RADIO SOUNDING IN THE MAGNETOSPERE AND TOPSIDE IONOSPHERE
description
Transcript of RADIO SOUNDING IN THE MAGNETOSPERE AND TOPSIDE IONOSPHERE
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RADIO SOUNDING IN THE MAGNETOSPERE AND TOPSIDE
IONOSPHERE
BW Reinisch1, DM Haines1, RF Benson2, K Bibl1, G Cheney1, SF Fung2, J Grebowsky2, JL Green2, X Huang1, R Manning3, and WWL Taylor4
1- University of Massachusetts Lowell, 2- NASA Goddard Space Flight Center,
3- Observatoire Paris-Meudon, 4- Raytheon STX
Deutsche URSI TagungKleinheubach
28. September 1998
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Space Weather Connection
• Solar Wind Effects
• Changing Magnetopause
• Changing Plasmasphere
• High Latitude Ionosphere
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OUTLINE
• The IMAGE Mission and RPI• http://image.gsfc.nasa.gov• http://ulcar.uml.edu/rpi
• The WARNING Mission and TOPADS • http ://www.rada.kiev.ua
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IMAGE Instruments
• Neutral Atom Imagers– High Energy Neutral Atom (HENA) imagers– Medium Energy Neutral Atom (MENA)
imagers– Low Energy Neutral Atom (LENA) imagers
• FUV Imagers– Spectrographic Imager (SI)– Geocorona (GEO) imager– Wideband Imaging Camera (WIC)
• EUV Imager– Extreme Ultra-Violet (EUV) imager
• Radio Sounder– Radio Plasma Imager (RPI)
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Orbital Characteristics
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Spectrographic Imager (SI)• SI Observations
– Far ultraviolet imaging of the aurora– Image full Earth from apogee
• Measurement Requirement– FOV: 15°x 15° for aurora (image full Earth from
apogee), – Spatial Resolution: 90 km– Spectral Resolution (top): Reject 130.4 nm and
select 135.6 nm electron aurora emissions.– Spectral Resolution (bottom): 121.6 nm
• Storm/substorm Observations– Image Time: 2 minutes generating 720
images/day• Derived Quantities
– Structure and intensity of the electron aurora (top)
– Structure
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Simulated RPI Plasmagram
• RPI browse product data will produce plasmagrams
• Echoes shown in solid line, density features in dashed line.
• Derived Quantities from Plasmagrams include:– Distance to Magnetopause,
Plasmapause, Polar Cusp (when observed)
– Magnetospheric shape (with model), structure, gross irregularities
– Storm conditions from a plasma/radio wave perspective
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Simulated RPI Plasmagram
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Space Weather Measurements
Instrument Data Product Derived Quantities
RPIPlasmagramEchomapf-t Spectrogram(1/orbit)
Distances toMagnetopause,Plasmapause, and PolarCusp,Ne ProfilesMagnetospheric Shapeand Irregularities,Storm Conditions
TOPADSIonogramEchomap
Topside ProfilesIrregularity StructuresPlasma Convection
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RPI Specifications
ITEM Spec. CommentRad. Power ≤40 W ≤10 W/monop.Antennas 3 orth. dipoles 2x500m, 20mFrequencies 3 kHz–3 MHz 10-1-105 e/cm-3
Bandwidth 300 Hz MatchedPulse Width 3.2 ms ? 480 km res.Range 20 RE SNR depend.
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RPI Waveforms
• short pulse (3.2 ms)
• long pulse (125ms)
• half-sec pulse
• 2-sec pulse
• n-chip complimentary phase codes,n=4,8,16
• chirp pulse (125 ms)
• staggered pulse sequence (768 chips)
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RPI Operational Modes
• Echo Sounding w. Antenna Tuning
• Relaxation w/o Antenna Tuning• Whistler Excitation (transmit f, receive diff. f’s)
• Thermal Noise Passive Reception
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Electric Field Ellipse+X +Y
+Z
E-Plane Normal = E x E’ EE’
Echo Amplitude = E2 + E'2
Polarization = Direction of E-Plane Normal
E
E’
E’ is phase quadrature sample of E
Radio Imaging
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Mapping of Reflection Points
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TOPSIDE AUTOMATED DOPPLER SOUNDER
TOPADS
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TOPADS Specifications
ITEM Spec. Comment
Rad. Power ≤ 10 W 1 dipole
Antennas 3 orth. dipoles 20 m each
Frequencies 0.5–30 MHz 103-107 el/cm-3
Bandwidth 30 / 4 kHz matched
Pulse Width 8x33 / 267 μs ? 5 km res.
Range 3000 km vertical&duct
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ISIS Topside Ionogram showing Plasma Resonance Modes
fN = O-mode Plasma ResonancefH = Gyro ResonancefT = Upper Hybrid ResonancefX = X-mode Plasma ResonancefZ = Z-mode Plasma Resonance
Plasma resonance frequencies provide In-situ Ne and Magnetic Field Intensity
Remote echoes provide vertical Ne profiles
Topside Sounding - 1971
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TOPADS Signal Processing
• High receiver sensitivity - 125 nV
• pulse compression - compl. phase code
• spectral coh. integration - ±1 kHz, 0.1 Hz res.
• chirping
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Topside Irregularity Measurement
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Signal/Noise for 20m Antennas
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Radiated Power vs Frequency - 20m Dipole
1
10
100
1000
10000
0.2 0.6 1 1.4 1.8 2.2 2.6 3 3.4 3.8 4.8 5.8 6.8
Freq (MHz)
Ia(mA)
Va
Pi (W)
Prad (mW)
Antenna Performance (20m Tuned Dipole)
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BACKUP
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Complementary CodePulse Compression
0 4 8 12 16 20t
(ms)
Code 1 Code 2
XmitPulse
XmitPulse
Echo Echo
Transmitted Pulsesand Raw Echoes(PRR = 100 Hz)
0 4 8 12 16 20t
(ms)
Received Echoesafter Compression(Effective PRR = 50 Hz)
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Sum CODE 1 + CODE 216a 16a
32a
+Code 1 Code 2
ResultSignal ProcessingGain = 15 db.
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Doppler Integration(8 Complementary Pulse Pairs, 1 Frequency, 2 Polarizations, 200 Hz PRR)
Echoes from 8 pulses Spectrum at 300 km
Signal Processing Gain = 9 db.
FFT
h(km)
t(ms)
020
406080100120
140
100 200 300 400 500 600
Samples at 300 km.
+3.13f
(Hz)-3.13
-9.38-15.6
+9.38+15.6+21.9
-21.9
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90140 190 240 290 340 390 440 490 540
-3.75
-2.06
-0.37
1.32
3.01
0
100
200
300
400
500
600
700
600-700
500-600
400-500
300-400
200-300
100-200
0-100
Actual Doppler SpectraMillstone Hill - CORIS DPS1 30-Jun-1997
(Courtesy of Alain Thomas)
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Sample Ionogram
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Quadrature Sampling
0 2 4 6 8 10 12 14t
(µs)
I Sample
Q Sample