Speaker: Emeritus Prof.  Kanaris Tsinganos (National and Kapodistrian University of Athens, Greece)  

Title:  "Solar Eclipses and Results from Proba 3.0 Mission"  

Abstract: Out of the several billions of G-type stars in the Milky Way and the trillions of other galaxies in the Universe, only the Sun, due to its proximity to Earth, is accessible to detailed observations of its atmosphere, something that affects via space weather our planet.  The density of the coronal plasma is extremely low, such that the solar corona scatters approximately one-millionth of the   photospheric photons that pass through it, with the result that the corona is overshined by the photosphere, and can only be seen during total solar eclipses.   Those impressive coronal images can be observed once in a year, since Thales predicted the first solar eclipse in Asia Minor, the 28th of May 385 B.C. An eclipse occurs because of the great cosmic coincidence, or Divine Providence that the angular diameter of the Sun and the Moon as seen from Earth are equal.  It should be mention also that Aristarchos calculated from the lunar and solar eclipses that the size of the Sun is much greater than that of the Earth and therefore, he argued, it is impossible such a large body like the Sun to revolve around a much smaller body like Earth, proposing thus the Heliocentric system, more than 2000 years before Copernicus. 

The launching of the twin spacecrafts of Proba 3 in Dec 2024, in a formation flight around the Earth started the new era of long duration, detailed observations of the corona in the range of the radial distances r of 1.1 R⊙ < r < 3 R⊙.  We shall discuss some first results from observations of the solar corona by the ASPIICS coronagraph aboard the Proba-3 mission. For example, ASPIICS  observes quasi-stationary structures, such as coronal loops, streamers, quiescent prominences and a variety of dynamic phenomena, such as erupting prominences, coronal mass ejections, jets, solar wind outflows and coronal inflows. Also, ubiquitous, weak and persistent small-scale dynamic features (blobs, outflows, jets), between 1.3 and 3 R⊙ observed at a high spatial (5.6 arcsec) and temporal (30 s) resolution for the first time, with speeds ranging  from 15 km/s to 500 km/s, expanding thus the range of scales at which the variable slow solar wind is observed to form. All these features appear to originate from streamers and pseudostreamers, thus providing important constraints on the role of small-scale dynamics in the cradle of the solar wind.