May 1st 2008SWPC/NOAA SWW Workshop New Ionosphere Products Proposed for SWPC Tim Fuller-Rowell, Mihail Codrescu, Rashid Akmaev, Eduardo Araujo-Pradere, Mike Husler, and Herb Sauer 1 NOAA Space Weather Prediction Center and/or CIRES University of Colorado 1 National Geophysical Data Center

May 1st 2008SWPC/NOAA SWW Workshop New SWPC “Ionosphere” Products: in transition or proposed D-Region absorption upgrade - FY08 GPS Ionosphere Positioning Correction (GIPC) - FY08 US-TEC short-term forecast - FY09

May 1st 2008SWPC/NOAA SWW Workshop New SWPC “Ionosphere” Products: in transition or proposed D-Region absorption upgrade - FY08 GPS Ionosphere Positioning Correction (GIPC) - FY08 US-TEC short-term forecast - FY09

May 1st 2008SWPC/NOAA SWW Workshop D-Region absorption in response to solar X-ray flare Driver: GOES X-rays Dayside response to flare Zenith angle dependence Frequency dependence Estimated recovery time based on current X-ray flux

May 1st 2008SWPC/NOAA SWW Workshop Combined flare and Polar Cap Absorption (PCA) ( Provided by Michael P. Husler, NOAA SEC) June 21, :00 UT Kp= 3 Color scale denotes frequency at which the ionospheric absorption equals 1 dB

Day/Night Absorption Algorithms developed by Sellers et al* Provides 30 MHz absorption estimates Driven by proton fluxes obtained in real-time by NOAA GOES Day/night differences due to electron attachment to O 2 in absence of UV radiation Day-time Abs A d = [ J(E>5.2 MeV)] 1/2 dB Night-time Abs A n = [J(E>2.2 MeV)] 1/2 dB *Sellers, B., F.A.Hanser, M.A. Stroscio, and G.K.Yates, The night and day relationships between polar cap riometer absorption and solar protons, Radio Sci., v12, pp , Twilight absorption bi-linear fit to values at  10  solar elevation angle A = A d [ El + 10] / 20 – A n [ El – 10 ] / 20 Recovery time-scale based on current GOES flux levels

Geomagnetic Latitude Dependence - Determine Cutoff Energy Effects The absorption at lower than polar cap latitudes are obtained from application of geomagnetic cutoff energies which include their dependence on geomagnetic activity (K p ) as derived from the results of Smart et al* and illustrated below. *Smart, D.F., M.A.Shea, E.O.Fluckiger, A.J.Tylka, and P.R.Boberg., Changes of calculated vertical cutoff rigidities at the altitude of the International Space Station as a function of geomagnetic activity, Proc. Int’l Cosmic Ray Conf., v7, pp , 2001

Frequency Dependence The absorption at a frequency, f, other than 30 MHz (A f ) is obtained from the approximate dependence of ionospheric absorption on the inverse power law of the frequency (e.g.: Patterson et al*) A f = (30/f) 1.5 A 30 *Patterson, J.D., T.P.Armstrong, and C.M.Laird, Correlation of solar energetic protons and polar cap absorption, J.Geophys. Res., 106, A1, pp ,2001.

Specimen Comparison with Observation: Thule 30 MHz Riometer Panel a): GOES particle fluxes. Panel b): Observed absorption with calculated day and night absorption Panel c): Observed and fully estimated absorption Panel d): Calculated solar elevation angles a) b) c) d)

Comparison of Calculation with observations provided by AFGL’s Thule Riometers for 11 largest events Top panels: GOES particle fluxes. 2 nd panels: Observed absorption with calculated day and night absorption 3 rd panels: Observed and fully estimated absorption 4 th panels: Calculated solar elevation angles

May 1st 2008SWPC/NOAA SWW Workshop Combined X-ray and PCA

May 1st 2008SWPC/NOAA SWW Workshop Polar Region Display - 10dB PCA depends on solar illumination O 2 - e - attachment process in the D-region

May 1st 2008SWPC/NOAA SWW Workshop New SWPC “Ionosphere” Products: in transition or proposed D-Region absorption upgrade - FY08 GPS Ionosphere Positioning Correction (GIPC) - FY08 US-TEC short-term forecast - FY09

May 1st 2008SWPC/NOAA SWW Workshop US-TEC Target Users: Positioning and Navigation community Collaboration between SWPC, NGS, FSL, and NGDC Kalman filter over CONUS + ground-based GPS data, IRI background model, solve for receiver biases 15-minute cadence 15 to 30 minute latency TEC unit accuracy (~ cm delay at L1 frequencies)

May 1st 2008SWPC/NOAA SWW Workshop Slant-Path TEC Maps 2-D maps of of slant path TEC over the CONUS for each GPS satellite in view updated every 15 minutes Applications: 1. Ionospheric correction for single frequency GPS 2. Support dual-frequency integer ambiguity resolution for more rapid decimeter and centimeter accuracy positioning Sat. 1 Sat. 5 Sat. 14 Sat. 29 …. etc A A A AB B B B C C C C C

May 1st 2008SWPC/NOAA SWW Workshop Ionosphere phase delay/advance for NGS in new RINEX format US-TEC slant TEC provides ionospheric correctors for RINEX files Sat. 29 AB C

May 1st 2008SWPC/NOAA SWW Workshop New SWPC “Ionosphere” Products: in transition or proposed D-Region absorption upgrade - FY08 GPS Ionosphere Positioning Correction (GIPC) - FY08 US-TEC short-term forecast - FY09

May 1st 2008SWPC/NOAA SWW Workshop Mid-latitude day-to-day variability in ionospheric total electron content

May 1st 2008SWPC/NOAA SWW Workshop The challenge in forecasting the ionosphere and total electron content 15 minute units 12hrs24hrs 15 min intervals 1hr forecast hr forecast 0.8

May 1st 2008SWPC/NOAA SWW Workshop VTEC Short-term Forecast Using USTEC 10-day average to predict the ionospheric behavior in to the next 1 to 2 hours., USTEC 10-day average USTEC 15-min data time  Now   – Departure of “now value” from the 10-day average. Now-24 h Now-24+  t    –  TEC in the 10-average between the value at now-24 h and now-24+  t  t < 6hrs Now+  t    

May 1st 2008SWPC/NOAA SWW Workshop New SWPC “Ionosphere” Products: in transition or proposed D-Region absorption upgrade - FY08 GPS Ionosphere Positioning Correction (GIPC) - FY08 US-TEC short-term forecast - FY09

May 1st 2008SWPC/NOAA SWW Workshop

May 1st 2008SWPC/NOAA SWW Workshop Latitude dependence

May 1st 2008SWPC/NOAA SWW Workshop US-TEC Validation Summary Differential TEC: Slant = 2.4 TEC units Vertical = 1.7 TEC units “Absolute” FORTE ray tracing: Slant = 2.7 TEC units Vertical = 1.9 TEC units Estimated US-TEC slant path total electron content uncertainty < 3 TEC units (equivalent to about 45 cm of signal delay at L1 frequencies) Estimate US-TEC vertical total electron content uncertainty < 2 TEC units (equivalent to about 30 cm of signal delay at L1 frequencies)

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May 1st 2008SWPC/NOAA SWW Workshop “Differential” Validation Integrate through US- TEC model at two different times. Compare directly to the phase difference in the original RINEX data file. As time separation increases, errors in US-TEC map become uncorrelated and approach true uncertainty. Araujo-Pradere et al. 2006

May 1st 2008SWPC/NOAA SWW Workshop US-TEC “Differential” Validation Validation stations not included in assimilation process Build up statistics every 5th day over 6 months Daily average RMSE for each site Slant path RMSE US-TEC IRI

Validation Statistics: “differential” TEC 2.4 TEC units

May 1st 2008SWPC/NOAA SWW Workshop Absolute validation: FORTE Fast Onboard Recording of Transient Events satellite (Los Alamos, Abe Jacobson) Phase or arrival time as function of frequency Separate O and X traces Fit to k/f 2 dependence provides TEC estimate Time of arrival Frequency Broad-band RF receiver MHz at 800 km altitude Designed to monitor lightning Pulse transmitted from Los Alamos (simulated lightning) Possible to estimate line-of-sight TEC between transmitter and FORTE satellite Broad-band signal/receiver eliminates phase ambiguity so produces an “absolute” TEC estimate (uncertainty estimate is about 1 to 2 TEC units) Issues are –bending of the rays, –plasmaspheric content, and having to sub-sample US-TEC vertical domain

May 1st 2008SWPC/NOAA SWW Workshop US-TEC/FORTE Statistics “Absolute”: using 178 FORTE observations between June 30, 2000, and November 27, 2001 All values in TECU Minter et al. 2006

May 1st 2008SWPC/NOAA SWW Workshop OPUS – GIPC (GPS Ionospheric Positioning Correction) SWPC (USTEC output is used to derive the ionospheric delay) RINEX Processed (a new I1 observable added to the RINEX file) RINEX No Processed (comment added to the file) NGS (quality control) Customer RINEX NGS Special Projects Users (NGS, surveyors, etc.) RINEX TRANSITION: 4 th quarter ‘08