A new solar telescope, scheduled to launch this winter, will
probe the sun's atmosphere and inner workings, helping scientists better
understand how solar storms.
During its five-year mission, the Earth-orbiting Solar
Dynamics Observatory (SDO) will seek to reveal how the sun's magnetic field
works, what governs the ups and downs of the
solar cycle and how solar
activity affects Earth.
"The sun is a magnetic variable star that fluctuates on
times scales ranging from a fraction of a second to billions of years,"
said Madhulika Guhathakurta, lead program scientist for the Living With a Star
program (of which SDO is a part) at NASA Headquarters in Washington, D.C.
"SDO will show us how variable the sun really is and reveal the underlying
physics of solar variability."
Tracing magnetic fields
SDO will measure and observe the sun's magnetic field, which
powers all solar activity. Flow of hot, ionized gases in the sun's convection
zone — the region inside the sun where hot gas parcels rise and transport
energy to the surface — act as electrical currents to generate the sun's
magnetic field.
The observatory will look at the fields at the surface of
the sun and use those measurements to infer exactly where the fields originate
inside the sun and where they are expressed as active regions, such as sunspots
and coronal loops, to where they eject particles into space as coronal mass
ejections and solar
flares (both of which can impact the function of satellites and electrical
grids on Earth).
The goal is to better understand how the sun's magnetic
field is generated and how its energy impacts solar radiation, which in turn
affects the rest of the solar system, including Earth.
Ups and downs
SDO will also follow changes in the sun's activity, which is
known to rise and fall on a roughly 11-year cycle. A solar cycle is at its
maximum when the greatest number of sunspots is counted in a year; the minimum
occurs when the fewest are seen. Both of these markers can only be recognized
after they have been passed.
And of course, the solar cycle doesn't always follow that
11-year course. Between 1645 and 1715, for example, sunspots were rarely
observed — a period called the Maunder Minimum — and Europe and North America
both experienced bitterly cold winters — a time known as the "Little Ice
Age." (The sun is currently in a lull, with next maximum expected
in 2013.)
The potential connection between low levels of solar
activity and Earth's climate are something scientists want to better understand
in the hopes that they could eventually learn to predict these ups and downs.
Tools for the job
To make all of these observations, SDO will use three
science instruments:
The Helioseismic and Magnetic Imager (HMI) will peer into
the sun and map the surface of the sun's magnetic fields, as well as the plasma
flows that generate magnetic fields.
The Atmospheric Imaging Assembly (AIA) will image the solar
atmosphere in multiple wavelengths that cannot be seen from the ground. HMI and
AIA will together link changes on the solar surface to the sun's interior.
The Extreme Ultraviolet Variability Experiment (EVE) will
measure how much energy the sun emits at extreme ultraviolet wavelengths, which
can only be observed from space because they are completely blocked out by
Earth's atmosphere. These wavelengths of light are important to study because
they can affect astronauts out in space.
SDO will watch the sun almost 24 hours a day as it orbits
the Earth in a figure-eight path. The spacecraft will take images of the sun
every few seconds with the visual quality of an IMAX movie, giving scientists
an unprecedented look at our parent star.
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