A model for estimating the relation between the Hall to Pedersen conductance ratio and ground magnetic data derived from CHAMP satellite statistics

Abstract

Abstract. The goal of this study is to find a way to statistically estimate the Hall to Pedersen conductance ratio α from ground magnetic data. We use vector magnetic data from the CHAMP satellite to derive this relation. α is attained from magnetic satellite data using the 1-D Spherical Elementary Current Systems (SECS). The ionospheric equivalent current density can either be computed from ground or satellite magnetic data. Under the required 1-D assumption, these two approaches are shown to be equal, which leads to the advantage that the statistics are not restricted to areas covered by ground data. Unlike other methods, using magnetic satellite measurements to determine α ensures reliable data over long time sequences. The statistical study, comprising over 6000 passes between 55 • and 76.5 • northern geomagnetic latitude during 2001 and 2002, is carried out employing data from the CHAMP satellite. The data are binned according to activity and season. In agreement with earlier studies, values between 1 and 3 are typically found for α. Good compatibility is found, when α attained from CHAMP data is compared with EISCAT radar measurements. The results make it possible to estimate α from the east-west equivalent current density J φ [A/km]: α=2.07/(36.54/|J φ |+1) for J φ <0 (westward) and α=1.73/(14.79/|J φ |+1) for J φ >0 (eastward). Using the same data, statistics of ionospheric and field-aligned current densities as a function of geomagnetic latitude and MLT are included. These are binned with respect to activity, season and IMF B Z and B Y . For the first time, all three current density components are simultaneously studied this way on a comparable spatial scale. With increasing activity, the enhancement and the equatorward expansion of the electrojets and the R1 and R2 currents is observed, and in the nightside, possible indications of a Cowling channel appear. During southward IMF B Z , the electrojets and the R1 and R2 currents are stronger and clearer than during northward B Z . IMF B Y affects the orientation of the pattern.

Empirically modelled Pc3 activity based on solar wind parameters

“…This ratio is considered to be relatively stable (e.g. Juusola et al, 2007), so it is not expected to cause large Pc3 amplitude modulation. Nevertheless, neither this effect nor the winter anomaly of Pc3 pulsations described by Verő et al (1995) were considered in our Pc3 activity models.…”

Statistical dependence of auroral ionospheric currents on solar wind and geomagnetic parameters from 5 years of CHAMP satellite data

“…The optimal displacement for each overflight was determined by minimizing the difference between the measured and computed B θ . If such a coordinate system could be found, where the difference was small enough, the overflight was termed 1-D (see Juusola et al, 2007, for more details). An example of the application of the 1-D SECS method for one overflight is shown in Fig.…”

Ionospheric midlatitude electric current density inferred from multiple magnetic satellites

“…However, when using a single satellite to estimate electric current density, it is difficult to avoid biasing the estimates by inclusion of contributions from regions outside the satellites' altitude range. This can be ameliorated in part by making geometrical assumptions about the regions being studied (or avoided), as in, for example, Juusola et al [2007]. Here we detail for the first time, multi-satellite estimated trends in the zonal ionospheric electric current density at a range of local time (LT) and phases of the solar cycle.…”