A fluxgate magnetometer for measuring magnetic fields. Click on image for full size (21K JPEG) Image courtesy the Auroral Observatory of the University of Tromso, Norway.

Scientists use a broad array of techniques and instruments to make the measurements needed for space weather investigations.

Solar Remote Sensing via Electromagnetic Radiation

Telescopic observations via spacecraft and ground-based observatories provide us with spectacular images of the Sun and the solar atmosphere. These observations are not confined to visible light, but range across the electromagnetic spectrum from radio waves and infrared (IR) images to ultraviolet (UV) and X-ray views. A relatively new technique called helioseismology allows us to probe the Sun's interior by watching pressure waves ripple across the photosphere. Coronagraphs create artificial eclipses at our whim, giving us great views of the Sun's atmosphere. Spectroscopy allows us to study the elemental composition of the Sun and provides information about temperature, magnetic field strength, and ionization levels.

Detecting Radiation in Geospace

The Sun emits many types of radiation, in the form of several types of subatomic particles and as electromagnetic radiation. Some types generate secondary cascades of particles when they crash into the gases in Earth's atmosphere. Radiation sensors, plasma wave detectors, and similar instruments on spacecraft and the ground measure the flux of protons, electrons, ions, neutrinos, and other types of radiation. Such sensors on some of the earliest artificial satellites led to the discovery of the Van Allen radiation belts which encircle our planet.

Optical techniques, broadly defined to include IR and UV "light", also aid studies of near-Earth "geospace". Images and spectroscopic studies help us understand the auroras, while extreme UV images from satellites reveal the structure of Earth's plasmasphere.

Probing Earth's Atmosphere with Radio Waves

Techniques and instruments employing radio waves help us probe the electrically charged layers of Earth's atmosphere collectively referred to as the ionosphere. Radars, antenna arrays called riometers, and similar devices allow us to determine which radio waves pass through, get absorbed by, and bounce off specific layers of the ionosphere.

Monitoring Magnetic Fields with Magnetometers

Various types of magnetometers detect the orientation and measure the strength of magnetic fields. A network of ground-based magnetometers tracks Earth's magnetic field, while similar instruments aboard orbiting satellites as well as interplanetary spacecraft monitor magnetic fields in near-Earth and deep space respectively.

A fluxgate magnetometer for measuring magnetic fields. Click on image for full size (21K JPEG) Image courtesy the Auroral Observatory of the University of Tromso, Norway.

How do scientists measure space weather? They put radiation detectors on satellites, they monitor changing magnetic fields with magnetometers, they watch the Sun with X-ray telescopes, and they bounce radar waves off layers of Earth's atmosphere. That, and a whole lot more!

Watching the Sun

Space weather starts at the Sun. Scientists watch the Sun with special telescopes. Some of the telescopes are on Earth, while others are on satellites. Some of the telescopes are for normal, visible light, but others are for different kinds of electromagnetic radiation. Some telescopes watch infrared (IR), ultraviolet (UV), or even X-ray radiation coming from the Sun.

Solar astronomers use an instrument called a coronagraph to view the Sun's atmosphere. They use another instrument, called a spectroscope, to detect the different kinds of elements in the Sun. A new technique called "helioseismology" even lets scientists "see" inside the Sun!

Detecting Radiation around Earth

The Sun gives off light, but it also shoots out radiation. Some of the radiation is in the form of subatomic particles. When the particles from the Sun get to Earth, radiation detectors on satellites and on Earth measure their types and energy levels.

When radiation from the Sun hits Earth's atmosphere, the radiation can make the atmosphere "glow". The aurora, or Northern and Southern Lights, are an example of this. We can study such "glows", and take pictures of them from Earth or from space. Their colors and shapes provide clues about the radiation that made them.

Using radar to study Earth's atmosphere

Some layers of Earth's atmosphere are electrically charged. The electrically charged layers are in a part of the atmosphere called the ionosphere. Changing space weather affects the ionosphere. Scientists study the ionosphere by bouncing radio waves off of it. They use radars and groups of antennas called riometers.

Measuring Magnetic Fields

Magnetic fields are an important part of space weather. As space weather changes, the strengths and directions of magnetic fields change. Scientists use instruments called magnetometers to measure changes in magnetic fields. There are magnetometers at many places on Earth. There are also magnetometers on satellites around Earth and even on spacecraft circling other planets or exploring different parts of our Solar System.

A fluxgate magnetometer for measuring magnetic fields. Click on image for full size (21K JPEG) Image courtesy the Auroral Observatory of the University of Tromso, Norway.

Even though the Sun is very far away, it has a big effect on Earth. It gives us warmth and light. Storms on the Sun can also bring about what scientists call space weather on Earth or near Earth (just outside our atmosphere).

How do scientists measure space weather? Lots of different ways!

Scientists Watch the Sun

Space weather starts at the Sun, so scientists watch the Sun with special telescopes. Some of the telescopes are on Earth, and some are out in space.

Scientists use other special instruments to look at the different layers of the Sun or to find out what makes up the Sun.

Measuring Radiation around Earth

The Sun gives off light, but it also shoots out radiation. When radiation from the Sun hits Earth's atmosphere, the radiation can make the atmosphere "glow". Maybe you've seen this glow (also called Northern and Southern Lights)? Scientists measure the types and energy levels of the radiation that makes it to Earth from the Sun.

Studying Earth's atmosphere

Scientists can tell a lot about the Sun by looking at how the Earth's atmosphere is reacting to particles that have arrived from the Sun. One layer of the atmosphere called the ionosphere is especially helpful for this. Scientists can look at how excited this layer is to see what might have come from the Sun to cause the excitement. Particles which are excited behave differently than ones that are more restful...sound like any students you know?

Measuring Magnetic Fields

Magnetic fields are an important part of space weather. As space weather changes, magnetic fields change. Scientists use instruments called magnetometers to measure these changes. There are magnetometers at many places on Earth. There are also magnetometers on satellites in space.