Detection and Characterization of Traveling Ionospheric Disturbances - - PowerPoint PPT Presentation

Ionospheric Effects Symposium 12-14 May 2015 Alexandria, VA

Keith Groves, Vadym Paznukhov, Eileen MacKenzie Boston College, Chestnut Hill, MA USA Terry Bullett

CIRES, University of Colorado, Boulder, CO keith.groves@bc.edu

Detection and Characterization of Traveling Ionospheric Disturbances (TIDs) with GPS and HF sensors

Outline

• Introduction and Motivation
• Technical Approach
• Preliminary results
• Summary

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Motivation

• Disturbances in the ionosphere can often be the limiting

factor in the performance of high frequency (HF) systems

• Current techniques to detect, characterize and correct for

such disturbances using sensors and models are inadequate

• The goal of this effort is to detect and characterize

disturbances with GPS sensors for comparison with effects

• n HF propagation
• The results will help us better understand the nature of

traveling ionospheric disturbances and improve our ability to interpret their signatures on specific sensors

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Technical Approach

1. Monitor high frequency (HF) propagation channels using available broadcasts on appropriate paths 2. Collect and correlate GPS total electron content (TEC) data to detect and characterize TID spectrum and dynamics 3. Determine suitability of GPS observations for meaningful prediction of HF propagation effects

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• A. Use the VIPIR ionosonde at Wallops Island, VA as the

primary HF receiver capable of measuring angle-of-arrival

• B. Use CORS and other available GPS receivers to measure

TEC signatures along the HF raypaths

• C. Install a compact (baseline < ~10 km) three GPS rx array to

test performance for TID characterization

Implementation

Aspects of Link Selection

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• WBCQ (Maine): longest path

(1200 km) mid-point over MA/NH supports compact GPS array analysis

• CHU (Ottawa): Geographic N-

S propagation path; Canada time reference: No frequency

• ffset or drift in transmitter
• WWCR (Nashville):

Predominantly E-W path ideal for dusk/dawn gradients; variety of frequencies used ensures available signal

The three proposed links each offer unique measurement opportunities

We are monitoring all three sites simultaneously for Doppler information

GPS install

• HF and GPS common data collection window

with all sensors spans 28 Aug - 16 September; 11 December to present…

• Both GPS and HF sensors show numerous

perturbations; a few cases have been examined for qualitative correlation

• Quantitative correlations just getting underway
• It appears data will support planned studies,

but it is not possible to predict outcome at this stage in the research

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Preliminary Data Analysis Summary

TID Signatures in HF Doppler

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Collected on a variety of frequencies at different times and different raypaths over just a few days

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Preliminary Analysis Case Study:

02 April 2300-0000 EDT WFF-CHU

• TID structure observed with ~45 min period

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Fluctuations Observed on PRN 17

• 80
• 79
• 78
• 77
• 76
• 75
• 74
• 73

37 38 39 40 41 42 43 44 45 46

Wallops CHU Latitude, deg Longitude, deg

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NYBH

Binghamton, NY Station is Nearest to Wallops-CHU Mid-Point

01:00 02:00 03:00 04:00 05:00 06:00 07:00 08:00 8 10 12 14 16 18 20 22 24 01:00 02:00 03:00 04:00 05:00 06:00 07:00 08:00

• 0.2

0.0 0.2 0.4 0.6

April 3, nybh Raw data Trend TEC Detrended dTEC Universal time

Detrended TEC

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TEC Fluctuations: Examining the Details

03:00 03:10 03:20 03:30 03:40 03:50 04:00

• 0.2

0.0 0.2 0.4

dTEC UT time Detrended TEC

HF Doppler and GPS TEC Correlation

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• Track principal frequency in a given HF channel
• Extract Doppler variations and take real FFT to detect TID

“power”

• Automated processing applied to reduce all HF data
• Reduction of GPS data performed separately

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HF Link TID Detection Processing

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GPS Data Processing

Spatial Filter Polynomial detrend, residual extraction

• GPS processing has more free parameters (space and time)
• Detrending process introduces artifacts; optimum approach still

under consideration

• Spatial filtering to limit responses to region near HF mid-points

may not be appropriate

• Signatures are geometry-dependent

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Combine HF and GPS Results

• Good, but not perfect, correlation in cases examined thus far
• GPS signatures may be strongly dependent on observing

geometry

• More analysis needed to quantify and understand correlations

• Minor storm activity on 12 September resulted in significant

large and medium scale TID generation observed by GPS

• Signatures were also observed on HF links

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Activity on September 12, 2014

Image courtesy of R. Predipta

• TIDs show a fairly abrupt “turn-on” on 12 Sep, during recovery

from negative DST excursion

• These are the strongest TID events observed through the

period 28 Aug-16 Sep

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12 September HF TIDs

• Ratio of responses on GPS and HF varies significantly
• Note large GPS signature at 19:00 corresponds to relatively

modest signature on HF; conversely, at 21:00 HF response exceeds GPS

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HF and GPS Data Comparison

• Higher frequencies show improved sensitivity to TID signatures
• Penetration into the medium increases as frequency increases
• These are not simply bottomside disturbances

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Higher Frequencies More Effective for TID Detection (i.e., more susceptible)

Summary

• Numerous cases for analysis of GPS TEC and HF signatures;

lots of activity detected; dynamic environments observed

• Activity in September highest in the post-sunset to midnight

period in both GPS and HF

• Preliminary comparisons show high qualitative comparison

between observations on HF and GPS, but magnitudes of responses vary significantly

• Signatures on both systems depend on observing geometry;

understanding this aspect of the observations will be critical to extracting TID parameters from data

• Multi-constellation GNSS observations should improve sensitivity

further and provide additional information on TID characteristics

• Data collection to continue through summer 2015; “optimum”

GPS algorithm development still ongoing

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Back-Up

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The Observing Capabilities of GPS Networks

• A single link observed from different stations can dial in a

desired position

• All visible links from a few sites expand coverage significantly
• It is usually possible to find a few links along the raypath,

though they may not come from the nearest station

24/7 Schedule

00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

2 3 4 5 6 7 8 9

5.110 4.840 3.330 9.980 9.330 7.850

Frequency, MHz Local Time

CHU WWCR WBCQ

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