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Solar Radiophysics with HF Radar
Workshop on Solar RadiophysicsWith the Frequency Agile Solar Radiotelescope (FASR)
23-25 May 2002Green Bank, WV
Paul RodriguezInformation Technology DivisionNaval Research LaboratoryWashington, DC The Solar & Lunar HAARP
Ionosphere
Magnetosphere
Selenosphere
Solar Wind
Solar Corona
Radial Distance
Effective Radiated
Power
Modification (growth and decay scales of irregularities)Long distance radiowave propagationDensity irregularity spectrumMeteor showers (Leonids; dusty plasmas)
Boundary and global scale dynamicsResponse to geomagnetic stormsMagnetospheric wave-particle interactions
Solar wind large scale density structuresBow shock irregularities and dynamics
Lunar surface penetration by HF radiowavesCharged lunar dust atmosphere?Lunar wake structure
Detection of near earth asteroids, comets
Detection of CMEs & prediction of geomagnetic stormsDensities, temperatures of solar coronaLarge scale structure, dynamics, wave spectrum
Range of Space Experiments with HF Radiowaves
1000 MW100 MW10 MW1 MW0.1 MW
0.05 Re
15 Re
30 Re
60 Re
1 AU
Planetary Surfaces0.5 AU
El Campo, Texas Solar Radar Antenna Array
NNNNN
SSSSS
EEEEE WWWWW
Operating Frequency: 38.25 MHzTransmitting Dipoles: 128 x 8 EW
Receiving Dipoles: 128 x 8 EW
128 x 4 NS
Total Area: 18,000 m2
Antenna Gain: 32-36 dBBeam Size (NS x EW): 1o x 6 o
Total Power: 500 kWEffect. Radiated Power: 1300 MW
Operated byMIT/Lincoln Laboratory 1961-1969
Motivation for initial solar radar experiments
• to determine radar cross section of the solar corona(however, it was recognized there was no ‘hard surface’ )
• to investigate dynamics of solar corona
Present scientific motivation
• profile of corona electron density
• backscatter from a hot, magnetized plasma
• remote sensing of wave-particle interactions in the corona(small scale dynamics)
• measurement of large scale MHD (i.e., CMEs)
• understanding of nonthermal development of variousspectra (density fluctuations, waves, radio, etc)
• direct measurements of stellar plasma and how it affectsplanetary environment
Solar Radar Performance
The radar equation is Pt Gt Ar σ p
Pr = where: 4πR2 4πR2
Pr - received power (watts) σ - scattering cross-section (m2)
Pt - transmitted power (watts) p - polarization fractionGt - transmitting antenna gain R - range to scattering cross-section (m)Ar - receiving antenna area (m2) Ro - solar radius (m)
R = 1.5 x 1011 m (1 AU)Ro = 7 x 108 m (solar radius)σ ~ 1 π Ro
2 = 1.54 x 1018 m2 ( typical value obtained by El Campo)
p = 0.5 (one of two polarizations)
N = kB T(f) B (noise power of sun), where
kB = 1.38 x 10-23 watt-s °K-1 (Boltzman’s constant)T(f) = noise equivalent temperature of sun (°K) B = receiver bandwidth (Hz)
0
10
20
30
40
50
21000 21500 22000 22500 23000 23500 24000
El Campo Solar Radar (38.25 MHz)C
ross
Sec
tion
(πR
o2 )
Serial DayDay Month Year
30 Jun 61 16 Sep 6912 Nov 62 26 Mar 64 8 Aug 65 21 Dec 66 4 May 68
El Campo Corona Echo Signal Spectrum
Typical RDA spectrum.
Among spectral typesobserved were“high corona echoes,”which may have beenCME signatures.
However, CMEs were unknown in the 1960s.
CME
SolarRadar
Solar Radar Detection of Earthward-Directed Coronal Mass Ejections
Frequency Shift
Power
Corona CME
Transmitted
Received
0
100
200
300
400
0 200 400 600 800 1000 1200 1400 1600
HF Doppler Shift from Earthward Motion of Coronal Mass Ejection
f Dp (9 MHz)f Dp (25 MHz)f Dp (38 MHz)
Fre
quen
cy S
hift
(kH
z)
CME Velocity (km/s)
The Doppler shifts expected for HF radarfrequencies of 9, 25, and 38 MHz, for the rangeof CME velocities observed with coronagraphs.
-10 0 10OFF ON
UTR-2 Return Signal Spectra UT 0927-0943
-10 0 10
Time (sec) Relative to Transition
ON OFF
10 20 30 40 50 60 seconds
0 10 20 30 40 50 60 seconds
8.920 MHz
8.880 MHz
FullPowerON/OFF
SURA Transmitted Signal UT 0911-0927
Solar Radar Experiment 21 July 1996
FrequencyShift (kHz)
8.925 MHz
FrequencyShift (kHz)
8.885 MHz
44
0
44
0
0
2
4
6
8
10
-10 -5 0 5 10
SURA / UTR-2 Solar Radar 21 July 1996
8.925 MHz
8.885 MHz
Relative Intensity
Time (sec)
ON
ON
OFF
Transmission Patterns
OFF
4500
5000
5500
6000
6500
0 5 10 15 20 25 30 35 40
SURA / UTR-2 Solar Radar 21 July 1996
8.925 spec
8.885 spec
Relative Spectral Intensity
Frequency Shift (kHz)
ReceiverFrequency
Integrated Return Signal Time Profiles and Spectra
HAARP Research Facility
Operated by Advanced Power Technologies, Inc. under contract from U. S. Air Force/ Navy
Current DesignRadiating x-dipoles: 48 180
Total area (m2): 20,000 124,000Transmitters: 96 360Power (kW): 960 3600ERP (MW): 190 3200Frequencies (MHz): 2.8 to 8 2.8 to 10
Gakona, Alaska
0
10
20
30
40
50
60
70
80
90
30 61 91 122 152 182 213 243 274 304 335 365
Sun As Seen From HAARP at UT 2000 (o), 2100 (◊), 2200 (∆), 2300 (x)LT 1100 (o), 1200 (◊), 1300 (∆), 1400 (x)
Alt
itud
e (d
eg)
Day of Year (2000)
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Solar Radar Window
LOFAR: CONCEPTUALLAYOUT
EachLOFAR Station
consists of256 Active Dipolesabove their ground
screens
~ 160 m (5 acres)
LOFAR will be:
• ≥ 40 stations
• ≥ 10,000 dipoles
• ≥ 1 km2 collecting area– 20x Arecibo
• ∆ν ~ 10-250 MHz
• ≥ 2 independent beams
Possible LOFARStation sites
VLA
Los Alamos
New Mexico
Active dipole
Ground Screen
~ 1
met
er
-10
-5
0
5
10
15
20
25
30
0. 1 10 100 1000 10000
HAARP Frequency = 10 MHz
LOFAR Effective Area ~ 106 m2 Solar Radar X-Section = 1
Net
Sig
nal/
Noi
se R
atio
(dB
)
Integration Time (s)
3.2
0.9
0.3
TotalPower(MW)
5-dBThreshold
Present HAARP Power
Design HAARP Power
HALO Solar Radar
Initial HAARP Power
Summary and Conclusions
• Solar radar experiments will ‘open’ a new window onplasma physics of the sun and magnetosphere.
• Solar radar has applications to many other phenomena oflocal astrophysics.
• HAARP is capable of being a solar radar, in bistaticconfiguration with existing and planned receiving arrays.
• The CME detection problem and geomagnetic stormeffects at earth is a practical motivating issue.