radio wave power distribution at hf frequencies as
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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
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