New models of Jupiter's magnetic field constrained by the Io flux tube footprint

Abstract

Abstract. Spherical harmonic models of the planetary magnetic field of Jupiter are obtained from in situ magnetic field measurements and remote observations of the position of the foot of the Io flux tube in Jupiter's ionosphere. The Io flux tube (IFT) footprint locates the ionospheric footprint of field lines traced from Io's orbital radial distance in the equator plane (5.9 Jovian radii). The IFT footprint is a valuable constraint on magnetic field models, providing "ground truth" information in a region close to the planet and thus far not sampled by spacecraft. The magnetic field is represented using a spherical harmonic expansion of degree and order 4 for the planetary ("internal") field and an explicit model of the magnetodisc for the field ("external") due to distributed currents. Models fitting Voyager 1 and Pioneer 1! magnetometer observations and the IFT footprint are obtained by partial solution of the underdetermined inverse problem using generalized inverse techniques. Dipole, quadrupole, octupole, and a subset of higher-degree and higher-order spherical harmonic coefficients are determined and compared with earlier models.

UV Io footprint leading spot: A key feature for understanding the UV Io footprint multiplicity?

“…We extracted 21-pixel wide stripes from the background subtracted images and stretched them in order to display the footprint shape as a function of the longitude mapped to Io's orbital plane. For this mapping, we used the VIP4 magnetic field model [Connerney et al, 1998]. The result is shown in Figure 3.…”

A pulsating auroral X-ray hot spot on Jupiter

“…The Chandra HRC observations therefore call into question earlier views that attribute the X-ray auroral emissions to energetic particles diffusing planetward from the outer regions of the Io plasma torus and precipitating in the atmosphere at latitudes UT) and each X-ray photon has been smeared by double the 0.4-arcsecond full-width halfmaximum point-spread-function of the high-resolution camera. A jovicentric graticule with 308 intervals is overplotted, along with the maximum equatorward extent of the L 5:9 (orange lines) and L 30 (green lines) footprints of the VIP4 model 16 magnetosphere. The auroral emissions are located at much higher latitudes than we expected on the basis of previous X-ray observations and indicate a connection with Jupiter's outer magnetosphere.…”

“…Further evidence that some process other than energetic ion precipitation from the inner magnetosphere is responsible for the bulk of the observed auroral X-rays is provided by the lack of expected correlation between the X-ray emission morphology and the surface magnetic ®eld strength (that is, the magnetic ®eld strength at 1R J ) as determined with the VIP4 model 16 (Fig. 2).…”

The Juno Waves Investigation

“…Binning Mode burst observations are scheduled primarily to target times when Juno is expected to cross various types of auroral features. Figure 29 shows a plot of the magnetic footprint of Juno for Perijove 1 on the northern hemisphere using the VIP4 magnetic field model (Connerney et al 1998). The nominal main auroral oval based on Hubble Space Telescope (HST) observations is also shown.…”