RPWI Team Meeting, 19-20 Sep. 2010, Roma

Magnetic Loop Antenna (MLA)

Scientific Objectives

A. Marchaudon, V. Krasnoselskikh, T. Dudok de Wit,

C. Cavoit, D. Lagoutte

(LPC2E/CNRS, France)

RPWI Team Meeting, 19-20 Sep. 2010, Roma

The Magnetic Loop Antenna (MLA) is designed to measure one component of the magnetic fluctuations at high frequency

Characteristics proposed:

• Diameter: 20 cm

• Mass: 250 g

• Power: 300 mW

• Frequency range: 100 kHz-45 MHz

• Sensitivity: 0.3 fT.Hz-1/2 at 1 MHz

The Magnetic Loop Antenna

RPWI Team Meeting, 19-20 Sep. 2010, Roma

Interest of MLA for Jupiter’s environment: - to complete multi-component wave measurements at high frequency

- to solve the problem of wave identification, by distinguishing between electrostatic and electromagnetic wave modes - to help locating and characterizing the sources as being of electric or of magnetic nature

- to determine the averaged refractive index of waves

- to allow new discoveries as magnetic fluctuations have never been measured in this frequency range around Jupiter, especially with close approach of Callisto and Ganymede

General Scientific Objectives of MLA

RPWI Team Meeting, 19-20 Sep. 2010, Roma

Energetic phenomena recurrently occur in the Jovian magnetosphere, characterized by intensifications of the auroral radio emissions and the creation of new sources of radiations in the outer regions of the Io torus

With MLA measuring magnetic fluctuations at high frequency, it would be possible:• to help studying the different characteristics of particle acceleration in the Jovian magnetosphere (radiation belts) as they show different spectral characteristics in the Jovian decametric radio bursts • to help studying the generation of specific types of radio emissions caused by particle precipitations in auroral regions of the Jovian magnetosphere, and how much the solar wind affect these emissions at Jupiter

Radio emissions of Jupiter

The moon Io enhances considerably Jupiter's emission of decametric (DAM) radio waves (1-40 MHz)

With MLA measuring magnetic fluctuations at high frequency, it would be possible:- to help differentiating between Io spin modulated emissions (Io-DAM) and emissions independent of the orbital phase of Io (non Io-DAM), in terms of intensity, source origin and possible solar wind control of these emissions- to help verifying emissions mechanism of S-bursts (very fine structure of Io-DAM emissions in the 20-30 MHz range)

Radio emissions controlled by Io

RPWI Team Meeting, 19-20 Sep. 2010, Roma

Galileo Observations:• A small portion of radio emissions correlates with the orbital phase of the other Galilean satellites in the low decametric range (2-6 MHz)

With:- multiple close fly-bys of the JGO spacecraft with Callisto and Ganymede, then orbit insertion around Ganymede, and- with MLA measuring magnetic fluctuations at high frequencyit would be possible:• to help studying the decametric radio emissions controlled by the moons• to help checking their source location and intensity• to help checking the possible existence of solar wind control of these emissions • to detect possible weaker sources of emissions or possible emissions modulation of the Jovian-moons interaction at higher frequencies

Radio emissions controlled by the Galilean satellites (except Io)

RPWI Team Meeting, 19-20 Sep. 2010, Roma

Ganymede as a source of radio emissions

Galileo Observations:• Intense plasma waves detected over a region of space nearly 4 times Ganymede’s diameter caused by its strong magnetic field (Gurnett et al., Nature, 1996)• Different type of waves: whistler-mode emissions, upper hybrid waves, electrostatic electron cyclotron waves and escaping radio-emissions

With:- orbit insertion of the JGO spacecraft around Ganymede, and- MLA measuring magnetic fluctuations at high frequencyit would be possible:• to solve the problem of wave identification in the close vicinity of Ganymede, by distinguishing between electrostatic and electromagnetic wave modes • to determine the averaged refractive index of waves Frequency-time spectrograms of the electric (a)

and magnetic (b) field intensities detected by the Galileo plasma wave instrument during the 27 June 1996 Ganymede fly-by, after Gurnett et al. (1996)