Magnetic environment: science of GIC

Transcription

1 First European Space Weather Week Magnetic environment: science of GIC Ari Viljanen and Risto Pirjola Finnish Meteorological Institute Antti Pulkkinen NASA/GSFC This presentation is a contribution to

2 First European Space Weather Week Contents 1) General scientific background 2) Operative calculation & some science 3) On-going and future science

3 First European Space Weather Week Before the modern space weather, there was GIC cosmic rays auroras S/C anomalies air drag j (r,t) particle radiation n(r,t) signal degradation B(r,t) E(r,t) GIC

4 First European Space Weather Week GIC deals with the inductive coupling between the ionosphere and the earth Activity of the Sun Propagation of the solar wind Magnetospheric processes Ionospheric processes Earth's structure (induction) Network configuration Geoelectric field at the Earth's surface GIC in ground based technological systems GIC problems Possible countermeasures, alarm systems, etc. Figure 1: Schematic GIC chain. Science blocks marked by blue.

5 First European Space Weather Week Modelling of the geoelectric field Ionospheric currents or ground magnetic data Earth s conductivity These results also applicable in magnetotelluric studies. 2. Modelling of GIC Discretely grounded systems Continuously grounded systems 3. Analysis of GIC effects

6 First European Space Weather Week GIC and db/dt are closely related 50 natural gas pipeline Mäntsälä (10 s values) GIC [A] 0 -dx/dt [nt/s] :30 06:40 06:50 07:00 07:10 07:20 07:30 20 Nurmijärvi observatory :30 06:40 06:50 07:00 07:10 07:20 07:30 Figure 2: Largest GIC measured in the Finnish natural gas pipeline.

7 First European Space Weather Week GIC is a manifestation of Faraday s law Roughly speaking: hor. ground electric field E dh/dt spatial integration ~ 90 deg any angle hor. magnetic field H geomagnetically induced current (GIC) Figure 3: Measured: ground magnetic field variation. To be determined: E and GIC.

8 First European Space Weather Week Space currents cause the varying magnetic field horizontal field H equivalent current J Figure 4: Potential theory states that the ground magnetic variation field can be explained by an equivalent current distribution at the ionospheric plane. Approximately, rotate H 90 degrees clockwise.

9 First European Space Weather Week Ionospheric currents flow all the time :07:00 70 o N 65 o N 0 o 40 o E 60 o N 20 o E max( H ) = 3843 nt Figure 5: Interpolated and rotated ground H at 20:07:00 UT on October 30, 2003, at the time of the GIC blackout in southern Sweden.

10 First European Space Weather Week Diversity of db/dt is eye-catching Two nearby timesteps, nearly identical patterns of ground H, but very different dh/dt: :06: :08:40 70 o N 70 o N 65 o N 65 o N 0 o 40 o E 0 o 40 o E 60 o N 60 o N 20 o E max( dh/dt ) = 28.4 nt/s 20 o E max( dh/dt ) = 34.1 nt/s

11 First European Space Weather Week Small scales are important t 1 t - 2 t 1

12 First European Space Weather Week Arising questions: Which ionospheric events cause large GIC? How do these events couple to magnetospheric and solar wind dynamics? What are the characteristic spatial and temporal scales related to these events? Are there any characteristic scales? Can we forecast such events? What features of these events can we forecast?

13 First European Space Weather Week Earth has a remarkable effect on the geoelectric field Ionospheric currents primary field E p Telluric currents secondary field E hor,s E hor,p Earth conductivity models are obtained from magnetotelluric studies A14 NALi A13 LYRi A12 HORi 75 A11 HOPi 75 A10 BJNi B E A R Baltic Electromagnetic Array Research Norwegian Sea A19 NORs B11 HEM B10 NOR A05 ANDi B14 LYC B15 ARV A07 TROi A03 ABKi B16 JOK A01 KIRi A04 KILi B23 ULL B22 BOD A09 SORi Bothnian Bay B21 SKE A06 MASi A02 MUOi B31 PEL B29 VIH B30 YLI A08 KEVi A20 OULs A15 IVA B35 SOD B34 MIS B33 OUL B42 SAL B41 KUO Barents Sea B40 LOT B49 UPO B48 TOP B50 LOV White Sea B47 LEH A23 LAU Vanern B05 ARE B02 LUD B01 ASK B09 BRA B08 SOD B07 UPS A18 KVIs A16 LOVi B13 HAR Gulf of Bothnia B12 MAR Baltic Sea B20 VOL B19 HON B18 AUR B17 HII B28 KIV B27 KOR B26 NUR B32 HAN B38 PUU B37 VIR Gulf of Finland B25 RAK B36 PEI B24 SIN B39 JUU B45 NII B44 PER B46 ILO Lake Ladoga Lake Onega MTS: Bx,By,Bz,Ex,Ey Oulu & Nurmijarvi 60 Uppsala & Edinburgh Goettingen & Potsdam St. Petersburg Lviv, Ukraina 55 TK km Observatories 40 GDS: Bx,By,Bz IMAGE/SAMNET 55

14 First European Space Weather Week Operative method - ground B :30:00 max = 382 nt Figure 6: Measured ground horizontal field rotated 90 deg clockwise to mimic ionospheric equivalent currents.

15 First European Space Weather Week Operative method - interpolated B 75 o N :30:00 70 o N 65 o N 60 o N 0 o 20 o E 40 o E Figure 7: Use of equivalent currents is a robust interpolation method.

16 First European Space Weather Week Operative method - earth s conductivity 5000 ohmm 500 ohmm 100 ohmm 3 km 6 km 5 km 10 ohmm 7 km 20 ohmm 23 km 1000 ohmm 106 km 1 ohmm Figure 8: Rough model of southern Finland. The local magnetotelluric relationship E(ω) Z(ω) B(ω) is the first approximation.

17 First European Space Weather Week Operative method - geoelectric field 21:29:00 21:30:00 21:31:00 21:32:00 max = 63 mv/km max = 57 mv/km max = 158 mv/km max = 432 mv/km 21:33:00 21:34:00 21:35:00 21:36:00 max = 470 mv/km max = 334 mv/km max = 226 mv/km max = 152 mv/km Figure 9: Snapshots of the calculated electric field. GIC is basically a measure for the electric field integrated along the conductors. The conductor system defines the relevant scales.

18 First European Space Weather Week Operative method - power grid 400 kv 220 kv Rauma

19 First European Space Weather Week Operative method - GIC 6 Rauma, GIC [A] modelled measured UT [h] Figure 10: Measured and modelled transformer neutral GIC.

20 First European Space Weather Week Operative method - ESA SDA Gasum Now!

21 First European Space Weather Week Science is progressing Classify quantitatively ionospheric currents causing large GIC. Apply pattern recognition methods originally used for auroral all-sky images :07:00 70 o N 65 o N 0 o 40 o E 60 o N 20 o E Figure 11: Scalar representation of equivalent currents.

22 First European Space Weather Week Forecasting GIC is demanding X [nt] NUR, black: measured, blue: "forecasted" dx/dt [nt/s] UT [h] Figure 12: Artificial example: not enough to forecast B fairly accurately.

23 First European Space Weather Week Summarising Recordings of the geomagnetic field reveal ionospheric (equivalent) currents Solid earth studies reveal the Earth s conductivity structure Ionospheric phenomena affecting GIC have highly varying spatial scales, which are determined by db/dt Operative nowcasting of GIC is well established Quantitative classification of GIC events is advancing Producing reliable GIC forecasts may require completely new ideas Producing GIC forecasts as accurately as forecasts for terrestrial weather may be impossible forever

24 First European Space Weather Week There are many scientific challenges of a general interest Investigate the basic nature of spatio-temporal variability of our geomagnetic environment Understand how our geomagnetic environment couples to the large scale dynamics of the magnetosphere Understand implications of the coupling and apply new knowledge to science of GIC