Space Weather

Posted on July 14, 2009 by Rashid Faridi

Material from the Sun coming towards the Earth. It is the Sun's magnetic field carried in this material that causes magnetic storms.

What are we talking about when we describe the weather on Earth? We usually think of temperature, the speed and direction of the wind, air pressure, whether rain or snow is falling…Basically, when we say “weather” we mean conditions in our atmosphere that change from time to time.

“Weather” in Space?

There is a kind of weather in space, too. It isn’t quite the same as weather on Earth (you can’t really have wind if there is no air!), but it is similar in some ways. When we hear someone talk about “space weather”, they are discussing conditions in space that change from time to time. Sometimes the Sun gives off more radiation, sometimes it gives off less. A flow of charged particles (not air!) called the “solar wind” constantly streams outward from the Sun. The speed and pressure of this “solar wind” change all the time. Space is filled with magnetic fields, which control the motions of charged particles. The strengths and directions of the magnetic fields often shift. Changes in radiation, the solar wind, magnetic fields, and other factors make up space weather, just like changes in temperature, rainfall, and winds make up weather on Earth.
Space Weather Starts at the Sun
Most of space weather starts at the Sun. The amazing amount of energy the Sun gives off is what makes space weather go. Sometimes there are storms on the Sun, called solar flares and Coronal Mass Ejections (CMEs). These storms fling showers of radiation and powerful magnetic fields outward through our Solar System. Most storms miss Earth completely, but some storms hit our home planet. Those are the space weather storms we care about the most!

Space Weather Around Earth

When space weather from the Sunreaches Earth, it runs into our planet’s magnetic field and its atmosphere. The radiation and magnetic fields in space weather swirl around Earth in very complex patterns. Earth is surrounded by a sort of magnetic bubble called the “magnetosphere”. How do space weather storms affect Earth? Partly this depends on what the storms from the Sun are like. But it also depends on how those storms flow around and through Earth’s magnetosphere.
Changing Space Weather

Like weather on Earth, space weather is always changing. Some space weather storms form in minutes or hours. An “active region” on the Sun can last for many days or weeks, causing space weather storms for that whole time. Earth’s weather has long cycles, such as the gradual changes in temperature that come with the changing seasons. The Sun, too, has cycles; for example, the 11-year long sunspot cycle that brings along stormy and calmer space weather at different times in the cycle. On Earth, we call long-term trends in weather “climate”. Space weather also has trends lasting decades or centuries, which we can think of as the “climate” of space weather. Finally, the Sun has changed during the billions of years it has been around. These changes in the Sun have caused long term “climate change” effects in our space weather.
Space Weather and People

Why are people interested in space weather? Why should you care about space weather? The Sun is the main source of energy for our planet. It makes plants grow and makes our weather go. Changes in the Sun could make a big change in our weather and climate on Earth. Radiation from space weather storms can damage satellites, like the ones used for cell phone communications. That radiation can also harm astronauts, or even people on some kinds of jet airplane flights. Really powerful space weather storms can even knock out the electricity over large areas. But not everything about space weather is bad. Effects of space weather can be beautiful, too. When radiation from a storm crashes into our atmosphere, it sometimes makes really cool light shows. These light shows are called the aurora, or the Northern Lights and the Southern Lights.

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Faults and earthquakes in China monitored from space

Posted on July 14, 2009 by Rashid Faridi
Interferogram over the Wenchuan earthquake

Interferogram over the Wenchuan earthquake

Western China is in a very seismically active area and has had many catastrophic earthquakes during its history. A joint European-Chinese team is using satellite radar data to monitor ground deformation across major continental faults in China to understand better the seismic cycle and how faults behave.

Using Synthetic Aperture Radar (SAR) satellite data and  SAR Interferometry (InSAR), along with GPS data, scientists participating in ESA’s Dragon 2 Programme have been able to measure the ground deformation that occurred during the Wenchuan earthquake that struck China’s Sichuan Province last May.

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Isro,India preparing satellite to map climate change

Posted on July 13, 2009 by Rashid Faridi

The Indian Space Research Organisation is working on a geostationary satellite, which it plans to hand over in two to three years to the Indian Meteorological Department (IMD) to help it unravel climate change trends.”The satellite will help IMD track the changing monsoon pattern and cloud shifts,” said G Madhavan Nair, chairman of the Space Commission and the Indian Space Research Organisation (Isro) and, secretary, department of space, Government of India.

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What Lies inside the Sun?

Posted on July 12, 2009 by Rashid Faridi

When a pond’s surface is calm, you can see more clearly into its depths. As it turns out, the same is true for the sun. Researchers are excited that the sun’s surface is calmer now than it’s been in almost a century. It’s a rare opportunity — the first since the Space Age began — to peer more clearly into the sun’s mysterious interior.

To take advantage of the opportunity, NASA is about to launch the Solar Dynamics Observatory (SDO). SDO is expected to launch this year, as early as November 2009. “That’s perfect timing,” says Dean Pesnell, a solar physicist at the Goddard Space Flight Center in Greenbelt, Md. “The sun is experiencing a century-class solar minimum, offering the clearest possible views.” “SDO will actually see through the sun’s surface,” added Pesnell. “The process is a little like taking an ultrasound of a pregnant mother. You can see the baby right through the skin.”

The sensor that performs this trick is called the Helioseismic and Magnetic Imager (HMI). It can sense acoustic waves moving  through the sun, and turn those waves into a fairly clear image of the interior. “There’s a lot going on inside the sun that we don’t understand,” notes Todd Hoeksema, a solar physicist at Stanford University, Palo Alto, Calif. where the HMI was built. “The Solar Dynamics Observatory is bound to deliver some big discoveries.”

The biggest discovery of all would be the inner workings of the solar dynamo. Deep beneath the sun’s visible surface, massive currents of electrically-charged gas (plasma) circulate in patterns that give rise to the sun’s powerful magnetic field. Almost all solar activity from sunspots to solar flares is regulated by this inner dynamo. “Understanding how the dynamo works is a holy grail for stellar physics,” says Pesnell. “It is the key to forecasting solar activity and space weather.” The problem is these deep flows are hidden from view.

The sun’s surface is bright and opaque, so it is impossible to look through it. Instead, solar physicists study the sun’s interior the same way that geologists look deep into the Earth—via seismology. Just as earthquakes trigger seismic waves that travel through the Earth, shifting mass in the sun sends pressure waves rippling through its interior. These p modes (p for pressure) bounce around inside the sun, causing the star to ring like an enormous bell. HMI detects the surface vibrations, which in turn can be analyzed to sunspots can get in the way of the waves, distorting their times and frequencies, making it tricky to figure out what’s really happening inside the complicated solar interior. That’s why the current lack of sunspots is good for helioseismology. “You have more sensitivity to what’s happening deep in the sun when there’s not as much interference from the surface,” Hoeksema explains. At the peak of the solar cycle, sunspots are numerous. So far in 2009, the sun’s surface has been free of sunspots about 80 percent of the time — the most tranquil it’s been since 1913. From a geosynchronous orbit 22,000 miles above Earth’s surface, SDO will observe helioseismic waves more precisely than ever before.

The current gold standard for observing the sun is a satellite called the Solar and Heliospheric Observatory, or SOHO, which maps helioseismic activity with mega-pixel resolution once every minute or so. HMI will up the ante to 16 megapixels every 45 seconds, resulting in a far more detailed view of the solar interior. SDO will also improve on SOHO by beaming its torrent of raw data down to Earth unprocessed. Because of limited download bandwidth, SOHO performs some calculations while the data are still onboard the spacecraft. Only the results are beamed to scientists. Since SOHO was launched in 1995, scientists have since devised better ways to process the data and correct for errors. But there’s no way they can apply these new techniques to SOHO imagery because the data have already been “crunched” by the time they leave the spacecraft. To give scientists full access to its original data, SDO will have a continuous, 150 megabit per second download link. In comparison, most home high-speed internet connections are only 1 to 10 megabits per second. Somewhere in all those p modes will be the telltale signs of solar jet streams, subsurface winds, proto-sunspots, and the solar dynamo itself — all “seen” with unprecedented clarity. With the sun so calm, now is a great time to look.

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