UMASS Lowell

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