The L5 consortium is an informal group of scientists that has been promoting science missions to Sun-Earth L5 since 2010. The most recent meeting was held in Boulder, CO in December 2014. The scientific potential was demonstrated by the Solar Terrestrial Relations Observatory (STEREO) when it was in quadrature with SOHO during 2010-2012. After a two-year hiatus, the Consortium meeting will again be held this year during October 17-20, 2017 at the Max Planck Institute for Solar System Research, Göttingen, Germany. The goal of L5 Consortium meetings has been to address open questions in heliophysics using future missions from L5 and L4.
Deploying a mission at Sun-Earth L5 has several key benefits for heliophysics, especially on magnetic structures inside and outside the solar surface. The benefits and measurements include: (1) magnetograms obtained from L5 can improve the surface magnetic field distribution used as input to MHD models that predict the background solar wind and, together with helioseismology, allow us to study the evolution of active regions for longer periods of time, (2) helioseismology from Sun-Earth line and L5 views will improve the coverage of the surface and thereby improve our ability to study the solar interior as well as allow us to perform stereoscopic seismology in the overlap region, (3) viewing CMEs off the Sun-Earth line appears to be critical in observing Earth-arriving parts of the CME, (4) L5 coronagraphic and wide-field observations may provide better estimates of near-Sun and propagating true speed of CME, which is an important input to models that forecast Earth-arrival times of CMEs, (5) backside and frontside CMEs can be readily distinguished even without locating the coronal source, (6) preceding CMEs in the path of Earth-affecting CMEs can be identified for a better estimate of the travel time, (7) a combination of EUV, coronagraph, and heliospheric imaging an track CME-shock complex from the Sun all the way to 1-AU for shock/flux rope evolution studies, (8) CIRs reach the L5 point a few days before they arrive at Earth, and hence provide significant lead time before CIR arrival, (9) L5 observations can provide advance knowledge of CME and CIR source regions (coronal holes) rotating to Earth view, (10) Energetic particle detection at multiple locations (L5 in combination with L1 and/or L4) is essential in gaining insight into the widespread nature of SEP events, especially in the energy range 300 MeV - 2 GeV that was not measured by STEREO.
The L5 consortium meeting at Max-Planck will involve discussion on the science and potential missions to L5 and L4.