HF PROPAGATION Results : Metal Oxide Space Cloud (MOSC) Experiment

Size: px

Start display at page:

Download "HF PROPAGATION Results : Metal Oxide Space Cloud (MOSC) Experiment"

Lorena Snow
5 years ago
Views:

1 HF PROPAGATION Results : Metal Oxide Space Cloud (MOSC) Experiment Dev Joshi Research Assistant Department of Physics, Boston College(BC) Institute For Scientific Research(ISR), BC ISR SEMINAR 1

2 Ionospheric Modification Experiments Rocket Ionosphere Metal Vapor Release HF Tx ALTAIR Incoherent Scatter RADAR HF Rx Two types of Ionospheric modification experiments : Ionization Depletion Ionization Enhancement 2

3 HF PROPAGATION Results : Metal Oxide Space Cloud Experiment Outline : Introduction Ionosphere Modification Experiment HF propagation in ionosphere Observations Modeling Results Conclusions 3

Ionospheric Modification Experiments Ionospheric Modification Experiments: Various materials have been injected into the high atmosphere creating perturbations to the ambient medium.

4 Ionospheric Modification Experiments Ionospheric Modification Experiments: Various materials have been injected into the high atmosphere creating perturbations to the ambient medium. To detect plasma drift velocities and electric fields. To create artificial comets. To exploit the ionosphere and magnetosphere as a plasma laboratory without walls. To increase or decrease the plasma density in the ionosphere to trigger large scale phenomenon. Payload for each rocket included Two canisters of samarium (5 kg yield) Dual Frequency RF Beacon (NRL CERTO) Ground diagnostics from 5 sites included: Incoherent Scatter Radar,GPS/VHF Scintillation Rxs, All-Sky Cameras, Optical Spectrograph, Ionosondes, Beacon Rx, HF Tx/RX 4

107 minutes (d) after the Shuttle thruster firing in Space Lab 2 mission.

5 Ionization Depletion and Enhancement Ionization Depletion Chemistry H 2 O, H 2, SF 6 An example with water and hydrogen molecules These panels show pre-event conditions (a) and the resultant perturbations at 14 minutes (b), 40 minutes (c), and 107 minutes (d) after the Shuttle thruster firing in Space Lab 2 mission. Ionization Enhancement Barium, Strontium, Xenon, Lithium, or Cesium: Photoionization Lanthanides: Photoionization and Chemi- ionization An image of enhanced plasma in MOSC experiment 5

6 RF propagation : Appleton formula The Appleton formula: n 2 = µ i χ 2 = 1 1 iz Y T 2 X 2 1 X iz ± Y T 4 1 X iz 2 +YL where, X = Ne2 є 0 mω 2, YL = ebl/mω, Y T = eb T /mω and Z = υ/ω A magnetoplasma is birefringent and anisotropic. Two characteristic modes Possible: + Ordinary mode - Extraordinary mode Reflection Condition: The positive sign : X = 1 And the negative sign gives X = 1 Y, X = 1 + Y Ordinary Wave Extra-ordinary Wave 6

7 RF propagation : Appleton formula When collisions are negligible : n 2 = µ 2 = 1 When the magnetic field is negligible : 2X(1 X) 2(1 X) Y T 2 ± Y T X 2 Y L n 2 = µ i χ 2 = 1 X 1 iz When both collisions and magnetic field effects are negligible : n 2 = µ 2 = 1 X = 1 f N = 9 N = ω p = n o e 2 2π ϵ 0 m Cold Plasma No collisions No magnetic field f N f 2 ; f N ; N is in electrons per cubic meter = plasma frequency Higher Electron Density Lower Electron Density α α Lower Refractive Index Higher Refractive Index α > α Refraction of radio waves by the ionosphere due to the changes in 7 the electron density

8 Determination of Electron Densities A T = Transmitter R = Receiver A Real Path Virtual Path B B Ionosphere Vertical Oblique Earth T R T C R Virtual Height : h = c h r 0 dh u h = r μ dh 0 8

9 Determination of Electron Densities Ionosonde Measures electron density profile up to the peak density height only (f f peak ) Incoherent Scatter Radar Measures direct scatter from electrons providing full height density profile (f >> f peak ) 9

ALTAIR Radar Advanced Research Project Agency (ARPA) Long-range Tracking and Identification Radar (ALTAIR) Dual Frequency: 150 MHz/422 MHz Max Bandwidth: 7

10 ALTAIR Radar Advanced Research Project Agency (ARPA) Long-range Tracking and Identification Radar (ALTAIR) Dual Frequency: 150 MHz/422 MHz Max Bandwidth: 7 MHz/18 MHz 46 m dish Peak Power VHF: 6.0 MW UHF: 6.4 MW Incoherent Scatter: Direct scatter from electrons in the ionosphere (10-4 m 2 ; equivalent to a ~dime!) 10

Transmitter/Receiver Geometry Rongelap N E Wotho MOSC Release Location & Likiep-Wotho Mid-Point Likiep ALTAIR Rongelap-Wotho link geometry is predominantly N-S and

11 Transmitter/Receiver Geometry Rongelap N E Wotho MOSC Release Location & Likiep-Wotho Mid-Point Likiep ALTAIR Rongelap-Wotho link geometry is predominantly N-S and great-circle path is far from release region Likiep-Wotho path is nearly E-W and release point lies nearly on mid-point of the link should be ideal for observing SmO+ layer 11

12 Kwajalein Atoll 12

13 Roi Namur 13

14 THE RELEASE : MOVIE 14

15 CLOUD 15

and Spread F formed within minutes after release

16 Two Releases : 01 May and 09 May 2013 Ionosphere during first release was disturbed, rising rapidly and Spread F formed within minutes after release Ionosphere during second release is canonical quiescent 16

Mission 41102 09 May 2013 Pre-Release Sweep Wotho Receiver Rongelap TX Likiep TX F region second hop F -region Ground Wave Sweeps from 2-30 MHz were completed every five (5) minutes - Plots show data

17 Mission May 2013 Pre-Release Sweep Wotho Receiver Rongelap TX Likiep TX F region second hop F -region Ground Wave Sweeps from 2-30 MHz were completed every five (5) minutes - Plots show data from only 2-14 MHz since no signatures were observed at higher frequencies Slightly higher peak frequencies on Wotho Likiep path relative to Rongelap-Wotho links probably due to longer path length, lower elevation angle propagation. 17

18 Mission May st Post-Release Sweep Wotho Receiver Rongelap TX Likiep TX F-layer Secondary Echo MOSC layer MOSC layer On the Wotho geometry the layer extends up to 10 MHz peak frequency There is also a prominent secondary F region echo; the time delays will allow us to calculate the range offsets The discrete nature of the echo suggests a localized perturbation that extends up to the F- region peak 18

Mission 41102 09 May 2013 2 nd Post-Release Sweep Wotho Receiver Rongelap TX Likiep TX F-layer Secondary Echo F-layer Secondary Echo MOSC layer MOSC layer The layer has now decreased to about 6 MHz

19 Mission May nd Post-Release Sweep Wotho Receiver Rongelap TX Likiep TX F-layer Secondary Echo F-layer Secondary Echo MOSC layer MOSC layer The layer has now decreased to about 6 MHz peak density The F-region perturbation extends only mid-way up the density profile The delay is much greater on the Rongelap link geometry compared to the Wotho geometry providing valuable information on the nature of the perturbation 19

Mission 41100 01 May 2013 3 rd Post-Release Sweep Wotho Receiver Rongelap TX Likiep TX MOSC layer?

20 Mission May rd Post-Release Sweep Wotho Receiver Rongelap TX Likiep TX MOSC layer? F region perturbation No clear signatures on Rongelap link A bottomside F-region perturbation remains on the Wotho-Likiep link, as well as a possible MOSC layer signature around 4 MHz 20

21 Second Release: 09 May

22 Ionospheric Models Goal : Model the Background Ionosphere and the Cloud Background Ionosphere : International Reference Ionosphere (IRI) Standard model of the empirical ionospheric climatology Developed by joint working group of Committee on Space Research (COSPAR) and International Union of Radio Science (URSI) Input variables : R12, iono_layer_parms = [fof2,hmf2,fof1,hmf1,foe,hme] Parametrized Ionospheric Model (PIM) Global model of theoretical ionospheric climatology Combination of four physics-based numerical ionospheric models Input Variables : F10.7 index, SSN, K p index Plots courtesy of William McNeil 22

23 IRI and ALTAIR Profiles BEFORE 30 SEC AFTER Approximately 30 seconds after release the MOSC cloud has a peak density of about 10 6 e - /cc, slightly less than the background ionosphere (Ne = 10 6 corresponds to a plasma frequency of 9 MHz). The layer is about 30 km in diameter by this time. 23

24 MOSC Launch 2: May 9, 2013 Modeling the Cloud Time Period for Modeling Cloud 24

25 MOSC Launch 2: May 9, 2013 Modeling the Cloud The averaged and symmetrized cloud profile is used to model the cloud in MATLAB with latitude/longitude increment at degree and height increment at km. The central pixel corresponds to MHz 25

$Ray Tracing Haselgrove Equations: Fermat s principle - δ mds = 0, m is ray refractive index and ds the element of path length Variational method ray path equations dx i = G, du i = - G ; G = u μ dt u$

26 Ray Tracing Haselgrove Equations: Fermat s principle - δ mds = 0, m is ray refractive index and ds the element of path length Variational method ray path equations dx i = G, du i = - G ; G = u μ dt u i dt x i Numerical Integration of ray path equations : Runge Kutta method Coleman Method : Point to point ray tracing Variational principle is discretized and resulting discretized equations solved PHaRLAP: HF radio wave ray tracing toolbox developed by DSTO, Australia 2D raytracing is an implementation of the 2-D equations developed by Coleman 3-D engine is based upon the equations of Haselgrove 26

27 Ray Tracing : Example 27

28 3D Ray Trace Analysis Rongelap To Wotho Rongelap Wotho MOSC Release Point HF signals received well off the great circle path to the receiver The artificial cloud bends the HF energy through large angles Excellent agreement between model and observations 28

29 3D Ray Trace Analysis Likiep To Wotho Wotho MOSC Release Point Likiep Likiep MOSC Wotho Great circle path to the receiver passes through the MOSC volume Multiple paths between ionosphere, cloud and receiver expected 29

Mission 41100 01 May 2013 Pre-Release Sweep Wotho Receiver Rongelap

30 Mission May 2013 Pre-Release Sweep Wotho Receiver Rongelap TX Likiep TX F-region Second hop F -region E - layer Ground Wave 30

Mission 41100 01 May 2013 1 st Post-Release Sweep Wotho Receiver Rongelap TX Likiep TX F-layer Secondary Echo MOSC layer MOSC layer Note that the

$One possibility is that the lower frequency components on the direct Likiep-Wotho link were actually blocked, refracted or ducted by the presence of$

31 Mission May st Post-Release Sweep Wotho Receiver Rongelap TX Likiep TX F-layer Secondary Echo MOSC layer MOSC layer Note that the Likiep signature is only evident in high end of frequency range, showing up near f = 8 MHz (~07:42 UT); one might conclude this is results from the temporal evolution of the cloud, yet the Rongelap link shows the signature beginning at less than 4 MHz at least 40 seconds earlier. One possibility is that the lower frequency components on the direct Likiep-Wotho link were actually blocked, refracted or ducted by the presence of the MOSC cloud. 31

Mission 41100 01 May 2013 2 nd Post-Release Sweep Wotho Receiver Rongelap TX Likiep TX MOSC layer MOSC layer

32 Mission May nd Post-Release Sweep Wotho Receiver Rongelap TX Likiep TX MOSC layer MOSC layer Peak density has decreased significantly over 5 minute time scale, primarily due to expansion of the cloud 32

Mission 41100 01 May 2013 3 rd Post-Release Sweep Wotho Receiver Rongelap TX Likiep TX MOSC layer F region perturbation The Rongelap path shows a low density

33 Mission May rd Post-Release Sweep Wotho Receiver Rongelap TX Likiep TX MOSC layer F region perturbation The Rongelap path shows a low density residual signature of the cloud The Likiep path shows an emerging perturbation in the F-region By 07:56 and beyond MOSC has disappeared and Spread F dominates 33

34 First Release: 01 May

an altitude. The technique is applied at all altitudes.

35 MOSC Launch 1: May 1, 2013 Modeling the Ionosphere The ALTAIR is modelled by applying the same relative differences as in PIM in lat-lon plane at an altitude. The technique is applied at all altitudes. As is seen, modeled ALTAIR fails to capture the shape of the high frequency tilt in PIM. 35

36 MOSC Launch 1: May 1, 2013 Modeling the Ionosphere The change in height of the peak density across longitudes in PIM isn t seen in the modeled ALTAIR ionosphere. 36

37 MOSC Launch 1: May 1, 2013 Modeling the Ionosphere An averaged shape function is chosen to apply to the change in the height of the peak density across longitudes. 37

38 MOSC Launch 1: May 1, 2013 Modeling the Ionosphere The applied shape function produced delay in good agreement except 9 MHz. 38

39 MOSC Launch 1: May 1, 2013 Modeling the Ionosphere The anchor profile is taken to be the average of three ALTAIR radar profiles. This gives delay to a good agreement with the observations. 39

40 MOSC Launch 1: May 1, 2013 Modeling the Ionosphere The modeled bottomside is in good agreement while the top side is above the observations. The removal of tilt due to the shape function shows further disagreement as it raises the upside. 40

41 Modeling : Optimization Method Optimization : Nalder Mead Down Hill Simplex Method ( Amoeba)* Nelder, J. and R. Mead,1965 Direct Method : No derivatives, only function values Idea : Move from high function (hot) areas to low function (cold) areas by reflections, expansions and contractions Amoeba Crawls Downhill with no assumption about function Built-in function in MATLAB : fminsearch *Minimization Technique suggested by Dr. Charles Carrano, ISR 41

42 Optimization : Model Ionosphere PIM doesn t have enough degrees of freedom to fit the ALTAIR radar profile while optimization of fof2 and hof2 in IRI closely matches the observed ALTAIR radar profile. Scale Vector = [ a b c. e] 42

43 Optimization : Delay results The IRI model, scaled and unscaled, doesn t match the observed delay. 43

44 Optimization : Delay results Optimization of the scaling vector matches only the upside Frequency specific optimization of the scale vector exactly reproduces the observed delay. 44

45 Conclusions Ray tracing confirms sounder observations to high degree of fidelity The change in ambient natural propagation environment due to small artificial modification can be successfully modeled Effects from arbitrary artificial plasma environments can be predicted with accuracy Optimization technique represents a new method of assimilating oblique ionosonde data to generate the background ionosphere (numerous applications for HF systems) Future Work : Modeling of natural disturbances in the low latitude propagation environment to understand the effects of Traveling Ionospheric Disturbances (TIDs) and Spread F on perpendicular and quasi-parallel (to B) paths. 46

46 Thank You. 47

Plasma Turbulence of Non-Specular Trail Plasmas as Measured by a High Power Large Aperture Radar

Space Environment and Satellite Systems Plasma Turbulence of Non-Specular Trail Plasmas as Measured by a High Power Large Aperture Radar Jonathan Yee and Sigrid Close Stanford University January 9, 2013