There will occur significant periods from thence during which electromagnetic coverage of the Sun's far hemisphere will be incomplete or nil. We are now approaching a decade during which the STEREO spacecraft will lose their farside vantage. For the past decade, NASA's twin STEREO spacecraft have given us full coverage of the Sun's far hemisphere in electromagnetic (EUV) radiation from the far side of Earth's orbit about the Sun. These seismic maps are useful for space weather forecasting. Computational analysis of the solar oscillations mapped in the Sun's near hemisphere, applying basic principles of wave optics to model the implied p modes propagating through the solar interior, gives us seismic maps of large active regions in the Sun's far hemisphere. They also interact strongly with active regions at the surfaces of both hemispheres, carrying the signatures of said interactions with them. The p modes propagate freely throughout the solar interior, reverberating between the near and far hemispheres. The p modes cause seismic ripples, which we call βthe solar oscillations.β Helioseismic observatories use Doppler observations to map these oscillations, both spatially and temporally. These waves, called β p modes,β are understood to be excited by convection in a thin layer beneath the Sun's surface. The interior of the Sun is filled acoustic waves with periods of about 5 min.
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