Possible Advantages of a Twin Spacecraft Heliospheric Mission at the Sun-Earth Lagrangian Points L4 and L5

Abstract

After the launch of STEREO twin spacecraft, and most recently of Solar Orbiter and Parker Solar Probe spacecraft, the next mission that will explore Sun-Earth interactions and how the Sun modulates the Heliosphere will be the “Lagrange” mission, which will consist of two satellites placed in orbit around L1 and L5 Sun-Earth Lagrangian points. Despite the significant novelties that will be provided by such a double vantage point, there will be also missing information, that are briefly discussed here. For future heliospheric missions, an alternative advantageous approach that has not been considered so far would be to place two twin spacecraft not in L1 and L5, but in L4 and L5 Lagrangian points. If these two spacecraft will be equipped with in situ instruments, and also remote sensing instruments measuring not only photospheric but also coronal magnetic fields, significant advancing will be possible. In particular, data provided by such a twin mission will allow to follow the evolution of magnetic fields from inside the Sun (with stereoscopic helioseismology), to its surface (with classical photospheric magnetometers), and its atmosphere (with spectro-polarimeters); this will provide a tremendous improvement in our physical understanding of solar activity. Moreover, the L4-L5 twin satellites will take different interesting configurations, such as relative quadrature, and quasi-quadrature with the Earth, providing a baseline for monitoring the Sun-to-Earth propagation of solar disturbances.

Investigating Remote-Sensing Techniques to Reveal Stealth Coronal Mass Ejections

“…Unfortunately after the loss of STEREO-B and with STEREO-A slowly approaching Earth, the capability to observe stealth CMEs from a viewpoint well-separated from the Sun-Earth line will be lost at least for a while. In the longer term, observations away from the Sun-Earth line, made for example by a STEREO-like, polar, or L4/L5 mission, would help to provide this capability (e.g., Vourlidas, 2015;Lavraud et al, 2016;Gibson et al, 2018;Bemporad, 2021). The four events analyzed here took place during different stages of the solar cycle, with Event 1 happening at solar minimum, Event 2 and Event 3 close to solar maximum, and Event 4 in the midst of the descending phase of the cycle.…”

Understanding the Origins of Problem Geomagnetic Storms Associated with “Stealth” Coronal Mass Ejections

“…In addition, these are science missions not dedicated to space weather operations, and most data are made available only with significant delays. For space weather monitoring, a solution would be to develop a network of observatories, starting with missions to the L5 or L4 Lagrange points (Vourlidas 2015;Posner et al 2021;Bemporad 2021) that could monitor CMEs travelling towards Earth. More ambitious plans to improve space weather predictions might include placing satellites at L3 to monitor the far side of the Sun, and placement in high-inclination (polar) orbits to monitor CMEs emitted from all solar longitudes-the benefits of solar observations from "unconventional" viewpoints were reviewed by Gibson et al (2018).…”

CMEs and SEPs During November–December 2020: A Challenge for Real‐Time Space Weather Forecasting

“…By then, the advantages of remote‐sensing observations of the Sun from two well‐separated viewpoints will be lost at least for a while (we note that SolO is equipped with a coronagraph and a heliospheric imager, but its rapidly changing heliocentric distance and longitudinal separation with Earth may not be optimal for forecasting purposes). Dedicated missions to the Lagrange L4 and/or L5 points (e.g., Bemporad, 2021; Posner et al., 2021; Vourlidas, 2015) may prove beneficial in this regard. This includes the European Space Agency's (ESA) Vigil (Pulkkinen et al., 2019) mission, which is currently in development to place a spacecraft equipped with remote‐sensing and in situ instruments at L5.…”