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Solar Irradiances, Geomagnetic Events, and Total Electron Content Beginning Oct 2003

Bouwer, S.D'., W.K. Tobiska', A. Komjathy'', B. Wilson'', X. Pi'', and A. Mannucci''

' Space Environment Technologies'' Jet Propulsion Laboratories

• Solar Irradiance Indices• Total Electron Content comparison of 28 Oct 04 (X-ray flare)

to 30 Oct 04 (Geomagnetic event)• Thermospheric and Ionospheric Effects• The SOLAR2000 Irradiance Model and E10.7

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Solar Indices and Active Region Evolution

• F10.7 significantly differs from E10.7(see page 9) over a solar rotation (and longer time scales)

– F10.7 cm flux (2800 MHz radio) represents a mixture of coronal and photospheric variations, and has no thermospheric effect

– E10.7 (the integrated 1-105 nm soft X ray and EUV flux in F10.7 units) represents both coronal and chromospheric variations, and better represents the energy input to the thermosphere

• In general, active region evolution has a dominant pattern of a rapid rise and gradual decay over 4-5 solar rotations

– A solar rotational effect in the flux seen at Earth is related to the relative opacity of the solar atmosphere to solar irradiances

• A better index to coronal variations is needed to better represent the X-ray irradiances

E10.7 and F10.7

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Images courtesy of the SOHO/EIT Consortium

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Solar Indices, 13 Oct to 9 Nov, 2003

• E10.7 (see page 9) represents the integrated spectrum from approximately 1-105 nm, with both chromospheric and coronal components

– Employs the Penticton F10.7 and NOAA SBUV Mg II data (in Ly-alpha units)

• A Daily Background X-ray index, Xb = weighted daily hourly minimum of 100*log((X-ray 1-8A flux)*10E+10),shows a different rotational modulation

– Time series curve of 1-8 A X-rays is due to the X-ray irradiance through an optically thin solar atmosphere as the evolving active region rotates across the disk

– Xb reduces the short-term logarithmic flares in the time series, creating a daily coronal index on a linear scale

Solar Indices, 13 Oct - 9 Nov, 2003

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Penticton F10.7 (+300)

Lya (From MgII c/w)Solar2000 E10.7 (+300)

QuickTime™ and aTIFF (LZW) decompressor

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"Halloween" Events, 13 Oct - 9 Nov 2003

Images courtesy of the SOHO/EIT Consortium

• Oct 28 and Nov 4 were primarily X-ray events (low Kp), although Oct 22-23 saw several M-class flares• At Earth, major Geomagnetic and particle events persisted throughout Oct 29-31

•In general, the variation of X-rays over a solar rotation is what we expect for an optically thin solar atmosphere

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Thermospheric Heating from Solar EUV Compared to Joule Heating

• Generally, Solar EUV is responsible for approximately 80% of thermospheric heating;

• Except during major geomagnetic disturbances, when Joule heating dominates

• Hemispheric particle power during solar-induced particle events is a 2nd-order effect

Daily Average Power Values for Max and Decline of Solar Cycle 23

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Climatology of Extreme Upper Atmosphere Heating Events, D.J. Knipp et. al., ASR, in press

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TIMED GUVI and Solar Indices, 12 Jul - 8 Aug 2002

• Thermospheric heating for a period of time similar to the Halloween events was measured by the TIMED GUVI instrument in 2002

• A suggestion of coronal components in the GUVI data may be represented by the daily background 1-8 Angstrom X-ray index Xb (1-minute 1-8 A X-ray flux red line in fig)

– The GUVI local minima near DOY 200 and the slowly declining slope after DOY 210 are not as apparent in the other solar indices as in Xb

– Flares in GUVI data correspond to GOES X-ray flares

• Can the 4-40 nm component in thermospheric heating be represented by a 1-8 A X-Ray index?

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Qeuv Heating Rate

• Thermospheric heating (Qeuv) by solar flux in soft X-ray and EUV wavelengths dominates thermospheric heating

• other derivative SOLAR2000 products include:

•derived sunspot number, Rsn (unitless),•exospheric temperature at 450 km, Tinf (K)•EUV hemispheric power, Peuv (GW)

• To the extent soft X-ray (in the 1-40 nm range, E1_40) is correlated with the 1-8 Angstrom index Xb, a new coronal proxy may be possible

Relative thermospheric Qeuv heating rate near solar maximum, calculated using the SOLAR2000 empirical model (see page 9)

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JPL Total Electron Content• TEC collected from over 100 GPS stations by the JPL Ionospheric and Atmospheric Remote Sensing Group• The X-Ray flare at 11 UT on Oct 28 is responsible for enhanced TEC

• Extensive latitudinal effect• Duration of enhanced TEC lasted only several hours

• In contrast, the geomagnetically induced TEC increase on Oct 30 was much larger, and persisted for several days

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SOLAR2000• SOLAR2000 is an empirical full-disk solar

irradiance model for accurately characterizing solar irradiance variability across the spectrum (1-1,000,000 nm at 1nm resolution)

– It is regularly improved using new satellite and rocket measurements and proxies, steadily improving it’s accuracy and applications

– It is compliant with the developing International Standards Organization (ISO) solar irradiance standard

– SOLAR2000 captures the essence of historically measured solar irradiances, expanding our knowledge about the quiet and variable Sun, including its historical envelope of variability

• E10.7 is the integrated SOLAR2000 estimated flux from 1-100 nm, converted to F10.7 units

– It more accurately estimates the input to thermospheric and ionospheric processes

– It can be used to improve other space physics models wherever F10.7 is used

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SOLAR2000 Products For Research and Engineering Applications

• A freely-available SOLAR2000 Research-Grade software package is available for studying historical solar-terrestrial variations.

– See http://www.spacewx.com• A SOLAR2000 Professional-Grade

(fee-based) software application is available for high-resolution nowcast and forecast operations

• The SOLAR2000 solar irradiance specification tool (and associated derivative products) have operational applications in satellite drag, radio communications, TEC, post-event analysis, etc.

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SOLAR2000 Forecasts

• SET employs an automated wavelet-based algorithm for predicting E10.7 (on time scales of hours to years)

• In extensive tests of the wavelet-based algorithm for predictions:

– The SET forecasts of F10.7 were at least as good as the NOAA/SEC forecaster predictions on 1-3 day time scales

– The E10.7 forecasts were significantly better on all time scales

• One-day F10.7/E10.7 forecasts are freely available at the http://www.spacewx.comwebsite

– Longer forecasts are one of the components in fee-based SOLAR2000 products

– Upgraded SOLAR2000 versions will improve forecasts

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Summary

• The Oct 2003 events demonstrate unique variations in both solar,thermospheric, and ionospheric measurements and indices

– Permitting the comparison of terrestrial effects due to a solar X-ray flare vs. a geomagnetic storm

• Solar Irradiance from soft X-rays and EUV (1-40 nm) are the principal driving forces to thermospheric and ionospheric variations

– Except during major geomagnetic events, when Joule heating dominates• SOLAR2000, the E10.7 index, and subsequent derived estimates (e.g.,

Qeuv, E1_40, Tinf) are effective proxies for estimating solar irradiance, thermospheric, and ionospheric variations

– SET is currently developing a better index representing coronal X-ray variations (i.e., the background X-ray index Xb and an associated flare index Xf) to improve the SOLAR2000 model and derivative solar-terrestrial proxies