total electron content 32n 115w, 2007-2009
DESCRIPTION
Total Electron Content 32N 115W, 2007-2009. Rachel Thessin, CSI 763, April 15, 2010. Data Overview. US TEC data from the National Geophysical Data Center Two data types: Ground GPS: CORS, RTIGS Sat GPS: GPS/Met Vertical TEC grids 1 deg x 1 deg 15 min resolution Oct 2004 – present - PowerPoint PPT PresentationTRANSCRIPT
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Total Electron Content32N 115W, 2007-2009
Rachel Thessin, CSI 763, April 15, 2010
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Data Overview US TEC data from the
National Geophysical Data Center
Two data types: Ground GPS: CORS, RTIGS Sat GPS: GPS/Met
Vertical TEC grids 1 deg x 1 deg 15 min resolution Oct 2004 – present Each day: 26 MB
compressed; 64 MB uncompressed
http://www.ngdc.noaa.gov/stp/IONO/USTEC/
TEC: total electron content (integral of electron density)
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Time Series Extracted TEC 2007-2009 at 32N 115W
Overlaps with 12/2009 5.8 mag earthquake
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Data Expectations TEC is a function of
Solar / geomagnetic activity
Time of day Day of year (season) Lat / Lon / Alt
2007 – 2009: Solar minimum Relatively flat solar
activity across three years
http://solarscience.msfc.nasa.gov/images/ssn_predict_l.gif
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Literature Review, 1 of 2 Dautermann et al ("Investigation
of ionospheric electron content variations before earthquakes in southern California, 2003 – 2004," Journal of Geophysical Research, VOL. 112, 2007)
11 year, 1 year, 27 day, 1 day, 12 hr
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Literature Review, 2 of 2 Bilitza (2001)
“International Reference Ionosphere 2000,” Radio Science, v. 36, n. 2, pp 261-275, March-April 2001
E region Solar influenced 24-hr periodicity related to SZA
F region plasma is transported along magnetic field lines 24-hr dependence related to LT
External drivers solar irradiance (11-year cycle) (and hence the use of F10.7 and
twelve-month running mean of SSN as inputs) Conclusion: IRI will miss the 27-day periodicity in the data
These periodicities are ephemeral and caused by “random” events.
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Time Series 2007-2009 at 32N 115W
Flat with daily varaitions
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Data Gaps 120 gaps among
103,000 data points 18 1-minute gaps and
112 gaps longer than 16 minutes
Linear Interpolation
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Data Distribution TEC varies daily
Sinuosoidal appearance
Most data values at peak or trough bimodal data distribution
Bounded on lower end, unbounded on upper end broader upper peak
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Autocorrelation Long correlation lag
Values correlated with counterparts one year later
Yearly cycle + flat solar activity
Short correlation lag Large variance in
correlation small lags apart
Daily variation in TEC
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Raw Periodogram Signal at period of 1 day; no other signals
Aliasing of this signal Data set is too short and flat to see 1-year, 11-year signals 12-hour – 1/(1/2 day) = 2 day-1; 27-day – 1/(27 days) = 0.037
day-1
1-year – 1/(365 days) = 0.0027 day-1
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Welchs Periodogram 8 equal-sized, overlapping windows with a
Hamming function shape leads to less high-freq noise
1-day and 12-hr signals visible
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Welch’s Periodogram, 60-day window Smaller window less high-freq noise 12 hr
signal becomes more visible
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Welch’s Periodogram, 10-day window Smaller window less high-freq noise 12 hr
signal becomes more visible No longer physically feasible to see 1 year or 27
day signals
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Error on Periodogram Bootstrap, n = 1000, l = 45
days Peak at 1 day is statistically
significant, as is peak at 12 hours
Aliasing peaks seem almost significant – meaning of 3 hour period?
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Error on Welch’s Bootstrap, n=1000, l =
45 days 1 day and 12 hour
signals statistically significant