residual-spectra
TRANSCRIPT
Basic assumption: The coherent/wave ULF power on closed field lines in the Pc5-Pc6 frequency band (e.g., due to field line resonances) is significantly enhanced relative to open field lines at OCB latitudes and can serve as a predictor of open/closed field line measurements
Algorithm: 1. Raw magnetic time
series data 2. Mean-subtract and
high-pass filter 3. Subset filtered data
into 1-hr segments, stepped forward every 10 min
4. For each data segment:�a. apply hanning window�b. estimate power spectrum and background power law�c. remove background power law
5. The resulting data product, R[t,f], is the dynamic residual spectrum
Estimating Coherent/Wave ULF Power: The Dynamic Residual Spectrum
Digitally High-Pass Filter (“Bass Cut / Detrend”)
1 2 Raw Data
3
Slice n’ Dice
Kevin Urban: Quiet-Time Observations of the Open-Closed Boundary
4 Algorithm: 1. Raw magnetic time
series data 2. Mean-subtract and
high-pass filter 3. Subset filtered data
into 1-hr segments, stepped forward every 10 min
4. For each data segment:�a. apply hanning window�b. estimate power spectrum and background power law�c. remove background power law
5. The resulting data product, R[t,f], is the dynamic residual spectrum
Kevin Urban: Quiet-Time Observations of the Open-Closed Boundary
Basic assumption: The coherent/wave ULF power on closed field lines in the Pc5-Pc6 frequency band (e.g., due to field line resonances) is significantly enhanced relative to open field lines at OCB latitudes and can serve as a predictor of open/closed field line measurements
Estimating Coherent/Wave ULF Power: The Dynamic Residual Spectrum
5
The Dynamic-Residual-Spectrum Estimate of Coherent Wave Power at a Site Algorithm:
1. Raw magnetic time series data
2. Mean-subtract and high-pass filter
3. Subset filtered data into 1-hr segments, stepped forward every 10 min
4. For each data segment:�a. apply hanning window�b. estimate power spectrum and background power law�c. remove background power law
5. The resulting data product, R[t,f], is the dynamic residual spectrum
Basic assumption: The coherent/wave ULF power on closed field lines in the Pc5-Pc6 frequency band (e.g., due to field line resonances) is significantly enhanced relative to open field lines at OCB latitudes and can serve as a predictor of open/closed field line measurements
Estimating Coherent/Wave ULF Power: The Dynamic Residual Spectrum
Kevin Urban: Quiet-Time Observations of the Open-Closed Boundary
10
20
10
20
20 40 60
Peri
od (
min)
UT (hours)
Relative Power
P3
August 6-8, 2008 MCM – Quiet Time vs. Storm Time
August 9-12, 2008
10
20
10
20
20 40 60
Peri
od (
min)
UT (hours)
Relative Power
P3
August 6-8, 2008 P2 – Quiet Time vs. Storm Time
August 9-12, 2008
10
20
10
20
20 40 60
Peri
od (
min)
UT (hours)
Relative Power
P3
August 6-8, 2008 P3 – Quiet Time vs. Storm Time
August 9-12, 2008
10
20
10
20
20 40 60
Peri
od (
min)
UT (hours)
Relative Power
P3
August 6-8, 2008 SPA – Quiet Time vs. Storm Time
August 9-12, 2008
10
20
10
20
20 40 60 Pe
riod
(mi
n)
UT (hours)
Relative Power
P3
August 6-8, 2008 MCM – Quiet Time vs. Storm Time
August 9-12, 2008
10
20
10
20
20 40 60
Peri
od (
min)
UT (hours)
Relative Power
P3
August 6-8, 2008 P2 – Quiet Time vs. Storm Time
August 9-12, 2008
10
20
10
20
20 40 60
Peri
od (
min)
UT (hours)
Relative Power
P3
August 6-8, 2008 P3 – Quiet Time vs. Storm Time
August 9-12, 2008
10
20
10
20
20 40 60
Peri
od (
min)
UT (hours)
Relative Power
P3
August 6-8, 2008 SPA – Quiet Time vs. Storm Time
August 9-12, 2008
10
20
10
20
20 40 60
Peri
od (
min)
UT (hours)
Relative Power
P3
August 6-8, 2008 MCM – Quiet Time vs. Storm Time
August 9-12, 2008
10
20
10
20
20 40 60
Peri
od (
min)
UT (hours)
Relative Power
P3
August 6-8, 2008 P2 – Quiet Time vs. Storm Time
August 9-12, 2008
10
20
10
20
20 40 60
Peri
od (
min)
UT (hours)
Relative Power
P3
August 6-8, 2008 P3 – Quiet Time vs. Storm Time
August 9-12, 2008
10
20
10
20
20 40 60 Pe
riod
(mi
n)
UT (hours)
Relative Power
P3
August 6-8, 2008 SPA – Quiet Time vs. Storm Time
August 9-12, 2008
10
20
10
20
20 40 60
Peri
od (
min)
UT (hours)
Relative Power
P3
August 6-8, 2008 MCM – Quiet Time vs. Storm Time
August 9-12, 2008
10
20
10
20
20 40 60
Peri
od (
min)
UT (hours)
Relative Power
P3
August 6-8, 2008 P2 – Quiet Time vs. Storm Time
August 9-12, 2008
10
20
10
20
20 40 60
Peri
od (
min)
UT (hours)
Relative Power
P3
August 6-8, 2008 P3 – Quiet Time vs. Storm Time
August 9-12, 2008
10
20
10
20
20 40 60
Peri
od (
min)
UT (hours)
Relative Power
P3
August 6-8, 2008 SPA – Quiet Time vs. Storm Time
August 9-12, 2008
Estimates of Coherent Wave Power at Multiple Antarctic Sites
AGO2 AGO3
SPA
MCM
Kevin Urban: Quiet-Time Observations of the Open-Closed Boundary
To automate open/closed field line determinations, we looked at band integrations over the Pc5 and Pc6 bands at each site, using the distribution at the highest-latitude site to define the open/closed threshold in each band.
Automating Open/Closed Field Line Determinations
x
Pc6 Band
Pc5 Band
We expect that at a given time, our magnetometer network (if fully operating) should produce a result like this.
Kevin Urban: Quiet-Time Observations of the Open-Closed Boundary