Effects of Magnetic Storms and Substorms on Atmospheric Electric Field Variations

1. Solar wind-magnetosphere-atmosphere coupling: effects of magnetic storms and substorms in atmospheric electric field variations KleimenovaN., Kozyreva O., Michnowski S., Kubicki M, Institute of the Earth Physics, Russia Institute of Geophysics, Poland

2. Atmospheric electricity The global electric circuit The global electric circuit is controlled by the global thunderstorm activity. Thunderstorm activity draws current upward from the ground. The ionosphere disperses the current globally, and it leaks back to the surface.

3. The important points: • 1. Despite being postulated since at least 150 years [Thomson (Lord Kelvin), 1860], the global electric circuit is still poorly quantified. • 2. Solar and magnetosphere activity influences due to ionosphere electric field disturbances may significantly control a global electric circuit state. • 3.The geoelectric circuit links weather and solar activity. It remains the open question whether this linkage is passive or involves active coupling.

4. The aimof our investigations is to study an atmospheric electricity response to the magnetic storms and substorms. • Our studying was based on the observations of the vertical electric field (Ez) at two ground-based points: the middle latitude Swider station as well as at the polar latitude Hornsundstation. • To avoid meteorological influences we used Ez data, obtained only under so called “fair weather” conditions, which request the absence of a rain, snow, fog, lower clouds, and wind velocity more 6 m/c.We could find not more than ~ 40-60 full days under “fair weather” condition in the year (i.e., ~12-15% of the total observations)

5. MIDDLE LATITUDES obs. Swider (Poland) Coordinates: GeomagneticΦ=47.8º, Λ=96.8º Local magnetic noon at ~10 UT Global thunderstorm activity Ez daily variations under Kp<2 Asia Africa

6. Magnetic storm effect in the Ez variations • We have analyzed 14 magnetic storms in 2000-2004 observed under “fair weather” periods. It was typical that themain phaseof the magnetic storms was accompanied by intense night-side magnetic substorms. • The storm-time Ez anomalies are better manifested by comparing the recorded data with Ez daily variations obtained under the quiet magnetic conditions (at least Kp<2).

7. Asia Ez Ez – Ez(quiet) Day side BEL Night CMO SOD

8. Africa BEL CMO SOD

9. Results • For the first time the magnetic storm effect was found in the mid-latitude Ez variations. • Our study showed that during the main phase of a magnetic storm a strong daytime negative Ez deviations were observed at middle latitudes simultaneously with magnetic substorm developing at nightside of the auroral zone under any local mid-latitude magnetic perturbations. • The considered Ez deviations could be associated with the interplanetary electric field enhancement and it deep penetration into the magnetosphere. • Another plausible reason could be related to the common ionosphere conductivity increasing due to substorm energetic electron precipitation because the high-latitude ionosphere is an important part of the global atmospheric electric circuit.

10. Two examples of the Forbush decrease influence to the Ez changes Dst AE Forbush decrease averaged Ez level Forbush Ez level The strong Ez depletion in the days of Forbush decrease development is seen.

11. In the polar regions, the interaction of the solar wind and the Earth's magnetic field causes the two-cell convection patterns in the polar ionosphere. Solar influence on the atmospheric electric field differs between middle and polar latitudes. _ + The polar cap potential can produce significant vertical electric fields (Ez) at the ground level.

12. Obs. Hornsund (Spitsbergen)COORDINATESΦ=74º, Λ=110.5º HOR

13. Substorm effects in Ez at polar latitudes (obs. Hornsund) morning night night morning 74º 64º Two examples of a negative Ez deviation during the night substorms and a positive Ez deviation during the morning substorms

14. Global structure of high latitude plasma convection during the considered morning substorms at Scandinavian meridian according to the SUPERDARN data

15. Global structure of high latitude plasma convection during the considered night-time substorms at Scandinavian meridian according to the SUPERDARN data

16. The auroral oval location during the considered substorm

17. Ez X

18. CONCLUSION Magnetic storms and substorms, caused by solar wind and interplanetary magnetic field disturbances, could influence to the global electric circuit state via changing of ionosphere conductivity due to particle precipitations or via cosmic rays, or via the direct interplanetary electric field penetration into magnetosphere, or via thepolar cap convection changes. Thus, the variations in the atmospheric electricity both in middle and polar latitudes represent one of the final stage of thesolar wind-magnetosphere-atmosphere coupling.

19. THANK YOU FOR ATTENTION! My coauthors: S. Michnowski, O Kozyreva, M.Kubicki

20. Magnetic storm initial phase SC Ez Pd Np HOR Vx B BXB Bx By Bz SOD Bz IMF = +36 nT