Introduction RRI – SuperDARN experiment Magnetoionic theory Results Conclusions

Radio wave power distribution at HFfrequencies as modelled for the Radio

Receiver Instrument (RRI) on the ePOPsatellite mission

G. C. Hussey, R. G. Gillies, G. J. Sofko, and H. G. James

SuperDARN Workshop 201130 May– 3 June

Dartmouth College, Hanover, New Hampshire, USA

Hussey et al. ISAS Dept. of PEP

HF radio wave power distribution

Introduction RRI – SuperDARN experiment Magnetoionic theory Results Conclusions

Outline

◮ Introduction◮ CASSIOPE-ePOP / RRI-SuperDARN experiment◮ Magnetoionic theory◮ Results◮ Conclusions

Hussey et al. ISAS Dept. of PEP

HF radio wave power distribution

Introduction RRI – SuperDARN experiment Magnetoionic theory Results Conclusions

The CASSIOPE – ePOP satellite◮ CAScade, Smallsat, and Ionospheric Polar Explorer

satellite◮ launch in late 2011??, 350–1500 km, elliptical, polar orbit◮ 8 scientific instruments constitute enhanced Polar Outflow

Probe (ePOP) mission◮ Radio Receiver Instrument (RRI) will measure radio waves

transmitted from ground-based radars such asSuperDARN

Hussey et al. ISAS Dept. of PEP

HF radio wave power distribution

Introduction RRI – SuperDARN experiment Magnetoionic theory Results Conclusions

RRI-SuperDARN experiment

Hussey et al. ISAS Dept. of PEP

HF radio wave power distribution

Introduction RRI – SuperDARN experiment Magnetoionic theory Results Conclusions

HF propagation in ionosphere

◮ Two Propagation modes (O- and X-modes)◮ Quasi-longitudinal (QL) propagation:

◮ wave propagation roughly parallel to B-field◮ modes have circular polarization states of opposite sense

◮ Quasi-transverse (QT) propagation:◮ wave propagation roughly perpendicular to B-field◮ modes have linear polarization states

◮ Between QL and QT propagation, two ellipses of oppositesense propagate

Hussey et al. ISAS Dept. of PEP

HF radio wave power distribution

Introduction RRI – SuperDARN experiment Magnetoionic theory Results Conclusions

Magnetoionic Polarization States

+ =

O−Mode Polarization

=

=

+

+

Resultant PolarizationX−Mode Polarization

QT Propagation

QL Propagation

In Between QT and QL

Hussey et al. ISAS Dept. of PEP

HF radio wave power distribution

Introduction RRI – SuperDARN experiment Magnetoionic theory Results Conclusions

SuperDARN Geometry

South

North

East

x−axis

West

Initial electric field orientation

Ray path through ionosphere

Magnetic field lines

(Transmitter location)

z−axis

y−axis

lie in xz−plane

Hussey et al. ISAS Dept. of PEP

HF radio wave power distribution

Introduction RRI – SuperDARN experiment Magnetoionic theory Results Conclusions

Mode Power Modelling◮ Upon entering the ionosphere, EM wave splits into the two

allowed modes

Initial polarization

O−mode

External B−field

y−axis

X−modex−axis

z−axis

Hussey et al. ISAS Dept. of PEP

HF radio wave power distribution

Introduction RRI – SuperDARN experiment Magnetoionic theory Results Conclusions

X-mode Relative Power (Saskatoon SD, 12.5 MHz)

X-mode relative power (dB)

0.00

10.0

20.0

30.0

40.0

N

EW

S

Elevation Angle = 0o

30o

60o

Magnetic North

Boresight

Hussey et al. ISAS Dept. of PEP

HF radio wave power distribution

Introduction RRI – SuperDARN experiment Magnetoionic theory Results Conclusions

X-mode Relative Power (PrinceGeorge SD, 12.5 MHz)

X-mode relative power (dB)

0.00

10.0

20.0

30.0

40.0

N

EW

S

Elevation Angle = 0o

30o

60o

Magnetic North

Boresight

Hussey et al. ISAS Dept. of PEP

HF radio wave power distribution

Introduction RRI – SuperDARN experiment Magnetoionic theory Results Conclusions

Consequence for HF Propagation Modelling

◮ backscatter by SuperDARN is dominated by X-mode (QT)due to radar geometry:

◮ north viewing radar with horizontally polarized wave →

essentially QT X-mode◮ ray path modelling may be better represented by X-mode

as opposed to O-mode◮ for transmitter frequencies near the plasma frequency:

◮ propagation and refractive index of modes can besignificantly different

◮ choice of appropriate mode to model is important

Hussey et al. ISAS Dept. of PEP

HF radio wave power distribution

Introduction RRI – SuperDARN experiment Magnetoionic theory Results Conclusions

Relative Power at RRI; altitude 1500 km; X = f 2p /f 2

radar

Extraordinary Mode Relative Power (X > 0.3)

0 20 40 60 80Latitude

0

5

10

15

20

25

Rela

tive

Pow

er (d

B)

f=14.5 MHz, Ne=1012 m-3, X=0.384

f=9.5 MHz, Ne=5*1011 m-3, X=0.447

f=12.5 MHz, Ne=1012 m-3, X=0.516

Tx

Hussey et al. ISAS Dept. of PEP

HF radio wave power distribution

Introduction RRI – SuperDARN experiment Magnetoionic theory Results Conclusions

Relative Power at RRI

Extraordinary Mode Relative Power (0.1 < X < 0.3)

0 20 40 60 80Latitude

0

5

10

15

20

25

Rela

tive

Pow

er (d

B)

f=14.5 MHz, Ne=5*1011 m-3, X=0.192

f=12.5 MHz, Ne=5*1011 m-3, X=0.258

Tx

Hussey et al. ISAS Dept. of PEP

HF radio wave power distribution

Introduction RRI – SuperDARN experiment Magnetoionic theory Results Conclusions

Relative Power at RRI

Extraordinary Mode Relative Power (X < 0.1)

0 20 40 60 80Latitude

0

5

10

15

20

25

Rela

tive

Pow

er (d

B)

f=14.5 MHz, Ne=1011 m-3, X=0.038

f=12.5 MHz, Ne=1011 m-3, X=0.051

f=9.5 MHz, Ne=1011 m-3, X=0.089

Tx

X−mode−only band

Hussey et al. ISAS Dept. of PEP

HF radio wave power distribution

Introduction RRI – SuperDARN experiment Magnetoionic theory Results Conclusions

Conclusions

◮ relative power distribution between O- and X-modes ofwave propagation were modelled for SuperDARN

◮ SuperDARN geometry results in X-mode polarizationdominating the transmitted signal at low elevation angleswhere:

◮ radar waves propagate in QT regime◮ backscatter is typically received by SuperDARN

◮ overhead and behind transmitter, propagation is mostly QLand the two modes have comparable power

◮ SuperDARN-RRI experiment will allow for a more detailedstudy of the scatter volume physics, as well as thelarge-scale ionospheric state

Hussey et al. ISAS Dept. of PEP

HF radio wave power distribution