Plasma interaction at Io and Europa

Transcription

1 Plasma interaction at Io and Europa Camilla D. K. Harris Tidal Heating: Lessons from Io and the Jovian System Thursday, Oct Jupiter s Magnetosphere 2. Moon-Magnetosphere Plasma Interaction 3. Precipitation, Sputtering, and Space Weathering 4. Signatures of Plumes 5. Magnetic Fields

2 Giant planet magnetospheres The magnetospheres of Jupiter and Saturn are Extremely large Dominated by rotation (~10 hrs) Weakly influenced by the solar wind At Io and Europa (inside of 10 R J ): Magnetospheric magnetic field is VERY STRONG! (Io: ~1800 nt, Europa: ~400 nt) Mostly southward. Io s volcanos are the major plasma source for the whole magnetosphere! 1 ton of plasma every second generated from the Io neutral cloud. Bagenal et al., Icarus, 2015 ~ 100 R J ~ 7,000,000 km!

3 <latexit sha1_base64="wxkx7kkensf+xyycnz2z5qtzzxc=">aaacfxicbva9swnbej3zm8avqkxnyhcswp0iwgztlcoyd0hc2nvsjut2b4/dosec+rm2fvpx7mtw2n9i6sa5wiq+whi8mdk388jecou+/+2trw9sbm0xdoq7e/shh6wj44bvqwg8zrtuphvsy6wier0fst5kdkcqllwzju6m9eytn1bo+bhhce8qoohfjbhfj7u6goxittgrlf2kpwnzjufoypcj1iv9dpqapyrhycs1th34cxyzalawysfftmp5qtmidnjb0zg6l24223dczp3sj5e27svizurfiywqa8cqdj2k4tau16bif7v2itfnnxnxkikp2dwosivbtabhk74wnkeco0kzew5xwobuuiyuogwxuc3ckeuucmgn+9rffswhs0oal5xarwqpv+xqbr5aau7hdc4ggguowj3uoa4mjdzdk7x5l9679+f9zlvxvhzmbbbgff0coekgjq==</latexit> <latexit sha1_base64="wxkx7kkensf+xyycnz2z5qtzzxc=">aaacfxicbva9swnbej3zm8avqkxnyhcswp0iwgztlcoyd0hc2nvsjut2b4/dosec+rm2fvpx7mtw2n9i6sa5wiq+whi8mdk388jecou+/+2trw9sbm0xdoq7e/shh6wj44bvqwg8zrtuphvsy6wier0fst5kdkcqllwzju6m9eytn1bo+bhhce8qoohfjbhfj7u6goxittgrlf2kpwnzjufoypcj1iv9dpqapyrhycs1th34cxyzalawysfftmp5qtmidnjb0zg6l24223dczp3sj5e27svizurfiywqa8cqdj2k4tau16bif7v2itfnnxnxkikp2dwosivbtabhk74wnkeco0kzew5xwobuuiyuogwxuc3ckeuucmgn+9rffswhs0oal5xarwqpv+xqbr5aau7hdc4ggguowj3uoa4mjdzdk7x5l9679+f9zlvxvhzmbbbgff0coekgjq==</latexit> <latexit sha1_base64="wxkx7kkensf+xyycnz2z5qtzzxc=">aaacfxicbva9swnbej3zm8avqkxnyhcswp0iwgztlcoyd0hc2nvsjut2b4/dosec+rm2fvpx7mtw2n9i6sa5wiq+whi8mdk388jecou+/+2trw9sbm0xdoq7e/shh6wj44bvqwg8zrtuphvsy6wier0fst5kdkcqllwzju6m9eytn1bo+bhhce8qoohfjbhfj7u6goxittgrlf2kpwnzjufoypcj1iv9dpqapyrhycs1th34cxyzalawysfftmp5qtmidnjb0zg6l24223dczp3sj5e27svizurfiywqa8cqdj2k4tau16bif7v2itfnnxnxkikp2dwosivbtabhk74wnkeco0kzew5xwobuuiyuogwxuc3ckeuucmgn+9rffswhs0oal5xarwqpv+xqbr5aau7hdc4ggguowj3uoa4mjdzdk7x5l9679+f9zlvxvhzmbbbgff0coekgjq==</latexit> <latexit sha1_base64="wxkx7kkensf+xyycnz2z5qtzzxc=">aaacfxicbva9swnbej3zm8avqkxnyhcswp0iwgztlcoyd0hc2nvsjut2b4/dosec+rm2fvpx7mtw2n9i6sa5wiq+whi8mdk388jecou+/+2trw9sbm0xdoq7e/shh6wj44bvqwg8zrtuphvsy6wier0fst5kdkcqllwzju6m9eytn1bo+bhhce8qoohfjbhfj7u6goxittgrlf2kpwnzjufoypcj1iv9dpqapyrhycs1th34cxyzalawysfftmp5qtmidnjb0zg6l24223dczp3sj5e27svizurfiywqa8cqdj2k4tau16bif7v2itfnnxnxkikp2dwosivbtabhk74wnkeco0kzew5xwobuuiyuogwxuc3ckeuucmgn+9rffswhs0oal5xarwqpv+xqbr5aau7hdc4ggguowj3uoa4mjdzdk7x5l9679+f9zlvxvhzmbbbgff0coekgjq==</latexit> Moon-magnetosphere plasma interactions magnetospheric plasma Sputtering: Magnetospheric ions liberate neutrals, feed a tenuous atmosphere. [Cassidy et al. 2013, Vorburger & Wurz 2018] B J To Jupiter Y Plasma flow X E = -u plasma x B J Ionization: Electrons & photons ionize neutrals, populating the ionosphere. Pick-up: Magnetospheric ions charge-exchange with neutrals, creating fast neutrals and pickedup ions.

4 detector to separate them by species and energy. The F detector m data used in this paper was processed by the pulse-height-analyzer o (pha) system. Electron count rates obtained in this manner can be separated with high energy resolution. For instance, there are ten m energy channels between about 500 and 1000 kev. In addition to c the pha data, a small group of channels from the high-energy (1 end of LEMMS are included and represent electrons measured in im a detector stack. j In Fig. 4, we show LEMMS electron data averaged and et binned 160 C. Paranicas al. / Icarus 234 covering the mission years Intensity is expressed as b electrons per cm2 s sr kev. Long-time averages are used so that lab ter in this analysis they will approximate the effects of weathering over time. Data used for this study were obtained along the orbital E distances of Mimas (r! 3.08RS), Tethys (r! 4.89RS), and Dione (r! 6.26RS), where RS is Saturn s equatorial radius (RS! 60,268 km), in very narrow radial corridors. We do not inu clude Enceladus in this study because of potential complications m associated with rapid resurfacing and because magnetic perturbaw tions in the moon s plasma wake can alter electron drift paths before they reach the moon. Rhea is somewhat outside the main u radiation belts of the planet and therefore not a focus of this work. p Precipitation, Sputtering, Space Weathering Thermal Plasma (<100 ev) Suprathermal plasma Paranicas et al., GRL, 2001 (Please see also my poster!) Paranicas et al., Icarus, 2014

5 400 Signatures of Plumes Bz (nt) 500 a 12:02 UT 105 fuh Bx (nt) :00 12:10 12:02 UT 103 Density (cm 3) :20 12:30 PWS inferred density MHD model density 800 Galileo MAG data Jupiter MHD model (with plume) 700 Flow x 600 MHD model (no plume) :50 Time b By (nt) :40 Electric spectral density (V2 m 2 Hz 1) Jia et al., Nature Ast., 2018ASTRONOMY NATURE LETTERS 800 B (nt) a Frequency (Hz) 700 LETTERS NATURE ASTRONOMY 600 X (RE) Y (RE) Z (RE) R (RE) 11:45 11:50 11:55 12:00 12:05 Time 12:10 12:15 12:20 12: Blöcker et al., JGR-SP, 2016 Galileo Fig. 1 Galileo MAG 0 data for the E12 flyby. Black lines show the MAG data. Green and red lines, respectively, show traces extracted from the MHD simulations without and with a plume included. Results are presented in EphiO coordinates, with x parallel to Europa s orbital velocity, y directed towards Jupiter and z 100 completing the right-handed system. The interval of anomalous changes (~12:00 to 12:03!UT) is bounded by vertical dashed lines, and closest approach is marked by and a grey arrow. In the range used for these measurements, the MAG sensor digitization step8 was 0.25!nT. Between 11:55 and 12:05!UT, one 200 or another of the 3 sensors saturated at the spacecraft rotation period. This required special processing, which increased the uncertainty to a level of a few nt. X, Y, Z and R given at the bottom of the figure indicate the spacecraft location and its radial distance from Europa s centre in units of RE in EphiO coordinates. 400 We placed a plume in the region of Europa s thermal anomaly using the structural and density parameters consistent with plume 10 b properties inferred from the previous telescopic observations Our simulation assumes Jupiter that upstream conditions are steady, with a plasma density of ~600 cm 3. The strong upper hybrid 11:40 11:50 12:00 12:10 12:20 12:30background 700 frequency emissions in Fig. Flow 2a indicate that the background dentime sity remained quite steady at this value until 12:06 ut, after which 800 it began to decrease, dropping to ~100 cm 3 by the end of the pass. Fig. 2 Galileo plasma wave data and derived plasma density for the It is not E12 flyby. a, Electric field power spectra. The upper hybrid frequency (fuh) clear whether the change of background density was a or spatial feature, such as exit from a possible region of that establishes the electron density is marked by black dashed temporal (from cold, high-density plasma referred to as a cold dense 800 the previous study14) and solid lines (this study). A pink arrow atanomalously 12:02! UT 19 blob. In either case, the density decrease should not have affected indicates the central time of the magnetic perturbation in Fig. 1. Bz (nt) 2 the analysis of the plume because it occurred only after the perturbations we were focusing on had diminished. The region of abrupt large-amplitude fluctuations that we link to a plume lasted <3 min, ending by ~12:03 ut, after which high-frequency fluctuations of the magnetic field are consistent with nominal background noise. For the purpose of this investigation, changes in the background conditions that were encountered about 0.7 Europa s radius (RE) beyond the signature of the plume and some 3 min after the spacecraft exited the region perturbed by its presence should not affect the results. As shown below, the simulation reproduced the rapidly changing magnetic field and plasma density signatures identified in the Galileo E12 data. No plume 700 With plume

6 Magnetic Fields Khurana et al., Science, 2011 Jovian background, No induction Warm solid mantle Various asthenospheres (Please see also my poster!)