Bencze, Pál

Kis, Árpád

Lemperger, István

Lethy, Ahmed

Menvielle, Michel

Novák, Attila

Szarka, László

Szendrői, Judit

Wesztergom, Viktor

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Extended Abstract, 22nd EM Induction WorkshopWeimar, Germany, August 24-30, 2014Modulation of the surface impedance: effect of geomagnetic activityIstvan Lemperger1, Viktor Wesztergom1 and Michel Menvielle2 and László Szarka1 and Pál Bencze1 and Attila Novak1 and Judit Szendrői1 and Arpad Kis1 and Ahmed Lethy31MTA CSFK GGI, Sopron, HUNGARY, lempi@ggki.hu2ISGI/LATMOS, Saint Maur des Fosses, FRANCE, michel.menvielle@latmos.ipsl.fr3NRIAG, Helwan,  EGYPT, ahmedellethy@gmail.comSUMMARYThe presentation introduces a study which demonstrates the slight modulation of surface electromagnetic impedance tensor according to varying geomagnetic activity. The results are based on registrations of telluric and geomagnetic variations besides observatory conditions.Keywords: geomagnetic activity, source effect, ionospheric currentsABSTRACTIn case of practical MT exploration the surface EM impedance is computed based on a simplification related to the nature of the ionospheric source of the  surface  EM  signals.  Assuming  that  the ionospheric  current  systems  result  in homogeneous surface electromagnetic variations, the  uncertainty  of  the  computed  surface electromagnetic  impedance  tensor  depends  only the duration of the EM observation. However the surface EM field can only be approached by plane waves in certain time periods and besides given uncertainty. The EM impedance may be sensitive to  magnetospheric  and  -indirectly-  interplanetary circumstances and solar activity.Four years continuous observation of telluric and surface  geomagnetic  components  allowed  to perform  a  representative  survey  to  discover  if geomagnetic  activity  has any effect  on observed EM impedance tensor.Geomagnetic  indices  (Dst,  ULF-index,  ASY-H, SYM-H)  have  been  used  to  classify  dates according  to  geomagnetic  activity.  Processing  to estimate the mean surface EM impedance tensor has been performed in each dataset,  each class separately. The sensitivity and the characteristics of the answer of the EM impedance tensor to the geomagnetic  disturbances  seems  to  be  definite. This  presentation  aims  to  briefly  summarize  the preliminary  results  of  our  study  based  on  the unique  dataset  of  the  Széchenyi  István Geophysical Obsevatory (Intermagnet code: NCK).ACKNOWLEDGEMENTSThis study was supported by the TAMOP-4.2.2.C–11/1/KONV-2012-0015  (Earth-system)  project sponsored  by  the  EU  and  European  Social Foundation.Page 1 of 1

Modulation of the surface impedance: effect of geomagnetic activity

Modulation of the surface impedance: effect of geomagnetic activity

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