Understanding CMEs using AIA and SWAP data
Lead Research Organisation:
University College London
Department Name: Mullard Space Science Laboratory
Abstract
The Sun is a dynamic and active star. Observations across the electromagnetic spectrum from gamma rays to radio have revealed that the Sun has a million degree atmosphere in which the most energetic explosions and eruptions in the Solar System take place. The explosions are known as solar flares and the eruptions are known as coronal mass ejections (CMEs). The energy source for these energetic phenomena is field-aligned electric currents in the Sun's atmospheric magnetic field. Understanding the physical processes that take place to convert this energy from magnetic to other forms such as kinetic and radiative and hence understand flares and CMEs, is a major aim in solar physics. The aim of this project is to study the evolution of the physical phenomena leading to the initiation of CMEs.
In many cases, a key aspect is that the magnetic field forms a CME is a configuration known as a "flux rope". These are bundles of twisted magnetic field, which can lose their stability and then erupt into the Solar System. However, observations indicate that the magnetic structure that erupts might not be the entire flux rope as initially formed, raising the question of what physical processes are occurring to evolve the configuration shortly before the CME. This project seeks to understand how flux ropes form and are modified before and during the eruption itself due to the influence of the surrounding coronal magnetic field. The project will use a range of data sets supplied by the SDO and Proba-2 spacecraft, as well as ground-based telescopes.
In many cases, a key aspect is that the magnetic field forms a CME is a configuration known as a "flux rope". These are bundles of twisted magnetic field, which can lose their stability and then erupt into the Solar System. However, observations indicate that the magnetic structure that erupts might not be the entire flux rope as initially formed, raising the question of what physical processes are occurring to evolve the configuration shortly before the CME. This project seeks to understand how flux ropes form and are modified before and during the eruption itself due to the influence of the surrounding coronal magnetic field. The project will use a range of data sets supplied by the SDO and Proba-2 spacecraft, as well as ground-based telescopes.
Publications
Palmerio E
(2021)
Investigating Remote-Sensing Techniques to Reveal Stealth Coronal Mass Ejections
in Frontiers in Astronomy and Space Sciences
O'Kane J
(2019)
Stealth Coronal Mass Ejections from Active Regions
in The Astrophysical Journal
O'Kane J
(2021)
The Magnetic Environment of a Stealth Coronal Mass Ejection
in The Astrophysical Journal
O'Kane J
(2021)
Solar origins of a strong stealth CME detected by Solar Orbiter
in Astronomy & Astrophysics
Nitta N
(2021)
Correction to: Understanding the Origins of Problem Geomagnetic Storms Associated with "Stealth" Coronal Mass Ejections
in Space Science Reviews
Nitta N
(2021)
Understanding the Origins of Problem Geomagnetic Storms Associated with "Stealth" Coronal Mass Ejections
in Space Science Reviews
Long D
(2021)
Localized Acceleration of Energetic Particles by a Weak Shock in the Solar Corona
in The Astrophysical Journal
Studentship Projects
| Project Reference | Relationship | Related To | Start | End | Student Name |
|---|---|---|---|---|---|
| ST/R505171/1 | 01/10/2017 | 24/12/2021 | |||
| 1911966 | Studentship | ST/R505171/1 | 01/10/2017 | 24/09/2021 | Jennifer O'kane |
| Description | Coronal mass ejections (CMEs) drive major space weather events, with the potential to adversely affect the near-Earth environment. Although CMEs can typically be identified using low coronal signatures such as solar flares, filament eruptions, and coronal dimmings, a type of CME with no apparent coronal signature was observed in 2009. The source region of these 'stealth' CMEs is difficult to identify and they are potentially geoeffective, making them particularly hazardous. In this thesis, I investigate the initiation and evolution of stealth CMEs using a variety of advanced image-processing techniques and magnetic field modelling. I identified faint signatures associated with the stealth CMEs that are comparable to the low-coronal signatures of classical CMEs, confirming that the same physical processes are taking place for these events. An examination of the global and local magnetic field configuration of the stealth CMEs then enabled me to quantify the evolution of the magnetic field before and after the eruptions, and show how the erupting structures were ultimately deflected into the heliosphere. Finally, I tracked the initial evolution of stealth CMEs and found that they do not typically exhibit the classic three-phase kinematic profile often observed for CMEs, instead evolving via a two-phase velocity profile in which their velocity slowly increases to the background solar wind speed. However, it was not possible to distinguish between the different models proposed to drive the eruptions, suggesting that these events do not typically have one specific driver. This work shows that stealth CMEs do exhibit very faint low coronal signatures, and that while difficult due to the weak magnetic field, modelling of these events is vital to investigate and understand their evolution. Further, it is necessary to have multi-viewpoint and multi-wavelength observation in order to predict and understand these events for future space weather forecasting. |
| Exploitation Route | The results obtained can be applied to improving the operation of solar and space weather focused missions such as the recently launched ESA Solar Orbiter spacecraft (launched February 2020), and the future ESA Lagrange L5 mission (launch planned for 2027). |
| Sectors | Aerospace, Defence and Marine,Other |
| Description | Space weather forecasting is vital to mitigating impacts on national infrastructure and human health. Space weather can have significant impacts on for example power grids, navigation, and aviation to name a few. Predicting and understanding Space weather events will ensure actions can be made in advance and impacts can be limited and less problematic for civilians. |
| Description | MSSL Travel Grant |
| Amount | £500 (GBP) |
| Organisation | University College London |
| Sector | Academic/University |
| Country | United Kingdom |
| Start | 10/2018 |
| End | 11/2018 |
| Description | RAS Travel Grant |
| Amount | £800 (GBP) |
| Organisation | Royal Astronomical Society |
| Sector | Academic/University |
| Country | United Kingdom |
| Start | 07/2019 |
| End | 07/2019 |
| Description | SDO Meeting Belgium - Conference Funding |
| Amount | € 350 (EUR) |
| Organisation | European Space Agency |
| Sector | Public |
| Country | France |
| Start | 10/2018 |
| End | 10/2018 |
| Description | Towards Future Research on Space Weather Drivers - Conference Funding |
| Amount | € 600 (EUR) |
| Organisation | European Space Agency |
| Sector | Public |
| Country | France |
| Start | 07/2019 |
| End | 07/2019 |
| Description | UCL Global and Santander Universities Grant |
| Amount | £1,874 (GBP) |
| Organisation | University College London |
| Sector | Academic/University |
| Country | United Kingdom |
| Start | 09/2019 |
| End | 10/2019 |
| Description | ISSI - Problematic Geomagnetic Storms |
| Organisation | International Space Science Institute (ISSI) |
| Country | Switzerland |
| Sector | Academic/University |
| PI Contribution | The ISSI team is working towards understanding the origins of problem geomagnetic storms. Many of these are caused by stealth CMEs (my area of expertise), and can also result from lack of instrumentation and vantage viewing points. The team was composed of experts in Solar physics, Solar wind physics, Magnetosphere physics, and modellers. My contribution to the team involved using the image processing techniques which I have used extensively in my own research, namely the multi-scale normalisation technique, and the non-radial graduated filter technique, to enhance both EUV images and White-Light coronagraph images. Additionally I contributed by interpreting the solar images, and eruptions that were likely causes of the geomagnetic storms. |
| Collaborator Contribution | Other members of the team worked on interpreting the in-situ data, looking for magnetic clouds and disturbances. There were also members of the team who are experts in modelling solar eruptions, and this was done for a number of events that we analysed. The team as a whole worked together to identify geomagnetic storms with no clear source region, and selected events to analyse in further detail for the review paper. |
| Impact | By bringing all of the different expertise and analysis together from each member of the ISSI team, we have produced a review paper on problem geomagnetic storms which is in the final stages before submission to Springer Journals. |
| Start Year | 2018 |
| Description | SWAP investigator - Royal Observatory Belgium |
| Organisation | Royal Observatory of Belgium |
| Country | Belgium |
| Sector | Academic/University |
| PI Contribution | My visit to the Royal Observatory Belgium included me teaching partners on how to use the Multi-Scale Gaussian Normalisation technique, and the Non-Radial Graduated Filter technique for Solar image processing and enhancement. |
| Collaborator Contribution | At the Royal Observatory Belgium, I was taught how to use the Graduated Cylindrical Shell Model and Triangulation methods using STEREO and SOHO coronagraph data, for triangulating and finding source regions of stealth CMEs - A vital contribution to my research and to my first research paper. |
| Impact | The methods and techniques taught to me at the Royal Observatory Belgium was a vital part of my first research paper, and is being used in my current research and will be used in my future research. |
| Start Year | 2018 |
| Description | UCL Global and Santander Universities Grant - IAFE |
| Organisation | University of Buenos Aires |
| Country | Argentina |
| Sector | Academic/University |
| PI Contribution | The aim of the visit to the Instituto de Astronom ´ia y F ´isica del Espacio in Buenos Aires was to work with Prof. Cristina Mandrini, who is head of the Solar Physics group at IAFE and a world-leading expert in modelling the solar magnetic field. By working with her, we intended to investigate the magnetic topology of "Stealth CME" events, look for null points where magnetic reconnection is more likely to occur in the solar atmosphere, and quantify how the solar magnetic field evolves before and after the eruption. My skillset for this collaboration involved a deep understanding of Stealth CMEs, the work that has been completed on these events, and the open science questions related to these events. Additionally I have gained knowledge and skills using image processing techniques on EUV and Coronagraph data. This approach produced clear signatures of magnetic reconnection and features suggestive of a solar filament, which is often observed as a precursor to a solar eruption. |
| Collaborator Contribution | Our Argentinian colleagues were then able to use their modelling techniques to extrapolate the solar magnetic field, enabling us to identify a null point located high up in the solar atmosphere where the magnetic field drops to zero. As the magnetic field surrounding null points is so low, they are regions where magnetic reconnection can occur, leading to a solar eruption. We were able to compute a series of different estimates of the solar magnetic field which allowed us to quantify how it evolved with time and ultimately how the erupting solar storm was deflected into the heliosphere. |
| Impact | The visit was incredibly useful, providing plenty of opportunities to learn and develop new skills and broaden my collaborative network. As a result of the trip I AM currently working on at least 2 projects which I will write up and submit to research journals. |
| Start Year | 2019 |
| Description | Organisation of MSSL Space work experience week |
| Form Of Engagement Activity | Participation in an activity, workshop or similar |
| Part Of Official Scheme? | No |
| Geographic Reach | Local |
| Primary Audience | Schools |
| Results and Impact | I organized and ran a work experience week at MSSL, which was aimed at a diverse group of A-level students. There were 35 pupils who attended the week, which involved space related workshops, talks and research projects, run by a number of the post-graduate students at MSSL. At the end of the week, the pupils were required to produce a report and a presentation on their research project. |
| Year(s) Of Engagement Activity | 2019 |