The Cool Alter-Ego of the Hot Solar Corona

Lead Research Organisation: University of St Andrews
Department Name: Mathematics and Statistics

Abstract

The Sun's corona or outer atmosphere has a staggeringly high temperature of several million degrees, over 200 times hotter than its surface. Explaining this feature, which is also present in most stars in the universe, represents one of the most outstanding unsolved puzzles in physics and astronomy.
However, coronal heating has a cool alter-ego. The corona is highly inhomogeneous and upholds a large amount of cold material, a cooling counterpart that is integral to coronal heating and through which unique insight can be gained. On Earth, the hotter and denser the air, the more it rains. Similar heating (evaporation) and cooling (condensation) cycles permeate the solar corona. Coronal cooling is mainly driven by the fundamental process of thermal instability, a mechanism that has recently been recognised as playing a major role in the solar corona but whose characteristics are still poorly understood. This cooling process leads to partially ionised, dense, multi-thermal and clumpy plasma that can drain back down to the solar surface as 'coronal rain', or remain magnetically suspended in the corona to form massive cool structures called prominences, whose destabilisation and eruption constitute the most hazardous phenomena for human exploration of space.
In this project I shall use my expertise in modelling waves and instabilities and my extensive experience in coordinated multi-wavelength observations with cutting edge instruments to investigate the coronal heating mechanisms and the formation of prominences and their eruption. I will strategically address coronal heating by investigating the atmospheric response to the heating in the form of cooling.

The characteristics of the thermal instability by-products, prominences and coronal rain, will be investigated by combining high resolution instruments for space (Hinode, IRIS, SDO) and ground (SST, ALMA) that allow for the first time the full temperature coverage of coronal cooling by thermal instability due to improved spatial, temporal and spectral resolution. The amount in the corona over time, the morphology and dynamics, will allow to develop quantitative models both of coronal heating and of coronal rain / prominence formation and eruption, and elucidate the solar atmospheric mass and energy cycle.

Numerical simulations (with Lare3D, AMR-VAC and Bifrost) and forward modelling (with FoMo and RH) will determine the observational signatures of the major heating candidate mechanisms, such as Alfvénic waves and magnetic reconnection in current sheets, which will then be compared with the observational results. The formation of thermal instability by-products will be investigated analytically and numerically and the cool chromospheric nature of this material will be exploited to achieve the highest resolution probe for the coronal magnetic field topology. This will provide a measure for elemental coronal structure and determine the spatial and temporal scales of the heating. The tracing of cold material and determination of heating mechanism signatures will allow to detect and quantify these mechanisms in action.

The loss of stability of prominences will be addressed by investigating novel ideas such as the MHD avalanche model, through which a kink instability of the small elemental structure can play a crucial role in the overall stability. The conversion of initial mutual magnetic helicity to self-helicity during the reconnection process will be investigated as a solution to the observed puzzling increase of twist during the eruption of prominences.

The St Andrews host institution is a world leader in the core subjects of this project: instabilities, waves and reconnection. Active collaboration and excellent project development opportunities are thus expected. My expertise gained through this project will be essential to fully exploit the capabilities for approved future solar projects such as Solar Orbiter, DKIST and Parker Probe.

Publications

10 25 50

Related Projects

Project Reference Relationship Related To Start End Award Value
ST/R004285/1 31/05/2018 30/07/2019 £433,450
ST/R004285/2 Transfer ST/R004285/1 31/07/2019 30/05/2023 £332,866
 
Description ISSI Team - Observed Multi-Scale Variability of Coronal Loops as a Probe of Coronal Heating
Amount CHF 24,000 (CHF)
Organisation International Space Science Institute (ISSI) 
Sector Academic/University
Country Switzerland
Start 01/2018 
End 12/2019
 
Description Collaboration with FHNW on Machine Learning applied to coronal rain observations 
Organisation FHNW, Switzerland
Country Switzerland 
Sector Academic/University 
PI Contribution My main contribution to this collaboration is as science expert in the field of coronal rain. We are jointly developing and refining machine learning algorithms to automatically detect coronal rain in the solar atmosphere. The main data used for this purpose is open data coming from the IRIS satellite.
Collaborator Contribution My main partner in this collaboration is Dr. Lucia Kleint at FHNW. A student of hers, Mr. Brandon Panos is also participating. FHNW provides a repository for the IRIS data, which therefore can be accessed very rapidly and through which the developed algorithms can be applied and checked efficiently. Both Dr. Kleint and Mr. Panos are actively involved in the development of these algorithms.
Impact - No output yet
Start Year 2018
 
Description Collaboration with UIB in SST observing campaign 2019 
Organisation University of the Balearic Islands
Country Spain 
Sector Academic/University 
PI Contribution A jointly submitted application for observing time at the Swedish 1-m Solar Telescope (SST; in La Palma, Canary Islands, Spain) has been approved for the 2019 observing campaign. Our observing campaign will focus on observations of coronal rain with the SST, which is the primary scientific target of my fellowship. My main contribution to this collaboration is as scientific expert on the topic of coronal rain and also as expert in observations at the SST. I may be travelling to La Palma in August 2019 to jointly conduct the observations.
Collaborator Contribution This application falls under Spanish time for the telescope usage. As such, the PI of this proposal is Prof. Ramón Oliver from Departament de Física, Universitat de les Illes Balears. Although this particular application was submitted early in January 2019, my collaboration with UIB and in particular with Prof. Oliver had started in 2015 around the topic of coronal rain. For this particular application Prof. Oliver will be joining also with a Master student of his, which will help in the analysis of the observations. In addition, Dr. Dato Kuridze (Aberystwyth University) will also be joining and will contribute with his expertise in polarimetry.
Impact - Grant for 10 days observing time at the SST during August 2019
Start Year 2019
 
Description Collaboration with UIB on SST observing campaign 2020 
Organisation University of the Balearic Islands
Country Spain 
Sector Academic/University 
PI Contribution A jointly submitted application for observing time at the Swedish 1-m Solar Telescope (SST; in La Palma, Canary Islands, Spain) has been approved for the 2020 and 2021 observing campaigns. Our observing campaign focus on observations of spicules and coronal rain with the SST. My main contribution to this collaboration is as scientific expert on the topic of coronal rain and also as expert in observations at the SST. I may be travelling to La Palma in August 2021 to jointly conduct the observations.
Collaborator Contribution This application falls under Spanish time for the telescope usage. As such, the PI of this proposal is Prof. Ramón Oliver from Departament de Física, Universitat de les Illes Balears. Although these applications were submitted early in January 2020 and January 2021, my collaboration with UIB and in particular with Prof. Oliver had started in 2015 around the topic of coronal rain and has now expanded to the topic of spicules. For this particular application Prof. Oliver will be joining also with a Master student of his, which will help in the analysis of the observations. In addition, Dr. Dato Kuridze (Aberystwyth University) will also be joining and will contribute with his expertise in polarimetry.
Impact DOI: 10.1051/0004-6361/202038546
Start Year 2019
 
Description Research visit to RoCS - 2018 
Organisation University of Oslo
Department Rosseland Centre for Solar Physics
Country Norway 
Sector Academic/University 
PI Contribution I have contributed to an on-going research as a coronal rain rain expert. We are currently writing a paper that will reflect this collaboration.
Collaborator Contribution The main collaborator at this institute for this current work is Dr. Clara Froment. She has contributed with the analysis of data obtained at the SST telescope. Other members of the institute are also involved in this collaboration.
Impact 10.1051/0004-6361/201936717
Start Year 2018
 
Description Space Science Review on MHD Kink waves in the solar atmosphere 
Organisation University of Warwick
Department Department of Physics
Country United Kingdom 
Sector Academic/University 
PI Contribution This partnership aims at writing a series of scientific review papers on the subject of MHD waves in the solar atmosphere. I contribute as a wave expert on the numerical modelling and observational sides. This scientific reviews have all been submitted to the Space Science Reviews journal, which is a peer reviewed, scientific journal of space science. At present two of them have been published.
Collaborator Contribution The SSR review brings together several experts from different institutions worldwide. This collaboration started with a meeting in Beijing in October 2019 at the ISSI-BJ center (NAOC).
Impact Published papers: 10.1007/s11214-020-00770-y 10.1007/s11214-020-00761-z 10.1007/s11214-021-00847-2 10.1007/s11214-021-00849-0 Accepted: 2021arXiv211213577A
Start Year 2019