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Space weather and its effects on Earth

Space weather and its effects on Earth

Space weather on Earth is chiefly influenced by magnetic storms and emissions of energy particles, in both cases caused by enhanced fluxes of protons and ions. these accelerated plasmas are called solar energetic particles (SEPs). They can be caused by two phenomena: impulsive SEP events caused by magnetic reconnection manifested as solar flares and gradual SEP events accelerated by strong shocks associated with coronal mass ejections (CMEs).

Studying both of these phenomena are important in the context of how space weather affects life on Earth. Strong and gradual SEP events are particularly interesting, since the accumulated energy of coronal mass ejections, shocks and enhanced fluxes of solar particles may cause damage to satellites orbiting our planet and interfere with some of the technologies we use. They are the causes of both the beautiful northern lights and the serious disruptions in electrical and telecommunication networks (such as the Carrington event) that happen because of exceptionally strong geomagnetic storms.

On 23 January 2012, the LASCO device on board the SOHO spacecraft has registered a coronal mass ejection and the resulting accelerated plasma flux made up of solar energetic particles. These particles appear here as white grains; they can be seen about four hours after a CME happens. Source: SOHO Observatory

Scientific literature offers several examples of the relationships between CMEs and peak SEP fluxes. Researchers from the Jagiellonian University Astronomical Observatory have proved that their innovative method based on ‘instantaneous speeds’ of SEPs can be employed in order to achieve much more precise measurements.

The research team have based their calculations on the images of CMEs registered by twin satellites called STEREO (Solar TErrestrial RElations Observatory). They also acquired additional data from SOHO (SOlar and Heliospheric Observatory), LASCO (Large Angle and Spectrometric Coronagraphs) and SECCHI (Sun Earth Connection Coronal and Heliospheric Investigation) in order to establish kinematic parameters. The research project also used data from three separate SEP fluxes capture on three energy frequencies by GOES-13 (Geostationary Operational Environmental Satellite). The paper also describes peak x-ray fluxes, which are connected to both of the abovementioned phenomena.

Scatter plots of maximum of SEP flux at three energy bands (>10 MeV (red), >50 MeV (blue), and >100 MeV (green)) vs the respective speed of CMEs (average speed-STEREO (panel a), maximum speed-STEREO (panel b), average speed-SOHO (panel c), maximum speed-SOHO (panel d) ). The open symbols represent disk events (longitude −20 < L < 45) and filled symbols represent west events (Longitude >45). There is one east event, on 31 August 2012 (longitude < −20; in yellow). This is the only event in the researchers' sample analysed by STEREO-B as it exhibited good quality. The solid curves are linear fits to the data points. Source: Authors.

Research shows that if instantaneous speeds of a given SEP flux are well-determined (which is true for a distance of up to 10 Sun’s radii), then the maximum flux correlated with a SEP emission can be easily estimated on the basis on the empirical model prepared by the authors of the paper. SEP events related to the Sun’s disk and western hemisphere can emit the strongest SEP ejections, since they have the strongest magnetic links with Earth due to the circumvolution of the Sun and our planet. The good correlation for proton fluxes with energies higher than 10 MeV proves the hypothesis that protons are accelerated mainly in shockwaves generated by impulsive CMEs that propagate in the interplanetary space. Particles with energies higher than 50 and 100 MeV are accelerated by the same events (shocks), but the process of their acceleration may also be influenced by the accompanying solar flares. However, solar flares and SEP fluxes are poorly correlated. This agrees with the hypothesis that shocks enhanced by CMEs are better accelerators of energy particles.


Original text:
Based on research paper by Anitha Ravishankar and Grzegorz Michałek: Non-interacting coronal mass ejections and solar energetic particles near the quadrature configuration of Solar TErrestrial RElations Observatory
Photograph at the top: STEREO A and B spacecraft on the opposing points of the Sun’s orbit. Source: NASA

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