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Sara Bertone
Ph.D. Student in Space Science and Technology, University of Trento
About Me
The solar atmosphere is divided into the photosphere, chromosphere, transition region and corona based on their distinct physical properties. The corona is the outermost layer and it extends for hundreds of thousands of kilometers into interplanetary space. The brightness of the corona in visible light is much lower than that of the solar disk, making it invisible to the naked eye except during a total solar eclipse or with dedicated instruments. The heating of the solar corona is one of the most curious and peculiar unsolved mysteries in solar physics. This phenomenon is characterized by the dramatic increase in temperature from the chromosphere to the corona over a very short distance in the transition region. The Sun undergoes a cycle of approximately eleven years, consisting of periods of maximum and minimum during which the corona changes significantly. Near the solar maximum, impulsive events become much more frequent, such as the expulsion of large quantities of plasma and magnetic field, the so-called coronal mass ejections (CMEs), and flares, which are sudden bursts of energy. Such impulsive events are generally a consequence of the rapid release of the energy stored in active regions. These energetic solar eruptions can excite various types of magnetohydrodynamic (MHD) waves in the corona, such as quasi-periodic fast-propagating (QFP) magnetosonic wave trains. The physical mechanism responsible for the generation and propagation of QFP wave trains in the solar corona remains poorly understood. While several events have been analyzed and modeled via numerical simulations, key questions regarding their origin and evolution remain open. To take a step forward towards the understanding of the phenomenon, we analyze a coronal event in which a CME was followed by the clear emergence of a QFP wave train. Using visible-light observations from the METIS coronagraph, we measure the physical parameters of the magnetosonic wave train. METIS is an instrument designed to study the solar corona, on board the Solar Orbiter spacecraft, a mission of the European Space Agency (ESA), launched in February 2020. The innovative instrument design has been conceived for simultaneously imaging the visible and ultraviolet emission of the Sun's corona. In particular, the high-cadence mode for the images in visible light allows the detection of the QFP wave trains which, otherwise, would be too fast to be observed, highlighting the instrument’s unique capability to investigate rapidly evolving coronal dynamics.
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