|dc.description.abstract||Ground- and space-based observations of solar flares from radio wavelengths to gamma-rays have produced considerable insights but raised several unsolved controversies. The last unexplored wavelength frontier for solar flares is in the range of submillimeter and infrared wavelengths. Although the central focus of this proposal is on the description of solar activity at GHz; sub-THz and THz frequencies, it will be essential to analyze their relationships to observations at other radio, visible and higher UV, X- and gamma-ray energy frequency ranges, attempting to find new clues to understand the processes of energy build up and explosive release in active regions. To attain these objectives we propose a special effort along the declining phase of the current Solar Cycle 24 (2014-2018), maintaining ongoing programs and recently implemented new experimental facilities at El Leoncito, Argentina Andes, high altitude observatory. The proposal includes Solar flare diagnostic from ground-based observations from mm- to submm-wavelengths, far infrared, visible, complemented by helio-physical surveys of solar cosmic rays, space-weather effects on low terrestrial ionosphere via VLF propagation anomalies and atmosphere electric field disturbances. Special efforts will be given for the interpretation of results from solar flare THz emission, associated emissions at other wavelengths, in radio, visible, UV, X- and gamma-rays. Attention will be given to high energy physical processes occurring in solar flare particle acceleration and their comparison to mechanisms in laboratory scale accelerators. All instruments, their installation, specialized emergency works for repairs were or are sponsored by grants and contracts from Brazilian agencies FAPESP, CNPq and Mackpesquisa, and by international agencies ICSU and US AFOSR. This proposal is submitted for the necessary support of the regular operation and supervision of all instruments, which are not funded by other agencies.