📚 Space Weather Glossary

Definitions and explanations of space weather terms

A B C D E F G H I K M P R S U X

A

Aurora

/ɔːˈrɔːrə/
Beautiful light displays in the sky caused by charged particles from the Sun interacting with Earth's atmosphere. Also known as the Northern Lights (Aurora Borealis) and Southern Lights (Aurora Australis).
Example: During geomagnetic storms, aurora can be seen at lower latitudes than usual.

Ap Index

/eɪ piː/
A daily average of geomagnetic activity based on measurements from multiple ground-based magnetometers. Ranges from 0 (quiet) to 400 (extreme storm).
Example: An Ap index of 50 indicates moderate geomagnetic activity.

B

BZ Component

/biː ziː/
The north-south component of the interplanetary magnetic field (IMF). Negative values can trigger geomagnetic storms by opening Earth's magnetic field to solar wind particles.
Example: A BZ component of -10 nT for several hours can cause a geomagnetic storm.

C

CME (Coronal Mass Ejection)

/siː em iː/
A massive burst of solar wind and magnetic fields from the Sun's corona. CMEs can cause geomagnetic storms when they reach Earth.
Example: A CME can take 1-3 days to reach Earth and cause aurora and power grid disturbances.

Corona

/kəˈroʊnə/
The outermost layer of the Sun's atmosphere, visible during solar eclipses. It's where solar wind originates and where CMEs are launched.
Example: The corona is much hotter than the Sun's surface, reaching millions of degrees.

D

Dst Index

/diː es tiː/
Disturbance storm time index that measures the strength of the ring current around Earth. Negative values indicate geomagnetic storm conditions.
Example: A Dst index of -100 nT indicates a moderate geomagnetic storm.

E

Electron Flux

/ɪˈlektrɒn flʌks/
The rate of high-energy electrons passing through a unit area. High electron flux can cause satellite charging and communication disruptions.
Example: Electron flux is measured in units of cm⁻²·s⁻¹·sr⁻¹ (electrons per square centimeter per second per steradian).

F

Flux

/flʌks/
The rate of flow of particles or energy through a given area. In space weather, we measure proton flux and electron flux.
Example: High flux values indicate more particles are impacting Earth's magnetosphere.

G

Geomagnetic Storm

/ˌdʒiːoʊmæɡˈnetɪk stɔːrm/
A temporary disturbance of Earth's magnetosphere caused by solar wind shock waves and/or magnetic field interactions. Can cause power grid fluctuations and aurora.
Example: The 1989 Quebec blackout was caused by a severe geomagnetic storm.

Geomagnetic Activity

/ˌdʒiːoʊmæɡˈnetɪk ækˈtɪvəti/
The level of disturbance in Earth's magnetic field caused by solar wind interactions. Measured by various indices like KP, Ap, and Dst.
Example: High geomagnetic activity can affect satellite operations and power grids.

H

Heliosphere

/ˈhiːliəˌsfɪər/
The vast region of space influenced by the Sun's magnetic field and solar wind. It extends far beyond the orbit of Pluto.
Example: The heliosphere protects the solar system from most cosmic rays.

I

IMF (Interplanetary Magnetic Field)

/aɪ em ef/
The magnetic field carried by the solar wind throughout the solar system. Its orientation affects how solar wind interacts with Earth's magnetosphere.
Example: The BZ component of the IMF is crucial for triggering geomagnetic storms.

Ionosphere

/aɪˈɒnəˌsfɪər/
The upper part of Earth's atmosphere where atoms are ionized by solar radiation. It reflects radio waves and is affected by space weather.
Example: Ionospheric disturbances can disrupt GPS and radio communications.

K

KP Index

/keɪ piː/
A measure of geomagnetic activity on a scale of 0-9, based on measurements from ground-based magnetometers around the world. Higher values indicate more active conditions.
Example: A KP index of 5 indicates minor geomagnetic storm conditions.

M

Magnetosphere

/mæɡˈniːtəˌsfɪər/
The region around Earth dominated by its magnetic field. It protects Earth from most solar wind particles and cosmic rays.
Example: The magnetosphere extends about 10 Earth radii on the sunward side.

P

Proton Flux

/ˈproʊtɒn flʌks/
The rate of high-energy protons passing through a unit area. High proton flux can cause satellite anomalies and radiation exposure.
Example: Proton flux is measured in pfu (proton flux units) where 1 pfu = 1 proton per cm² per second per steradian.

R

Radiation Storm

/ˌreɪdiˈeɪʃən stɔːrm/
A period of high radiation levels caused by high-energy particles from solar flares or CMEs. Can affect satellites and astronauts.
Example: Radiation storms are classified as S1 (minor) to S5 (extreme) based on proton flux levels.

S

Solar Flare

/ˈsoʊlər flɛər/
A sudden, intense burst of radiation from the Sun's surface. Flares are classified by their X-ray intensity: A, B, C, M, and X (with X being the most intense).
Example: An X-class solar flare can cause radio blackouts and radiation storms.

Solar Wind

/ˈsoʊlər wɪnd/
A stream of charged particles (mostly protons and electrons) that flows outward from the Sun at speeds of 300-800 km/s.
Example: The solar wind carries the Sun's magnetic field throughout the solar system.

Sunspot

/ˈsʌnspɒt/
A dark area on the Sun's surface caused by intense magnetic activity. Sunspots are associated with solar flares and CMEs.
Example: The number of sunspots varies in an 11-year solar cycle.

U

UV (Ultraviolet)

/ˌʌltrəˈvaɪələt/
Electromagnetic radiation with wavelengths shorter than visible light. Solar UV radiation affects Earth's ionosphere and can cause communication disruptions.
Example: Increased UV radiation during solar flares can enhance ionospheric ionization.

X

X-ray

/ˈeks reɪ/
High-energy electromagnetic radiation. Solar X-rays are used to classify solar flares and can cause ionospheric disturbances.
Example: X-ray flares are classified by their peak X-ray flux in watts per square meter.
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