Average auroral configuration parameterized by geomagnetic activity and solar wind conditions

Abstract

Abstract. Average proton and electron auroral images are compiled from three years of observations by the IMAGE spacecraft, binned according to concurrent K P and upstream solar wind conditions measured by the ACE spacecraft. The solar wind parameters include solar wind velocity, density, and pressure, interplanetary magnetic field (IMF) magnitude and orientation, and an estimate of the magnetopause reconnection rate. We use both (a) the overall variation in brightness in the images and (b) the variation in location of the aurorae with respect to the binning parameters to determine which parameters best order the auroral response. We find that the brightness varies by a factor of ∼50 with K P , a similar amount with estimated dayside reconnection voltage, ∼15 with the IMF, ∼3 with solar wind density, ∼2 with solar wind velocity, and ∼5 with pressure. Clearly, geomagnetic activity as measured by K P and auroral dynamics are closely associated. In terms of the solar wind-magnetosphere coupling that drives auroral dynamics, the IMF is of paramount importance in modulating this, with solar wind speed and density playing a lesser role. Dayside reconnection voltage, derived from the solar wind velocity and IMF magnitude and orientation, orders the data almost as well as K P , though we find a plateau in the auroral response between voltages of 100 and 150 kV. We also discuss changes in configuration and overall size of the average auroral oval with upstream conditions.

Dynamic subauroral ionospheric electric fields observed by the Falkland Islands radar during the course of a geomagnetic storm

“…The corresponding latitudes of the DMSP spacecraft at these cut‐off times have been used to derive the boundaries (illustrated for the electrons (ions) by the thick black (grey) curves) in Figure 4a, by fitting to a circle offset from the pole by 4° toward midnight. This offset is based on a number of studies of auroral configuration [e.g., Milan et al , 2010], which show the average auroral location to be shifted in this way, and also proves to be consistent with subsequent analyses discussed later in this paper. The boundaries have been identified as corresponding to the maximum rate of change in the mean energy flux, within the latitude range 50° to 60°.…”

“…Use of the AACGM coordinate system enables the magnetically near‐conjugate northern hemisphere BKS radar field‐of‐view to be directly compared on the same map and this is indicated by the dashed outline. A model auroral oval (for Kp = 6) [after Milan et al , 2010] is included for reference. The + and × symbols correspond to the locations of a chain of ground magnetometers and are discussed below.…”

“…Data from the four individual beams in the field‐of‐view (from left to right, beams 2, 6, 10 and 14) are discussed in the text. The mapped conjugate location of the northern hemisphere BKS radar field‐of‐view is indicated by the dashed line and a model auroral oval (for Kp = 6) [after Milan et al , 2010] is included for reference. The + and × symbols indicate the locations of a chain of ground magnetometers.…”

Performance and air-shower reconstruction techniques for the JEM-EUSO mission

“…• for Kp = 8 (Milan et al, 2010). In conclusion we can assume that the ISS trajectory does not cross the pole-ward border of the auroral oval during the period 2000 till 2011.…”

Photometry of dayside auroras during solar minimum 1This article is part of a Special issue that honours the work of Dr. Donald M. Hunten FRSC who passed away in December 2010 after a very illustrious career.

“…Milan et al [18] have parameterized such auroral configurations according to magnetic activity and solar wind conditions. And it has been shown that when B z switches from strongly northward to strongly southward, there is a major shift in both the location and intensity of the observed dayside aurora [8,14].…”