loading page

Influence of off-Sun-Earth line distance on the accuracy of L1 solar wind monitoring
  • +2
  • Stephen E. Milan,
  • Jennifer Alyson Carter,
  • Gemma E. Bower,
  • Amy L Fleetham,
  • Brian J. Anderson
Stephen E. Milan
University of Leicester

Corresponding Author:[email protected]

Author Profile
Jennifer Alyson Carter
University of Leicester
Author Profile
Gemma E. Bower
University of Leicester
Author Profile
Amy L Fleetham
University of Leicester
Author Profile
Brian J. Anderson
John Hopkins Univ.
Author Profile

Abstract

Upstream solar wind measurements from near the L1 Lagrangian point are commonly used to investigate solar wind-magnetosphere coupling. The off-Sun-Earth line distance of such solar wind monitors can be large, up to 100 RE. We investigate how the correlation between measurements of the interplanetary magnetic field and associated ionospheric responses deteriorates as the off-Sun-Earth line distance increases. Specifically, we use the magnitude and polarity of the dayside region 0 field-aligned currents (R0 FACs) as a measure of IMF BY-associated magnetic tension effects on newly-reconnected field lines, related to the Svalgaard-Mansurov effect. The R0 FACs are derived from Advanced Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) measurements by a principal component analysis, for the years 2010 to 2016. We perform cross-correlation analyses between time-series of IMF BY, measured by the Wind spacecraft and propagated to the nose of the bow shock by the OMNI technique, and these R0 FAC measurements. Typically, in the summer hemisphere, cross-correlation coefficients between 0.6 and 0.9 are found. However, there is a reduction of order 0.1 to 0.15 in correlation coefficient between periods when Wind is close to (within 45 RE) and distant from (beyond 70 RE) the Sun-Earth line. We find a time-lag of around 17 minutes between predictions of the arrival of IMF features at the bow shock and their effect in the ionosphere, irrespective of the location of Wind.