Modelling and Multi-wavelength Observations of Solar Flare Heating
Lead Research Organisation:
Queen's University Belfast
Department Name: Sch of Mathematics and Physics
Abstract
Our Sun is perceived to be a fairly benevolent star, bathing our planet in live-giving heat and light. But every 11 years or so, its behaviour changes, from quiescent to turbulent and back again. During periods of increased activity the Sun's twisted and contorted magnetic field continually undergoes episodes of complex reconfiguration to liberate vast quantities of pent-up energy. This energy goes into heating the solar plasma to temperatures of tens of millions of degrees and accelerating particles to near-relativistic velocities. Precisely how this energy conversation takes place remains an open question, and I aim to tackle this problem over the course of this Fellowship by capitalising upon the most advanced theoretical models and observational datasets currently available.
Modern society is becoming increasingly dependent upon evermore advanced technologies. These systems, such as satellite communication, national power grids, and the Global Positioning System (GPS), are all susceptible to changes in the Sun's behaviour; more commonly referred to as space weather. Space weather typically comprises two phenomena: solar flares and coronal mass ejections (CMEs). CMEs are clouds of charged particles ejected off the Sun at millions of miles per hour, reaching the Earth in 2-3 days, where they can interfere with electrical systems and generate spectacular aurora, while solar flares are intense bursts of radiation that span the entire electromagnetic spectrum from radio waves to gamma-rays. This radiation traverses the Sun-Earth distance in just 8 minutes, and the ultraviolet (UV) component is known to change the composition and dynamics of our atmosphere. This can affect the motion of satellites in low Earth orbit, disrupt long-wave radio communication, and affect the transmission of GPS signals.
During solar flares, much of the UV radiation is emitted by the chromosphere; a dense layer between the Sun's visible photosphere and the tenuous outer corona. The chromosphere is also where the bulk of a flare's energy emanates during its initial stages, and is the origin of material that occupies the overlying coronal loops. However, the mechanism by which the released energy gets transferred to the lower solar atmosphere remains elusive. It is commonly assumed that the delivery mechanism is a beam of high-energy electrons, and yet these particles are unable to penetrate to the depths at which the most energetic emission is believed to originate. Other proposed processes include heat conduction, relativistic ions, magnetic waves, or radiative backwarming. Fortunately, much of the radiation emitted contains a wealth of diagnostic information with which to probe the heated plasma. This allows us to distinguish between various heating mechanisms by measuring changes in temperature, density, velocity, etc, and comparing them to the predictions of theory.
While solar flares may emit radiation across the entire spectrum, our spectral coverage is somewhat lacking in parts. Most remote sensing instruments - both in space and on the ground - are often designed to look at a very limited wavelength range. Therefore in order to build a more complete picture of the flaring solar atmosphere, coordinated observations between different instruments are crucial. A core goal of this research is therefore to search for and catalog flaring events observed by a variety of instruments simultaneously, as well as planning future coordinated observing campaigns. For parts of the spectrum that are not yet observable, outputs from numerical simulations shall be used to fill in the gaps. This will help to prepare for instrumentation that will come online during the course of the project. Similarly, there are regions of stellar flare spectra that are unobservable due to absorption by the interstellar medium. The outcomes of this research shall assist in characterising this emission on other stars, especially that which can affect exoplanet atmospheres.
Modern society is becoming increasingly dependent upon evermore advanced technologies. These systems, such as satellite communication, national power grids, and the Global Positioning System (GPS), are all susceptible to changes in the Sun's behaviour; more commonly referred to as space weather. Space weather typically comprises two phenomena: solar flares and coronal mass ejections (CMEs). CMEs are clouds of charged particles ejected off the Sun at millions of miles per hour, reaching the Earth in 2-3 days, where they can interfere with electrical systems and generate spectacular aurora, while solar flares are intense bursts of radiation that span the entire electromagnetic spectrum from radio waves to gamma-rays. This radiation traverses the Sun-Earth distance in just 8 minutes, and the ultraviolet (UV) component is known to change the composition and dynamics of our atmosphere. This can affect the motion of satellites in low Earth orbit, disrupt long-wave radio communication, and affect the transmission of GPS signals.
During solar flares, much of the UV radiation is emitted by the chromosphere; a dense layer between the Sun's visible photosphere and the tenuous outer corona. The chromosphere is also where the bulk of a flare's energy emanates during its initial stages, and is the origin of material that occupies the overlying coronal loops. However, the mechanism by which the released energy gets transferred to the lower solar atmosphere remains elusive. It is commonly assumed that the delivery mechanism is a beam of high-energy electrons, and yet these particles are unable to penetrate to the depths at which the most energetic emission is believed to originate. Other proposed processes include heat conduction, relativistic ions, magnetic waves, or radiative backwarming. Fortunately, much of the radiation emitted contains a wealth of diagnostic information with which to probe the heated plasma. This allows us to distinguish between various heating mechanisms by measuring changes in temperature, density, velocity, etc, and comparing them to the predictions of theory.
While solar flares may emit radiation across the entire spectrum, our spectral coverage is somewhat lacking in parts. Most remote sensing instruments - both in space and on the ground - are often designed to look at a very limited wavelength range. Therefore in order to build a more complete picture of the flaring solar atmosphere, coordinated observations between different instruments are crucial. A core goal of this research is therefore to search for and catalog flaring events observed by a variety of instruments simultaneously, as well as planning future coordinated observing campaigns. For parts of the spectrum that are not yet observable, outputs from numerical simulations shall be used to fill in the gaps. This will help to prepare for instrumentation that will come online during the course of the project. Similarly, there are regions of stellar flare spectra that are unobservable due to absorption by the interstellar medium. The outcomes of this research shall assist in characterising this emission on other stars, especially that which can affect exoplanet atmospheres.
Publications
Simões P
(2019)
The Spectral Content of SDO/AIA 1600 and 1700 Å Filters from Flare and Plage Observations
in The Astrophysical Journal
Milligan R
(2020)
Lyman-alpha Variability During Solar Flares Over Solar Cycle 24 Using GOES-15/EUVS-E
in Space Weather
Matthews S
(2021)
The high-energy Sun - probing the origins of particle acceleration on our nearest star
in Experimental Astronomy
Quinn S
(2021)
Flare-induced Sunquake Signatures in the Ultraviolet as Observed by the Atmospheric Imaging Assembly
in The Astrophysical Journal
Monson A
(2021)
Flare-induced Photospheric Velocity Diagnostics
in The Astrophysical Journal
Millar D
(2021)
The effect of a solar flare on chromospheric oscillations
in Monthly Notices of the Royal Astronomical Society
Milligan R
(2021)
Solar Irradiance Variability Due to Solar Flares Observed in Lyman-Alpha Emission
in Solar Physics
Sellers S
(2022)
Call and Response: A Time-resolved Study of Chromospheric Evaporation in a Large Solar Flare
in The Astrophysical Journal
McLaughlin S
(2023)
Formation Of The Lyman Continuum During Solar Flares
McLaughlin S
(2023)
Formation of the Lyman Continuum during Solar Flares
in The Astrophysical Journal
Greatorex H
(2023)
Observational Analysis of Lya Emission in Equivalent-magnitude Solar Flares
in The Astrophysical Journal
Herde V
(2023)
Spicules in IRIS Mg ii Observations: Automated Identification
in The Astrophysical Journal
Description | COVID-19 Pandemic Research Enabling Fund |
Amount | £30,000 (GBP) |
Organisation | Queen's University Belfast |
Sector | Academic/University |
Country | United Kingdom |
Start | 03/2022 |
End | 07/2022 |
Description | NASA Heliophysics Supporting Research |
Amount | $343,643 (USD) |
Funding ID | NNH19ZDA001N-HSR |
Organisation | National Aeronautics and Space Administration (NASA) |
Sector | Public |
Country | United States |
Start | 09/2020 |
End | 09/2023 |
Description | Observations of Lyman-alpha Emission in Solar Flares |
Amount | £226,842 (GBP) |
Funding ID | ST/W001144/1 |
Organisation | Science and Technologies Facilities Council (STFC) |
Sector | Public |
Country | United Kingdom |
Start | 03/2022 |
End | 03/2024 |
Description | Queen's University Belfast - New Lecturer Startup Funds |
Amount | £10,000 (GBP) |
Organisation | Queen's University Belfast |
Sector | Academic/University |
Country | United Kingdom |
Start | 08/2019 |
Description | DAISI - NASA Small Explorer mission proposal |
Organisation | National Aeronautics and Space Administration (NASA) |
Country | United States |
Sector | Public |
PI Contribution | I am on the science advisory team that are working to propose a Small Explorer (SMEX) class mission to NASA at the next announcement of opportunity. We are currently outlining the science goals of the mission and the specifications of the instrument required to address them. |
Collaborator Contribution | The proposal is being led by Dr. Amy Winebarger from NASA Marshall Space Flight Center and Dr. Stephen Bradshaw at Rice University, Texas. |
Impact | None so far. Still in the proposal drafting phase. |
Start Year | 2021 |
Description | DAISI - NASA Small Explorer mission proposal |
Organisation | Rice University |
Country | United States |
Sector | Academic/University |
PI Contribution | I am on the science advisory team that are working to propose a Small Explorer (SMEX) class mission to NASA at the next announcement of opportunity. We are currently outlining the science goals of the mission and the specifications of the instrument required to address them. |
Collaborator Contribution | The proposal is being led by Dr. Amy Winebarger from NASA Marshall Space Flight Center and Dr. Stephen Bradshaw at Rice University, Texas. |
Impact | None so far. Still in the proposal drafting phase. |
Start Year | 2021 |
Description | NASA/GSFC |
Organisation | National Aeronautics and Space Administration (NASA) |
Department | Goddard Space Flight Center |
Country | United States |
Sector | Public |
PI Contribution | I led two distinct research projects that involved collaborators at NASA/GSFC. 1) the detection of 3-minute oscillations in full-disk Lyman-alpha emission during a major solar flare, and 2) a quantitative analysis of multi-instrument solar flare observations, and an interactive widget that allows a user to search for solar flare datasets spanning multiple instruments. Portions of these projects, such as travel to NASA/GSFC and to conferences in the US to present the findings, were funded under my previous NASA Living With A Star research grant, which is administered by the Catholic University of America. |
Collaborator Contribution | 1) Drs. Ireland and Fleck are leading experts in wave phenomena in the solar atmosphere, and their contribution was invaluable to the interpretation of the analysis that I had conducted. 2) Dr Ireland also has background in statistics, which was vital in evaluating how successful (or otherwise) the solar flare community have been in coordinating observations of flares. Kim Tolbert also helped develop the interactive widget, and set up hosting and automating of the underlying code to be constantly updated on servers at NASA/GSFC. |
Impact | Two refereed publications to date. Milligan et al. (2017) and Milligan & Ireland (2018). |
Start Year | 2016 |
Description | SNIFS Sounding Rocket |
Organisation | University of Colorado Boulder |
Department | Laboratory for Atmospheric and Space Physics (LASP) |
Country | United States |
Sector | Academic/University |
PI Contribution | I am a Co-Investigator on a NASA funded sounding rocket, SNIFS (Solar eruptioN Integral Field Spectrograph), which is due to launch in April 2024 to observe a solar flare. The rocket will observe in the Lyman-alpha line of neutral hydrogen, which I have published several papers on in recent years. I will be involved in the planning the science goals, selecting the target of opportunity, and analysis of the data. |
Collaborator Contribution | The project was conceived, designed and led by Dr. Phillip Chamberlin at LASP/University of Colorado Boulder, with collaborators at NASA Goddard Space Flight Center who will assist in the set up of the instrument, and colleagues at Harvard-Smithsonian Center for Astrophysics who will participate in the modelling aspect of the project. |
Impact | No outputs are anticipated until after the launch date of April 2023. |
Start Year | 2020 |
Description | Solar-C/SoSPIM |
Organisation | ETH Zurich |
Country | Switzerland |
Sector | Academic/University |
PI Contribution | I have been invited to be a member of the Science Team for the SoSPIM instrument on JAXA's Solar-C mission, which is scheduled for launch in 2026. |
Collaborator Contribution | Solar-C is a mission of international cooperation with Japan, US (NASA), and the European countries (ESA and individual agencies), with a target launch in mid-2020s. The Japan's domestic structure is led by ISAS/JAXA and NAOJ, which are in charge of developing the spacecraft and its telescope EUVST. The general management of this mission is done by ISAS/JAXA, whereas NAOJ leads the telescope development and also participates in the development of the satellite system and the grating. |
Impact | N/A |
Start Year | 2020 |
Description | ESPOS Seminar |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Professional Practitioners |
Results and Impact | I gave a talk as part of the European Solar Physics Online Seminar series on my recent research on solar flares. |
Year(s) Of Engagement Activity | 2020 |
URL | https://espos.stream/2020/11/19/Milligan/ |
Description | ETH-Zurich Seminar |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Professional Practitioners |
Results and Impact | After my ESPOS seminar, I was invited to give an online seminar to the solar physics group at ETH-Zurich. |
Year(s) Of Engagement Activity | 2021 |
Description | Irish National Astronomy Meeting - Lyman-Alpha Variability During Solar Flares |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | National |
Primary Audience | Professional Practitioners |
Results and Impact | I gave a talk to at the Irish National Astronomy Meeting in August 2021 on my research on Lyman-alpha variability during solar flares. |
Year(s) Of Engagement Activity | 2021 |
URL | https://astronomers.ie/inam-2021/ |
Description | MAVEN Project Science Group meeting |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Professional Practitioners |
Results and Impact | I was asked to give a talk to the MAVEN science team on research I conducted using observations of solar flares taken by the MAVEN spacecraft which is in orbit around Mars. |
Year(s) Of Engagement Activity | 2021 |
Description | National Astronomy Meeting 2021: Lyman-Alpha Variability During Solar Flares |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | National |
Primary Audience | Professional Practitioners |
Results and Impact | I gave a talk at the National Astronomy Meeting in July 2021 on my research into Lyman-alpha variability during solar flares. |
Year(s) Of Engagement Activity | 2021 |
URL | https://nam2021.org/ |
Description | Public lecture on the partial solar eclipse of 10 June 2021 |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | National |
Primary Audience | Public/other audiences |
Results and Impact | I gave a public talk on how to the view the 10 June 2021 partial solar eclipse safely, and on eclipses in general. |
Year(s) Of Engagement Activity | 2021 |
Description | QUB/ARC Seminar |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | Local |
Primary Audience | Professional Practitioners |
Results and Impact | I gave a talk on my recent research after accepting a lectureship position at Queen's University Belfast. |
Year(s) Of Engagement Activity | 2019 |
Description | The Conversation UK - "I'm a solar eclipse chaser: here's what to expect from this week's partial solar eclipse" |
Form Of Engagement Activity | A magazine, newsletter or online publication |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Media (as a channel to the public) |
Results and Impact | I wrote an article for The Conversation (UK) on the partial solar eclipse that was visible from the UK in June 2021. |
Year(s) Of Engagement Activity | 2021 |
URL | https://theconversation.com/im-a-solar-eclipse-chaser-heres-what-to-expect-from-this-weeks-partial-e... |