Space Weather


Interplanetary Magnetic Field


Magnetospheric Response: Voltage Across the Polar Cap

Solar X-rays:

Geomagnetic Field:




X Ray Flux (watts/sq meter)



A less than 10-8 Very Low Background
A between 10-8 and 10-7 Low Background
B between 10-7 and 10-6 Moderate Background
C between 10-6 and 10-5 High Background/Low Flare
M between 10-5 and 10-4 Moderate Flare
X between 10-4 and 10-3 High Flare
Y greater than 10-3 Extreme Flare

 Within these levels, a number is used to specify the flux. Hence a value M3.2 indicates that the flux is 3.2 × 10 -5 watts/metre2.

The Y classification of flares is new; and these extremely large flares are often still classed as X flares with a qualifying number greater than 10. Hence a Y1.6 flare is exactly the same as an X16 one.

X-Ray Flux

The solar X-ray flux arises from two factors. Firstly, there is flux coming from sunspot regions and other features - the background flux - and this varies slowly from day to day. Secondly, solar flares produce large amounts of X-ray flux, but this is concentrated to the duration of the flare which is usually from minutes to several hours.

The GOES x-ray plots shown here are used to track solar activity and solar flares. Large solar x-ray flares can change the Earth’s ionosphere, which blocks high-frequency (HF) radio transmissions on the sunlit side of the Earth. Solar flares are also associated with Coronal Mass Ejections (CMEs) which can ultimately lead to geomagnetic storms. SWPC sends out space weather alerts at the M5 (5x10-5 Watts/mw) level. Some large flares are accompanied by strong radio bursts that may interfere with other radio frequencies and cause problems for satellite communication and radio navigation (GPS).

Proton Flux

Proton Event products are issued for several thresholds and for two particle energy levels. The ≥10 MeV products match the NOAA Solar Radiation Storm (S-scale) thresholds (10, 100, 1000, 10000, 100000 pfu), based upon values observed or expected on the primary GOES satellite. The ≥100 MeV products are based on a single flux threshold of 1 proton flux unit (pfu).

When solar flares occur, high-energy protons reach the Earth. As these particles directly penetrate the satellites orbiting the Earth, they cause errors in various electronic devices. This phenomenon is called Single Event Upsets (SEUs). The energy of protons is measured by using three energy levels: >=10MeV, >=50MeV, and >=100MeV.

The K-index, and by extension the Planetary K-index, are used to characterize the magnitude of geomagnetic storms. Kp is an excellent indicator of disturbances in the Earth's magnetic field and is used by SWPC to decide whether geomagnetic alerts and warnings need to be issued for users who are affected by these disturbances.

The principal users affected by geomagnetic storms are the electrical power grid, spacecraft operations, users of radio signals that reflect off of or pass through the ionosphere, and observers of the aurora.

How SDO Sees the Sun
The Solar Dynamics Observatory (SDO) provides views of the Sun in detail never before possible. Launched on February 11, 2010, SDO provides ultra high-definition imagery of the Sun in 13 different wavelengths, utilizing two imaging instruments, the Atmospheric Imaging Assembly (AIA) instrument and the Helioseismic and Magnetic Imager (HMI). Each wavelength is based on one or two types of ions -- though slightly longer and shorter wavelengths produced by other ions are also part of the picture. Each wavelength was chosen to highlight a particular part of the sun's atmosphere, from the solar surface to the upper reaches of the sun's corona.
For more technical information about which ions produce which wavelengths, scroll down to the descriptions for each, below the graphic.

Neutron Monitor
Galactic and solar cosmic ray particles entering the earth's atmosphere with energy above 0.5 GeV undergo nuclear interactions, producing secondary whose effects can be extended down to the sea level. The development of the neutron monitor by J. A. Simpson (Simpson,1957) provided an improved method of detecting low-energy neutron secondary that are not slowed by ionization loss. These secondary fall in the energy range of a few hundred MeV up to about one GeV. So the neutron monitors are most sensitive to the low energy (1-20 GeV) portion of the spectrum. Neutron monitors with their reliability and basic simplicity offered a means of studying the longer-term temporal variations while their sensitivity and high counting rates made possible the observation of short term intensity changes as well
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