Filling the Gap: Observing Coronal Mass Ejections Continuously Through the Low-, Middle-, and Outer Corona

Abstract: On April 8 of this year a large portion of the United States will be able to view one of the most amazing natural phenomena – a total solar eclipse that will sweep across the nation. Although beautiful, solar eclipses are too infrequent and short to reveal the amazing dynamics and power of the Sun, where enormous energy concentrations can build and suddenly unleash in powerful Coronal Mass Ejections (CMEs). CMEs influence planetary atmospheres and in turn effect the technology that we are becoming ever more dependent upon, so understanding their initiation is critical to predicting these events and limiting the impact they have on society.

Coronagraphs simulating solar eclipses have been used to more frequently observe the solar corona, and led to the discovery of CMEs in the early 1970’s. From the decades of observations since, two leading camps have arisen describing the initiation of CMEs: resistive models that are driven by magnetic reconnection and the competing ideal models that first start with large motions. The first part of this talk will summarize key characteristics of each type of model, with focus on specific observations are needed to finally discriminate between the models. Regardless of the very different physics driving these models, they all seem to agree with observations simply due to the lack of observational constraints, mainly in the critical ‘gap’ region where CMEs are accelerated in the middle corona. This observational gap lies above the full-Sun EUV imagers such as SDO/AIA and GOES/SUVI, and under the occulted region of the white-light coronagraphs.

NASA, ESA, and the Heliophysics community have recently realized the need to fill this observational gap of the middle corona and observe CME eruptions continuously progressing from the low, middle, and then through the outer corona. The remainder of this talk will focus on three of these missions that are in development or are being proposed to make these critical CME measurements: the Sun Coronal Eruption Tracker (SunCET), the Vigil Instruments for Imaging and Solar Irradiance (VIISI), and the Operational Miniaturized Coronagraph (OMCOR). Finally, two other future mission concepts will be presented that can provide critical insights into CME initiation and dynamics: The Spherical Occulter Coronagraph CubeSat (SpOC Cube) and the Origin of Solar Eruptions (ONSET) mission. These missions all make high-cadence coronal images while filling their role to continuously observing the complete corona from very near the solar surface to the outer corona and into the heliosphere, most importantly observing the current gap where CMEs are initiated. The dynamics and processes observed by these instruments will help distinguish between CME models to finally understand the different or dominant processes that initiate a CME.