In situ ionospheric current measurements during ROSE rocket flights: evidence for tilted current layers

Data recorded by the DC magnetometer on board the ROSE payloads launched into regions of moderate substorm activity have been interpreted in terms of current densities. Adopting generally accepted assumptions on the geometry of the currents, vertical profiles of the Hall current density could be computed. Systematic differences between the results of the upleg and downleg suggest that the assumption of a horizontal current sheet might not be applicable. Reasonable agreement between the observations of both legs is achieved if the Hall current layer is considered to be perpendicular to the ambient geomagnetic field lines.