Abstract
AbstractWe present observations of Jupiter's magnetic field and plasma obtained with the NASA Juno spacecraft during February 2018, along with simultaneous Hubble Space Telescope (HST) observations of the planet's auroras. We show that a few‐day transient enhancement of the azimuthal and radial magnetic fields and plasma temperature was coincident with a significant brightening of Jupiter's dawn‐side main auroral emission. This presents the first evidence of control of Jupiter's main auroral emission intensity by magnetosphere‐ionosphere coupling currents. We support this association by self‐consistent calculation of the magnetosphere‐ionosphere coupling and radial force balance currents using an axisymmetric model, which broadly reproduces the Juno magnetic field and plasma observations and the HST auroral observations. We show that the transient enhancement can be explained by increased hot plasma pressure in the magnetosphere together with increased iogenic plasma mass outflow rate. Overall, this work provides important observational and modeling evidence revealing the behavior of Jupiter's giant magnetosphere.
Highlights
The dynamics of Jupiter's magnetosphere are dominated by planetary rotation, combined with the centrifugal outflow of plasma originating from the volcanic moon Io (e.g., Vasyliunas, 1983)
We present observations of Jupiter's magnetic field and plasma obtained with the NASA Juno spacecraft during February 2018, along with simultaneous Hubble Space Telescope (HST) observations of the planet's auroras
We show that a few‐day transient enhancement of the azimuthal and radial magnetic fields and plasma temperature was coincident with a significant brightening of Jupiter's dawn‐side main auroral emission
Summary
The dynamics of Jupiter's magnetosphere are dominated by planetary rotation, combined with the centrifugal outflow of plasma originating from the volcanic moon Io (e.g., Vasyliunas, 1983). The steady state angular velocity profile is dependent on the Pedersen conductivity, the iogenic plasma mass outflow rate, and the magnetodisc field structure (Cowley et al, 2002; Hill, 1979; Nichols & Cowley, 2003, 2004) The latter is associated with an azimuthal current arising from radial stress balance in the magnetosphere (Caudal, 1986; Mauk & Krimigis, 1987). We show that a transient brightening of the ME was directly associated with increased azimuthal magnetic field ( torque on the middle magnetospheric plasma), along with enhanced radial field ( radial forces) and plasma temperatures This represents the first direct evidence of a connection between varying ME intensity and the M‐I coupling currents. We show that the transient enhancement can be explained by variation in the hot plasma pressure in the magnetosphere and in the iogenic plasma mass outflow rate
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