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Extreme precision radial-velocity spectrometers enable extreme precisionstellar spectroscopy. Searches for low-mass exoplanets around solar-type starsare limited by the physical variability in stellar spectra, such as theshort-term jittering of apparent radial velocities. To understand the physicalorigins of such jittering, the solar spectrum is assembled, as far as possible,from basic principles. Surface convection is modeled with time-dependent 3Dhydrodynamics, followed by the computation of hyper-high resolution spectraduring numerous instances of the simulation sequences. The behavior ofdifferent classes of photospheric absorption lines is monitored to identifycommonalities or differences between different classes of lines: weak orstrong, neutral or ionized, high- or low-excitation, atomic or molecular. ForFe I and Fe II lines, the radial-velocity jittering over the small simulationarea typically amounts to +-150 m/s, scaling to about 2 m/s for the full solardisk. Most photospheric lines vary in phase but with different amplitudes amongdifferent classes of lines. Radial-velocity excursions are greater for strongerand for ionized lines, decreasing at longer wavelengths. The differencesbetween various line-groups are about one order of magnitude less than the fulljittering amplitudes. By matching very precisely measured radial velocities tothe characteristic jittering patterns between different line-groups shouldenable to identify and to remove a significant component of the stellar noiseoriginating in granulation. To verify the modeling toward such a filter,predictions of solar center-to-limb dependences of jittering amplitudes arepresented for different classes of lines, testable with spatially resolvingsolar telescopes connected to existing radial-velocity instruments.

Solar Photospheric Spectrum Microvariability I. Theoretical searches for proxies of radial-velocity jittering