This picture shows material from the Sun coming towards the Earth. It is the Sun's magnetic field carried in this material that causes magnetic storms. Click on image for full size (30K GIF) Image courtesy NASA.

Weather on Earth is the set of ever-changing ambient conditions in our atmosphere. Its elements include temperature, air pressure, wind speed and direction, humidity, precipitation, and so on. Space weather is the set of ever-changing ambient conditions in the space within our Solar System. Its elements include electromagnetic radiation, the solar wind of charged particles which flows outward from the Sun, and the force of the Interplanetary Magnetic Field (IMF) which spirals outward from our parent star.

Space Weather Starts at the Sun

The Sun is the primary driver of space weather. Storms on the Sun, in the form of solar flares and Coronal Mass Ejections (CMEs), can launch showers of radiation and powerful magnetic fields into interplanetary space. We are most concerned about local impacts of space weather, meaning those storms which are directed at Earth and influence our home planet.

Space Weather at Earth and in Near-Earth Space (Geospace)

When a cold front on Earth encounters a mountain range the local weather conditions are influenced by the local topography. Similarly, when a strong pulse in the solar wind generated by a CME encounters Earth's magnetic field, the solar wind and Earth's magnetosphere interact in complex ways to influence the net results of the "storm" on Earth and in near-Earth space.

Short-term and Long-term Changes in Space Weather

Some of our space weather comes as short-lived storms which can last minutes to hours to days. The Sun also undergoes cycles in its level of activity that span years to decades, causing longer-term variations in space weather. Finally, the Sun has changed substantially over the multi-billion year history of our Solar System, producing long term "climate change" effects in our space weather.

How does Space Weather affect People and Human Society?

Why is space weather of interest to humans? Since sunlight is the primary driver of Earth's weather, variations in the Sun's output may influence weather and climate on Earth. Radiation from space weather storms can endanger astronauts and can damage and destroy satellites, such as those used for cell phone communications. Some electrical power grids have been knocked out of commission by especially powerful solar storms. Such storms can be sources of beauty as well as destruction. The marvelous displays of the aurora (the Northern and Southern Lights) are caused by collisions of particles energized by solar storms with gases in Earth's upper atmosphere.

This picture shows material from the Sun coming towards the Earth. It is the Sun's magnetic field carried in this material that causes magnetic storms. Click on image for full size (30K GIF) Image courtesy NASA.

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 you 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 Sun reaches 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 Should I Care?

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.

This picture shows material from the Sun coming towards the Earth. It is the Sun's magnetic field carried in this material that causes magnetic storms. Click on image for full size (30K GIF) Image courtesy NASA.

You know about the weather on Earth. If someone asks you about the weather in your city today, you might say whether or not it's cloudy, whether rain or snow is falling, or if it's windy.

"Weather" in Space?

But did you know that there is a weather in space too? When you hear someone talk about "space weather", they are talking about conditions in space that change from time to time. These changing conditions could be the amount of radiation from the Sun or how the the "solar wind" is flowing that day. Even magnetic fields in space can affect space weather. Changes in radiation, the solar wind, and magnetic fields make up space weather, just like changes in temperature, rainfall, and winds make up weather on Earth.

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, and these storms fling showers of radiation and powerful magnetic fields out into the Solar System. Most storms miss Earth, but some storms hit our planet. Those are the space weather storms we care about the most!

Space Weather Around Earth

When space weather from the Sun reaches Earth, it runs into a sort of magnetic bubble that surrounds the Earth called the "magnetosphere". How do space weather storms affect Earth? This depends on what the kind of storms from the Sun. It also depends on how those storms interact with the Earth's magnetosphere.

Changing Space Weather

Like weather on Earth, space weather is always changing. Just like Earth's weather changes with the changing seasons, space weather changes with a 11-year long sunspot cycle. At different times in the cycle, the Sun will be more stormy or more calm.

Space Weather and People - Why Should I Care?

Why are people interested in 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. Storms from the Sun can hurt satellites, like the ones used for cell phones. That radiation can also hurt astronauts if they are in space when a storm comes. Really big space weather storms can even knock out the electricity over large areas. But not everything about space weather is bad. Sometimes storms makes really cool light shows. These light shows are called the aurora, or the Northern Lights and the Southern Lights.