Modelling and Multi-wavelength Observations of Solar Flare Heating
Lead Research Organisation:
University of Glasgow
Department Name: School of Physics and Astronomy
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
Milligan R
(2017)
Detection of Three-minute Oscillations in Full-disk Lya Emission during a Solar Flare
in The Astrophysical Journal Letters
Procházka O
(2017)
Suppression of Hydrogen Emission in an X-class White-light Solar Flare
in The Astrophysical Journal
Keenan F
(2017)
An assessment of Fe xx-Fe xxii emission lines in SDO/EVE data as diagnostics for high-density solar flare plasmas using EUVE stellar observations
in Monthly Notices of the Royal Astronomical Society
Machado M
(2018)
Lyman Continuum Observations of Solar Flares Using SDO/EVE
in The Astrophysical Journal
Milligan RO
(2018)
On the Performance of Multi-Instrument Solar Flare Observations During Solar Cycle 24.
in Solar physics
Machado M
(2018)
Lyman Continuum Observations of Solar Flares Using SDO/EVE
Procházka O
(2018)
Reproducing Type II White-light Solar Flare Observations with Electron and Proton Beam Simulations
in The Astrophysical Journal
Young P
(2018)
A Si iv/O iv Electron Density Diagnostic for the Analysis of IRIS Solar Spectra
in The Astrophysical Journal
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
Monson A
(2021)
Flare-induced Photospheric Velocity Diagnostics
in The Astrophysical Journal
Milligan R
(2021)
Solar Irradiance Variability Due to Solar Flares Observed in Lyman-Alpha Emission
in Solar Physics
Millar D
(2021)
The effect of a solar flare on chromospheric oscillations
in Monthly Notices of the Royal Astronomical Society
Description | Lord Kelvin Adam Smith Research Fellowship |
Amount | £100,000 (GBP) |
Funding ID | 200490-01 |
Organisation | University of Glasgow |
Sector | Academic/University |
Country | United Kingdom |
Start | 03/2017 |
End | 02/2022 |
Title | Skylab NRL SO82B calibrated data of the flare SOL1973-09-07 and plage observed on 1973-09-11 |
Description | |
Type Of Material | Database/Collection of data |
Year Produced | 2018 |
Provided To Others? | Yes |
Title | Solar Flare Finder |
Description | Solar Flare Finder is an interactive widget available in SSWIDL (SolarSoftWare Interactive Data Language). It allows a user to search for solar flares observed by various combinations of space-based instruments to answer specific science questions. They can also search by magnitude, location on the solar disk, etc. The database itself is hosted by the RHESSI group at NASA Goddard Space Flight Centre. |
Type Of Material | Database/Collection of data |
Year Produced | 2017 |
Provided To Others? | Yes |
Impact | The creation of this database allowed us to provide a statistical analysis of how well the solar physics community have been performing in capturing solar flares with various combinations of space-based instrumentation. The findings were published in Milligan & Ireland (2018). |
URL | https://hesperia.gsfc.nasa.gov/sff/ |
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 | AGU 2017 |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Professional Practitioners |
Results and Impact | In December 2017 I presented a poster at the American Geophysics Union meeting in New Orleans. My findings included the detection of a 3-minute oscillation in hydrogen Lyman-alpha emission during a major solar flare. This was detected in full-disk irradiance measurements indicating that these oscillations could contain significant amount of energy. |
Year(s) Of Engagement Activity | 2017 |
URL | https://fallmeeting.agu.org/2017/ |
Description | BBC Documentary: Space Truckers |
Form Of Engagement Activity | A broadcast e.g. TV/radio/film/podcast (other than news/press) |
Part Of Official Scheme? | No |
Geographic Reach | National |
Primary Audience | Public/other audiences |
Results and Impact | My occupation prior to being a scientist was as a truck driver. I wanted to combine these two skill sets to create a "reality style" TV show where I would be hauling a piece of scientific/astronomical equipment, while explaining its significance to the audience during the journey. In April 2017 I ended up hauling the "brains" of the Irish LOFAR (I-LOFAR) radio telescope from the Netherlands to Ireland. This haul was documented by Stellfy Media/Sony for BBC Northern Ireland and aired in December 2017. |
Year(s) Of Engagement Activity | 2017 |
URL | http://www.bbc.co.uk/programmes/b09hls66 |
Description | Cafe Scientifique |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | Local |
Primary Audience | Public/other audiences |
Results and Impact | General public talk on the current state of solar activity and the recent total solar eclipse across the continental United States. |
Year(s) Of Engagement Activity | 2017 |
URL | https://www.gla.ac.uk/events/cafescientifique/events/past/thesleepinggiantthecurrentstateofsolaracti... |
Description | Contributed Talk at FRESWED 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 gave a contributed talk at the Towards Future Research on Space Weather Drivers meeting in San Juan, Argentina. |
Year(s) Of Engagement Activity | 2019 |
Description | Contributed Talk at RHESSI XVIII workshop |
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 contributed talk on my research on the behavior of Lyman-alpha emission during solar flares at the RHESSI XVIII workshop in Minneapolis, Minnesota. |
Year(s) Of Engagement Activity | 2019 |
Description | Down Recorder newspaper article |
Form Of Engagement Activity | A magazine, newsletter or online publication |
Part Of Official Scheme? | No |
Geographic Reach | Local |
Primary Audience | Public/other audiences |
Results and Impact | The local newspaper in the town that I grew up - The Down Recorder - did an article on me ahead of the airing of my BBC documentary "Space Truckers". |
Year(s) Of Engagement Activity | 2017 |
URL | http://thedownrecorder.co.uk/pages/?title=Space_Truckers_Ryan_on_small_screen_moving_computer_across... |
Description | GIST Podcast |
Form Of Engagement Activity | A broadcast e.g. TV/radio/film/podcast (other than news/press) |
Part Of Official Scheme? | No |
Geographic Reach | Regional |
Primary Audience | Public/other audiences |
Results and Impact | After giving a Cafe Scientifique talk at Waterstones, Glasgow, I was approached by the Glasgow Skeptics to do a podcast for Glasgow Insight into Science and Technology (GIST) on the current state of solar activity and the recent total solar eclipse across the continental Unites States. |
Year(s) Of Engagement Activity | 2017 |
URL | https://the-gist.org/podcast/podcast-18-cafe-scientifique-sleeping-giant/ |
Description | Interview for Radio Ulster |
Form Of Engagement Activity | A broadcast e.g. TV/radio/film/podcast (other than news/press) |
Part Of Official Scheme? | No |
Geographic Reach | Regional |
Primary Audience | Public/other audiences |
Results and Impact | As publicity for my BBC show, Space Truckers, I did a live (trans-Atlantic) interview with Gerry Kelly for Radio Ulster. |
Year(s) Of Engagement Activity | 2017 |
URL | http://www.bbc.co.uk/programmes/b09h66tz |
Description | Invited Talk at the RHESSI XVIII workshop |
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 an invited talk on the Max Millennium Program for Solar Flare Research at the RHESSI XVIII Workshop in Minneapolis, Minnesota. |
Year(s) Of Engagement Activity | 2019 |
Description | Invited talk at SunDC meeting on Exoplanet Space Weather |
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 invited to give a talk on Sun-As-A-Star observations of solar flares at Johns Hopkins University, Maryland, and how they may relate to stellar flares and their influence on exoplanets. |
Year(s) Of Engagement Activity | 2018 |
URL | https://pyoung.org/gsfc/SUNDC%202018_v1-1.pdf |
Description | NASA Press Release |
Form Of Engagement Activity | A press release, press conference or response to a media enquiry/interview |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Public/other audiences |
Results and Impact | NASA issued a press release on my discovery of oscillations in the solar chromosphere in response to a major solar flare. |
Year(s) Of Engagement Activity | 2017 |
URL | https://www.nasa.gov/feature/goddard/2017/nasa-detects-solar-flare-pulses-at-sun-and-earth |
Description | NASA Press Release on Space Truckers |
Form Of Engagement Activity | A press release, press conference or response to a media enquiry/interview |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Public/other audiences |
Results and Impact | NASA issued a press release on my transition from truck driver to astrophysicist, and on my BBC Documentary "Space Truckers" in which I hauled the supercomputer that would drive the I-LOFAR radio telescope, from the Netherlands to Ireland. |
Year(s) Of Engagement Activity | 2017 |
URL | https://www.nasa.gov/feature/goddard/2017/ryan-milligan-on-the-open-road-to-the-universe |
Description | Poster at AGU 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 presented a post on my work on Lyman Continuum Observations of Solar Flares Using SDO/EVE at the Americal Geophysical Union meeting in Washington DC. |
Year(s) Of Engagement Activity | 2018 |
URL | https://fallmeeting.agu.org/2018/ |
Description | Poster at NAM/EWASS |
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 poster on the detection of 3-minute oscillations in hydrogen Lyman-alpha emission in response to a major solar flare at the National Astronomy Meeting/European Week of Astronomy and Space Science in Liverpool, UK. |
Year(s) Of Engagement Activity | 2018 |
URL | https://eas.unige.ch/EWASS2018/ |
Description | Poster at the AAS/SPD 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 gave a poster on my research on the behavior of Lyman-alpha emission during solar flares at the AAS/SPD meeting in St. Louis, Missouri. |
Year(s) Of Engagement Activity | 2019 |
Description | RAS Solar Orbiter Working Group |
Form Of Engagement Activity | A formal working group, expert panel or dialogue |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Professional Practitioners |
Results and Impact | In November 2017 the RAS hosted a working group for the upcoming Solar Orbiter mission. I gave a brief presentation on the recent discovery of oscillations in hydrogen line emission during a solar flare. The EUI instrument on Solar Orbiter will routinely observe this emission and so knowledge of these oscillations could be important for the interpretation of future science results. |
Year(s) Of Engagement Activity | 2017 |
URL | https://www.ras.org.uk/component/gem/?id=484 |
Description | RHESSI XVI |
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 on the detection of 3-minute oscillations in hydrogen Lyman-alpha emission in response to a major solar flare at the 16th RHESSI workshop in Boulder, CO. I was also on the Scientific Organising Committee for this workshop. |
Year(s) Of Engagement Activity | 2017 |
URL | https://rhessi16.boulder.swri.edu |
Description | Talk at Space Glasgow meeting |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | Regional |
Primary Audience | Industry/Business |
Results and Impact | I gave a talk on my BBC documentary, Space Truckers, as a way of making connections in the space industry to solicit potential projects that could be filmed for further future episodes. As a result, I was invited to the Skyrora company in Edinburgh to view their rocket assembly workshop, and also to give a talk at the UK Space Careers conference. |
Year(s) Of Engagement Activity | 2018 |
URL | https://www.eventbrite.com/e/2nd-space-glasgow-research-conference-tickets-50266239676 |
Description | Talk at TESS/SPD 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 gave a talk at the Triennial Earth-Sun Summit in Lessburg, Virginia on Multi-Instrument Solar Flare Observations During Solar Cycle 24. |
Year(s) Of Engagement Activity | 2018 |
URL | https://connect.agu.org/tess2018/home |
Description | Talk at the National Student Space Conference |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | National |
Primary Audience | Undergraduate students |
Results and Impact | I was invited to give a talk at the National Student Space Conference in Edinburgh, UK on my career path from truck driver to NASA scientist. Many students said that they were inspired by my talk. |
Year(s) Of Engagement Activity | 2019 |
URL | https://ukseds.org/aurora/?p=nssc2019 |
Description | Talk at the SDO Science Workshop |
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 about my recent research on Lyman Continuum Observations of Solar Flares Using SDO/EVE, at the SDO Science Workshop in Ghent, Belgium. |
Year(s) Of Engagement Activity | 2018 |
URL | https://register-as.oma.be/sdo2018/ |
Description | Washington Post Q&A for the Total Solar Eclipse |
Form Of Engagement Activity | A press release, press conference or response to a media enquiry/interview |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Public/other audiences |
Results and Impact | I was approached by the Washington Post to partake in a live online Q&A session ahead of the total solar eclipse across the continental United States in August 2017. I answered questions from the general public on all aspects of this event. |
Year(s) Of Engagement Activity | 2017 |
URL | https://live.washingtonpost.com/qa-eclipse-coverage-live-20170815.html?hpid=hp_no-name_no-name%3Ahom... |