Letters of Intent received in 2017

LoI 2019-1981
Magnetic flux ropes: Generation, emergence, disruption, and transport

Topics

- Origin and transport of magnetic flux ropes through the solar/stellar interior, theory and models
- Emergence of magnetic flux ropes through the photosphere
- Flux rope characteristics and physical properties in the solar/stellar atmosphere
- Theory and models of initiation and evolution of coronal mass ejections (CMEs)
- Models, detection, and evolution of flux ropes in the heliosphere, their impact on Earth and throughout the solar system
- Ground-based observations of flux ropes in the corona: What can we learn from total solar eclipses?
- Flux ropes in astrospheres, stellar flares-CME connection
- Stellar prominences
- Implications of stellar CMEs on exo-space weather
- Upcoming space- and ground-based instrumentation for understanding the physics of flux ropes, their evolution, and related phenomena (DKIST, Solar Orbiter, Parker Solar Probe, LLAMA, etc.)

Rationale

Magnetic flux ropes are omnipresent in the Sun, from its interior to its atmosphere. It is believed that they originate at the base of the convective zone and that, after travelling through it, they constitute the building blocks of active regions. Theoretical and numerical models of flux rope formation and evolution are still controversial in determining the conditions for their survival of the constant buffeting of convective motions during their rise through the convective zone. Similar problems arise in understanding their emergence through the photosphere. Once they reach the solar atmosphere and expand filling up the corona, they can interact with other magnetic structures leading to the most violent solar events -- flares, coronal mass ejections (CMEs), and energetic particle events. Other flux ropes, which support prominences, are likely to be formed in the solar atmosphere and may remain stable for several solar rotations, reforming even after eruption. What are the conditions for their formation and what causes their destabilization are still key unanswered questions.

Magnetic flux ropes are observed over a wide range of spatial scales throughout the heliosphere. Large scale flux ropes, associated with magnetic cloud structures within interplanetary CMEs, were the first to be detected from space. These structures impact the Earth’s magnetosphere producing the strongest geomagnetic storms. They are also observed to contribute to Forbush decreases in low-energy cosmic rays. However, there is evidence for the existence of a distinct, but less well understood, category of small-scale magnetic flux ropes in the solar wind, the origin of which is still being debated.

Whereas it is observationally well established that Sun-like and cooler stars generate flares, stellar CMEs are very difficult to observe. Stellar CMEs, which in analogy to solar CMEs could be caused by the eruption of large-scale flux ropes, may play an important role in mass and angular momentum losses of young Sun-like stars. Furthermore, it is likely that the observed superflares, with energies of up to 10000 times the energy of a large solar flare might be associated with very large stellar CMEs. Such a powerful event may have significant implications for the physical conditions and the eventual habitability of orbiting exoplanets. Since planetary habitability depends, among other factors, also on the conditions and stability of the planetary atmosphere, all processes contributing to atmospheric erosion may severely restrict the habitability of a planet, even if it orbits within the habitable zone of its host star.

The symposium aims to shed light on the fundamental physics of these different sets of flux rope structures, their transport, interaction, relevance for solar/stellar environments and plausible impact on their planets. This symposium will bring together scientists from diverse, interdisciplinary areas such as solar, interplanetary, stellar, and planetary physics to review the current state of our understanding of the role of magnetic flux ropes, to exchange ideas, and identify relevant issues whose understanding needs coordinated interdisciplinary scientific efforts.

The symposium will be held in the city of San Juan, San Juan Province, which is symbolic as it hosts all solar instruments in Argentina. Most of these instruments are the result of Argentinean-Brazilian collaborations. In recent years, Argentina and Brazil have developed a critical mass of researchers (several hundreds) in the topics covered by this symposium; thus, the chosen city is ideal to host the symposium and the symposium itself is expected to have a significant impact on the scientific community of both nations and other countries in the region, some of which have recently joined IAU. This will create a lasting legacy of the meeting.

The venue will be the Convention Center “Intendente Guillermo Barrena Guzmán” with an auditorium of 625 seats in two levels, modern audio and projection facilities, comfortable areas for minor group discussions and display of posters. San Juan “Domingo Faustino Sarmiento Airport” is served by direct flights from Buenos Aires, Mendoza, and Santiago de Chile. Buenos Aires “International Ministro Pistarini Airport” is served by by the large majority of international airlines and Mendoza “International El Plumerillo Airport” has direct flights from Santiago de Chile and several cities in Brazil.

Furthermore, the symposium date is timely in two different aspects. On one side, San Juan City is by the edge of the zone of totality of the solar eclipse on 2 July 2019, which will easily allow transportation of the symposium participants to witness the eclipse. Two sites have been already explored, where totality will last for around 2.28 minutes, one by the 40 National Highway close to the foothills of the Andes Mountains (50-minute drive from San Juan) and another one in a valley to the west (between the foothills and the Andes themselves) close to the city of Bella Vista (90-minute drive from San Juan). The final decision for the location to witness the eclipse will be taken on site based on weather conditions at that time. On the other hand, September 2019 is the expected date for the first light of the Large Latin-American Millimeter Array (LLAMA), an Argentinian-Brazilian project to build and operate a 12-m radio-telescope that will observe from 45 to 900 GHz and that will have VLBI capabilities. In VLBI mode, working together with the Atacama Large Millimeter Array (ALMA), it will have a resolution better than 0.001 arcsec at 1 mm wavelength, bringing unprecedented images of the solar atmosphere with a spatial resolution of the order of 1 km.