Observation of Electron Conics by Juno: Implications for Radio Generation and Acceleration Processes

P. Louarn; F. Allegrini; D. J. McComas; P. W. Valek; W. S. Kurth; N. André; F. Bagenal; S. Bolton; R. W. Ebert; M. Imai; S. Levin; J. R. Szalay; R. J. Wilson

doi:10.1029/2018GL078973

Observation of Electron Conics by Juno: Implications for Radio Generation and Acceleration Processes

P. Louarn, F. Allegrini, D. J. McComas, P. W. Valek, W. S. Kurth, N. André, F. Bagenal, S. Bolton, R. W. Ebert, M. Imai, S. Levin, J. R. Szalay, R. J. Wilson

Astrophysical Sciences

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Abstract

Using Juno plasma, electric and magnetic field observations (from JADE, Waves, and MAG instruments), we show that electron conic distributions are commonly observed in Jovian radio sources. The conics are characterized by maximum fluxes at oblique pitch angles, ~20°–30° from the B field, both in the upward and downward directions. They constitute an efficient source of free energy for the cyclotron maser instability. Growth rates of ~3 to 7 × 10⁴ s⁻¹ are obtained for hectometric waves, leading to amplification by e¹⁰ with propagation paths of 50–100 km. We show that stochastic acceleration due to interactions with a low-frequency electric field turbulence located a few 10⁴ km above the ionosphere may form the observed conics. A possible source of turbulence could be inertial Alfvén waves, suggesting a connection between the auroral acceleration and generation of coherent radio emissions.

Original language	English (US)
Pages (from-to)	9408-9416
Number of pages	9
Journal	Geophysical Research Letters
Volume	45
Issue number	18
DOIs	https://doi.org/10.1029/2018GL078973
State	Published - Sep 28 2018

All Science Journal Classification (ASJC) codes

Geophysics
Earth and Planetary Sciences(all)

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10.1029/2018GL078973

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@article{83995d12269841b8983e219cd70ab23e,

title = "Observation of Electron Conics by Juno: Implications for Radio Generation and Acceleration Processes",

abstract = "Using Juno plasma, electric and magnetic field observations (from JADE, Waves, and MAG instruments), we show that electron conic distributions are commonly observed in Jovian radio sources. The conics are characterized by maximum fluxes at oblique pitch angles, ~20°–30° from the B field, both in the upward and downward directions. They constitute an efficient source of free energy for the cyclotron maser instability. Growth rates of ~3 to 7 × 104 s−1 are obtained for hectometric waves, leading to amplification by e10 with propagation paths of 50–100 km. We show that stochastic acceleration due to interactions with a low-frequency electric field turbulence located a few 104 km above the ionosphere may form the observed conics. A possible source of turbulence could be inertial Alfv{\'e}n waves, suggesting a connection between the auroral acceleration and generation of coherent radio emissions.",

author = "P. Louarn and F. Allegrini and McComas, {D. J.} and Valek, {P. W.} and Kurth, {W. S.} and N. Andr{\'e} and F. Bagenal and S. Bolton and Ebert, {R. W.} and M. Imai and S. Levin and Szalay, {J. R.} and Wilson, {R. J.}",

note = "Funding Information: The French part of this work is supported by CNRS and CNES. The research at the University of Iowa was supported by NASA through contract 699041X with Southwest Research Institute. The JNO-E/J/SS-WAV-3-CDR-SRVFULL-V1.0, JNO-J/SW-JAD-3-CALIBRATED-V1.0, and JNO-J/SW-JAD-2-UNCALIBRATED-V1.0 data sets were obtained from the Planetary Data System (PDS) at http://pds.nasa.gov/. Funding Information: The French part of this work is supported by CNRS and CNES. The research at the University of Iowa was supported by NASA through contract 699041X with Southwest Research Institute. The JNO-E/J/SS-WAV-3-CDR- SRVFULL-V1.0, JNO-J/SW-JAD-3- CALIBRATED-V1.0, and JNO-J/SW-JAD-2- UNCALIBRATED-V1.0 data sets were obtained from the Planetary Data System (PDS) at http://pds.nasa.gov/. Publisher Copyright: {\textcopyright}2018. American Geophysical Union. All Rights Reserved.",

year = "2018",

month = sep,

day = "28",

doi = "10.1029/2018GL078973",

language = "English (US)",

volume = "45",

pages = "9408--9416",

journal = "Geophysical Research Letters",

issn = "0094-8276",

publisher = "American Geophysical Union",

number = "18",

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TY - JOUR

T1 - Observation of Electron Conics by Juno

T2 - Implications for Radio Generation and Acceleration Processes

AU - Louarn, P.

AU - Allegrini, F.

AU - McComas, D. J.

AU - Valek, P. W.

AU - Kurth, W. S.

AU - André, N.

AU - Bagenal, F.

AU - Bolton, S.

AU - Ebert, R. W.

AU - Imai, M.

AU - Levin, S.

AU - Szalay, J. R.

AU - Wilson, R. J.

N1 - Funding Information: The French part of this work is supported by CNRS and CNES. The research at the University of Iowa was supported by NASA through contract 699041X with Southwest Research Institute. The JNO-E/J/SS-WAV-3-CDR-SRVFULL-V1.0, JNO-J/SW-JAD-3-CALIBRATED-V1.0, and JNO-J/SW-JAD-2-UNCALIBRATED-V1.0 data sets were obtained from the Planetary Data System (PDS) at http://pds.nasa.gov/. Funding Information: The French part of this work is supported by CNRS and CNES. The research at the University of Iowa was supported by NASA through contract 699041X with Southwest Research Institute. The JNO-E/J/SS-WAV-3-CDR- SRVFULL-V1.0, JNO-J/SW-JAD-3- CALIBRATED-V1.0, and JNO-J/SW-JAD-2- UNCALIBRATED-V1.0 data sets were obtained from the Planetary Data System (PDS) at http://pds.nasa.gov/. Publisher Copyright: ©2018. American Geophysical Union. All Rights Reserved.

PY - 2018/9/28

Y1 - 2018/9/28

N2 - Using Juno plasma, electric and magnetic field observations (from JADE, Waves, and MAG instruments), we show that electron conic distributions are commonly observed in Jovian radio sources. The conics are characterized by maximum fluxes at oblique pitch angles, ~20°–30° from the B field, both in the upward and downward directions. They constitute an efficient source of free energy for the cyclotron maser instability. Growth rates of ~3 to 7 × 104 s−1 are obtained for hectometric waves, leading to amplification by e10 with propagation paths of 50–100 km. We show that stochastic acceleration due to interactions with a low-frequency electric field turbulence located a few 104 km above the ionosphere may form the observed conics. A possible source of turbulence could be inertial Alfvén waves, suggesting a connection between the auroral acceleration and generation of coherent radio emissions.

AB - Using Juno plasma, electric and magnetic field observations (from JADE, Waves, and MAG instruments), we show that electron conic distributions are commonly observed in Jovian radio sources. The conics are characterized by maximum fluxes at oblique pitch angles, ~20°–30° from the B field, both in the upward and downward directions. They constitute an efficient source of free energy for the cyclotron maser instability. Growth rates of ~3 to 7 × 104 s−1 are obtained for hectometric waves, leading to amplification by e10 with propagation paths of 50–100 km. We show that stochastic acceleration due to interactions with a low-frequency electric field turbulence located a few 104 km above the ionosphere may form the observed conics. A possible source of turbulence could be inertial Alfvén waves, suggesting a connection between the auroral acceleration and generation of coherent radio emissions.

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U2 - 10.1029/2018GL078973

DO - 10.1029/2018GL078973

M3 - Article

AN - SCOPUS:85053901471

SN - 0094-8276

VL - 45

SP - 9408

EP - 9416

JO - Geophysical Research Letters

JF - Geophysical Research Letters

IS - 18

ER -

Observation of Electron Conics by Juno: Implications for Radio Generation and Acceleration Processes

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