The EUI instrument on the Solar Orbiter spacecraft has obtained the most
stable, high-resolution images of the solar corona from its orbit with a
perihelion near 0.4 AU. A sequence of 360 images obtained at 17.1 nm, between
25-Oct-2022 19:00 and 19:30 UT is scrutinized. One image pixel corresponds to
148 km at the solar surface. The widely-held belief that the outer atmosphere
of the Sun is in a continuous state of magnetic turmoil is pitted against the
EUI data. The observed plasma variations appear to fall into two classes. By
far the dominant behavior is a very low amplitude variation in brightness (1%)
in the coronal loops, with larger variations in some footpoint regions.
No hints of observable changes in magnetic topology are associated with such
small variations. The larger amplitude, more rapid, rarer and less-well
organized changes are associated with flux emergence. It is suggested therefore
that while magnetic reconnection drives the latter, most of the active corona
is heated with no evidence of a role for large-scale (observable) reconnection.
Since most coronal emission line widths are subsonic, the bulk of coronal
heating, if driven by reconnection, can only be of tangentially discontinuous
magnetic fields, with angles below about 0.5cS​/cA​∼0.3β, with
β the plasma beta parameter (∼0.01), and cS​ and cA​ sound and
Alfv\'en speeds. If heated by multiple small flare-like events, then these must
be ≲1021 erg, i.e. pico-flares. But processes other than
reconnection have yet to be ruled out, such as viscous dissipation, which may
contribute to the steady heating of coronal loops over active regions