Self Statement FOR KRISHAN KHURANA
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I use the tools of Plasma Physics, Magnetohydro-dynamics, electromagnetics and Signal Processing in my explorations of the solar system. Using these tools, I have obtained new insights in research areas as diverse asplanetary bow shocks, planetary magnetic fields, magnetospheric convection driven by rotation and reconnection, and subsurface oceans in the icy Galilean satellites. In the following section, I give an overview of the progress I have made in the last four years. Then I discuss my future plans.
Current Research
Research on the Jovian Magnetosphere
Structure and dynamics of Jovian magnetosphere
I have studiedobservations from variousJupiter-bound spacecraft to understand asymmetries and convection in its magnetosphere over the last decade. I have shown that on the dawnside the convection driven by the solar wind reaches the middle magnetosphere.I have also shown that the azimuthal currents are much stronger on the nightside (~ 144 MA between the radial distances of 10 and 50 RJ) than they are on the dayside (~ 88 MA in the same distance range). Continuing on the theme of asymmetries, we have now shown that the current sheet lags from the prime meridian as a strong function of local time and radial distance (paper 102) presumably because of asymmetries in plasma outflow and Alfvén velocity in the magnetosphere. Further confirmation of asymmetries is provided in the research paper under preparation (#2) where we find that the current sheet half-thicknessis < 3 RJ on the dawnside but exceeds 10 RJ on the dusk side in the outer magnetosphere. From the analysis of electron plasma density data we also show that the plasma is very tenuous on the dusk side. These observations provide further support for the role of solar wind driven convection in Jupiter’s magnetosphere.
Global models of Jupiter’s and Saturn’smagnetospheric field
I have been funded by NASA to utilize the vast magnetic field dataset from Galileo, Ulysses, Voyager and Pioneer spacecraft to construct new empirical models of Jupiter’s magnetospheric field. These models are required by space scientists to characterize the field and plasma environment of the magnetosphere. The models also find use in studies of particle dynamics (bounce and drift of plasma, plasma diffusion into and out of the radiation belts, changes in pitch angle distributions of plasma from convection etc. For this purpose, I construct magnetic field modules that yield the field of planetary interior, planetary current sheet, planetary magnetotail and planetary magnetopause. I have used a technique called generalized deformation method to construct the models. I am collaborating with Dr. Nikolai Tsyganenko, a well-known expert on magnetic field modeling for this project.
Research on the Jovian satellites
Liquid water on Europa and other icy Galilean satellites .
From the Galileo magnetic field observations obtained from the encounters of Europa, Ganymede and Callisto Prof. Kivelson and I have shown that these oceans possess subsurface oceans under ice layers ranging in thicknesses from 20 km to 150 km. I have continued the work on understanding these oceans and their influence on field and plasma distributions. In paper 113 we show that the induction field from the Europan ocean distorts both the location and shape of the Alfvén wing as postulated by Prof. Fritz Neubauer of CologneUniversity in a 1999 publication. I am currently writing a chapter on the electromagnetic induction from Europa for a new book on Europa expected to be published in late 2008.
Internal fields in Jovian satellites
In previous years, in a series of publications we placed upper limits on the internal fields of the four Galilean satellites based on Galileo magnetometer observations. In a new work published this year, I explore the consequence of the internal magnetic field on the surface of Ganymede [Paper 116]. I show that the boundaries of Ganymede’s polar caps (polar regions on the surface of Ganymede marked by bright frost deposits) lie very close to the open-closed boundary of the magnetic field topology. This finding is consistent with the idea that Jupiter’s plasma has access to the surface of Ganymede in the polar regions and creates fine frosty material through plasma sputtering. The lower latitude regions are inaccessible to plasma bombardment.
In yet another work in preparation [Khurana et al, 2007, to be submitted to JGR], by using Galileo magnetic field data we show that the wake of Ganymede can be detected as far as 60 RG behind Ganymede. We speculate on the type of instabilities that exist in the wake and why the wake does not fill up immediately behind Ganymede.
Plasma Pick-up Near the Galilean satellites
Not only do Io and Europa interact with the Jovian plasma, they also act as principal sources for it. In a series of earlier papers using ion-cyclotron waves as probes, we showed the presence of plasma pick-up of ions of S, O, Mg, and Cl near Io and Europa. In paper 92, we show that the Alfvén wing resulting from plasma pick-up near Io is highly filamented.
Research on the Saturnian Magnetosphere
I am a member of the Magnetometer team of Cassini Spacecraft Mission to Saturn. To support the team work, I am constructing a global model of Saturn’s magnetospheric field on the lines of my work for Jupiter. I have already constructed an initial version of the model which I have presented at the AGU and EGU meetings and the team is now evaluating it. Further work is continuing to incorporate more data from the magnetotail. I am working on a first draft of the paper to be submitted to JGR on this topic.
I am currently investigating the rotational periodicities observed in the field and plasma data in Saturn’s magnetosphere. In a series of talks I have shown that in the axisymmetric field of Saturn, its current sheet is tilted by ~ 10. This is an exciting but puzzling result. I have recently developed a model that shows that the current sheet tilt develops from the longitudinal asymmetry of its ring current in the presence of a large solar elevation angle. I have also developed a heuristic model that explains how the particle and current density longitudinal asymmetries are maintained in the magnetosphere. This work will be presented as an invited talk at the Fall AGU meeting. A manuscript is also in initial stages of preparation.
Research on the Saturnian Icy Satellites
Over the last seven years, I have collaborated with the Magnetometer Team on Cassini to plan the observations along the spacecraft trajectories during close icy satellite flybys. We are now beginning to receive data from these flybys.
One of the earlier finding from the MAG observations is that Enceladus possesses an extended exosphere resulting from its south-pole water plume. I have modeled the observed magnetic field from the three flybys of Enceladus (paper 115) and show that the amount of plasma pick-up is quite small (1-3 kg/s). The rest of the neutral material (100-300 kg/s) escapes the exosphere of Enceladus to populate the neutral torus of Saturn.
In a research paper in press (Khurana et al. 2007), I show that Tethys and Rhea are inert objects devoid of any internal magnetic fields or ionospheres. I also show that the sub-magnetosonic nature of the plasma interaction has interesting consequences for the absorption of plasma.
Observations from Dione show that it also acts as a mass-loading obstacle to Saturn’s plasma. In a manuscript soon to be submitted to the Journal Nature (research paper under preparation #3), we make the case that Dione also possesses a dynamic atmosphere maintained by one or more vents.
Collaboration with scientist from IGPP and external institutions
I actively seek out and am invited by prominent planetary scientists for collaborations in different areas of planetary and space research. This is reflected in the diversity of my publications.
Future Research
In the immediate future, I plan to work on several different projects described below.
Global models of Jupiter and Saturn’s magnetospheric field
As already detailed above, the work on this front is bearing fruit and in the next couple of years, I hope to have published several papers detailing the global models.As new data from Cassini become available, I will extend the scope of the Saturnian model further.
Modeling of Saturnian Icy Moon magnetic field signatures
As discussed above, I am taking the lead on modeling the Cassini magnetic signatures from the icy moons of Saturn. I have used the Biot-Savart equations to model the mass-loading moons Enceladus and Dione.Recently, I have begun a new collaboration with Dr. Pavel Travnicek from the Academy of Science of Czech Republicto perform hybrid simulations of the interactions of these moons with Saturn’s plasma. These self consistent simulations should help us put better limits on the amount of plasma pick-up and help define processes involved in mass-loading of Saturn’s magnetosphere.
Periodicities in the magnetosphere of Saturn
As already discussed I am currently finalizing a new model that explains the rotational periodicities in the magnetosphere of Saturn. I plan to further collaborate with other Cassini scientists to figure out the details of this synchronous process that maintains the asymmetries of Saturn’s magnetosphere.
Induction studies of Europa at multiple frequencies
In a NASA funded investigation I am currently exploring if the existing Galileo data contain hints of induction at the orbital period of Europa. All of our previous investigations have relied on the rotational period of Jupiter to provide the sounding signal. If induction amplitude can be obtained at multiple frequencies, we should be able to place better limits on the conductivity and the thickness of the Europan ocean.
Themis intercalibrations and science
I am a co-investigator on the Themis spacecraft mission that is studying magnetic substorm processes in the Earth’s magnetosphere. I plan to use techniques developed for Cluster II to intercalibrate the magnetometers onboard the spacecraft so that accurate values of magnetic field can be obtained for the Themis mission. I will also collaborate in the analysis of the Themis data to understand the processes which cause magnetic substorms in the Earth’s magnetosphere.
Community service
I routinely referee papers for the Journal of Geophysical Research and Geophysical Research Letters, Planetary and Space Science Letters, Annales Geophysicae and Science. Areas in which I have reviewed papers are: ULF waves in other magnetospheres, structure and dynamics of planetary magnetosphere, convection in the planetary magnetospheres, interaction of Jovian satellites with the Jovian magnetosphere, the structure and motion of planetary bow shocks, the motion of dusty plasmas and electromagnetic induction in planetary bodies.
I also routinely review funding proposals for NASA, NSF and Israel Science Foundation. I also participate in NASA panels to select proposals for NRA funding.
Organizational Activities
Co-organized the Division IV symposia on outer planets with Prof. Toshi Mukai and Prof. Andy Nagy for IAGA/IUGG held in Hanoi,Vietnam in August, 2001.
Organized the Division III session entitled “GAIII.14: How do the Magnetospheres of Other Planets and their Satellites Compare with the Earth's Magnetosphere?" in the IUGG meeting held in Sapporo, Japan.
Co-organized with Dr. John Cooper of GSFC a special session on JIMO magnetospheric science at the Fall AGU 2003 meeting on the topic of “Radiation-induced atmospheres, ionospheres, and surface chemistry at the Galilean moons.”..
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Organized Slichter Lectures delivered by Prof. Don Gurnett, April 4-8, 2005.
Organized special sessions at the spring and fall AGU meetings on icy satellites over the last two years.
Teaching and Other Educational Activities
I regularly contribute to the educational activities of the institute and the department. For example:
- During winter 2000, I jointly taught the 200 C graduate level class on “Introduction to Space Plasmas” with Prof. Margaret Kivelson. We divided the teaching and grading load equally among us.
- I regularly give lectures on the calibration of magnetometers and on the topic of time series analysis in the Space Science Instrumentation and Analysis class taught by the ESS faculty (Russell, McPherron and Kivelson).
- I sometimes fill in for Prof. M. Kivelson and Prof. R. McPherron in their Space Physics classes (mainly ESS 200C) when they are away on travel. Various areas in which I have given lectures are (1) Foundations of magnetohydrodynamics (MHD), (2) Theory and analysis of MHD waves, and (3) Modeling of magnetic field and electric currents in space plasmas.
Other minor Contributions:
- I have provided financial assistance from my grants to several undergraduate students who have assisted me over the years with my research projects.
- Over the last ten years, I have given a lecture every year on space physics research conducted by IGPP to the students in the HC-40 program conducted by Prof. Bill Newman.
Committee duties
IGPP colloquium and Conference committee 1994-1998.
IGPP Merit review committee 1997-1999.
Served on a NASA panel to define the objectives of a Europa lander to study the prebiotic chemistry. (1998-2000, Chaired by Prof. Chris Chyba).
Advised the Space Studies Board (Committee on Lunar and Planetary Exploration) on defining the specifications for the Europa Orbiter, Feb-March 1998.
Member IGPP colloquium and Conference committee 2004 – 2005.
Member National Research Council (NRC) Decadal Survey of Solar System Exploration, 2001-2002.
Member Europa Focus Group 2002-2003.
Member NRC committee COMPLEX (Committee on Planetary and Lunar Exploration) 2002-2005.
Member Space Science Board appointed committee on Nuclear Power Enabled Missions, 2004.
Member Science Definition Team (SDT) for Jupiter Icy Moon Orbiter (JIMO) 2003-2004.
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Member NASA’s Planetary Data System Working Group (PDSWG) 2004-2006.
Member NASA SDT for Europa Orbiter. 2005-2007.
Member NRC committee on Solar and Space Physics (CSSP). 2007-2010.
Editorial Services
Editor for Special Volume of ICARUS on JIMO magnetospheric environment papers. 2004.
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Edited the special volume of Advances in Space Research, JASR-D04, 2006 on Cassini related science papers.
Editing a book on “Europa” in University of Arizona Press Space Science Series with co-editors, Robert Pappalardo of JPL and Prof. William McKinnon of WashingtonStateUniversity.
Honors, Awards
NASA Group achievement awards, 1991,1993, 1995.
Reporter Reviewer for division III of IAGA on the topic of “Magnetospheres of the outer planets” 2001-2004.
IGPP Distinguished Researcher Award, 2004.
Memberships of professional bodies
Member: American Geophysical Union
Associate Member: American Physical Society
Associate Member: Division of Planetary Sciences, American Astronomical Society.
Publications
Publications in exploration geophysics
1. Pal P. C., K. K. Khurana, and P. Unnikrishnan, Two examples of spectral approach to source depth estimation in gravity and magnetics, Pure and Applied Geophysics (Pageoph), 117, 772, 1978--79.
2. Pal P. C. and K. K. Khurana, Comparison of correlogram and spectral approaches for optimal station spacing in magnetic surveys; Geophys. Res. Bulletin: N.G.R.I., India, 18, 193, 1980.
3. Khurana, K. K., S. V. Seshagiri Rao, and P. C. Pal, Frequency domain least-squares inversion of thick dike magnetic anomalies using Marquardt's algorithm, Geophysics, 46, 1745, 1981.
Publications in Space Physics
4. Khurana, K. K., M. G. Kivelson, T. P. Armstrong and R. J. Walker, Voids in Jovian magnetosphere revisited: Evidence of spacecraft charging, Journal of Geophysical Research, 92, 13399, 1987. 6A8859
5. Khurana K. K., and M. G. Kivelson, Ultra low frequency MHD waves in Jupiter's middle magnetosphere, Journal of Geophysical Research, 94, 5241, 1989a. 88JA04266
6. Khurana K. K., and M. G. Kivelson, On Jovian plasma sheet structure, Journal of Geophysical Research, 94, 11791, 1989b. 89JA00626
7. Kivelson M. G., C. F. Kennel, R. L. McPherron, C. T. Russell, D. J. Southwood, R. J. Walker, C. M. Hammond, K. K. Khurana, R. J. Strangeway, P. J. Coleman, Magnetic field studies of the solar wind interaction with Venus from the Galileo Flyby, Science, 254, 1518, 1991. 91Sci2531518
8. Khurana, K. K., S. H. Chen, C. M. Hammond and M. G. Kivelson, Ultralow frequency waves in the magnetotails of the Earth and the outer planets, Advances in Space Research, 12, (8) 57, 1992. 92ASR12857
9. Khurana K. K., A generalized hinged-magnetodisc model of Jupiter's nightside current sheet, Journal of Geophysical Research, 97, 6269, 1992. 92JA00169
10. Kivelson M. G., K. K. Khurana, J. D. Means, C. T. Russell, and R. C. Snare, The Galileo magnetometer investigation, Space Science Review, 60, 357, 1992. 92SSR357
11. Khurana K. K., and M. G. Kivelson, Inference of the angular velocity of plasma in the Jovian magnetosphere from the sweepback of magnetic field, J. Geophys. Res., 98, 67, 1993. 92JA01890
12. Khurana, K. K., ULF waves in other magnetospheres -- observations and possible source mechanisms, Ann. Geophysicae, 11, 973, 1993. 93AG11973
13. Kivelson, M. G, C. F. Kennel, R. L. McPherron, C. T. Russell, D. J. Southwood, R. J. Walker, K. K. Khurana, P. J. Coleman, C. M. Hammond, V. Angelopoulos, A. J. Lazarus, and R. P. Lepping, The Galileo Earth Encounter: The magnetometer and allied measurements, J. Geophys. Res., 98, 11,299, 1993. 92JA03001
14. Kivelson, M. G., L. F. Bargatze, K. K. Khurana, D. J. Southwood, R. J. Walker, and P. J. Coleman, Jr., Magnetic field signatures near Galileo's closest approach to Gaspra, Science, 261, 331, 1993. 93Sci261331
15. Khurana , K. K., and M. G. Kivelson, A variable cross-section model of the bow shock of Venus, J. Geophys. Res., 99, 8505, 1994. 93JA0357
16. Kivelson, M. G., A. Prevost, F. V. Coroniti, K. K. Khurana, and D. J. Southwood, Galileo Flybys of Earth: The nature of distant shock, Adv. Space Res., 16, (4)197, 1995. ASR161971995
17. Wang, Z., M. G. Kivelson, S. Joy, K. K. Khurana, C. Polanskey, D. J. Southwood and R. J. Walker, Solar wind interaction with small bodies: 1. Whistler wing signatures near Galileo's closest approach to Gaspra and Ida, Adv. Space Res., 16, (4) 47, 1995. ASR16471995
18. Kivelson, M. G., Z. Wang, S. Joy, K. K. Khurana, C. Polanskey, D. J. Southwood and R. J. Walker, Solar wind interaction with small bodies: 2. What can Galileo's detection of magnetic rotations tell us about Gaspra and Ida, Adv. Space Res., 16, (4)59, 1995. ASR16591995
19. Khurana, K. K., M. G. Kivelson, L. A. Frank, and W. R. Paterson, Observations of magnetic flux ropes and associated currents in Earth's magnetotail with the Galileo spacecraft, Geophys. Res. Letters, 22, pp. 2087-2090, 1995. 95GL01518
20. Khurana, K. K., M. G. Kivelson, and L. A. Frank, The relationship of magnetic flux ropes to substorms, Adv. Space Res., 18, 59, 1995. ASR185995
21. Kivelson, M. G., and K. K. Khurana, Models of flux ropes embedded in a Harris neutral sheet: Force free solutions in low and high beta plasmas, in press, J. Geophys. Res., 100, 23,637, 1995. 95JA01548
22. Kivelson, M.G., K.K. Khurana, R. J. Walker, E. L. Kepko, D. Xu, Flux ropes, Interhemispheric conjugacy, and Magnetospheric current closure, J. Geophys. Res., 101, 27341, 1996. 96JA02220