First Results of Phase Scintillation from a Longitudinal Chain of ASTRA’s SM-211

GPS TEC and Scintillation Receivers

Irfan Azeem, Geoff Crowley, Adam Reynolds, and Julio Santana, ASTRA, Boulder, CO

Donald Hampton, Geophysical Institute, University of Alaska Fairbanks, AK

contact: iazeem@astraspace.net

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Outline

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Ionospheric Irregularities

● Introduction● CASES GPS Receiver● Data Used● Results

Scintillation ClimatologyCase Studies: Phase Scintillation

During Auroral EventsScintillation Occurrence Statistics

● Summary and Conclusions

● Atmospheric & Space Technology Research Associates (ASTRA),Boulder, CO

● Small business specializing in space environment modeling/prediction and space technology innovation

ASTRA Core Competencies

Science Technology

Applications Bringing It All Together

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ASTRA: Overview

Numerical Modeling

Instrument Development

Data Assimilation

Scientific Software

Space Systems

Core Competencies

• Physics-Based Modeling

• Real-Time Specification

• Ionospheric Electron Density

• High-Latitude Electrodynamics

• Satellite and Ground Sensors

• Time-Frequency Analysis

• Wavelet Analysis

• GPSRO

• GPS TEC/Scint†

• HF TID Mapper †

• Low Power Ionosonde

• NSF DICE

• AFRL DIME

• SMC SENSE

• UV Sensor

• Neutral Wind Sensor

† Commercially AvailableCurrently hiring GPS Engineers!

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Introduction● Significant insights into the structure and evolution of

the ionosphere have been enabled by the increasing use of GPS receivers

● In the US, this development has largely been concentrated in the contiguous states while the high latitude ionosphere has been poorly represented, due primarily to remoteness and lack of infrastructure

● Several GPS receivers (ASTRA CASES model SM-211) were deployed in Alaska, for the purpose of documenting and understanding GPS scintillation at high latitudes, and to study the effects on operational GPS-dependent systems

● Goal is to improve the temporal and spatial resolution of ionospheric remote sensing in a region of poor coverage but of high geospace interest

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Q. What is the variability of observed GPS scintillations and the observed auroral precipitation in different geophysical regions at high latitudes?

Q. What is the relative contribution of hard and soft auroral precipitation to high latitude GPS phase scintillations?

Introduction

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CASES GPS

Dual frequency (L1 and L2C)CASES GPS Receiver

● Software radio architecture● Remote reconfigurability● Full control of receiver behavior, products, and

cadences● Specialized tracking loops● Multiple comm. Interfaces● Time to first channel lock

● Cold start ~60s● Hot start ~15s

● Low CostData Type

Per Channel High Rate Data

Per Channel Low Rate Data

Per Channel Scint Params

Other

Default Data Rate 100 Hz 1 Second 60 Seconds 1 SecondConfigurable Rate? Yes, 50 or 100 Hz Yes, >= 1 Second Yes Yes, >= 1 Second

Available Parameters

• Integrated Carrier Phase

• In-Phase Accumulation

• Quadrature Accumulation

• GPS Time

• Receiver Time

 

• Pseudorange-based TEC• Phase-based delta TEC• Pseudorange• Integrated Carrier Phase• GPS Time, Receiver Time• Doppler Frequency• SV Elevation, SV Azimuth• C/N0• Data Validity Flag, Cycle

Slip Flag• Signal Acquisition Status• PRN, SV Health

• S4

• σϕ

• o

• Scint Power Ratio• GPS Time• Reference Channel

Status• PRN

• Receiver X/Y/Z Position

• Receiver X/Y/Z GPS Time

• Receiver Time• Velocity• Receiver Clock

Error• Receiver Clock

Error Rate• Nav Solution Flag

Connected Autonomous Space Environment Sensor

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CASES ALASKA CHAIN

● Four CASES GPS receivers deployed in Alaska: November 2012● Kaktovik (70.1° N, 143.6° W) ● Fort Yukon (66.6° N, 145.2° W)● Poker Flat (65.1° N, 147.4° W)● Gakona (62.4° N, 145.2° W).

CASES SM-211 GPS

10M Hz Ref

External Storage

Kaktovik

Fort Yukon

Poker Flat

Gakona

http://cases.astraspace.net

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Fort Yukon

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Quiet Conditions

Active Conditions

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Multi-Instrument Dataset

RESULTS

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Phase scintillation results from Alaska CASES GPS receivers.

We also show auroral emission data from an All-Sky Imager (ASI) and a meridian spectrograph, both located at PFRR.

The auroral emission data is correlated with phase scintillation measurements to show correspondence between auroral activity and scintillation severity.

Results

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Climatology Bin data into 30-min

segments for each day of observations

Elevation mask of 20°1. Severity of phase

scintillation decreases with decreasing latitude.

2. Largest phase scintillations occur near magnetic midnight.

3. Time of peak scintillation occurrence at KAK and FYU shifts slightly to later local time from November to February.

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CASES STUDIES

Measurements from CASES Alaskan chain also highlighted several discrete events when all CASES GPS receivers recorded elevated phase scintillations.

Strong scintillation was seen on November 14th, November 20th, December 25th, January 17th, and January 26th, in all four receiver sites.

Phase scintillation data from a few selected dates and show measurements of auroral conditions prevailing in the Alaskan sector on these days.

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November 12, 2012

Each color indicates a different PRN

Elevation mask of 20° is used

Phase scintillation activity on November 12, 2012 from all four stations in the CASES Alaskan chain.

Kp index was low for majority of the time and increased only moderately after 2100 UT

Increased phase scintillation at Kaktovik, Fort Yukon, and Poker Flat after 2100 UT

(a)

(b)

(c)

(d)

(e)

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November 12, 2012

Auroral emission intensities at three discrete wavelengths, 577.7 nm, 427.8 nm, and 630.0 nm, are shown

Auroral activity on November 12, 2012 measured by the PFRR meridian spectrograph.

Most of the auroral activity was observed poleward of 67° N.

(a)

(b)

(c)

1 sec integration at each elevation

The altitudes for the figures are 100 km for 427.8 nm, 110 km for 557.7 and 250 km for 630.0 nm.

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November 12, 2012

Two scintillation events observed in Kaktovik data (at1000 UT and 1400 UT)

Enhancements in sigma_phi appears to be associated with the brightening of red line auroral emission

Locations south of Kaktovik show no significant auroral activity and no scintillations

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(a)

(b)

(c)

(d)

(e)

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November 13, 2012

Significant phase scintillation is present on November 13, 2012.

Scintillation strength decreases southward of Kaktovik

Kp = 3+

(a)

(b)

(c)

(d)

(e)

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November 13, 2012

Auroral intensities of the 557.7 nm and 427.8 nm channels were much weaker than the 6300 nm auroral emission.

The observed correspondence between phase scintillations and the red line intensity enhancements, suggest that the high latitude scintillation events are probably associated with F-region irregularities.

(a)

(b)

(c)

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November 13, 2012

Auroral activity was located poleward of Poker Flat (65.1° N) and most of the moderate phase scintillation values were also seen at or poleward of Poker Flat.

At 1300 UT the aurora drifted towards lower latitudes with the equatorward edge of the aurora extending to latitudes near Gakona.

The phase scintillation data from the Gakona site also show increased scintillation during this period characterized by the auroral equatorward transition.19

(a)

(b)

(c)

(d)

(e)

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ASI movies

Phase scintillations observed on November 14, 2012 from Poker Flat superimposed on PFRR ASI movie.

Nighttime phase scintillation enhancement is localized and occurs across the auroral arc, confirming previous observations in the Canadian sector by Prikryl et al. [2011].

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What is the local time variation of phase scintillation at high latitudes?

MLT variation of phase scintillation at Kaktovik for different levels of scintillation strength.

Occurrence Statistics

Red: weak

Diurnal variation

Blue: moderate

Pre-midnight maximum

Black: strong

Pre-midnight maximum

Occurrence Statistics

FYU PFRR

GAK

The weak scintillation events show a diurnal variation at all sites with a well-defined minimum near 0000 MLT.

Strongest scintillation events tend to be night time phenomena

Conclusions● Four CASES SM-211 GPS receivers deployed in Alaska● Demonstrates our ability to map scintillation in real-time, and to

provide space weather services to GPS users. ● Multi-instrument analysis was performed to understand the role

of energetic electron precipitation on high-latitude scintillations.● There are two main findings of the present study:

1. The severity of phase scintillation decreases with decreasing latitude, and

2. The largest phase scintillations occur near magnetic midnight.● We hypothesize that energetic particle precipitation on the night-

side might be responsible for the irregularities associated with these phase scintillation events.

● Weak scintillations, which show a clear diurnal behavior, possibly generated by cusp precipitations.

● Future studies will investigate this hypothesis with additional radar data on ionospheric irregularities and particle precipitation.

● Data are for sale, under a data-buy agreement● ASTRA is hiring GPS engineers

Summary and Conclusions