134
Moreover, the most recent observations have shown that the solar atmosphere is
an extremely dynamic environment, generated and permeated by a continuous interplay of the plasma and the magnetic field. Such interplay, which drives the solar
activity at timescales from seconds to centuries, modulates the solar particulate and
magnetic fluxes that impose electromagnetic forces within the whole heliosphere.
That same interplay has a fundamental role in hugely diverse astrophysical systems,
such as the evolution of magnetic features in the solar atmosphere, the heating of
solar and stellar coronae, the acceleration of jets from active galactic nuclei and
gamma ray bursts, and the heating of the medium of galaxies.
New instruments able to measure solar magnetic field in high resolution and at
sufficient cadence to study dynamics, either directly through spectropolarimetry or
indirectly through proxy-magnetometry, are now available to solar observers.
However, most recent observations and numerical models show that the magnetic
field is most likely structured in the solar atmosphere on scales well beyond what
can be observed or simulated today or in the foreseeable future. This motivates the
current drive for the construction of the next generation of large aperture telescopes
and space missions capable of observing and extracting the physical structure of the
solar atmosphere at fundamental spatial and temporal scales. Examples are the
ground-based European Solar Telescope (EST, Collados et al. 2013) and the Solar
Orbiter mission (Mueller et al. 2020).
Indeed, we are still missing critically important elements in our understanding of
the processes of plasma-field interaction in the solar atmosphere and heliosphere
due to the lack of proper observations and measurements of solar plasma properties.
For example, modern observations show that spicules are distributed all over the
solar surface at any given time; they are believed to channel a lot of energy into the
solar corona and thus heat it, but their role in the heating of the outer solar atmosphere still remains unexplained due to the lack of instruments capable of measuring magnetic fields in spicules before they disappear.
In the 1850s, Secchi began to study the dynamics of solar structures and their
relation to phenomena observed on Earth. Space weather events are particularly
significant threats to modern society, owing to our increased dependency on the
electric infrastructure (Hapgood 2011; Schrijver et al. 2012). Although we know
that the plasma-field interplay in the solar atmosphere is responsible for the evolution of large-scale magnetic features – which are observed to be the source and
location of instabilities affecting the space weather – we still lack the knowledge
needed to predict the evolution of solar magnetic regions. In particular, recent highresolution observations have shown that sunspots consist of dynamically evolving
small-scale and short-lived features that combined form coherent large and longliving sunspots and drive their evolution. Despite the recent breakthrough in solar
imaging from ground-based and space-born telescopes, it is clear that the fundamental scales of the observed processes are still unresolved. Just as it was for
Secchi’s daily research, the limit of current observations motivates the design and
construction of larger aperture telescopes and development of new
instrumentation.
I. Ermolli and M. Ferrucci
Moreover, the most recent observations have shown that the solar atmosphere is
an extremely dynamic environment, generated and permeated by a continuous interplay of the plasma and the magnetic field. Such interplay, which drives the solar
activity at timescales from seconds to centuries, modulates the solar particulate and
magnetic fluxes that impose electromagnetic forces within the whole heliosphere.
That same interplay has a fundamental role in hugely diverse astrophysical systems,
such as the evolution of magnetic features in the solar atmosphere, the heating of
solar and stellar coronae, the acceleration of jets from active galactic nuclei and
gamma ray bursts, and the heating of the medium of galaxies.
New instruments able to measure solar magnetic field in high resolution and at
sufficient cadence to study dynamics, either directly through spectropolarimetry or
indirectly through proxy-magnetometry, are now available to solar observers.
However, most recent observations and numerical models show that the magnetic
field is most likely structured in the solar atmosphere on scales well beyond what
can be observed or simulated today or in the foreseeable future. This motivates the
current drive for the construction of the next generation of large aperture telescopes
and space missions capable of observing and extracting the physical structure of the
solar atmosphere at fundamental spatial and temporal scales. Examples are the
ground-based European Solar Telescope (EST, Collados et al. 2013) and the Solar
Orbiter mission (Mueller et al. 2020).
Indeed, we are still missing critically important elements in our understanding of
the processes of plasma-field interaction in the solar atmosphere and heliosphere
due to the lack of proper observations and measurements of solar plasma properties.
For example, modern observations show that spicules are distributed all over the
solar surface at any given time; they are believed to channel a lot of energy into the
solar corona and thus heat it, but their role in the heating of the outer solar atmosphere still remains unexplained due to the lack of instruments capable of measuring magnetic fields in spicules before they disappear.
In the 1850s, Secchi began to study the dynamics of solar structures and their
relation to phenomena observed on Earth. Space weather events are particularly
significant threats to modern society, owing to our increased dependency on the
electric infrastructure (Hapgood 2011; Schrijver et al. 2012). Although we know
that the plasma-field interplay in the solar atmosphere is responsible for the evolution of large-scale magnetic features – which are observed to be the source and
location of instabilities affecting the space weather – we still lack the knowledge
needed to predict the evolution of solar magnetic regions. In particular, recent highresolution observations have shown that sunspots consist of dynamically evolving
small-scale and short-lived features that combined form coherent large and longliving sunspots and drive their evolution. Despite the recent breakthrough in solar
imaging from ground-based and space-born telescopes, it is clear that the fundamental scales of the observed processes are still unresolved. Just as it was for
Secchi’s daily research, the limit of current observations motivates the design and
construction of larger aperture telescopes and development of new
instrumentation.
I. Ermolli and M. Ferrucci