SWFX 07: It Came from the Sun
Copyright 2009, MIT Haystack Observatory
VOICE-OVER: Space weather is something we experience because we live near
a star. When the Sun is active, we experience a LOT of space weather. Out in
the countryside near Boston Massachusetts, scientists at MIT’s Haystack
Observatory track what happens when the Sun stirs up a little space weather.
Crossfade from opening title sequence to Phil against a backdrop of SOHO and
STEREO sequences.
PHIL: Atmospheric scientists have tracked the Sun’s variability for many years.
We’ve noticed that it goes through periods of higher activity — followed by times
when it is fairly quiet. During active times, we see more sunspots, flares, and
coronal mass ejections. When it’s quiet, we see very little change.
Crossfade to SOHO sequences of Hallowe’en outburst and aftermath.
On October 28, 2003, the Sun erupted in a spectacular fashion not once but
several times over a period of about a week. Those events came to be known as
the Halloween solar storms and they taught us a great deal about what happens
to our upper atmosphere during periods of high solar activity.
During these events, billions of tons of plasma streamed out from the Sun past
the Earth and planets making these some of the largest solar storms ever
recorded.
The storms began with a powerful solar flare, followed by a coronal mass
ejection of particles aimed directly at Earth. Here is a view of one of these
events from the SOHO orbiting satellite observatory.
Crossfade to Phil and colleagues examining data during meeting.
At Haystack Observatory, we tracked the effects of this storm high in the
ionosphere over the continental United States. What we were interested in was
how plasma in the ionosphere acted at mid-latitudes — during the storm and
shortly thereafter.
Phil against backdrop with TEC defined by graphics and animated plots.
We paid close attention to changes in the total electron content — that is, the
total number of electrons in the plasma in a vertical column through the upper
atmosphere. During periods when the Sun is quiet, that measurement will be as
low as 10 TEC units, or even lower.
For the Hallowe’en outburst, we measured a dramatic ionospheric storm front
sweeping across the continental United States. At one point, TEC values
exceeded one hundred fifty units — a very large value.
Using our radars, satellite imagers, and the worldwide GPS receiver network, we
were able to watch as the charged particle fronts migrated. These fronts can
move from the tropical and mid-latitude regions of the planet very quickly — at
about a kilometer per second. And, after about 45 minutes, they end up all the
way at the polar regions.
Crossfade to view of Haystack radar moving.
From the ground, Haystack instruments measured these effects because we
could use our large radar to observe the ionosphere. In particular, our reflected
radar signals were changed by the motion of the plasma. GPS ground receivers
added data about how their signals were slowed down or disrupted by these
same plasma changes.
Crossfade to Phil and TEC animation sequences from Goddard.
And, we used ultraviolet data from the IMAGE satellite in near-Earth space to
reveal even larger-scale changes in the plasma cloud which surrounds the Earth
and rotates with it. By combining these different views, our science team, and
others around the world, were able to understand and map the effect of the
Hallowe’en solar outburst on Earth’s upper atmosphere.
Crossfade to Phil and colleagues at Haystack looking at data.
We continue to monitor the ionosphere during periods of both low and high solar
activity. What we learn will benefit people in a great many ways: from earlywarning systems when flares and outbursts threaten Earth, to information
valuable to electric power grid operators keeping the lights on.
Crossfade to Phil and summary against Sun-Earth connection image.
We also gain a deeper understanding of the Sun-Earth connection and how it
ultimately affects our planet.