What is space weather?

In simple terms space weather can be defined as how solar activity can have unwanted effects on technological systems and human activity, be it in near-Earth space or on the ground. Our local space weather is a function of our location in the solar system, the behavior of the Sun, and the nature of Earth's magnetic field and atmosphere. There also exist several official space weather definitions, for example:

"Conditions on the Sun and in the solar wind, magnetosphere, ionosphere, and thermosphere that can influence the performance and reliability of space-borne and ground-based technological systems and can endanger human life or health." [U.S. National Space Weather Program, 1995]

"Space weather is the physical and phenomenological state of natural space environments. The associated discipline aims, through observation, monitoring, analysis and modelling, at understanding and predicting the state of the Sun, the interplanetary and planetary environments, and the solar and non-solar driven perturbations that affect them; and also at forecasting and nowcasting the possible impacts on biological and technological systems." [European Cooperation in Science and Technology (COST) 724 Action, 2007]

What are solar flares?

Solar flares occur when magnetic energy that has been built up is suddenly released. Radiation is emitted from radio waves through optical emission to Xrays and gamma-rays. As the magnetic energy is released plasma is heated and particle beams are accelerated in the solar atmosphere. Solar flares are very hard to predict because they depend on what the Sun's magnetic field is doing and identifying reliable pre-cursors work is still in progress.

What are coronal mass ejections?

Coronal Mass Ejections [CMEs] are huge ejections of magnetised plasma in the Sun’s outer atmosphere and are seen as bright features moving outwards through the corona at speeds from 100 to over 2000 km/s. When a CME enters the interplanetary medium its name is changed to “Interplanetary Coronal Mass Ejection [ICME]”. Most ICMEs contain intense magnetic flux ropes, the so-called “Magnetic Clouds”.

What are solar energetic particle events?

Solar Energetic Particle [SEP] events are associated with solar flares and/or the shock wave generated by a CME. SEPs are mainly protons, electrons, and α-particles with small admixtures of 3He-nuclei and heavier ions up to iron. They are sporadic and difficult to predict, lasting from minutes to days with energies from a dozen keV to a few GeV.

Why are solar energetic particle events a problem?

Solar Energetic Particles [SEP] events can cause single event effects in electronics onboard spacecraft, as well as aircraft, and with time the cumulated dose can have fatal consequences (e.g. solar cell degradation). SEP events are also worrisome for the health of astronauts as they can cause radiation sickness and death in extreme cases.

What are geomagnetic storms?

Geomagnetic Storms are temporary disturbances in the Earth’s magnetosphere caused by solar wind disturbances associated primarily with Earth-bound ICMEs and to a smaller extent by “Corotating Interaction Regions ” that are caused by the solar wind high-speed streams originating in equatorial coronal holes. These storms are the major space weather events in the Earth’s magnetosphere.

Why are geomagnetic storms a problem?

Geomagnetic storms are associated with flux enhancements in Earth’s outer radiation belt that have been found to be related to surface charging and deep dielectric charging onboard satellites. Geomagnetic storms can also perturb the ionosphere causing problems for Global Positioning System (GPS) navigation and satellite communications, and high frequency (HF) radio communications on airplanes flying over high-latitude regions can be seriously disrupted during storms. They are also associated with geomagnetically induced currents (see: “What are geomagnetically induced currents?”).

What are geomagnetically induced currents?

Geomagnetically induced currents are phenomena at the ground end of the space weather chain that can have devastating consequences for electrical power transmission systems, oil and gas pipelines, telecommunications cables and railways. They are due to the geomagnetic perturbations produced by enhanced currents that flow in the magnetosphere–ionosphere system during geomagnetic storms.

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