Study of Variation of Polar Cap Potential During Geomagnetic Storm Events of 24 November 2001 and 24 August 2005 as Observed From LFM and BATS‐R‐US Simulation

Abstract

In this paper we examine variation of polar cap potential (PCP) during two storm events that occurred on 24 November 2001 and 24 August 2005 using Lyon‐Fedder‐Mobarry (LFM) and Block‐Adaptive‐Tree‐Solarwind_Roe‐Upwind‐Scheme (BATS‐R‐US) simulations and compare it to Weimer model. These events were simulated for zero, pure By, pure Bz, and full IMF conditions separately, and the PCP obtained were compared with the zero IMF PCP value as a baseline (viscous) potential. For southward IMF, PCP is defined as sum of reconnection and viscous, whereas for northward IMF, it is peak to peak potential, which either will be viscous potential or reconnection potential, whichever is larger. Both events were simulated for a constant ionospheric conductivity of 5 mhos and the variation of PCP was found to be consistent with previous literatures. Furthermore, we found that BATS‐R‐US PCP fluctuated similar to LFM PCP for most parts although their PCP values did not exactly match. We observed that BATS‐R‐US PCP also goes below viscous value for northward IMF condition, something which was observed previously in LFM simulation only. We also found that BATS‐R‐US PCP is more sensitive to smaller fluctuation of IMF compared to LFM. For 24 August 2005 event, we found the PCP reach up to 550 and 440 kV and the viscous potential reached up to 120 and 110 kV for BATS‐R‐US and LFM, respectively. Similarly, for 24 November 2001 event PCP reached up to 800 and 400 kV and viscous potential reached up to 300 and 200 kV, respectively, for BATS‐R‐US and LFM.