Energy flows in stellar coronae

Lead Research Organisation: University of Cambridge
Department Name: Applied Maths and Theoretical Physics

Abstract

The Sun is the only star that we can study in detail, from its interior to the outer atmosphere (corona) and the solar wind, which permeates the entire solar system. The solar corona is also an unique laboratory that we can use to understand fundamental plasma processes that occurr throughout the universe (most of which is composed of magnetised plasma). The solar irradiance and particle flux fundamentally affect space weather, our atmosphere and the global climate of our planet. Yet, we have so far failed to understand many fundamental questions about the Sun (and stars in general). The standard model of the Sun has recently been called into question. We still do not know the prime mechanisms that heat the solar corona to millions of degrees, that cause flares and eruptions, that accelerate particles, that produce the strongest emission in the Extreme Ultra Violet (EUV). We also know very little about the solar irradiance in the EUV or X-rays, and its potential effects on the global climate of our planet. As for other stars, we know that most have strong X-ray emission, however the processes that produce these X-rays are still largely unknown. This is a golden age for the physics of the solar corona, with a wealth of data gathered by recent (SOHO, TRACE, RHESSI) missions, now complemented with Hinode (Solar-B), and soon with STEREO, SDO. The two EUV spectrometers (SOHO/CDS, Hinode/EIS) have a strong UK involvement. I believe that it is timely to invest more resources into the analysis and interpretation of these spectroscopic data, because they hold the key to advance our understanding of the solar corona. The current sensitivity and resolution of EIS will allow novel studies. In particular, I intend to couple observations with theoretical modeling to understand which processes dominate the energy release and flow in the corona, by taking into account non-equilibrium and non-thermal effects in the plasma. In particular, I will study the location and evolution of heating in coronal loops in relation with the changes of the magnetic field, and energy flows during flares, in relation to chromospheric evaporation. Spectral observations and realistic atmospheric models will also shed light on the problem of why the brightest EUV lines are so bright, so in the future we will also be able to predict their emission. I also plan to use the unique 10-year long SOHO observations to characterise for the first time the EUV spectral irradiance and its variations with the solar cycle. We will then be able to study any possible effects on global climate. With the same observations I will also obtain the physical characteristics of the solar corona during the last cycle. With these and some modeling, it will be possible to simulate in detail the X-ray emission from other stars. With these simulations, and Chandra and XMM-Newton observations of stars of different ages, it will be possible to understand in which cases the observed X-ray emission could be due to the presence of a hot corona similar to an active Sun. Provision of accurate atomic data forms an integral part of this proposal, given their importance for plasma diagnostic and modeling. I plan to continue the work on the ions for the EUV and X-rays, and to provide atomic data to allow studies of non-equilibrium and non-thermal effects, which are presumably important in the solar corona.

Publications

10 25 50
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Alexander C (2011) Hinode observations and 3D magnetic structure of an X-ray bright point in Astronomy & Astrophysics

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Badnell N (2016) Atomic processes for astrophysical plasmas in Journal of Physics B: Atomic, Molecular and Optical Physics

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Barstow M (2008) Stellar And Galactic Environment survey (SAGE) in Experimental Astronomy

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Barstow M (2008) Stellar and galactic environment survey (SAGE) in Astrophysics and Space Science

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Bemporad A. (2009) Multispacecraft observations of a prominence eruption in ANNALES GEOPHYSICAE

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Bemporad A. (2009) Multispacecraft observations of a prominence eruption in ANNALES GEOPHYSICAE

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BenMoussa A (2013) On-Orbit Degradation of Solar Instruments in Solar Physics

 
Description My long-term project has managed to achieve, thanks to many different grants, the original goal of producing accurate solar radiances and irradiances in the extreme ultraviolet. For the first time, we have these measurements along a full solar cycle, from 1998 to 2014. So we are now able to quantify the solar changes of the EUV irradiance, and where these changes are originating.

I have also developed a better understanding of the solar spectrum by calculating and benchmarking new atomic data.
Exploitation Route The EUV irradiances are part of the EU FP7 SOLID framework,
which has produced observed and modelled spectral irradiances of the Sun. The SOLID results are used to improve global circulation models of the climate which in turn provide an input to the IPCC reports.
The atomic data are widely used. As part of the work, I produced a radiometric calibration for the SOHO CDS instrument, for its entire lifetime. The PI institute is currently providing calibrated data for the entire mission using my calibration.
Sectors Aerospace, Defence and Marine,Education,Environment

 
Description The EUV irradiances are part of the EU FP7 SOLID framework, which has produced observed and modelled spectral irradiances of the Sun. The SOLID results are used to improve global circulation models of the climate which in turn provide an input to the IPCC reports. The atomic data that I have calculated and benchmarked have a wide distribution and are used not just within astrophysics, but also by fusion research via the ADAS consortium, the main diagnostic modelling package found at all major fusion laboratories in the world (including the European JET and ITER). The CHIANTI atomic data have been made available to VAMDC (www.vamdc.eu), a large European consortium of providers of atomic and molecular data. VAMDC data are used by a very wide community, including industries that are researching and developing new lighting sources.
First Year Of Impact 2015
Sector Education,Environment,Other
Impact Types Societal

 
Description Consolidated bridging grant
Amount £120,000 (GBP)
Funding ID ST/J001570/1, PI: Gordon Ogilvie 
Organisation Science and Technologies Facilities Council (STFC) 
Sector Academic/University
Country United Kingdom
Start 10/2012 
End 03/2015
 
Description Consolidated grant
Amount £248,560 (GBP)
Funding ID ST/P000665/1 
Organisation Science and Technologies Facilities Council (STFC) 
Sector Academic/University
Country United Kingdom
Start 04/2017 
End 03/2020
 
Description Consolidated grant
Amount £100,000 (GBP)
Organisation Science and Technologies Facilities Council (STFC) 
Sector Academic/University
Country United Kingdom
Start 04/2014 
End 03/2017
 
Description SOLID FP7 network
Amount € 75,000 (EUR)
Funding ID EC FP7 CP 313188 
Organisation European Commission 
Sector Public
Country European Union (EU)
Start 12/2012 
End 11/2015
 
Title CHIANTI 
Description CHIANTI is the reference atomic database for ions for use in astrophysics. The last update was in 2015 and it has been used to model solar irradiances, among other applications. CHIANTI is widely used within VAMDC, an EU infrastructure for atomic and molecular data. 
Type Of Material Database/Collection of data 
Provided To Others? Yes  
Impact A few thousands of citations. 
URL http://www.chiantidatabase.org
 
Title CHIANTI database v.8 
Description The culmination of nearly 6 years of work was the v.8 CHIANTI database, where the models for the solar spectral lines important for irradiance were updated. 
Type Of Material Database/Collection of data 
Year Produced 2015 
Provided To Others? Yes  
Impact The database is used world-wide, has about 3000 direct citations, and about 300 indirect ones /year. 
URL http://chiantidatabase.org
 
Title EUV solar irradiance 
Description I have produced within SOLID a database of solar EUV irradiances during 1998-2014. They are being used to benchmark modelling, which in turn will be used as solar forcing by climate modellers. 
Type Of Material Database/Collection of data 
Provided To Others? No  
Impact Not yet. Work is in progress. 
 
Description APAP-Network Ref: PP/E001254/1 
Organisation University of Strathclyde
Department Department of Physics
Country United Kingdom 
Sector Academic/University 
PI Contribution I have done atomic physics calculations, have benchmarked them against experimental data, and used them for the analysis of spectra from stellar coronae. I have also distributed the atomic data within CHIANTI and VAMDC (an EU FP7 network).
Collaborator Contribution Prof. N.R.Badnell (PI of the grant,University of Strathclyde) has developed and mantained the codes used for atomic physics calculations, and I have collaborated with him on various projects.
Impact In the Jan 2006 - Dec 2010 timeframe the APAP team published 101 refereed papers. They are all highest-quality papers, describing atomic data which are used world-wide by almost all atomic databases and modelling codes, and are directly or indirectly cited by hundreds of refereed papers per year.
Start Year 2008
 
Description Associated scientist with CfA on various missions/proposals 
Organisation Harvard University
Department Harvard-Smithsonian Center for Astrophysics
Country United States 
Sector Academic/University 
PI Contribution Contribute to various proposals for space missions (COSIE, MAGIXS), to the analysis of current missions (IRIS). Also contributed to AIRSPEC, an new infrared spectrometer, and DKIST, a ground-based solar telescope.
Collaborator Contribution Provide access to data and resources.
Impact Various research papers.
Start Year 2010
 
Description Co-I of Solar Orbiter instruments 
Organisation Rutherford Appleton Laboratory
Department RAL Space
Country United Kingdom 
Sector Public 
PI Contribution I am co-I and associated scientisto of the Solar Orbiter SPICE, EUI, METIS instruments. I am contributing in refining the best science and operating modes
Collaborator Contribution building instruments, calibration, on-board software
Impact Most of the outcomes will come in the future. A few papers are in progress.
Start Year 2010
 
Description Co-I of Solar Orbiter instruments 
Organisation University College London
Department Department of Space and Climate Physics (MSSL)
Country United Kingdom 
Sector Academic/University 
PI Contribution I am co-I and associated scientisto of the Solar Orbiter SPICE, EUI, METIS instruments. I am contributing in refining the best science and operating modes
Collaborator Contribution building instruments, calibration, on-board software
Impact Most of the outcomes will come in the future. A few papers are in progress.
Start Year 2010
 
Description DAMTP RG 
Organisation University of Cambridge
Department Department of Applied Mathematics and Theoretical Physics (DAMTP)
Country United Kingdom 
Sector Academic/University 
PI Contribution I have collaborated on various activites, student supervision, seminars, outreach, other than research.
Collaborator Contribution We have collaborated on many projects as the publications clearly show.
Impact See publication list.
Start Year 2008
 
Description ISSI team meeting (2018-2019) on solar abundances - Solar Orbiter 
Organisation University of Orsay
Department Space Astrophysics Institute
Country France 
Sector Academic/University 
PI Contribution This is an international collaboration with several researchers/institutes, to study how to link in-situ with remote-sensing observations with Solar Orbiter. I contributed in terms of atomic data, diagnostics, and a specific project on active regions.
Collaborator Contribution Each partner will contribute on the basis of their expertise.
Impact The collaboration only started.
Start Year 2018
 
Description ISSI team meeting on non-equilibrium plasma 
Organisation Astronomical Institute Czech Republic
Country Czech Republic 
Sector Academic/University 
PI Contribution This is an international collaboration among experts on diagnostics of non-equilibrium plasma. Del Zanna and Mason contributed in terms of atomic data and diagnostics, and wrote part of a long review.
Collaborator Contribution Each partner contributed to the review.
Impact Dudik et al., Sol. Phys., 2017. DOI: 10.1007/s11207-017-1125-0
Start Year 2012
 
Description Invited lectures 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? Yes
Geographic Reach Local
Primary Audience Schools
Results and Impact This was a very large audience keen to learn about the recent research on the solar atmosphere. I received many questions and congratulations from the audience. I have also given lectures at schools to children on a few occasions (the last one in 2015 was the solar eclipse)

N/A
Year(s) Of Engagement Activity 2011,2014,2015
 
Description Open Day 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? Yes
Geographic Reach Local
Primary Audience Public/other audiences
Results and Impact This event is targeted to children, and is regularly visited by hundreds of people during one day.

Many children become very enthusiastic about studying physcis and astronomy. These events can affect some of them for life.
Year(s) Of Engagement Activity 2009,2011,2012,2014