Comparative planetary infrared aurorae

Lead Research Organisation: University of Leicester
Department Name: Physics and Astronomy

Abstract

Planetary aurorae, like the Earth's aurora borealis and aurora australis, are formed by energetic charged particles streaming along the planet's magnetic field lines into the upper atmosphere from the surrounding space environment. However, differences in the source of these charged particles means there are considerable variations between the aurora of different planets. On Earth's, the aurorae are dominated by the effect of interactions between the magnetic field and the solar wind. Jupiter and Saturn are far more massive and also rotate more quickly than the Earth and as a result the magnetic fields of these planets are much stronger. This results in currents that connect between the planet and the nearby space environment, shielded from the solar wind. Uranus has a magnetic field that is even more different to the Earth's and this too produces currents that connect with the planet. These currents produce aurora that differ significantly from those usually seen on Earth. Our work uses telescopes on the ground and in orbit around Saturn to observe the aurorae of the gas giants at infrared wavelengths. This allows us to not only measure the varying brightness of the aurora across the planet, but also show how the ions in the upper atmosphere of the planets move as a result of the currents which cause the aurora. Using these observations we have been able to show that the aurorae seen on the gas giants are, in fact, produced by a variety of current systems, some connected to the solar wind as at Earth and others with processes within the local space environment. However, we have also observed many features that remain unexplained by either process. In this programme of research we intend to use observations of the gas giant aurorae to significantly improve our understanding of the different processes that lead to the formation of these aurora by better characterising them directly. In the past year, a significant programme of observations were made of the aurorae of both Jupiter and Saturn, in support of the New Horizons flyby in February 2007. This consist of highly detailed ultraviolet (UV) images taken by the Hubble Space Telescope, together with a ground-based infrared (IR) campaign, which will allow us to directly compare the fine-scale images directly with the spectral data for the first time. As a part of the international Uranus at Equinox observing campaign, we also took the first-ever image of the upper atmosphere of a gas giant, correcting for the distortional effect of looking through the Earth's atmosphere. This allows us to observe the upper atmosphere of Uranus at an unprecedented accuracy. In addition to this, we have led the anaylsis of new images of Saturn's aurora taken by the VIMS instrument aboard the Cassini spacecraft, in orbit around around the planet. These have given us views of the aurora, presenting us with a whole new set of emission that looks unlike anything seen before on Saturn, or any other planet. We intend to analyse this new wealth of data to understand the differences between the aurorae of different planets. In showing the extent to which the solar wind controls the aurora on each of these planets and comparing this with what we know about the surrounding space environment, it will be possible to understand the way solar wind influences on a planet's upper atmospheres change with the planetary configuration. Some of these effects, that are too small to properly distinguish on the Earth, are far more powerful and dominant on other planets Thus, our observations will also allow us to better understand the details of how energy flows from the Sun to the Earth.

Publications

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Badman, SV And Tao, C And Kasahara, S And Kimura, T And Fujimoto, M And Andrews, DJ And Cowley, SWH And Provan, G And Melin, H And Stallard, T And Lamy, L And Brown, RH And Baines, KH (2012) Rotational modulation and local time dependence of Saturn's infrared H3 + auroral intensity in Journal of Geophysical Research A: Space Physics

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Clarke, JT And Nichols, J And Gérard, JC And Grodent, D And Hansen, KC And Kurth, W And Gladstone, GR And Duval, J And Wannawichian, S And Bunce, E And Cowley, SWH And Crary, F And Dougherty, M And Lamy, L And Mitchell, D And Pryor, W And Retherford, K And Stallard, T And Zieger, B And Zarka, P And Cecconi, B (2009) Response of Jupiter's and Saturn's auroral activity to the solar wind, Journal of Geophysical Research in Journal of Geophysical Research

 
Description • The discovery of a seasonal variation in temperature within the upper atmosphere of Uranus
• Detailed comparisons between the IR and UV aurora, using a multi-instrument observations by Cassini
• Comparative investigation of the velocity wind structures seen at Jupiter and Saturn
• A sequence of direct mission support observations for both the Cassini Spacecraft, and the Hubble Space Telescope
• Equinoctial observations of Saturn's auroral region, showing the differences in the auroral conditions in each pole
• Initial detection of non-auroral variations across Saturn's ionosphere
• Direct measurement of the auroral response of Saturn's ionosphere to the volcanic plume from Enceladus
• The first spectral measurements of Jupiter's infrared aurora using adaptive optics (on ESO's VLT)
• Analysis of the H3+ ionosphere of Neptune, showing current models to over-predict H3+ emission by a factor of at least 3.
Exploitation Route We have a significant number of observations of Jupiter, Saturn, Uranus and Neptune that will continue to be useful over an extended period, allowing the measurement of long-term affects, and compare changes in auroral conditions due to solar wind and internal magnetospheric variation - these observations are available to a wider academic community. Our mission support observations helped develop a much broader sequence of combined observations of Saturn in 2013. It also resulted in the identification of a 'Ring-Rain' feature, that has been published in Nature in 2013, and now represents an entirely new field of study for Saturn, involving modellers and observers.
Sectors Other

 
Description We have used our observations as a platform for encouraging interactions with the general public, and to stimulate discussions about astronomy and science more generally. Detailed discussions have come through the use of interactive discussions on websites such as Reddit, though a programme called Live from the Observatory, both telecasting on own own and in direct collaboration with the Keck telescope, as well as Q and A sessions with members of the public at the telescopes, we have actively shown science in action. Our science has been disseminated through press releases and directly though interactions with the media, resulting in resources that have been used for public talks, including the Griffith Park observatory in LA.
First Year Of Impact 2009
Sector Education,Leisure Activities, including Sports, Recreation and Tourism,Culture, Heritage, Museums and Collections
Impact Types Cultural

 
Description Keck Travel funding for observations
Amount $2,000 (USD)
Organisation National Aeronautics and Space Administration (NASA) 
Sector Public
Country United States
Start 03/2011 
End 03/2011
 
Description Boston University Imaging Science Team 
Organisation Boston University
Department Imaging Science
Country United States 
Sector Academic/University 
PI Contribution Have provided observing experience, as well as inputs into Jupiter and Saturn aeronomy modelling
Collaborator Contribution Modelling of ionosphere/atmosphere of Jupiter and Saturn, as well as discussions over access to Boston University observatories. Sharing of HST images of Jupiter and Saturn in the UV
Impact Significant enhancement of both observing and modelling. One publication following on from the modelling of Jupiter's equatorward regions.
Start Year 2009
 
Description Cassini Auroral Planning Team 
Organisation National Aeronautics and Space Administration (NASA)
Department Cassini Mission
Country United States 
Sector Public 
PI Contribution We have been heavily involved in the planning of VIMS observations, both in providing details of the needed infrared observations from the spacecraft itself, as well as in timing the observations with ground-based support
Collaborator Contribution Our involvement in the planning team has directly resulting in having Cassini observations coincide with the timing of potential observations from Mauna Kea - using this, we have had great leverage in getting observing time at the NASA IRTF telescope, assisting greatly in our research.
Impact Outputs from this collaboration will be highly significant, once the current set of observations are complete. It will allow us to tie together ground-based and space based observations for the first time.
Start Year 2010
 
Description Cassini MAG data 
Organisation Imperial College London
Department Department of Physics
Country United Kingdom 
Sector Academic/University 
PI Contribution We have used the magnetometer data in combination with both VIMS and ground-based data, in order to better understand the influences on the auroral region of Saturn
Collaborator Contribution Provision of calibrated Cassini magnetic field data
Impact We have used the magnetometer data to provide context to our observations, which have helped shape the discussions of a number of our papers. We are also more directly comparing the results of our observations with MAG in an upcoming paper, the results of which we have presented at conferences.
 
Description Cassini UVIS data 
Organisation University of Colorado Boulder
Department Laboratory for Atmospheric and Space Physics (LASP)
Country United States 
Sector Academic/University 
PI Contribution We have used the data in combination with the VIMS data set, the first time this has been done in detail.
Collaborator Contribution In providing access to UVIS data, we have begun a detailed study of the comparative morphologies of the UV and IR aurora. This has so far resulted in material for presentations at conferences and is currently being written up for publication.
Impact We have used the results in several presentations. In addition, the use of combined data from the Cassini mission is something that is of high priority within the Cassini community and our using these instruments is providing us with an increased profile within this international community.
Start Year 2009
 
Description Cassini VIMS data and planning 
Organisation University of Arizona
Department Lunar and Planetary Laboratory
Country United States 
Sector Academic/University 
PI Contribution We are part of the official VIMS/MAG collaboration and are leading the analysis of the VIMS data, and have also been heavily involved in planning the VIMS observations in the Cassini Solstice extended mission
Collaborator Contribution In making the VIMS dataset available, we have been able to do significant research, including a Nature paper in 2008
Impact Significant scientific advances, including a Nature paper, as well as access to the Auroral planning team and higher status within the infrared space mission community.
Start Year 2008
 
Description Exploring the upper stratosphere of Saturn 
Organisation Kyunghee University
Country Korea, Republic of 
Sector Academic/University 
PI Contribution We have provided an analysis of VIMS observations, identifying and describing the methane fluorescence from the upper stratosphere.
Collaborator Contribution They have provided detailed high-resolution spectral measurement, allowing us to identify specific methane emissions within the stratosphere. The have also collaborated with proposed observations, adding significant adacemic weight to the observation request.
Impact Jointly, we are currently working on research that could potentially result in a number of publications, both looking at altitudinal profiles of temperature, and the neutral winds in the upper stratosphere.
Start Year 2014
 
Description Gemini support staff: planetary observations 
Organisation Gemini Observatory
Country United States 
Sector Academic/University 
PI Contribution Authorship of H3+ publications, particularly of Uranus.
Collaborator Contribution As support observer on Uranus observations, Tom Geballe's expertise greatly improve the observations. Also significant input in writing papers.
Impact Several papers, in particular the Uranus publications.
 
Description Ground-based observations and HIRIMS l'Observatoire de Paris 
Organisation Observatory of Paris
Department Laboratory for Space Science and Astrophysical Instrumentation
Country France 
Sector Charity/Non Profit 
PI Contribution We have used observations made by this collaborator in our long term study of Uranus. We are also Co-I status on their proposed JUICE instrument HIRIMS, which remains under negotiation for inclusion into the selected instrument MAJIS.
Collaborator Contribution The provision of observational data of Uranus. PI leadership on instrument proposal.
Impact Our paper on the long-term variability of Uranus.
 
Description Ground-based observations at University of Texas 
Organisation University of Texas
Department Department of Astronomy
Country United States 
Sector Academic/University 
PI Contribution We have used observations made by this collaborator in our long term study of Uranus.
Collaborator Contribution We have made a significant number of observations and proposals together, allowing a combined access to observations of Saturn and in particular Uranus.
Impact Our paper on the long-term variability of Uranus, as well as significant observing proposals and observations.
 
Description IAPS/INAF-Rome 
Organisation International Association for the Philosophy of Sport (IAPS)
Country Italy 
Sector Charity/Non Profit 
PI Contribution Provided ground-based support observations for the JIRAM team, allowing calibration of that instrument using our data as a guide
Collaborator Contribution Have provided significant discussions for both future planning of the observations of JIRAM, and for past observations on Cassini and Galileo
Impact Safeguarded our publications from being trumped by IAPS publications
Start Year 2010
 
Description Imperial ionospheric modelling 
Organisation Imperial College London
Department Department of Physics
Country United Kingdom 
Sector Academic/University 
PI Contribution We have provided important input for the Saturn models developed at Imperial, providing essential information about the ionosphere in the 50-70 latitude region - away from both Cassini equatorial occultation measurements and auroral values previously published.
Collaborator Contribution We have worked with the ionospheric and atmospheric modelling group at Imperial on an informal basis, in order to better understand our observations in the broader context - this context has been useful for writing several papers. We are now in the process of directly collaborating on a number of projects, comparing ionospheric models with direct measurements on both a narrow and wide planetary scale.
Impact Our collaboration has helped in indirect ways in the past, but, partly through the ISSI Team Galand meetings, we have begun directly calibrating both our Cassini and ground-based work. We envisage this resulting in publications in the next 12-18 months.
 
Description Planetary Atmospheric Physics Lab, Tohoku Univeristy 
Organisation Tohoku University
Department Planetary Atmospheric Physics Lab
Country Japan 
Sector Academic/University 
PI Contribution We are currently collaborating on observations of Jupiter's auroral region. I have successfully been awarded a number of collaborative observing proposals with Tohoku as collaborating co-i's.
Collaborator Contribution We have been included on a number of observing proposals made to Subaru and IRTF. We are also working with TOhoku in the upcoming EXCEED mission, which will look at the UV aurora.
Impact Our observation proposals have been strengthened by the collaboration, and we will have access to the EXCEED dataset.
Start Year 2012
 
Description Space Science and Engineering Center, U. of Wisconsin-Madison 
Organisation University of Wisconsin-Madison
Department Space Science and Engineering Center
Country United States 
Sector Academic/University 
PI Contribution Working actively with Kevin Baines, having written a number of successful Keck proposals with him as PI, have co-observed these proposals with him. Have also started co-editing a Saturn book with him. Collaborated on VIMS observations.
Collaborator Contribution Strongly supported our Cassini ground-based support programme. Helped promote both our ground-based observations and VIMS work.
Impact Three years of successful Keck observations, ultimately leading to 1 Nature paper, 1 other publications with 2 more papers already written. VIMS association contributed to 1 more Nature paper and numerous other publications.
Start Year 2007
 
Description UCL observation team 
Organisation University College London
Department Department of Physics & Astronomy
Country United Kingdom 
Sector Academic/University 
PI Contribution In collaborating on both the observation, reduction, analysis and scientific output from our combined research, we have made significant advances that would not have been possible by one individual team. We have worked on the majority of the observations, from inception to completion, including reduction and have shared in the analysis of this data.
Collaborator Contribution Observations to major telescopes have been co-written with astronomers at UCL, providing a joint research depth that has significantly improved our observational outcomes.
Impact We have produce a significant amount of work using ground-based observations, some still in analysis, and have produced papers studying Saturn, Uranus and Neptune based on observations that come from this collaboration. In particular, the Uranus paper was produced using observations covering 16 years of observations, many made by the UCL team.
 
Description University of Liege UV auroral image data 
Organisation University of Liege
Department Department of Astrophysics, Geophysics and Oceanography
Country Belgium 
Sector Academic/University 
PI Contribution Joint investigations of UV images of Saturn's auroras using HST and Cassini UVIS data
Collaborator Contribution Ditto
Impact Numerous joint publications in peer-reviewed journals
 
Description VIMS analysis at JAXA 
Organisation Japanese Aerospace Exploration Agency
Department Institute of Space and Astronautical Science
Country Japan 
Sector Public 
PI Contribution We have provided reduced and cleaned data to the collaborators and have discussed the data and analysis in detail
Collaborator Contribution We have worked together on analysing the results of the VIMS instrument
Impact We have one paper published and a number of others in the process of begin completed and have worked together in discussions with the VIMS team.
Start Year 2010
 
Description Consultant for BBC Stargazing Live programme 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Type Of Presentation Keynote/Invited Speaker
Geographic Reach National
Primary Audience Media (as a channel to the public)
Results and Impact Managed to fix the wording for how Gas Giant aurora were presented by Brian Cox, highlighting the work that we do within the UK

Several pieces were produced for the BBC, but not used, but specific wording was used on the national broadcast.
Year(s) Of Engagement Activity 2014
 
Description Live broadcasts from the summit of Mauna Kea 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? No
Type Of Presentation Keynote/Invited Speaker
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact Providing a streaming webcam from the summit of Mauna Kea. At times this was directed towards a particular group and at others, we fielded questions from the general public. We made the first ever web boradcast from the summit to the Mauna Kea Visitor's Center, fielding questions from a crowd of 40 people, the first time this had ever been done.

While this is a relatively new activity, we are looking into how we can expand it's influence. However, within days of the first Mauna Kea Visitor Center broadcast, we have heard that the Keck telescope is considering doing a similar broadcast once a month. This suggests we are at the vanguard of a much wider opening up of observation at the summit to the public, directly driven by this first ever attempt.
Year(s) Of Engagement Activity 2011,2012,2013
 
Description Presentations to the Mauna Kea Visitor's Center 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? No
Type Of Presentation Keynote/Invited Speaker
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact During periods when observing second half nights or on acclimatisation nights at Mauna Kea, I visit the Mauna Kea Visitor's Center and give presentations on the life of an astronomer, as well as answering questions one-to-one during the star tours. Numbers vary between 20-60 a night and are generally a captive audience, since they have travelled to Mauna Kea to view the stars.

Many people have not realised the importance of UK astronomy on the global scale - this is a great way to showcase our science to an audience who are actively interested in astronomy.
Year(s) Of Engagement Activity 2009,2010,2011,2012,2013
 
Description Speaker at the Cassini-Huygens Analysis and Results from the Mission telecon 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Type Of Presentation Keynote/Invited Speaker
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact The Cassini Telecon is a well represented way to disseminate science done by the Cassini mission, and includes an active audience at the time of presentation, as well as the presentation being archived on a publically accessible part of the NASA JPL website.

Having our work presented in such a high frequency location as the JPL site will have opened up our Cassini work to a far wider audience than is usually possible.
Year(s) Of Engagement Activity 2010
 
Description Stargazing Live at the National Space Centre 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Type Of Presentation Keynote/Invited Speaker
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact 50 member of the public interacted with the talk, and subsequent questions.

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Year(s) Of Engagement Activity 2012