Energy Flux and Characteristic Energy of Electrons Over Jupiter's Main Auroral Emission

Allegrini, F.; Mauk, B. H.; Clark, G.; Gladstone, G. R.; Hue, V.; Kurth, W. S.; Bagenal, F.; Bolton, S. J.; Bonfond, Bertrand; Connerney, J. E. P.; Ebert, R. W.; Greathouse, T. K.; Imai, Masafumi; Levin, S. M.; McComas, D. J.; Saur, Joachim; Szalay, J. R.; Valek, P. W.; Wilson, R.

doi:10.1029/2019ja027693

Cited by 47 publications

(90 citation statements)

References 106 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…We note that Allegrini et al (2020) map the main auroral oval as observed by Juno UVS to 50 R J using the JRM09 internal field model of Connerney et al. (2018) plus the Connerney et al.…”

Section: Discussionmentioning

confidence: 90%

“…(2019). The JADE‐E electron data were calculated using the in‐flight calibration parameters given in Allegrini et al (2020). The electron data are computed as 1‐D moments, proton data are computed from the JADE‐I Species 3 plus Species 4 products, while heavy ion data come from JADE‐I Species 5 (for more details see McComas et al., 2017).…”

Section: Datamentioning

confidence: 99%

See 1 more Smart Citation

An Enhancement of Jupiter's Main Auroral Emission and Magnetospheric Currents

et al. 2020

Self Cite

View full text Add to dashboard Cite

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. 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.

show abstract

“…We note that Allegrini et al (2020) map the main auroral oval as observed by Juno UVS to 50 R J using the JRM09 internal field model of Connerney et al. (2018) plus the Connerney et al.…”

Section: Discussionmentioning

confidence: 90%

Section: Datamentioning

confidence: 99%

An Enhancement of Jupiter's Main Auroral Emission and Magnetospheric Currents

et al. 2020

Self Cite

View full text Add to dashboard Cite

show abstract

“…In practice, the factor to normalize the distribution function is c 3 10 −18 /n e , where n e is the density (in cm −3 ). Here n e ≃ 1 cm −3 at 07:36:40, and n e ≃ 6 cm −3 at 07:37:26 and 07:37:28, and n e ≃ 2 cm −3 at 07:37:43 (see Figure 1f), which is probably slightly overestimated (Allegrini et al, 2020), leading to underestimated growth rate.…”

Section: The Cmi: Determination Of the Emission Parametersmentioning

confidence: 92%

“…This shadowing mostly affects the electrons with large pitch angles, and it also affects the lower energy more than the higher-energy electrons. The shadowing was qualitatively reproduced with a simple ray tracing simulation in Allegrini et al (2017Allegrini et al ( , 2020.…”

Section: Electron Distribution Functionmentioning

confidence: 99%

Ganymede‐Induced Decametric Radio Emission: In Situ Observations and Measurements by Juno

Louis

Allegrini

Kurth

et al. 2020

Geophysical Research Letters

Self Cite

View full text Add to dashboard Cite

At Jupiter, part of the auroral radio emissions are induced by the Galilean moons Io, Europa, and Ganymede. Until now, they have been remotely detected, using ground-based radio telescopes or electric antennas aboard spacecraft. The polar trajectory of the Juno orbiter allows the spacecraft to cross the magnetic flux tubes connected to these moons, or their tail, and gives a direct measure of the characteristics of these decametric moon-induced radio emissions. In this study, we focus on the detection of a radio emission during the crossing of magnetic field lines connected to Ganymede's tail. Using electromagnetic waves (Juno/Waves) and in situ electron measurements (Juno/JADE-E), we estimate the radio source size of ∼250 km, a radio emission growth rate >3 × 10 −4 , a resonant electron population of energy E = 4-15 keV and an emission beaming angle of = 76-83 • , at a frequency ∼1.005-1.021 × f ce. We also confirmed that radio emission is associated with Ganymede's downtail far ultraviolet emission. Plain Language Summary The Juno spacecraft crossed magnetic field lines connected to Ganymede's auroral signature in Jupiter's atmosphere. At the same time, Juno also crossed a decametric radio source. By measuring the electrons during this radio source crossing, we determine that this emission is produced by the cyclotron maser instability driven by upgoing electrons, at a frequency 0.5% to 2.1% above the cyclotron electronic frequency with electrons of energy 4-15 keV. 1. Introduction With the arrival of Juno at Jupiter in July 2016, the probe passes above the poles once per orbit, every 53 days and acquires high-resolution measurements in the auroral regions (Bagenal et al., 2017). In particular, the instruments Waves (radio and plasma waves, Kurth et al., 2017), JADE-E (Jovian Auroral Distributions Experiment-Electrons, McComas et al., 2017), and MAG (Magnetometer, Connerney et al., 2017) offer a unique opportunity to investigate in situ the Jovian radio emissions produced in these polar regions. These instruments enable constraints on the position of the sources (

show abstract

“…JEDI ion observations near the polar region have revealed both upward and downward proton beams (Mauk et al, 2017c(Mauk et al, , 2018(Mauk et al, , 2020, proton conics with much larger energies than their terrestrial counterparts (Clark et al, 2017), constrained energetic heavy ion charge states (Clark et al, 2020), and revealed an auroral environment with both similarities and significant differences to Earth's (Mauk et al, 2017c). JADE and JEDI observations have enabled the characterization of identifiable auroral zones (Allegrini et al, 2020;Mauk et al, 2020), generally organized by latitude. One of Juno's important discoveries is that Jupiter's auroral emissions can be generated (a) during mono-directional, downward acceleration-Zone I: thought to be the upward electric current region and (b) during bidirectional electron acceleration-Zone II: thought to be the downward electric current region (Mauk et al, 2020).…”

mentioning

confidence: 99%

Proton Outflow Associated With Jupiter's Auroral Processes

Szalay

Allegrini

Bagenal

et al. 2021

Geophysical Research Letters

Self Cite

View full text Add to dashboard Cite

The source of protons in the Jovian magnetosphere has been historically difficult to determine experimentally. The volcanic moon Io is the primary source of plasma in the magnetosphere, inputting ∼10 3 kg s −1 of heavy ions (e.g., Bagenal & Delamere, 2011). Approximately 10% of the total magnetospheric number density is attributed to protons (e.g., Dougherty et al., 2017), which are not sourced by Io. The proton influx necessary to account for this population from 5 to 30 R J (Jovian radii) has been estimated to be 2.5-13 kg s −1 (Bodisch et al., 2017). There are at least three possible sources of protons in Jupiter's magnetosphere: solar wind, icy moons, and ionospheric outflow. Solar wind leakage across the magnetopause boundary is one possible source (e.g., Delamere et al., 2015), yet it is difficult to explain how such protons would be transported to the inner magnetosphere via this mechanism. Since Jupiter is likely not undergoing standard a Dungey cycle (McComas & Bagenal, 2007), it is also difficult to attribute magnetospheric protons to the solar wind, particularly in the innermost regions. Of the icy moons, Europa sustains a neutral torus of many species including hydrogen (e.g., Smith et al., 2019), which can charge exchange with the local plasma environment, however, at much lower quantities than necessary to source the magnetospheric proton population (e.g., Bagenal & Dols, 2020). The focus of this study is to constrain the ionospheric outflow source of protons. The outflow has been previously estimated to be 35 kg s −1 (Nagy et al., 1986) integrating over the entire polar region, and 18.7-31.7 kg s −1 (Martin et al., 2020) at high latitudes between Io's M-Shell and up to and including the auroral oval, with 4.3-8.5 kg s −1 estimated to specifically outflow from the auroral oval. Both theoretical estimates are sufficient to explain the source of protons in Jupiter's magnetosphere, but the mechanisms of ionospheric outflow have not been previously observed.

show abstract

Energy Flux and Characteristic Energy of Electrons Over Jupiter's Main Auroral Emission

Cited by 47 publications

References 106 publications

An Enhancement of Jupiter's Main Auroral Emission and Magnetospheric Currents

An Enhancement of Jupiter's Main Auroral Emission and Magnetospheric Currents

Ganymede‐Induced Decametric Radio Emission: In Situ Observations and Measurements by Juno

Proton Outflow Associated With Jupiter's Auroral Processes

Contact Info

Product

Resources

About