Characteristics of the Jupiter Io‐D Decametric Radio Source
Collaborators:M. Imai, Kyoto UniversityK. Imai, Kochi National
College of Technology, JapanJ. Thieman, U. Md‐BaltimoreR. Flagg, RF AssociatesW. Greenman, WG Consulting
MOP 2015 1
Long Wavelength Array (LWA1), Socorro, NM
Chuck Higgins, Middle Tennessee State UniversityTracy Clarke, Naval Research LabFrancisco Reyes, U. of FloridaDave Typinski, AJ4CO Observatory
Acknowledgements:U. New MexicoTN Space Grant Consortium
The LWA1 Array
22
A collaboration of the following institutions: U. New Mexico, Virginia Tech, Los Alamos NL, JPL, the Naval Research Lab, Caltech, Harvard, NRAO, and the Air Force Research Lab
Imai et al., 2010
from Ellingson, IEEE, 2013Location Socorro, NM, near VLABandwidth 10‐88 MHzAntennas 256 crossed‐dipoles (sky
noise dominated)Polarizations Dual linearBandwidth 16 MHz x 2 tunings X 4
beamsBeams 4 independently‐steerable
2 tunings per beamBeam FWHM < 3.2 × [(74 MHz)/]Instrument 6 kJy at zenith System Equiv.
Sensitivity Flux Density (SEFD) [1 Jy = 10‐26 W/m2/Hz]
Beam Sensitivity ≈ 8 Jy (5σ) for 1 s, 16 MHz, Z = 0 (inferred from SEFD)
Array Geometry256 Antenna stands, 100 m x 110 m elliptical footprint + 2 outrigger antennas for calibrationPseudo‐random arrangement – to suppress aliasing
JupiterSpectra
01 Dec 2012
3
LWA1 Instrument•Excellent observing conditions•Fine Temporal & Spectral Resolution: 0.21 ms and 5 kHz•Data Volume: up to ~1 TB/hour
RHC Polarization
LHC Polarization
Stokes V
Upper TuningLower Tuning
Io‐A
Io‐C
For more informationPoster #8 T. Clarke: Probing Jovian DAM with the LWA1
Poster #9 M. Imai: Jupiter DAM common observations with LWA1, NDA, and URAN-2
Poster #41 K. Imai: Jupiter’s modulation lanes observed by LWA1
AJ4CO Observatory
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• 8‐element TFD Array• Polarizations: dual circular• HPBW 24 MHz: 30 EW, 12 NS at zenith• Beam steering: max 45 from zenith• Dual polarization Spectrograph (DPS), 16‐32 MHz Tunable, 2 MHz IF bandwidth
Terminated Folded Dipoles (TFD)
5
Radio Sources
Background Color Map: 50 years of University of Florida Radio Observatory (UFRO) data
bKOM – broadband kilometric emission
HOM – hectometricemission
Non‐Io‐DAM –decametric (related to HOM)
Io‐DAM – decametric emission tied to Io flux tube and Io torus
Io‐D Studies
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• Southern hemisphere source• f = < 3 ‐ 24.5 MHz• X‐mode emission• Highly LH circularly polarized (0.85)• Isolated arc structures (vertex early)• Io‐C/Io‐D emission cone
• Envelope shape caused by source along southern Io‐flux tube (Io’s frame)
• Io‐D Beaming angle 80
Queinnec and Zarka, 1998
Io‐B
Io‐D
Io‐D
Io‐D Observations
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• LH Circularly Polarized• Vertex Early arc structure
• Excellent correlation between AJ4CO (Florida) and LWA1 (New Mexico)
Stokes V
AJ4CO Observatory20 Jan 2015RCP
AJ4CO Observatory20 Jan 2015LCP
LWA1 Observatory20 Jan 2015
Freq
uency (M
Hz)
15 20
25
Io‐B
Io‐D
Io‐B
Io‐D
Io‐D Observations
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Stokes VLWA1 Observatory14 Nov 2013
Freq
uency (M
Hz)
12 14
16
LWA110 Jan 2015
fmax = 26 MHz
Io‐DModulation LanesS‐bursts
S‐bursts
L‐bursts
Io‐D Observations
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• CML and Io‐phase ranges need redefinition (f‐dependent)
• Peak frequency can tell us something about the emission cone
LWA Io‐D Observations * Peak frequency
Io‐DIo‐D
Io‐A Io‐C
Io‐B
non‐Io‐A
Io‐D S‐bursts
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AJ4CO Observatory20 Jan 2015
Span: 210 ms, Bandwidth: 2 MHzResolution: 205 us, 4.88 kHzS‐burst drift rates: – 10.5 MHz/s at 18 MHz
Span: 110 sRes.: 157 ms
53 kHz
RCP Io‐B S‐bursts
LCP Io‐D S bursts
LCP Io‐D narrow‐band S bursts
Io‐DS‐Bursts
Resolution: 0.25 ms and 10 kHzTimespan: 1.44 sS‐burst Drift Rates: –12 MHz/s at 19 MHz
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27 Dec 2012
From Clarke et al., 2014
Io‐D S‐burst Drift Rates
From Zarka et al., (1996)
• Io‐related emission• High‐Intensity millisecond bursts
• CMI emission: 5 keVelectrons accelerated from Io to Jupiter – Mirrored near Jupiter resulting in a loss cone of amplified X‐mode waves
• Adiabatic theory predicts the maximum drift rates (30 MHz/s)
S‐burst Drift Rate vs Frequency
How do the drift rates correlate with the sources?
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XXX
LWA1 & AJ4CO Io‐D Observations
X
Summary•Io‐D emission is prevalent•Io‐D CML and Io‐phase ranges need redefinition (f‐dependent)•Io‐D peak frequency = 26 MHz ‐‐‐> the southern hemisphere emission cone structure
•Io‐D modulation lanes•S‐bursts in Io‐D source are common – useful for emission theories
•LWA1 is an excellent instrument for Jupiter decameter studies‐ Excellent spectral and temporal resolution‐ Shows fine structures and polarization (Modulation lanes, L‐ and S‐
bursts, narrow band (N) events and S‐burst/N‐event interactions)
•LH and RH emission can be used for Faraday rotation studies
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Juno Mission – Ground‐based DAM Coordinated observations are being planned
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Data Reduction and Analysis
North
East
X
Y
Basis change to r, l
Use Fourier transforms to convert to frequency spectra
Convert to Stokes V V=R2‐L2
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