13:32

0°

90°

13:1713:27

13:3713:47

14:02 270°kR H2

200400600800100012001400

[Louis et al., 2019]

Figure 5

Study of Jupiter radio emissions with the ExPRES code, Juno/Waves (radio) and Juno/JADE (electrons) instruments

Abs

trac

t

C. K. Louis1,2,3, P. Louarn1, S. L. G. Hess4, B. Cecconi2,3, P. Zarka2,3, L. Lamy2,3, W. S. Kurth5, F. Allegrini6, S. Aicardi7, A. Loh2 (1) IRAP, Toulouse, France, (2) LESIA, Observatoire de Paris CNRS, UPMC - Meudon, France, (3) USN, Observatoire de Paris - Nançay, France, (4) ONERA-The French Aerospace Lab, FR-31055

Toulouse, France, (5) Department of Physics and Astronomy, University of Iowa, Iowa City, Iowa, USA (6) Southwest Research Institute, San Antonio, Texas, USA, (7) DIO, Observatoire de Paris, PSL Research University, CNRS, Paris, France

2. Calculation of beaming angle θCMI resonant condition:

2 choices : or ≠ 0- vr|| = 0, then f=fce Γr-1

- vr|| ≠ 0 then f ~ fce Γr

with N the refraction index, given by the Appleton-Hartree cold plasma dispersion equation (detailed and exact calculations in Louis et al., 2019, A&A)

with the Lorentz factor

fce

f fce fce,max~

Figure 1

Context. Earth and outer planets are known to produce intense non-thermal radio emissions through a mechanism known as Cyclotron Maser Instability (CMI), requiring the presence of accelerated electrons generally arising from magnetospheric current systems. In return, radio emissions are a good probe of these current systems and acceleration processes. The CMI generates highly anisotropic emissions and leads to important visibility effects, which have to be taken into account when interpreting the data. Several studies showed that modeling the radio source anisotropic beaming pattern can reveal a wealth of physical information about the planetary or exoplanetary magnetospheres that produce these emissions. Aims. We present a numerical tool, called ExPRES (Exoplanetary and Planetary Radio Emission Simulator), which is able to reproduce the occurrence in time-frequency plane of R-X CMI-generated radio emissions from planetary magnetospheres, exoplanets or star-planet interacting systems. Special attention is given to the computation of the radio emission beaming at and near its source.

Methods. We explain what physical information about the system can be drawn from such radio observations, and how it is obtained. These information may include the location and dynamics of the radio sources, the type of current system leading to electron acceleration and their energy and, for exoplanetary systems, the magnetic field strength, the orbital period of the emitting body and the rotation period, tilt and offset of the planetary magnetic field. Most of these parameters can be remotely measured only via radio observations.

Results. The ExPRES code provides the proper framework of analysis and interpretation for past, current and future observations of planetary radio emissions, as well as for future detection of radio emissions from exoplanetary systems (or magnetic white dwarf-planet or white dwarf-brown dwarf systems). Our methodology can be easily adapted to simulate specific observations, once effective detection is achieved.

Perspectives. In-situ observations to better constrain the process (emission frequency, electrons energy, beaming angle, electron distribution function) using Juno/JADE

5. Perspectives• Simulation of Jovian hectometer, broadband kilometer and Io-independent decameter emissions (Boischot et al. 1981, Imai et al. 2008, 2011).• Multi-instrumental comparison during the ~60 source crossing events:

- Determination of θ (perpendicular or oblique ?).- Connection with UV emission (need to use Juno/UVS observation)?- Observation of loss cone or conics (Louarn et al., 2018)?- What about the plasma frequency (no emission if fpe/fce > 0.1)?

• Results During a source crossing:

- intensification at energies of a few keV - see Fig. 4;- strong loss-cone (loss of upward electrons) - see Fig. 4;- Intensification of downward electrons and UV emissions at the footprint of the magnetic field lines (edge of the main auroral oval) - see Figs. 4&5.

—> What triggers/stops the instability and the emission process?

[Louis et al., 2017b]

[Louis et al., 2020, in prep.]

f~fce

1 M

Hz

40 MHz

ve-e-

B

M Ω

Radiated waves

Position of individual radio sources (magnetic field + fmin-fmax)

Emission cone: - opening angle θ - thickness Δθ

Electron distribution function (needed to theoretically compute CMI-driven emission cone)

Schematic diagram

of ExPRES

simulations input parameters

[Queinnec & Zarka, 1998]

[Hess et al., 2008]

Observations

Simulations

1.Computes the beaming angle θ (using the Cyclotron Maser Instability, CMI) of individual radio sources emission around a magnetized planet and tests at each time/frequency step whether the radiated waves are visible or not for a given observer (see Fig. 1).

2.Produces dynamic spectra of visible radio sources - see Fig. 2

Conditions :• High magnetized depleted plasma• Accelerated electrons (~keV)

1. ExPRES Principle Figure 2

• Available under MIT licence on GitHub within https://github.com/maserlib/ExPRES.• Available for run-on-demand: https://voparis-uws-maser.obspm.fr.

• Precomputed ExPRES simulation runs available through (Cecconi et al. 2018a,b): http://maser.obspm.fr/data/serpe/, the EPN-TAP (Erard et al. 2018): http://voparis-tap-maser.obspm.fr/tableinfo/expres.epn_core, or the MASER das2 Server:http://voparis-das-maser.obspm.fr/das2/server (Piker 2017).

[Wu, 1985] [Hilgers, 1992;

Zarka et al., 1998, 2001, 2004]

Juno Waves - Electric Field Spectral Density%{USER_PROPERTIES.xCacheResInfo}

dataset z units are "dB" while zaxis is "V**2 m**-2 Hz**-1"

13:35:00No Data

13:35:30No Data

13:36:00No Data

13:36:30No Data

13:37:00No Data

13:37:30No Data

13:38:00No Data

13:38:30No Data

13:39:00No Data

2017-02-02 (033) 13:35 to 13:39???

4600

4800

5000

5200

5400

Freq. (

kHz)

0

5

1 0

1 5

2 0

2 5

3 0

dB abo

ve baca

kgroun

d

4600

4800

5000

5200

5400

Freq

uenc

y (k

Hz)

0

dB (A

bove

Bac

kgro

und)

10

20

30

Elec

trons

goi

ng d

own

‘Strong’ loss-cone no loss-cone

Intensification @ Ee-~ keV

no/‘weak’ loss-cone

Work in progress …

Local radio sources from Juno/Waves

‘Strong’ precipitations (—>UV)

Elec

trons

goi

ng u

pEl

ectro

ns

ener

gyPi

tch

angl

eRa

dio

emis

sion

in

tens

ity

Figure 4

4. M

ulti-

inst

rum

enta

l com

paris

ons

Upward electrons

Downward electrons

Juno/JADE

Juno/Waves

Contact : corentin.louis@oirap.omp.eu

Figure 3• Results at Jupiter - Reproduction of the radio emissions time frequency morphology (Hess et al., 2008, 2010a, 2011, Ray&Hess 2008) - see Fig. 2.

- Prediction and detection of new radio emissions, induced by Europa and Ganymede (Louis et al., 2017a).

- Estimation of natural radio emissions that will pollute the radar measurements of the Jupiter Icy Moon Explorer (JUICE) spacecraft (Cecconi et al., 2012).

- Prediction and interpretation of Juno/Waves radio observations (Louis et al., 2017b) - see Fig. 3.

3. S

imul

atio

n R

esul

ts