Interplanetary Magnetic Field
Magnetospheric Response: Voltage Across the Polar Cap
How SDO Sees the SunThe 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.
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