THE APPLICATION OF 3-D MHD MODELS OF THE HELIOSPHERE TO UNDERSTANDING OF CENTURY-SCALE VARIATIONS IN GALACTIC COSMIC RAYS
Lead Research Organisation:
University of Southampton
Department Name: Sch of Physics and Astronomy
Abstract
Galactic Cosmic Rays are highly energetic particles which move at very close to the speed of light. They are generated at the shock fronts produced when a star explodes - a supernova. These particles constantly bombard the Earth and are important for a number of reasons. 1. They cause malfunctions in the electronics on board aircraft and spacecraft and they are also a health hazard for astronauts and even for passengers in aircraft. . We call the study of these effects 'space weather'. 2. Cosmic rays have an influence on climate which we do not yet understand. They produce ionisation in the atmosphere which allows currents to flow and a global circuit of driven by thunderstorms. There have also been suggestions that cosmic rays assist in the formation of clouds. This is still highly controversial, but we do know that variations in cosmic rays since the last ice age are connected with detected changes in climate. This may well be because the brightness of the Sun is linked to how many cosmic rays reach Earth, but this connection is far from being understood. 3. When cosmic rays smash into atmospheric particles, they generate characteristic products that we call cosmogenic isotopes. These are washed out of the atmosphere in snow and rain and are stored in ice sheets, tree trunks and ocean sediments. Taking cores into these reservoirs allows us to study how much of an isotope was deposited at a given time which can be dated by counting the tree rings, or the layers of clean and dirty snow in the ice sheet (corresponding to winter and summer), or from the small fossils and volcanic dust found in an given layer of ocean sediment. These give us a unique record that extends back over several millennia. Because they are produced by cosmic rays which are shielded from away from Earth's atmosphere by the magnetic field of the Sun and of the Earth, these cosmogenic isotopes can tell us much about how these fields have changed in recent millennia. This proposal is aimed at letting us use these isotopes to study how the Sun has changed in the past few centuries. On these timescales, the variation of Earth's magnetic field is slow and the changes in cosmic rays and cosmogenic isotopes are caused by a magnetic field that is produced in the Sun and the pulled out of it by a continuous outflow of charged particles called the solar wind. We are particularly interested in recent centuries for two reasons: 1. Understanding any influences of the Sun on climate over these timescales is important for the correct prediction of how much our climate will be changed in the future by greenhouse gasses. 2. Around 1700, the Sun behaved in a very unusual way. We call this period the Maunder minimum after the scientist who first noted the almost complete lack of sunspots at this time. There was much debate as to whether or not this was a real effect or if wars and famine had just caused the early astronomers not to abandon their studies. Cosmogenic isotopes tell us that the Sun was indeed different in the Maunder minimum compared to today and so give us a key insight into how and why the Sun has changed. If we are to interpret cosmogenic isotopes in terms of what the Sun was doing in the past, we must understand how the solar magnetic field modulates the fluxes of cosmic rays arriving at Earth. The area around our Sun dominated by this magnetic field is called the heliosphere and in recent years complex models of how the heliosphere behaves and varies have been developed. Our previous work allows us to see that these models can be used to understand most of the shielding of cosmic rays from the Sun and this proposal is aimed at letting us be the first to exploit this. Our results also show that the widely-accepted theory of how this happens is inadequate in some important respects. The results of our work will have great implications for our understanding of how the Sun has varied and what effects cosmic rays have on us.
Publications
Davis C
(2009)
Stereoscopic imaging of an Earth-impacting solar coronal mass ejection: A major milestone for the STEREO mission
in Geophysical Research Letters
Finch I
(2008)
Effects of solar wind magnetosphere coupling recorded at different geomagnetic latitudes: Separation of directly-driven and storage/release systems
in Geophysical Research Letters
Gray L
(2010)
SOLAR INFLUENCES ON CLIMATE
in Reviews of Geophysics
Lockwood M
(2009)
Excess open solar magnetic flux from satellite data: 1. Analysis of the third perihelion Ulysses pass
in Journal of Geophysical Research: Space Physics
Lockwood M
(2009)
Excess open solar magnetic flux from satellite data: 2. A survey of kinematic effects
in Journal of Geophysical Research: Space Physics
Lockwood M
(2007)
Fly me to the Moon?
in Nature Physics
Lockwood M
(2009)
THE RISE AND FALL OF OPEN SOLAR FLUX DURING THE CURRENT GRAND SOLAR MAXIMUM
in The Astrophysical Journal
Lockwood M
(2009)
Solar change and climate: an update in the light of the current exceptional solar minimum
in Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences
Lockwood M
(2009)
THE ACCURACY OF USING THE ULYSSES RESULT OF THE SPATIAL INVARIANCE OF THE RADIAL HELIOSPHERIC FIELD TO COMPUTE THE OPEN SOLAR FLUX
in The Astrophysical Journal
Lockwood M
(2007)
The Rough Guide to the Moon and Mars
in Astronomy & Geophysics
Description | Our initial aim was to use numerical models of both the heliosphere and of cosmic ray propagation to understand how the Sun shields Earth from galactic cosmic rays (GCRs - particles energised in violent events such as galactic supernovae and which have a number of effects at Earth). The shielding is caused by structures in the heliospheric magnetic field generated by the Sun. Our initial research using the ENLIL numerical MHD model of the heliosphere (initiated using solar magnetograph data) did not predict the timing and nature of heliospheric structures seen by near-Earth satellites with sufficient accuracy to allow the numerical modelling of the flux of galactic cosmic rays reaching Earth that we have envisaged in the proposal. However the means to improve this situation became available in the form of the HI instruments on board the STEREO spacecraft. Using these imagers allowed us to make the first stereoscopic observations of an Earth-impacting coronal mass ejection and the first remote sensing observations (of any kind) of corotating interaction regions: both of which scatter cosmic rays. These enabled us to show that the depth and duration of the resulting depression to cosmic ray fluxes depends on the latitudinal extent of the structure- explaining why the heliospheric current sheet tilt is statistically related to the cosmic ray fluxes. The work contributed to 18 publications (including some on the effects of cosmic rays on Earth's atmosphere) and gained international acclaim, garnering 2 international young scientist awards for the PDRA (Rouillard) and contributing to a lifetime award for the PI (Lockwood). It also enabled the hugely successful and award-winning Solar Stormwatch citizen science programme. |
Exploitation Route | The prediction of cosmic ray fluxes that our research has brought closer is vital for the long-term evolution of the aviation industry (cosmic rays upset aircraft avionics and set significant radiation doses for crew and other frequent fliers on polar routes). The design of spacecraft hardware requires knowledge of the radiation environment which our work has helped to quantify and predict. The prospect of manned exploration of the moon and Mars also depends critically on proper understanding of the cosmic ray environment. |
Sectors | Aerospace Defence and Marine Electronics Environment Healthcare Transport Other |
URL | http://spd.aas.org/docs/prizetalks/2014/rouillard_harvey/ |
Description | The results have already been used to identify effects on cosmic rays on the atmosphere - both in cloud edge effects of atmospheric electricity and in the catalytic destruction of polar ozone in the stratosphere. In addition the work was combined with understanding of long-term solar changes to predict changes in the cosmic ray fluxes experienced by electronics, crew and passengers on polar aircraft flights. |
First Year Of Impact | 2011 |
Sector | Aerospace, Defence and Marine,Electronics,Environment,Other |
Impact Types | Societal Policy & public services |
Description | Phillip Leverhulme Research Prize |
Amount | £70,000 (GBP) |
Funding ID | UoR project number H5177900 |
Organisation | The Leverhulme Trust |
Sector | Charity/Non Profit |
Country | United Kingdom |
Start | 11/2014 |
End | 10/2017 |
Title | The solar stormwatch CME catalogue |
Description | The resulting catalogue consists of 144 Coronal Mas Ejections (CMEs) over the period January 2007 to February 2010, of which 110 were observed by STEREO-A and 77 12 were observed by STEREO-B. For each CME the time-elongation profiles 13 generated by the citizen scientists are averaged into consensus profiles along 14 each position angle the event was observed. Using single spacecraft fitting techniques, we etimate the speed, direction, solar source region and latitudinal width of each CME. This shows that, at present, the Solar Stormwatch catalogue contains almost exclusively slow CMEs. This will be very useful scientifically as solar activity has bee exceptionally low (compared to the space age before then) and so the catalogue will give much needed understandimg of typical CME behavioiur in quiet periods which have been an issue of increasing recent debate |
Type Of Material | Database/Collection of data |
Year Produced | 2013 |
Provided To Others? | Yes |
Impact | Yet to accrue |
Description | RAL Space, Rutherford Appleton Laboratory |
Organisation | Rutherford Appleton Laboratory |
Department | RAL Space |
Country | United Kingdom |
Sector | Academic/University |
PI Contribution | Under the project PI, R.A. Harrison, the team at RAL Space produced the extraordinary and exceptional HI instruments for the STEREO mission. By observing the weak scattered F-corona whilst blocking the vastly greater intensity of direct sunlight, these instruments have revolutionised remotes sensing of the heliosphere. This collaboration enabled the work that the PDRA (Rouillard) was able to do with these instruments |
Collaborator Contribution | Tutorials of the instrument performance. Rapid data delivery for identified events |
Impact | Roughly half the outputs listed used HI data and so came directly from this collaboration. The collaboration was not so much multi-disciplinary but brought the experimental expertise and excellence of the RAL team with the analysis and theory expertise of the team funded on the grant |
Start Year | 2007 |
Description | The Solar Stormwatch Citizen Science Project |
Form Of Engagement Activity | Participation in an activity, workshop or similar |
Part Of Official Scheme? | Yes |
Geographic Reach | International |
Primary Audience | Public/other audiences |
Results and Impact | There are over 20,000 registered users of solar stormwatch and 13,000 twitter followers (not all of whom are registered users). Roughly 1/3 are in the UK, 1/3 in the US and 1/3 in the rest of the world. Please note that the pull-down menu options give here do not come close to considering the full implications and power of this citizen science project. For example, I selected "To share information" above for the main purpose but the project does a great deal more than this by engaging the public and allowing them to make real contributions to science. Similarly I have selected "Increase in requests for further information" for the most important impact which is arguably true (as the chat rooms demonstrate real and lasting engagement in a way that, for example, a lecture or lecture series never can. The project has generated 5 scientific papers including a new and comprehensive catalogue of transient solar events (Barnard et al., recently accepted by the Journal Space Weather, doi: 10.1002/2014SW001119), to which over 16,000 citizen scientists made contributions by analysing the data. The e-mail chat rooms where users discuss issues reveal how much the users engage with the science and learn about the scientific method. As well as attracting a very large number of members (exceeding 20,000 to date), Solar Stormwatch has won the Best Innovative Site award in the Innovative or Experimental category at the prestigious Best of the Web Awards, presented at the international Museums and the Web conference held in Denver, USA. The e-mail chat rooms where users discuss issues reveal how much the users engage with the science and learn about the scientific method (and at the same time provide a very valuable social purpose: for example small chat rooms have evolved from the main science discussion groups of disabled users, another for cancer sufferers, etc. - this is because a sizeable fraction of users are largely housebound for medical reasons and the project has given them an involvement in science they would not otherwoise have had. |
Year(s) Of Engagement Activity | 2009,2010,2011,2012,2013,2014 |
URL | http://www.solarstormwatch.com/why_scientists_need_you |