Ionospheric midlatitude electric current density inferred from multiple magnetic satellites. Issue 9 (5th September 2013)

• Record Type: Journal Article
• Authors: Shore, R. M.; Whaler, K. A.; Macmillan, S.; Beggan, C.; Olsen, N.; Spain, T.; Aruliah, A.
• Is Part Of: Journal of geophysical research. Volume 118:Issue 9(2013:Sep.)
• Page Start: 5813
• Page End: 5829
• Publication Date: 2013-09-05
• Subjects: satellite geomagnetism -- ionosphere -- electric current density -- CTIP model -- midlatitude -- F region; Magnetospheric physics -- Periodicals; Space environment -- Periodicals; Cosmic physics -- Periodicals; Planets -- Atmospheres -- Periodicals; Heliosphere (Astrophysics) -- Periodicals; Geophysics -- Periodicals; 523.01
• DOI: 10.1002/jgra.50491
• Languages: English
• ISSNs: 2169-9380

Abstract

Abstract : [1] A method for inferring zonal electric current density in the mid‐to‐low latitude F region ionosphere is presented. We describe a method of using near‐simultaneous overflights of the Ørsted and CHAMP satellites to define a closed circuit for an application of Ampère's integral law to magnetic data. Zonal current density from sources in only the region between the two satellites is estimated for the first time. Six years of mutually available vector magnetic data allows overlaps spanning the full 24 h range of local time twice. Solutions are computed on an event‐by‐event basis after correcting for estimates of main and crustal magnetic fields. Current density in the range ±0.1 μA/m 2 is resolved, with the distribution of electric current largely matching known features such as the Appleton anomaly. The currents appear unmodulated at times of either high‐negative D s t or high F 10.7, which has implications for any future efforts to model their effects. We resolve persistent current intensifications between geomagnetic latitudes of 30 and 50° in the postmidnight, predawn sector, a region typically thought to be relatively free of electric currents. The cause of these unexpected intensifications remains an open issue. We compare our results with current density predictions made by the Coupled Thermosphere‐Ionosphere‐Plasmasphere model, a self‐consistent, first‐principles, three‐dimensional numerical dynamic model of ionospheric composition and temperatures. This independent validation of our current density estimates highlights good agreement in the broad spatiotemporal trends we identify, which increases confidence in our results. Key Points: Presents multi‐satellite‐measured ionospheric F-region electric current density Electric current density intensifications resolved at post-midnight midlatitudes Our estimates show good spatiotemporal agreement with CTIP model predictions