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.
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
Antolin P
(2019)
Influence of Resonant Absorption on the Generation of the Kelvin-Helmholtz Instability
in Frontiers in Physics
Antolin P
(2019)
Thermal instability and non-equilibrium in solar coronal loops: from coronal rain to long-period intensity pulsations
in Plasma Physics and Controlled Fusion
Cheung M
(2019)
Multi-component Decomposition of Astronomical Spectra by Compressed Sensing
in The Astrophysical Journal
De Pontieu B
(2019)
The Multi-slit Approach to Coronal Spectroscopy with the Multi-slit Solar Explorer (MUSE)
in The Astrophysical Journal
Froment C
(2019)
Multi-scale observations of thermal non-equilibrium cycles in coronal loops
in Astronomy & Astrophysics
Guo M
(2019)
Heating Effects from Driven Transverse and Alfvén Waves in Coronal Loops
in The Astrophysical Journal
Howson T
(2019)
Resonant absorption in expanding coronal magnetic flux tubes with uniform density
in Astronomy & Astrophysics
Ishikawa R
(2020)
Temporal and Spatial Scales in Coronal Rain Revealed by UV Imaging and Spectroscopic Observations
in Solar Physics
Johnston C
(2019)
The effects of numerical resolution, heating timescales and background heating on thermal non-equilibrium in coronal loops
in Astronomy & Astrophysics
Karampelas K
(2019)
Amplitudes and energy fluxes of simulated decayless kink oscillations
Karampelas K
(2019)
Amplitudes and Energy Fluxes of Simulated Decayless Kink Oscillations
in Frontiers in Astronomy and Space Sciences
Kohutova P
(2020)
Self-consistent 3D radiative magnetohydrodynamic simulations of coronal rain formation and evolution
in Astronomy & Astrophysics
Kriginsky M
(2020)
Ubiquitous hundred-Gauss magnetic fields in solar spicules
in Astronomy & Astrophysics
Kriginsky M
(2020)
Ubiquitous hundred-Gauss magnetic fields in solar spicules
Luna M
(2019)
Fundamental transverse vibrations of the active region solar corona
in Astronomy & Astrophysics
Pagano P
(2019)
MHD simulations of the in situ generation of kink and sausage waves in the solar corona by collision of dense plasma clumps
in Astronomy & Astrophysics
Description | This award corresponds to the first year of the STFC / ERF Fellowship. During this first year many papers were published that laid the foundations of the major results achieved in the following years. The results are displayed in the second part of this award. |
Exploitation Route | The details of these are explained in the second part of this award. |
Sectors | Other |
Description | This award corresponds to the first year of the STFC ERF. The findings of the ERF have made an impact, and this first year greatly contributed to its achievement. The findings, however, cannot be attributed to this first year and will be included in the section corresponding to the continuation, once it is finished. |
First Year Of Impact | 2020 |
Sector | Aerospace, Defence and Marine,Education |
Description | ISSI Team - Observed Multi-Scale Variability of Coronal Loops as a Probe of Coronal Heating |
Amount | SFr. 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 |