Occurrence statistics of magnetic impulsive events

Abstract

Abstract. In this study, we perform a statistical investigation of magnetic impulse events identified in the Greenland magnetometer stations through the years 1995-2001. We focus on occurrence statistics that can be determined reliably with an automatic event identification procedure. Durin the first two years we observed almost 40% more events than in the following years. Season is not a significant factor in event occurrence. Event occurrence peaks near 12:00 UT, corresponding to approximately 10:00 magnetic local time (MLT) at the west coast of Greenland. More events occur prior to local noon than after. Event days are not distributed evenly. Large amplitude events, particularly, tend to appear on consecutive days. Events are observed at lower latitudes at earlier local times in a way consistent with the projection of the outer magnetospheric boundary into the ionosphere. Event latitude depends on dipole tilt angle in a manner similar to that reported for the cusp. Events occur during intervals of enhanced K p . The main reason for this is that the events themselves contribute to the K p index. Events exhibit a preference for high solar wind velocity. In particular, the large amplitude events occur during high-speed streams. A slight preference for lower density and more radial interplanetary magnetic fields, as compared to the nominal solar wind distribution, is also observed. However, both the nominal solar wind and event distribution exhibit large differences from year to year, indicating that events occur under a broad range of conditions.

Magnetospheric response to magnetosheath pressure pulses: A low‐pass filter effect

“…The current was enhanced due to the groups of pulses most prominently at around 70° geomagnetic latitude and above (red areas in Figure ). This is consistent with the occurrence distribution of magnetic impulse events (MIEs) often associated with TCVs [e.g., Moretto et al , ]. Note that the number of magnetometers (pink squares) at these high latitudes is however small.…”

Simultaneous traveling convection vortex events and Pc1 wave bursts at cusp latitudes observed in Arctic Canada and Svalbard

“…[] study, which also used MACCS data, and Moretto et al . [], who used data from both the eastern and western coasts of Greenland. As Zesta et al .…”

“…The statistical study of Moretto et al . [], which also required a TCV signature in two longitudinally separated regions, illustrated the complexity of the spatial pattern of these events. Their statistical results, like those of Zesta et al .…”

Patterns of simultaneous observations of high-latitude magnetic impulses (MIEs) and impulsive bursts in the Pc1–2 band

“…Most MIEs are observed during quiet or moderate geomagnetic activity (Kp$1-3) (Glassmeier et al, 1989;Moretto et al, 2004). The maximum of impulse occurrence falls within the latitudinal range 70-761 (Sibeck and Korotova, 1996).…”

“…The major attention in these publications is focused on an examination of the connection of MIEs with solar wind plasma parameters and interplanetary magnetic field (IMF) conditions (Bering et al, 1990;Sibeck and Korotova, 1996;Kataoka et al, 2003;Moretto et al, 2004).…”