Eastward propagation of a plasma convection enhancement following a southward turning of the interplanetary magnetic field

Abstract

On October 27th 1984, high‐latitude ionospheric convection was observed by the European incoherent scatter (EISCAT) radar. For a nine‐hour period, simultaneous observations of the interplanetary magnetic field (IMF) were obtained sunward of the Earth's bow shock. During this period, the IMF abruptly turned southward, having previously been predominantly northward for approximately three hours, and a strong enhancement in convection was observed 11 ± 1 minutes later. Using the very high time resolution of the EISCAT data, it is shown that the convection enhancement propagated eastward, around the afternoon magnetic local time sector, at a speed of the order of 1 kms−1. These results are interpreted in terms of the effects of an onset of steady IMF‐geomagnetic field merging and are the first to show how a new pattern of enhanced convection is established in the high latitude ionosphere.

High-time resolution conjugate SuperDARN radar observations of the dayside convection response to changes in IMF B<sub>y</sub>

“…These speeds are consistent with previously observed propagation speeds outside the merging gap (e.g. Lockwood et al, 1986;Saunders et al, 1992), and this supports our interpretation of the Halley-Sanae time delay.…”

“…Observations suggest that the speed of this tailward expansion is between 1 and 10 kms À1 depending on the magnetic local time of observation (e.g. Lockwood et al, 1986;Todd et al, 1986;Etemadi et al, 1988;Saunders et al, 1992). However, the speed of the global ionospheric response to IMF changes is a matter of current debate.…”

A numerical model of the ionospheric signatures of time-varying magneticreconnection: I. ionospheric convection

“…The antisunward propagation of a change in the ionospheric convection electric field was first reported by Lockwood et al (1986), who used the EISCAT (European Incoherent Scatter) radar to observe the consequent increase in F-region ion temperatures following a southwardturning of the IMF, as seen just outside the bow shock by the AMPTE (Active Magnetospheric Particle Tracer Explorer) spacecraft. This heating is caused by collisions between the convecting ions and neutral thermospheric atoms whose motion cannot respond as rapidly.…”

A decade of the Super Dual Auroral Radar Network (SuperDARN): scientific achievements, new techniques and future directions

“…The first two panels are characterized by the relatively weak convection (U PC * 15 kV) that prevailed through a long preceding period of northward IMF. The convection Early models and observations suggested that global convection reconfigured in response to IMF variations on timescales of tens of minutes, and that the onset of a response was delayed by increasing amounts away from the noon sector (Lockwood et al 1986;Todd et al 1988;Saunders et al 1992). A similar scenario was observed in SuperDARN flow velocity data by Taylor et al (1998) in response to a northward turning of the IMF; sunward flows appeared almost immediately in the noon sector (within *2 mins) following the northward turning, but the flow within the radar fields-of-view took *20 mins to completely reconfigure.…”