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Mai Mai Lam (University of Reading)

Department of Meteorology. Atmospheric dynamical responses to solar-wind-driven current density changes in the global electric circuit. Mai Mai Lam (University of Reading) Mervyn P. Freeman and Gareth Chisham (British Antarctic Survey) Thanks to: VarSITI organisers;

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Mai Mai Lam (University of Reading)

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  1. Department of Meteorology Atmospheric dynamical responses to solar-wind-driven current density changes in the global electric circuit Mai Mai Lam (University of Reading) Mervyn P. Freeman and Gareth Chisham (British Antarctic Survey) Thanks to: VarSITI organisers; Mathew Owens (Reading); Leverhulme Trust for financial support www.gec-bas.info First VarSITI General Symposium Albena, Bulgaria, 6 -10 June 2016

  2. Outline • The Mansurov effect • Extend to global study • Altitude-time lag signature • Antarctic temperature patterns • Summary • The Mansurov effect is a polar surface pressure anomaly • - solar-wind-driven changes to • global atmospheric electric circuit • vertical fair-weather current Jz Mansurov et al., 1974; Page, 1989; Tinsley and Heelis, 1993; Burns et al., 2007, 2008; Lam et al., 2013, 2014

  3. Thunderstorms maintain a vertical electrical potential difference • between the ground and the ionosphere~ 250 kV • Leads to vertical ‘fair-weather’ current Jz • Different solar-wind-driven perturbations to Jz correlated to different • large-scale, day-to-day atmospheric variations Global atmospheric electric circuit + + + + + + + Ionosphere Fair Weather Current Jz + - Vi Surface - - - - - - - -

  4. A day-to-day correlation – the Mansurov effect Daily-mean IMF By Daily-mean Electric Potential of Ionosphere in Polar Regions ? Globally, the effect is clearest in Antarctica [field sig. 0.3%] Daily-mean Polar Ionosphere to Ground Potential Difference Day-to-day Polar Surface Pressure Anomaly Amplitude 1 - 2 hPa

  5. Solar-wind driven • Persistence ~10 days • Periodicity time lag • ~27 day; max. at zero • V, Jz driven • Opposite sign N & S • Lag ~ 0 days 12 UT Polar Surface Pressure Anomaly The polar Mansurov effect antarctic arctic Daily-mean dawn-dusk Interplanetary Magnetic Field IMF By (nT) ± polar daily-mean, solar-wind-induced ionospheric electric potential difference

  6. Internal generator • (thunderstorms and • electrified rain clouds) • Same sign slope N & S • Lag ~ days • Amplitude 3 - 4 hPa 12 UT Polar Surface Pressure Anomaly The Burns effect antarctic arctic Vertical Electric Field Anomaly (V/m) from Vostok electric field mill data Global, daily-mean, internal ionospheric electric p.d.

  7. (Mansurov) (Burns) Burns and Mansurov effects compared Surface pressure anomaly (hPa) Burns et al. 2008

  8. 87% of modelled daily p.d. controlled by daily-averaged By • < 1% controlled by • daily-averaged Bz •  daily timescale Vi dependence on By and Bz: indication of a daily timescale Daily-averaged p.d. above Vostok (kV) Daily averaged IMF By (nT) Vi Burns et al. 2007 Daily averaged IMF Bz (nT)

  9. Summary of Mansurov effect so far… Daily-mean IMF By Daily-mean Electric Potential of Ionosphere in Polar Regions Globally, the strongest and simplest effect is in Antarctica Daily-mean Polar Ionosphere to Ground Potential Difference clouds? (Tinsley et al.) Day-to-day Polar Surface Pressure Anomaly

  10. Outline • The Mansurov effect • Extend to global study • Altitude-time lag signature • Antarctic temperature patterns • Summary • The solar wind drives a polar surface pressure perturbation • There is an associated effect at mid latitudes

  11. Zero time lag, surface pressure study • Use 12 UT NCEP/NCAR reanalysis surface pressure, • 2.5 x 2.5 latitude / longitude grid. • Remove seasonal cycle to get : p(, ) • Bin p in daily averages of IMF By for1999–2002 • By 3 nTBy - 3 nT • Find latitude longitude

  12. IMF By- associated surface pressure anomaly Lam et al. 2013

  13. By-related signs of ∆p and ∆Jz Antarctic and Arctic SuperDARN ionospheric potential Lam et al. 2013

  14. Whole hemisphere study Quasi-stationary Rossby (planetary) waves North C Orange circles at 30 and 70 ~ 4 – 6 waves at mid-latitudes (m = 4 - 6)

  15. 2D surface pressure ordered by IMF By resembles QS Rossby wavefield N • 2D variation in the southern hemisphere • does not look as regular as in the north • However, 50S section shows m = 3 present Planetary wave m = 3 S x Surface pressure (hPa) Longitude ()

  16. Mid-latitude IMF By effect could be important N • Size of pressure anomaly similar to • that in polar regions: ~ 1 - 2 hPa • Corresponding zonal winds similar to • initial uncertainties in ensemble • numerical weather predictions of ~ 1 m/s • Rossby wave field key in determining • trajectories of storm tracks • Importance of small effects • (nonlinear dynamics) S Lam et al. 2013

  17. Summary of global study • Changes in IMF By correlate to changes in surface pressure poleward of • 30. For zonal average, largest effect near poles • Mid-latitude effect: difference in surface pressure for high positive and • negative IMF Byresembles planetary wave field • 2 stages • (i) Direct action of ionospheric potential on polar pressure via GEC • (ii) Changes to polar atmospheric pressure modify • quasi-stationary Rossby waves via zonal wind • Small, polar solar-wind influence on upper atmosphere may influence • populated regions • Acknowledgments: • NCEP Reanalysis data provided by NOAA/OAR/ESRL PSD, Boulder, Colorado, USA, from http://www.esrl.noaa.gov/psd/ • OMNI data obtained from GSFC/SPDF OMNIWeb interface http://omniweb.gsfc.nasa.gov • Software to produce plots of ionospheric potential written by Ellen Pettigrew

  18. Outline • The Mansurov effect • Extend to global study • Altitude-time lag signature • Antarctic temperature patterns • Summary • Not just a surface pressure effect – starts in lower troposphere and propagates upwards to the tropopause

  19. Time-lag altitude signature: geopotential height with By • Extend surface studies upwards to examine troposphere and • lower stratosphere • 12 UT NCEP/NCAR reanalysis geopotential height at p levels, • 2.5 lat. /long. grid. • Remove seasonal cycle to get : h(, , p; t) • Bin h in daily averages of IMF Byfor 1999-2002:time lag  • By 3 nT By - 3 nT • Take difference: ∆h(, , p; ) latitude 17 pressure levels longitude Lam et al. 2014

  20. Variation with height: field mean  70 S 10 hPa (m) Log pressure (hPa) ~ height (km) time lag (days) 1000 hPa Difference of mean geopotential height anomaly for 2 By bins Lam et al. 2014

  21. Field mean  70 S Difference of mean geopotential height anomaly for 2 By bins ~ height (km) • Significant correlation (1%) of • IMF By and geopotential height: • in troposphere and base of • stratosphere • for ~10 day interval, peaking for time lag > 0 (solar wind leads atmosphere) >1% masked 230 hPa time lag (days) Lam et al. 2014

  22. Field mean  70 S Difference of mean geopotential height anomaly for 2 By bins ~ height (km) • Significant correlation (1%) of • IMF By and geopotential height: • in troposphere and base of • stratosphere • for ~10 day interval, peaking for time lag > 0 (solar wind leads atmosphere) • time lag of peak increases with altitude >1% 250 hPa time lag (days) 1000 hPa Lam et al. 2014

  23. Summary of altitude/time-lag study • Changes in IMF Bycorrelate to significant changes in pressure: • - in troposphere and base of stratosphere (Antarctica) • - on timescale of days • - peak in correlation occurs with higher time lag at high altitudes • so signal propagates vertically • - in contrast with UV/ozone and • EPP/ozone mechanisms • NCEP Reanalysis data: NOAA/OAR/ESRL PSD, Boulder, Colorado, USA, • OMNI data: GSFC/SPDF OMNIWeb interface • COST action TOSCA: financial assistance to attend meetings • Gary Burns (AAD), Brian Tinsley (Dallas) for invaluable discussions

  24. Outline • The Mansurov effect • Extend to global study • Altitude-time lag signature • Antarctic temperature patterns • Summary • We have identified the temperature anomaly of the Mansurov effect

  25. Bin surface air temperature with By • 12 UT NCEP/NCAR reanalysis surface air temperatures, 2.5 x 2.5 • Remove seasonal cycle to get : T(, , t=0) • Bin T in daily averages of IMF Byfor 1999-2002 and season: • By 3 nT By - 3 nT • Take difference ∆T(, ) for each season • Use Wilcoxon Rank Sum test for significance of difference on grid Freeman and Lam, 2016, in prep.

  26. Variation with season of IMF By-related T anomaly from 30S SUMMERAUTUMNWINTERSPRING 0.9 C3.2 C2.4 C1.6 C Mean of 5 and 95 percentile levels • Seasonal • Regional • Peak magnitudes in autumn and winter of 2 - 3 C poleward of 60 S

  27. IMF By- related T anomalies in autumn Confidence levels contours: 10% (grey), 1% (white) Freeman and Lam, 2016, in prep.

  28. Similar to variation with season of zonal mean SAT SUMMERAUTUMNWINTERSPRING Freeman and Lam, 2016, in prep.

  29. Variation with season of zonal mean T Meridional gradient in Tz largest in autumn/winter  role for meridional winds

  30. Autumn geostrophic winds 1.5 0.5 0.0 -0.5 -1.5 hPa` IMF By - related p anomaly… …superimposed on zonal surface air temperatures Freeman and Lam, 2016, in prep.

  31. By - related sea surface T and p anomalies in autumn Geostrophic approximation: wind onto, or off of, the continent v on to Antarctica v off of Antarctica on to Antarctica: ∆T 0 off of Antarctica: ∆T 0 masked at 10%

  32. Summary of By - related sea surface T in Antarctica • Size seasonally dependent, largest amplitudes in autumn • and winter of about 2-3C [5/95 percentile] • Consistent with zonal mean surface air temperature Tz • Spatial distribution of ∆T consistent with Tz and By – related surface air pressure anomaly (∆p) • Mansurov temperature signature • NCEP Reanalysis data: NOAA/OAR/ESRL PSD, Boulder, Colorado, USA, • OMNI data: GSFC/SPDF OMNIWeb interface • Mathew Owens for financial and moral support! • John Turner (BAS) for invaluable discussions

  33. Overall summary • The Mansurov effect is a polar surface pressure anomaly that varies with solar-wind-driven changes to the global atmospheric electric circuit. • There is an associated mid-latitude effect which may involve atmospheric planetary waves. • It is not just a surface pressure effect – perturbations start in the lower troposphere and propagate upwards to the tropopause. • By - related temperature anomalies are seasonal and regional. • Zero time lag, near Antarctic coast peaks in autumn/winter, 2 - 3C • One of a number of Jz-related tropospheric phenomena [see Tinsley, 2008; Lam and Tinsley, 2015]

  34. Elements of a possible mechanism • Galactic cosmic rays (GCR) ionise atmosphere • Ions attach to aerosol particles  equilibrium +ve: –ve ratio • Thunderstorms drive a global atmospheric electric circuit • Downward current density Jz = Vi /(RM + RT ); Vi ,R vary (with solar inputs) • Jzflow leads to space charge at conductivity boundaries • Jz - related space charge perturbs the +ve: –ve ratio • Charge on aerosols particles (and on droplets) affects ‘scavenging rate’ of • aerosols by droplets • Therefore Jzcan perturb cloud formation processes • Amplification: via effects on albedo, IR opacity, cloud cover, balance in • long/short-wave radiation; storm invigoration Tinsley and Zhou, 2015

  35. CCN concentration and storm invigoration Pristine 0C Direction of airflow Ice and snow crystals Graupel Raindrop Cloud droplets Aerosols Hazy 0C Growing Mature Dissipating Rosenfeld et al. Science 2008

  36. Frontiers of UK GEC research external influences/drivers solar wind IMF ion sources EPP, GCR ionosphere WP3b R5 upper & middle atmosphere chemistry and conductivity J J atmospheric ionisation R2 WP3b R1 WP3a R4 WP1b R3 WP1a 250 kV J convective generator IR absorption 250  50 kV stratus cloud bb bb lightning rates WP2 T, p mid latitudes high latitudes

  37. Significance (Wilcoxon + field testing) high, except equatorial region N S Lam et al. 2013

  38. Change in latitudinal wavelength 2D QS Rossby waves • Coriolis force varies linearly in co-latitude  • Stationary solutions for wind in longitudinal and latitudinal directions • Integer number of azimuthal Rossby waves, m • Geostrophic approximation – horizontal motion balanced by pressure • force • Wavelength in latitudinal direction: • depends on meridional gradient of zonally-averaged pressure, • which changes with IMF By • Could account for Rossby-wave-like form of Lam et al. 2013

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