2014 LWS/HINODE/IRIS Workshop, Portland OR, Nov 2-6, 2014 Jacob Bortnik, Xin Tao, Wen Li, Jay M....
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Transcript of 2014 LWS/HINODE/IRIS Workshop, Portland OR, Nov 2-6, 2014 Jacob Bortnik, Xin Tao, Wen Li, Jay M....
2014 LWS/HINODE/IRIS Workshop, Portland OR, Nov 2-6, 2014
2014 LWS/HINODE/IRIS Workshop, Portland OR, Nov 2-6, 2014
Jacob Bortnik, Xin Tao, Wen Li, Jay M. Albert, Richard M. Thorne
Many thanks to the NSF/DOE partnership in basic
plasma physics, award # ATM-0903802; DE-SC0010578
Understanding the effects of data-driven repetitive chorus elements on the scattering characteristics of energetic radiation belt electrons
Radiation belt dynamics: Collective, incoherent wave
effects• Particles drift around
the earth• Incoherently
accumulate scattering effects of: – ULF– Chorus– Hiss (plumes)– Magnetosonic
• Characteristic effects of each waves are different and time dependent
Thorne [2010] GRL “frontiers” review
The wave environment in space
Meredith et al [2004]
Objective
2. Quasilinear theory- Waves are all weak- Wideband & incoherent- Interactions
uncorrelated- Global modeling
1. Single-wave/test-particle
- Waves can be strong
- Narrowband & coherent
- Interactions all correlated
- Microphysics
USReality, somewhere in this
region …
When are nonlinear effects important?
2||
||||
||
sin2
sin2
w
w
dv qB v Bv
dt m B z
v vqBdv Bv v
dt m k B z
dkv
dt
adiabatic
phase
Example simple case: field aligned wave, non-relativistic particles
wave
When are nonlinear effects important?
“driving”force
“restoring”force
Conditions for NL:- Waves are “large”
amplitude- Inhomogeneity is “low”,
i.e., near the equator- Pitch angles are
medium-high
Large amplitude whistler waves
Cattell et al. [2008], First reports of large amplitude chorus, STEREO B~ 240 mV/m, ~ 0.5-2 nTMonotonic & coherent (f~0.2 fce, ~2 kHz)Oblique (~ 45 - 60), TransientL~3.5 – 4.8, MLT~2 – 3:45, Lat ~ 21°-26°, AE ~800 nT
Li et al. [2011], Burst mode observations from THEMIS: Large amplitude chorus is ubiquitous, midnight-dawn, predominantly small wave normal angles
Three representative cases
(a) small amplitude, pT wave(b) Large amplitude waves(c) Large amplitude, oblique, off-equatorial resonanceBortnik et al. [2008]
[Bortnik et al., 2014]
Diffusion surfaces
•Resonant interaction: Which particles are affected?
Non-relativistic form:
Relativistic form:
•Resonant diffusion surface: confinement in velocity space
•Non-relativistic form:
Resonant diffusion in velocity space
[Bortnik et al., 2014]
Subpacket structure: a Two-wave
model
Two-wave model
Tao et al. [2013] subpacket structure modifies the single-wave scattering picture
Subpacket structure: full spectrum model
Tao et al. [2012b], GRL
Subpacket structure: full spectrum model
Tao et al. [2012b], GRL
Sequence of chorus elements
Tao et al. [2014]:Model a sequence of chorus elements, chosen at random from THEMIS observation, randomly chosen initial phase, initiated at equator.
Comparison with quaslinear theory
Model the chorus wave power with a fitted Gaussian, and use SDE approach to simulate the “diffusive spread”
Case 1: high repetition, low amplitude
Repetition rate δt/τ=0.4 , BRMS=10 pT.
Test particle and SDE (QL-diffusion) results agree very well.
Case 2: low repetition, low amplitude
Repetition rate δt/τ=1.2 , BRMS=10 pT.
Test particle and SDE (QL-diffusion) results disagree: spreading is non-Gaussian, heavy tails and thin core.
Case 3: low repetition, med. amplitude
Repetition rate δt/τ=1.2 , BRMS=80 pT.
Test particle and SDE (QL-diffusion) results disagree: spreading is non-Gaussian, large positive bias and thin core.
Summary and conclusions• AIM: Bridge the ‘limiting’ paradigms:
1. Quasilinear theory: weak, broadband waves, linear scattering
2. Single-wave/test-particle: finite amplitude, narrowband & coherent, linear or nonlinear scattering
3. Reality: somewhere inbetween?
• Subpacket structure: periodicity of amplitude modulation relative to Bw defines mode of interaction. “Realistic” wave packet tends to linearize response.
• Repetitive chorus elements:1. High repetition rate & low amplitude: QL works well2. Low repetition rate & low amplitude: heavy tails, thin core 3. Low repetition rate & med. amplitude: large +ve bias, thin
core
BACK UPS
Large Plasma Device at UCLA
• Operated under Basic Plasma Science Facility (NSF/DOE)
• 18m long, 60 cm diam• B up to 3.5 kG (0.35 T)
10 independent power supplies
• Plasma by diode switch ~1 MW, Ne>2x1012
cm-3, Te=6-15 eV• 450 radial ports,
computer controlled scanning probes
• 20 kHz-200 MHz wave generator with 20 kW tuned RF amplifier
Experimental setup
ω-k||v||=Ωe
W-P interaction
5. Single particle motion example
Wave:– Bw = 1.4 pT = 0° – 2 kHz (~0.28
fce)– Constant with
latitude
Particle:– E = 168.3 keV eq = 70° 0 =
Cumulative changes when d/dt~0, i.e., resonance
Experimental setup
ω-k||v||=Ωe
Outline
1. Introduction to wave-particle interactions
2. Diffusion3. The wave-particle
interaction experiment at the LAPD (Large Plasma Device) Fourier’s monograph on heat diffusion
was submitted handwritten to the Institut de France in 1807- rejected! [Phys. Today, 62(7) 2009]
Amplitude threshold of QLT
Tao et al. [2012] Quasilinear diffusion coefficients deviate from test-particle results in a systematic way.