Geomagnetic storms – basic terms, data, plots and graphs


A coronal mass ejection (CME) that erupted on March 15, 2013, hit Earth's magnetic field at 06:00 UTC on March 17, 2013. The solar wind speed reached 700 km/s and sparked a moderately strong G2 (Kp=6) geomagnetic storm and minor S1 solar radiation storm. NOAA/SWPC reported the geomagnetic field has been at quiet to unsettled levels for the past 24 hours. 

For those of you, who don't fully understand the data given above, here are few explanations to help you better understand space weather and geomagnetic storms. Here is a short help on understanding the basic terms, data, plots and graphs.

An artistic view of geomagnetic storm. Captures show where the CME forms, where is solar wind and how it affect our magnetosphere (Credit: K.Endo/The Watchers)

geomagnetic storm is a temporary disturbance of the Earth's magnetosphere caused by a disturbance in the interplanetary medium. A geomagnetic storm is caused by a solar wind shock wave and/or cloud of magnetic field which interacts with the Earth's magnetic field. The increase in the solar wind pressure initially compresses the magnetosphere and the solar wind's magnetic field will interact with the Earth’s magnetic field and transfer an increased amount of energy into the magnetosphere.

The disturbance in the interplanetary medium which drives the geomagnetic storm may be due to a solar coronal mass ejection (CME) or a high speed stream of the solar wind originating from a region of weak magnetic field on the Sun’s surface or coronal holes. Coronal mass ejections release huge quantities of matter and electromagnetic radiation into space above the sun's surface. The particles typically take between one and three days to reach Earth, where they can pose a hazard to satellites and electronic systems in orbit and on the planet's surface.The ejected material is a plasma consisting primarily of electrons and protons.

NOAA/SWPC plot shows levels of protons, electrons, HP component and estimated Kp index (Credit: NOAA/SWPC)

Geomagnetic storms are major disturbances of the magnetosphere that occur when the interplanetary magnetic field (IMF) turns southward and remains southward for a prolonged period of time. If the IMF points south – a condition scientists call "southward Bz", then the IMF can partially cancel Earth's magnetic field at the point of contact. Southward Bz's often herald widespread auroras, triggered by solar wind gusts or coronal mass ejections that are able to inject energy into our planet's magnetosphere.

On March 17, 2013, NOAA/SWPC's Estimated Planetary K-index show Kp=6 levels which is basically, a moderate geomagnetic storm. Kp-indices of 5 or greater indicate storm-level geomagnetic activity. Geomagnetic storms have been associated with satellite surface charging and increased atmospheric drag.

NOAA Scales Activity
Range 1 (minor) to 5 (extreme)
NOAA Scale 


Geomagnetic Storms * 

Previous 24 hour G-scale value

Current G-scale value
Solar Radiation Storms 

Previous 24 hour S-scale value

Current S-scale value
Radio Blackouts 

Previous 24 hour R-scale value

Current R-scale value


Estimated Planetary K-Index plot shows threshold at Kp=6 levels or G2 geomagnetic storm conditions (Credit: NOAA/SWPC)

The Kp scale summarize the global level of geomagnetic activity. The NOAA G-scale was designed to correspond, in a straightforward way, to the significance of effects of geomagnetic storms. NOAA/SWPC use estimates of the planetary average Kp index to determine Geomagnetic Storm (NOAA Space Weather Scale) level, as follows:

Kp-index – Geomagnetic Storm Level

Kp=5 – G1
Kp=6 – G2
Kp=7 – G3
Kp=8 – G4
Kp=9 – G5

G2 or Moderate Geomagnetic Storm can cause voltage alarms at high-latitude power systems , long-duration storms may cause transformer damage, HF radio propagation can fade at higher latitudes, and aurora could be seen as low as New York and Idaho (typically 55° geomagnetic lat.). Corrective actions to orientation may be required for satellites and spacecrafts by ground control and possible changes in drag affect orbit predictions.

The strongest on NOAA scale is G5 or Extreme Geomagnetic Storm. G5 storm can generate widespread voltage control problems and protective system problems, some grid systems may experience complete collapse or blackouts. Transformers may experience damage. Spacecraft operations may experience extensive surface charging, problems with orientation, uplink/downlink and tracking satellites. G5 storm can cause pipeline currents reaching hundreds of amps, HF (high frequency) radio propagation may be impossible in many areas for one to two days, satellite navigation may be degraded for days, low-frequency radio navigation can be out for hours, and aurora has been seen as low as Florida and southern Texas (typically 40° geomagnetic lat.).

Sky turned green on St. Patrick's Day.  Auroras have been seen s as far south as Colorado, US and in Europe over Ireland, Iceland, UK, Finland, Sweden, Norway, Latvia, Estonia, Russia, Poland, and even Slovakia. Red auroras were seen from New Zealand and Australia. For great images of auroras visit Space Weather's aurora gallery.

Beautiful aurora display above Delta Junction Alaska on March 17, 2013 (Image credit: Christy Olson-Groppel  via SpaceWeather gallery)

A space radiation storm happens when an explosion on the Sun accelerates solar protons toward Earth. The NOAA Space Environment Center has defined five types of radiation storms, ranging from mild to extreme. NOAA/SWPC issued S1 or Minor Solar Radiation Storm warning on March 17, 2013. S1 Solar Radiation Storm can spark minor impacts on HF radio in the polar regions. The strongest on scale, S5 or Extreme Solar Radiation Storm presents unavoidable high radiation hazard to astronauts on EVA (extra-vehicular activity), also high radiation exposure to passengers and crew in commercial jets at high latitudes. Some satellites may be rendered useless, memory impacts can cause loss of control, may cause serious noise in image data, star-trackers may be unable to locate sources; permanent damage to solar panels possible. S5 storm can generate complete blackout of HF (high frequency) communications through the polar regions, and position errors make navigation operations extremely difficult.

During the CME impact, solar protons can penetrate deeper into the Earth's magnetosphere and ionosphere. Regions where deeper penetration can occur includes the polar regions and South Atlantic magnetic anomaly.

GOES 5-minute averaged integral proton flux (protons/cm2-s-sr) as measured by the SWPC primary GOES satellite for energy thresholds of >=10, >=50, and >=100 MeV. SWPC's proton event threshold is 10 protons/cm2-s-sr at >=10 MeV. GOES13 Proton flux plot shows the rise in proton level. (Credit: NOAA/SWPC)

WSA-ENLIL Solar Wind Prediction model shows the latest forecast of conditions in the solar wind. The solar wind is a fast-moving stream of charged particles emanating from the Sun and moving outwards towards the Earth and planets. It shows the direction and speed of major solar eruptions known as Coronal Mass Ejections (CMEs) which can disrupt the flow of the solar wind and produce disturbances that strike the Earth known as geomagnetic storms.

This is WSA-ENLIL model. The circular plots on the left are a view from above the North Pole of the Sun and Earth, as if looking down from above. The Sun is the yellow dot in the center and the Earth is the green dot on the right. Also shown are the locations of the two STEREO satellites. These plots often depict spiral structures, due to solar rotation. CLICK ON THE IMAGE TO VIEW AN ANIMATION

This is WSA-ENLIL model. The circular plots on the left are a view from above the North Pole of the Sun and Earth, as if looking down from above. The Sun is the yellow dot in the center and the Earth is the green dot on the right. Also shown are the locations of the two STEREO satellites. These plots often depict spiral structures, due to solar rotation. (Credit: NASA/SolarHam) CLICK ON THE IMAGE TO VIEW AN ANIMATION

You can watch an animated model of March 15, 2013 CME path here.






Planetary K-index
Now: Kp= 6 storm
24-hr max: Kp= 6 storm


Interplanetary Mag. Field
Btotal10.3 nT
Bz0.5 nT north



The Radio Sun
10.7 cm flux: 126 sfu

You can watch solar and space weather activity in real-time in our Space Weather Station.

Sources: SWPC, SpaceWeather.com, SolarHam,

Featured image credit: SOHO


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  1. it sounds as if we are priming ourselves for a modern day Babylon. My questions are
    1) Without a more robust network –
    What will happen to our data that we WILL NEED IF these aethereal systems start to crash? It doesn’t take too much imagination to see that certain sectors shall be?
    2) If humans are going to create STRESS UPON OUR HABITAT by a factor of 4 (give or take a Billion) then, what sectors shall be lost? It seems that without too much imagination maybe we could live together or apart within this planet’s sphere.
    3) If this is the ONLY PLANET we can, without an anomaly, live on then is it a good idea to plunder our resources JUST for OURSELVES? Without too much imagination it seems that a species who consumes THE RESOURCES we do then maybe we should protect something – even if it’s only ourselves.

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