, bright, outward-moving ring with the sun
at its center, or a halo," said AFRL geophysicist David Webb. "Our SMEI cameras
have detected two of them within the last week, which were part of a series of
major events centered around two huge sunspot groups on the sun," he added. An
image of the first event in this series appears in Figure 1. Fig. 2 shows two
white light images of the Sun showing the motion of the sunspots over 5 days.
SMEI, in a sun-synchronous polar orbit around the Earth, can detect even fast,
Earth-bound CMEs up to a day before their arrival, providing valuable early
warning of an impending storm unobtainable until now. Warning time is truly of
the essence here, given that one solar eruption this week took only took 19
hours to reach the Earth. Seeing CMEs in this distance range (20-180 degrees
from the sun) is a new capability that along with other space environment
sensors promises to greatly enhance the space weather "big picture."
"Although the jury is still out on what impact all this recent solar activity
has had on satellites and ground communications, we expect that SMEI, only in
its first year of operation, will better enable us to predict future solar
events and provide earlier warning of incoming CMEs," he said. "Then we can take
preventative measures to protect sensitive electronics, in space as well as on
the ground."
IMAGE CAPTIONS:
[Figure 1:
http://www.vs.afrl.af.mil/News/images/03-28-A.jpg (62KB)]
Partial field of view of SMEI camera 3 on Oct. 29 at 02:10 UT. The + sign
denotes the Sun’s position and the dark circle is an excluded zone around the
Sun. This is a difference image of the previous orbit subtracted from the
present one. Arrows point to bright/dark arcs to the upper right and the bright
structure to the lower left that are parts of the halo CME. Black/white areas
are contamination by particles in Earth orbit.
[Figure 2:
http://www.vs.afrl.af.mil/News/images/03-28-B.jpg (43KB)]
White light images of the Sun on Oct. 23 and 28, both at 00:00 UT. From SOHO MDI
instrument.
