About this Research Topic
Stellar and solar activity research has a long history. First telescope observations of sunspots date back to the 17th century, and a 400-year history of sunspot number is available today, showing the 11-year magnetic cycle and its long term trends. Correlation with Earth climate has been studied extensively, notably the Maunder minimum in connection with the “Little Ice Age” between 1645 and 1715. In the early twentieth century, the magnetic nature of the sunspots and the solar activity cycle was established. In the 1950s, the dynamo theory for the regeneration of magnetic field through the interplay of rotation and turbulence was proposed. Stellar activity was first explicitly introduced in the 1950s, when its magnetohydrodynamic character was also suggested. In the following years the advent of space missions in the UV and X-rays permitted to observe activity in the outer atmosphere of the Sun and late-type stars. Considering the “Sun as a star” and observing stellar activity at different mass, rotation, age, etc., proved crucial for progress in this field. Interest in this area is growing considerably, especially in connection with exoplanet science and for providing crucial stellar age dating methods.
Stellar activity manifests as variations of the whole stellar electromagnetic spectrum and of emitted energetic particles, resulting from variations of surface magnetism, flares, coronal mass ejections and winds. These phenomena may profoundly affect the dynamics, chemistry, and climate of exoplanets and sometimes even the retention of the exoplanetary atmosphere, favoring or impeding the formation of early life in a planet. The presence of magnetic spots, convective turbulence, and granulation induces a radial velocity `jitter', producing a signal similar to that of a transiting exoplanet. Stellar activity has also an impact in the derivation of accurate elemental abundances in the stellar atmosphere. Significant advances in this field have been made thanks to multi-wavelength observations, Zeeman Doppler imaging, differential rotation estimates and large surveys by ground and space-born instruments, and by increasingly realistic simulations of the dynamo and magneto hydrodynamic processes operating at different scales. The Daniel K. Inouye Solar Telescope, Solar Orbiter and Parker Solar Probe are providing new insights about how magnetic energy is stored and dissipated at different spatial and temporal scales, throughout solar-like atmosphere and wind.
In future, we expect to answer several critical issues. What is the stellar activity evolution at late ages in the main sequence? How stellar activity and extrasolar space weather affects the star—planet system? What are the conditions that allow a planet to harbor life? How the initial conditions, binarity, and environment affect the stellar activity evolution? What does the rotation—activity-age relationship tell us about dynamo mechanisms? What is the role of the tachocline and of the meridian circulation in the dynamo mechanism? What causes Maunder-type Grand Minima?
This Research Topic aims to give for the first time a complete overview on stellar magnetic activity summarizing the state-of-the-field and current case studies on main-sequence stars, as well as challenging the community on what has still to be discovered and unveiled.
We welcome
(a) Reviews and Mini-Reviews about the past discoveries on stellar magnetic activity of main-sequence stars.
(b) Original Research, Methods and Brief Research Report, as well as Reviews and Mini-Reviews, that present the state of the art and the ongoing studies.
(c) Hypothesis & Theory, Perspective and Opinion on the challenges and prospective for the future.
The authors are invited to look at the details of each article type here
This Research Topic is part of the "Past, Present and Future" collection series. Other titles in the series are:
- Past, Present and Future of Gravitational Wave Research
Stellar activity manifests as variations of the whole stellar electromagnetic spectrum and of emitted energetic particles, resulting from variations of surface magnetism, flares, coronal mass ejections and winds. These phenomena may profoundly affect the dynamics, chemistry, and climate of exoplanets and sometimes even the retention of the exoplanetary atmosphere, favoring or impeding the formation of early life in a planet. The presence of magnetic spots, convective turbulence, and granulation induces a radial velocity `jitter', producing a signal similar to that of a transiting exoplanet. Stellar activity has also an impact in the derivation of accurate elemental abundances in the stellar atmosphere. Significant advances in this field have been made thanks to multi-wavelength observations, Zeeman Doppler imaging, differential rotation estimates and large surveys by ground and space-born instruments, and by increasingly realistic simulations of the dynamo and magneto hydrodynamic processes operating at different scales. The Daniel K. Inouye Solar Telescope, Solar Orbiter and Parker Solar Probe are providing new insights about how magnetic energy is stored and dissipated at different spatial and temporal scales, throughout solar-like atmosphere and wind.
In future, we expect to answer several critical issues. What is the stellar activity evolution at late ages in the main sequence? How stellar activity and extrasolar space weather affects the star—planet system? What are the conditions that allow a planet to harbor life? How the initial conditions, binarity, and environment affect the stellar activity evolution? What does the rotation—activity-age relationship tell us about dynamo mechanisms? What is the role of the tachocline and of the meridian circulation in the dynamo mechanism? What causes Maunder-type Grand Minima?
This Research Topic aims to give for the first time a complete overview on stellar magnetic activity summarizing the state-of-the-field and current case studies on main-sequence stars, as well as challenging the community on what has still to be discovered and unveiled.
We welcome
(a) Reviews and Mini-Reviews about the past discoveries on stellar magnetic activity of main-sequence stars.
(b) Original Research, Methods and Brief Research Report, as well as Reviews and Mini-Reviews, that present the state of the art and the ongoing studies.
(c) Hypothesis & Theory, Perspective and Opinion on the challenges and prospective for the future.
The authors are invited to look at the details of each article type here
This Research Topic is part of the "Past, Present and Future" collection series. Other titles in the series are:
- Past, Present and Future of Gravitational Wave Research
Keywords: Stellar activity, Magnetic Field, Stellar Atmosphere, Chromosphere, Coronae, Flares, Stellar Rotation, Solar-Like Stars
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