Some Recent Advances in Ionospheric Modification Research

Size: px

Start display at page:

Download "Some Recent Advances in Ionospheric Modification Research"

Nathaniel Owen
5 years ago
Views:

1 Some Recent Advances in Ionospheric Modification Research W. A. Scales Director, Center for Space Science and Engineering Research Bradley Department of Electrical and Computer Engineering Crofton Department of Aerospace and Ocean Engineering Virginia Tech, Blacksburg, Virginia HAARP Collaborations: A. Mahmoudian 1, M. Bordikar 1, H. Fu 1, A. Samimi 1, P. Bernhardt 2, S. Brisinski 2 and M. McCarrick 3 EISCAT Collaborations: H. Fu 1, S. Brisinski 2, A. Senior 4, M. Kosch 4, and M. Rietveld 5 1 Virginia Tech, Blacksburg, Virginia 2 Naval Research Laboratory, Washington D.C. 3 Marsh Creek. LLC, Gakone, Alaska 4 Lancaster University, Lancaster, UK 5 EISCAT Facility, Tromso, No

2 The old days at Cornell: circa Potential Space Scientist? Sounding Rocket Payload Space Plasma Wave Measurements injected ions Space-borne active experiment work at Cornell (with Prof. Paul Kintner) started my career off: Space Plasma Waves (particularly in the VLF range) Wave-Particle Interactions Perpendicular Ion Acceleration (so-called ion conics) An artificial way of replicating natural processes in the aurora borealis

3 Outline Overview of Ionospheric Modification Research Basics of Stimulated Electromagnetic Emission SEE during such experiments Modulation of Polar Mesospheric Clouds PMCs during such experiments Conclusions

4 Ionospheric Modification First experiments performed around 1970 in the U.S. and as early as 1961 in the former U.S.S.R. Many results were classified and released years later. The basic concept is to modify the ionosphere with high power HF radio waves as a laboratory for investigating nonlinear plasma physics. High frequency HF O-mode EM waves propagating nearly vertical are used for accessibility to resonances at the plasma and upper hybrid resonance altitude layers. Phenomena typically observed include: Field-aligned plasma structuring/striations (10 km along field; 10 meters across) Anomalous absorption of the pump wave Broadband absorption of other EM waves within about 200 khz of the pump wave Stimulated Electromagnetic Emissions SEE within 300 khz of the pump wave Excitation of electrostatic waves (i.e. Langmuir, upper hybrid, electron Bernstein) Electron acceleration/heating Optical emissions/airglow

Heating Facilities Around the World A: Sura (1975-Present) B: Platteville, CO (1970-1984) C: Arecibo (1971-1998,

5 Heating Facilities Around the World A: Sura (1975-Present) B: Platteville, CO ( ) C: Arecibo ( , 2013) D: EISCAT (1980-Present) E: HIPAS, AK (1985-Present) F: HAARP, AK (1995-Present) G: SPEAR (2003, present) 5

Bo Thide Uppsala University Wideband SEE as a Diagnostic Tool SEE f pump pump pump SEE < f f f f 0 > 3 f ce 0 3 ce 0 3 ce SEE SEE Data recorded at HAARP Visited Cornell ~ 1987 Wideband SEE has been

6 Bo Thide Uppsala University Wideband SEE as a Diagnostic Tool SEE f pump pump pump SEE < f f f f 0 > 3 f ce 0 3 ce 0 3 ce SEE SEE Data recorded at HAARP Visited Cornell ~ 1987 Wideband SEE has been shown to vary systematically on fast and slow time scales (milliseconds to seconds). Wideband SEE varies with transmit frequency proximity to electron gyro-frequency harmonics nfce where fce 1.4 MHz. From this behavior, SEE has been developed into a powerful low cost diagnostic during ionospheric heating at EISCAT (Norway), Sura and Zimenki (Russia) and also Arecibo (Puerto Rico) and HIPAS (Alaska). Diagnostic information includes characterization of: plasma turbulence, field-aligned 6 striations, electron temperature, heating interaction altitude, ect.

Stimulated Electromagnetic Emission (SEE) Stimulated

radiation generated during ionospheric pumping.

and SEE was first observed experimentally by Thide et al.

Reflection Height 5 km Upper Hybrid Altitude SuperDARN radar ω =

km altitude Well over one dozen (12) spectral lines have been

7 Stimulated Electromagnetic Emission (SEE) Stimulated Electromagnetic Emission (SEE) is secondary electromagnetic (EM) radiation generated during ionospheric pumping. A form of SEE was first predicted by Stenflo and Trulsen [1978] and SEE was first observed experimentally by Thide et al. [1982] at EISCAT. Reflection Height 5 km Upper Hybrid Altitude SuperDARN radar ω = ω 0 pe ω = ω 0 UH F-Region Ionosphere SEE EE EE EE BB 0 EE ~ 200 km altitude Well over one dozen (12) spectral lines have been observed and studied in the wideband SEE spectrum (within khz of the transmit frequency) Leyser [2000]. MUIR radar SEE receiver HAARP HF Transmitter 7

8 Parametric Decay Instability Matching conditions: ωω 0 = ωω HHHH + ωω LLLL kk 0 = kk HHHH + kk LLLL Dispersion Relation : Porkolab (1972); Ono et al. (1980) εε ωω ss + ββ ee 2 4 χχ ii ωω ss εε ee ωω ss εε ee ωω 1 2 = 0 where: εε ωω = 1 + χχ ii ωω + χχ ee ωω, εε ee ωω =1 + χχ ee ωω, ωω 0 = ωω ss + ωω 1 χχ jj ωω = 1 kk 2 λλ DDDD 2 χχ 1 + ζζ jjj Γ kk 2 ρρ 2 jj ZZ(ζζ jjjj ) ii ωω ss 1 + iiνν jj kk vv tttt ζζ jjj Γ kk 2 ρρ jj 2 ZZ(ζζ jjjj ) 8

9 First Discovery of Narrowband SEE at HAARP Narrowband SEE will be defined as SEE within 1 khz of the pump frequency and often within 100 Hz. Narrowband SEE was actually predicted in the late 1970 s. Narrowband SEE lines However, it was first definitively observed at HAARP decades later [Norin et al., 2009] with the ion acoustic (IA) line of Stimulated Brillouin Scatter SBS (Δf a few 10 s of Hz). HAARP thus enabled new opportunities for SEE diagnostics since this was a major breakthrough. HAARP has unique characteristics that allowed this discovery, the primary of which is the transmit power. The second discovery in Narrowband SEE was that of geomagnetic field effects which produces the electrostatic ion cyclotron line (EIC) [Bernhardt et al., 2010] (Δf ~ f ci ~ 50 Hz). First measurements of threshold power for narrowband SEE generation at HAARP [Mahmoudian et al., 2013]. Such SEE is generated through the Stimulated Brillioun Scattering SBS process. ~ 100MW ERP threshold for IA line ~ a few 100MW ERP threshold for EIC line

Discovery of Narrowband SEE Ion Gyro-harmonic Lines Narrowband SEE exhibits new spectral features for heating close to electron gyro-harmonics f nf (within

f f 0 2 ce SuperDARN UH irregularities observed with narrowband SEE Subsequently, extensive measurements, theory, and computational modeling have been

630nm optical emissions observed with narrowband SEE These show two characteristic types of spectra 1) involving discrete lines at ion (O + )

10 Discovery of Narrowband SEE Ion Gyro-harmonic Lines Narrowband SEE exhibits new spectral features for heating close to electron gyro-harmonics f nf (within a few 10 s of khz). 0 ce The initial observations were reported by Bernhardt et al. [2011] for second gyro-harmonic heating. f f 0 2 ce SuperDARN UH irregularities observed with narrowband SEE Subsequently, extensive measurements, theory, and computational modeling have been reported [Scales et al., 2011: Samimi et al. 2012, 2013: 2014; Fu et al., 2013: Mahmoudian et al., 2013]. 630nm optical emissions observed with narrowband SEE These show two characteristic types of spectra 1) involving discrete lines at ion (O + ) gyro-harmonics, and 2) the other involving a broadband emission. Initial connections have been made between these emissions and field aligned irregularities at the upper hybrid UH layer and also airglow measurements. Samimi et al. [2013] Mahmoudian et al. [2013]

Polar Mesospheric Clouds PMC (NLC observed from space) Aeromony of Ice in the Mesosphere (AIM) satellite image of Polar Mesospheric Clouds (PMC) in the northern summer polar

11 Polar Mesospheric Clouds PMC (NLC observed from space) Aeromony of Ice in the Mesosphere (AIM) satellite image of Polar Mesospheric Clouds (PMC) in the northern summer polar region on July 15, The orientation is with the United States down in the plot. The goal of AIM is to investigate the formation and evolution of PMCs (Russell et al. 2009).

12 Typical profiles of neutral atmospheric temperature and ionospheric plasma density s n d ~ m 3 Dusty plasma region Plasma Density (m -3 ) 12

13 Basic Concept of A Dusty Plasma A standard electron-ion plasma imbedded with an additional charged component of micron or submicron-sized particulates. 2 2 Inter-grain distance a is less than the Debye length λ = λ λ / λ + λ (i.e. r d <<a<λ D ) Dust-in-plasma is defined by (i.e. r d << λ D <a). Inclusion of dust changes relative concentration of ions and electrons which leads to new physics (i.e. charging, diffusion, wavemodes). The Coulomb coupling parameter (Γ c >>1) or weakly (Γ c <<1) coupled. Γ = c 2 Qd ak T a exp λ B d D D De Di De Di determines whether strongly Appropriate altitude ranges in the mesosphere can be described as a dusty plasma from such criteria r d - a r d Dust particle charged to Z d charges 13

14 Charging and Diffusion Timescales τ e 1 = I + I 2 8π n v r Charging Time: chg 1sec. e i e te d Diffusion Time : (Ambipolar) τ dif λ ν in 2πvthi 2 T (1 + T e i 1 )(1 + zd 0n n e0 d 0 ) 1sec.(50 MHz) For turn-off overshoot: For turn-on overshoot: / << 1 τ dif τ chg / >>1 τ dif τ chg This has important consequences as the heater frequency is varied (also for larger dust radii). Behavior at heater turn-on may start to become markedly different in this frequency range. 14

15 Schematic of Current EISCAT PMSE Heating Experiments ~ 85 km altitude 3-4 km PMC ( Dust/ice Layer) nm sized dust y (west) z (north) Heating Cycle PMSE 40s-ON 140s-OFF x (down) Heating Facility EISCAT Heating Facility UHF Radar (900MHz) VHF Radar (224MHz) Morro Radar (56MHz) HF Radar (7.9MHz) 15

16 Historical Perspective on PMSE Heating Experiments Chilson et al. (2000): First active modulation of PMSE experiment. Showed suppression of PMSE during heater turn-on. Argued to be due to diffusion by Rapp and Lubken (2000) from heating T e increase. Havnes et al. (2003), Havnes (2004): First theoretical model that reproduced much of the basic behavior observed during experiments at 224 MHz at EISCAT. Predicted suppression at turn-on and an overshoot at turn-off however limited for lower frequencies due to Boltzmann electron assumption. 16

17 Irregularity Temporal Variation With Radar Frequency Turn-Off Overshoot Turn-On Overshoot Time (sec) radar echoes δ ; λ =2 λ n e radar irregularity 17

18 Summary and Conclusions Active ionospheric modification experiments is still a vibrant area of research. New discoveries in recent years provide further opportunity for remote sensing studies of the near earth space. My career path down this road started with my studies at Cornell in active space experiments as well as plasma physics from LPS faculty. I am indebted for all the opportunities and all the life long friends from my Cornell experience its been an exciting trip!

Ion gyro-harmonic structuring in the stimulated radiation spectrum and optical emissions during electron gyro-harmonic heating

JOURNAL OF GEOPHYSICAL RESEARCH: SPACE PHYSICS, VOL. 118, 127 1287, doi:1.12/jgra.5167, 213 Ion gyro-harmonic structuring in the stimulated radiation spectrum and optical emissions during electron gyro-harmonic