Definition of Space Weather

There is no full agreement among all the member of the international communities on the definition of space weather. Therefore, we list above the definition of space weather according to some organizations (in alphabetical order):

  1. American Meteorological Society (AMS): “Space weather refers to the variable conditions on the Sun and in the space environment that can influence the performance and reliability of space-borne and ground-based technological systems, as well as endanger life or health.”1.
  2. Asia Oceania Space Weather Alliance (AOSWA): “Space weather is the electromagnetic condition in the near-space around the Earth and it affects telecommunications, broadcast, satellite positioning and many of other social infrastructures”2.
  3. European Space Agency (ESA): “Space weather refers to the environmental conditions in Earth’s magnetosphere, ionosphere and thermosphere due to the Sun and the solar wind that can influence the functioning and reliability of space-borne and ground-based systems and services or endanger property or human health. Space weather deals with phenomena involving ambient plasma, magnetic fields, radiation, particle flows in space and how these phenomena may influence man made systems. In addition to the Sun, non-solar sources such as galactic cosmic rays can be considered as space weather since they alter space environment conditions near the Earth”3.
  4. S .Office of Science and Technology Policy of The White House: “Space weather refers to the dynamic conditions of the space environment that arise from interactions with emissions from the sun, including solar flares, solar energetic particles, and coronal mass ejections” (Wackler, 2015).
  5. World Meteorological Organization (WMO): “Space weather encompasses the conditions and processes occurring in space, including on the sun, in the magnetosphere, ionosphere and thermosphere, which have the potential to affect the near-Earth environment”4.

In common, all of these statements try to encompass the Solar-Terrestrial environment, including the Sun, the Interplanetary Medium, the Magnetosphere or Geomagnetic Field (with all its extent), and the Earth Atmosphere. Some of them focused in the phenomenology observed in this environment (e.g. solar flares, solar energetic particles, coronal mass ejection, ambient plasma, magnetic fields) others pay attention to the effect of such phenomena into the Earth environment or into the technological object/systems exposed to these phenomena (e.g. space-borne and ground-based systems and services like telecommunications, broadcast, satellite positioning). The definition provided by ESA is the only one to consider galactic cosmic rays as space weather. Ultimately, the WMO definition is the most generic physical-based description, which includes not only the possibility to encompass the galactic cosmic ray as recalled by ESA, but also a supernova explosion, which are events capable to accelerate the material of the star up to a velocity of up to 10% of the speed of light, i.e. 30,000 km/s, and drive a shock wave into the surrounding interstellar medium (Heger et al., 2003). In simple words, this would wipe out the live on Earth in case a supernova explosion occurred close to the Earth. Therefore, we consider the following definition for space weather:

Space weather encompasses the conditions and processes occurring in space, which have the potential to affect the near-Earth environment and/or the human being or the current technological assets.


Heger, A.; Fryer, C. L.; Woosley, S. E.; Langer, N.; Hartmann, D. H. (2003). “How Massive Single Stars End Their Life”. The Astrophysical Journal 591: 288. arXiv:astro-ph/0212469. Bibcode:2003ApJ…591..288H. doi:10.1086/375341

Wackler T. (2015) National Science and Technology Council; National Space Weather Strategy Notices. Federal Register, vol. 80. No. 83, page. 24296-24297, April 30.


1 Available online at

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