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Space weather glossary

If you are puzzled by any space weather terminology, have a look at our glossary.

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Active Region

Areas of the sun with rapidly changing magnetic activity. They have the potential to produce coronal mass ejections and solar flares.

Aurora Borealis / Aurora Australis

The Northern/Southern lights, caused by interactions between the solar wind and Earth’s magnetic field.

Corona

The outer atmosphere of the sun with low density and high temperature. Visible as an extended bright region around the sun during solar a solar eclipse.

Coronal hole

A region of the corona with a relatively low density and temperature. Coronal holes are the source of high speed solar wind streams.

Coronal Mass Ejection (CME)

An ejection of material from the sun’s surface into interplanetary space. If the material is directed towards the Earth, the event may result in a geomagnetic storm.

Image: Courtesy of SOHOconsortium. SOHO is a project of international cooperation between ESA and NASA.

D-region

The lowest layer of the ionosphere, only existing during daylight hours. HF absorption is strongest in this region.

Electromagnetic spectrum

A continuous spectrum of energy waves of varying wavelengths, travelling at 300,000km/s (the speed of light). In order of decreasing wavelength, the spectrum includes: radio waves, microwaves, infrared, visible light, ultraviolet, x-rays and gamma waves.


Image: NASA's Imagine the Universe

Electrons

Negatively charged subatomic particles.

Filaments

Arcs of plasma on the sun’s surface. Filaments observed on the edge of the sun are known as prominences. Occasionally, a filament may burst, emitting bright plasma from the sun’s surface. This is known as a 'filament eruption'.

Geomagnetic field

The magnetic field around the Earth. Geomagnetic field lines can be approximated to that of a simple bar magnet.

Geomagnetic storm

A temporary disturbance in the Earth’s magnetosphere caused by a large burst of solar wind which interferes with the Earth’s magnetic field.

Geosynchronous Orbit

A circular orbit above the Earth’s equator, with a period of 24 hours. The result is that the orbiting body permanently remains above the same position on Earth.

GNSS/GPS

Global Navigation Satellite System. The Global Positioning System (GPS) is an example of GNSS.

Heliosphere

The region of space in which solar wind has a significant influence. This region encompasses the entirety of the solar system.

Heliocentric Orbit

The orbit of an object around the sun.

HF Comms

Communication systems relying on the use of high frequency (HF) radio waves.

Ionosphere

The region of the Earth's atmosphere exposed to ionising radiation. It ranges from 60km to 1,000km in altitude.

L1 orbit

A point on the Sun-Earth line, 1.5 million km from the Earth. Gravitational stability in this region results in a stable orbit..

Magnetogram

An image displaying the strength and location of magnetic field regions on the sun.


Image: Courtesy of NASA/SDO and the AIA, EVE, and HMI science teams.

MOSWOC

Met Office Space Weather Operations Centre.

NOAA

National Oceanic and Atmospheric Administration.

Plage

Bright and hot patches in the Sun's chromosphere. Plage are associated with concentrations of magnetic fields and sources of strong ultraviolet radiation.

Plasma

A super-heated, ionised gas of charged particles, accounting for 99% of all visible matter in the Universe.

Protons

Positively charged subatomic particles.

Radio blackout

During a large space weather event, the ionosphere may start to absorb HF radiation instead of reflecting it. This causes problems with communication systems.

Radio Waves

Low energy electromagnetic radiation, used for long distance communication.

Solar cycle

The 11-year periodic change in the sun’s activity, including changes in the levels of radiation and solar wind emitted.

Solar flare

The sudden release of magnetic energy in the form of electromagnetic radiation, originating from the sun’s atmosphere.

Solar Radiation Storm

Interactions between charged particles (predominantly protons and electrons) and the Earth’s magnetic field. The charged particles originate from the sun following a solar flare or coronal mass ejection, and travel at 1/3 the speed of light.

Solar Wind

The outward flow of charged particles (primarily electrons and protons) from the sun.

Space weather spacecraft

See table below

Sunspot

A region on the sun’s surface with a concentrated magnetic field, resulting in lower temperatures and a darker colour.

SWPC

Space Weather Prediction Centre, NOAA.

X-Ray Burst

A burst in high energy electromagnetic radiation from the sun, causing radio blackouts on Earth

 

Space weather spacecraft

ACE

Name

Launched

Orbit

Objectives
 

 

Advanced Composition Explorer

1997

L1

Observe particles of varying origins to provide near-real-time information on solar wind conditions.

DSCOVR

Name

Launched

Orbit

Objectives
 

Deep Space Climate Observatory

2015

L1 point

Measure solar wind density, velocity and temperature to provide
high-reliability warnings of incoming geomagnetic storms.

GOES-13/ GOES-15

Name

Launched

Orbit

Objectives

Geostationary Environment Satellite System

2006/2010

Geosynchronous

Monitor near-Earth space for space weather. The precursor to DSCOVR.

SDO

Name

Launched

Orbit

Objectives
 

 

Solar Dynamics Observatory

2010

Inclined geosynchronous

Image the Sun across different wavelengths to detect features appearing at varying depths of the Sun’s surface and investigate the causes of solar variability

Image: Courtesy of NASA/SDO and the AIA, EVE, and HMI science teams.
 

 

 

 

SOHO

Name

Launched

Orbit

Objectives
 

 

Solar and Heliospheric Observatory

1995

L1

Measure magnetic field regions in the chromosphere and corona, investigating the emission of solar wind.

Image: Courtesy of SOHOconsortium. SOHO is a project of international cooperation between ESA and NASA.

 

 

 

STEREO

Name

Launched

Orbit

Objectives
 

Solar Terrestrial Relations Observatory

2006

Heliocentric

Study space weather through stereoscopic views of the Sun.

Image: Courtesy of STEREO consortium

 
 

 

 

                                                       

 

 

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