PWI

Plasma Wave Investigation (PWI)

External view of the Mio spacecraft and the location of the PWI sensors [Figure 3 of Kasaba et al., 2020].

Measurement Principle

The Plasma Wave Investigation (PWI) aboard the BepiColombo Mio (Mercury Magnetospheric Orbiter, MMO) (Kasaba et al. 2020a) will enable the first observations of electric fields, plasma waves, and radio waves in and around the Hermean magnetosphere and exosphere. The PWI has two sets of receivers (EWO with AM2P, SORBET) connected to two electric field sensors (MEFISTO and WPT) and two magnetic field sensors (SCM: LF-SC and DB-SC). After full deployment of all sensors following insertion into Mercury orbit, the PWI will start its measurements of the electric field from DC to 10 MHz using two dipole antennas with a 32-m tip-to-tip length in the spin plane and the magnetic field from 0.3 Hz to 20 kHz using a three-axis sensor and from 2.5 kHz to 640 kHz using a single-axis sensor at the tip of a 4.5-m solid boom extended from the spacecraft’s side panel. Those receivers and sensors will provide (1) in-situ measurements of electron density and temperature that can be used to determine the structure and dynamics of the Hermean plasma environment; (2) in-situ measurements of the electron and ion scale waves that characterize the energetic processes governed by wave–particle interactions and non-MHD interactions; (3) information on radio waves, which can be used to remotely probe solar activity in the heliocentric sector facing Mercury, to study electromagnetic-energy transport to and from Mercury, and to obtain crustal information from reflected electromagnetic waves; and (4) information concerning dust impacts on the spacecraft body detected via potential disturbances.

Members

Principal Investigator
Yasumasa Kasaba (Tohoku University, Japan)
Co-PI of PWI (EWO)
Hirotsugu Kojima (Kyoto University, Japan)
Co-PI of PWI (SORBET)
Karine Issautier (LESIA Observatoire de Paris, France)
Co-PI of PWI (MEFISTO)
Jan-Erik Wahlund (IRFU, Sweden)
Co-PI of PWI (LF-SC)
Satoshi Yagitani (Kanazawa University, Japan)
Lead Co-I of PWI (AM2P)
Pierre Henri (LPC2E & Lagrange, France)
Lead Co-I of PWI (MEFISTO)
Tomas Karlsson (KTH, Sweden)
Lead Co-I of PWI (MDP-PWI)
Yoshiya Kasahara (Kanazawa University, Japan)
Lead Co-I of PWI (WPT)
Atsushi Kumamoto (Tohoku University, Japan)
Lead Co-I of PWI (DB-SC)
Fouad Sahraoui (LPP-Ecole Polytechnique, France)

Sub-instruments of PWI

Subunits of the PWI and their providers [Table 2 of Kasaba et al., 2020]

Receivers Installed in PME [PWI-MGF Electronics box]
EWO EFD [Electric Field Detector],
WFC [Wave-Form Capture], and
OFA [Onboard Frequency Analyzer]		 Kyoto Univ. (Japan) with Japan: Kanazawa Univ., Toyama Pref. Univ., Tohoku Univ.
SORBET [Spectroscopie Ondes Radio & Bruit Electrostatique Thermique] LESIA, CNRS, Observatoire de Paris (France)
AM2P [Active Measurement of Mercury’s Plasma] LPC2E/CNRS (France)
Sensors
WPT [Wire-Probe anTenna] Tohoku Univ. (Japan) with Japan: JAXA, Toyama Pref. Univ., Kyoto Univ.
MEFISTO [Mercury Electric Field In-Situ Tool] KTH (Sweden) with
Sweden: IRF-Uppsala
Finland: Finnish Meteorological Inst.,
Norway: Univ. Oslo
France: LPC2E
LF-SC [Low-Frequency Search Coils] Kanazawa Univ. (Japan)
DB-SC [Dual-Band Search coil] LPP/CNRS, Ecole Polytech. (France)
MDP [Mission Data Processor] MDP team (Tohoku Univ., JAXA)
PWI Software Kanazawa Univ. (Japan) with
Japan: Tohoku Univ., Kyoto Univ.
Hungary: Eotvos Univ. (Hungary)
with receiver teams
Extension Control Software MAST+WPT team (JAXA, Tohoku Univ.)

Primary scientific objectives of the PWI

Summary of the primary scientific objectives of the PWI [Table 3 of Kasaba et al., 2020]

Scientific objectives Receivers Sensors
E-field B-field
EWO SORBET AM2P WPT
MEFISTO		 LF-SC DB-SC
Global structure and dynamics of the Hermean plasma environment Global characterization of plasma densities and temperatures x x x x
Global convections in the plasma environment x x
Global connection between the plasma environment and the planet without the ionosphere x x x x x
Global response of the plasma environment to the solar wind x x x x x x
Global wave propagations in the plasma environment x x x x x
Supply to and loss in the plasma environment x x x x x x
Energy transfer and scale coupling processes in the Hermean plasma environment Characterizations of the Hermean substorms and reconnections x x x x x x
Global distributions of electron and ion scale waves x x x x
Waves at boundaries and transition regions x x x x x
Characterizations of the Hermean aurora x x x x x x
Characterization of the non-gyrotropic effects x x x x x
Solar wind and interplanetary environment in the inner solar system Probing the solar activity facing Mercury by the radio-wave measurements x x x x
In-situ solar wind measurements in the inner solar system x x x x x x
Characterizing the interplanetary dusts in the inner solar system x x

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