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

Abstract

[1] Traveling convection vortices (TCVs), which appear in ground magnetometer records at near-cusp latitudes as solitary~5 mHz pulses, are a signature of dynamical processes in the ion foreshock upstream of the Earth's bow shock that can stimulate transient compressions of the dayside magnetosphere. These compressions can also increase the growth rate of electromagnetic ion cyclotron (EMIC) waves, which appear in ground records at these same latitudes as bursts of Pc1 pulsations. In this study we have identified TCVs and simultaneous Pc1 burst events in two regions, Eastern Arctic Canada and Svalbard, using a combination of fluxgate magnetometers and search coil magnetometers in each region. By looking for the presence of TCVs and Pc1 bursts in two different sequences, we have found that the distribution of Pc1 bursts was more tightly clustered near local noon than that of TCV events, that neither TCVs nor Pc1 bursts were always associated with the other, and even when they occurred simultaneously their amplitudes showed little correlation. Magnetometer data from GOES-12 were also used to characterize the strength of the magnetic compressions at geosynchronous orbit near the magnetic equator. Compressions > 2 nT at GOES-12 occurred during 57% of the Canadian TCV events, but during~85% of the simultaneous TCV/Pc1 burst events. There was again little evident correlation between TCV and GOES-12 compression amplitudes. We have also documented unusually low EMIC wave activity during this deep solar minimum interval, and we attribute the low occurrence percentage of combined events in this study to this minimum.

Multi‐instrument observations from Svalbard of a traveling convection vortex, electromagnetic ion cyclotron wave burst, and proton precipitation associated with a bow shock instability

“…A statistical study of TCV / Pc 1 burst events by Posch et al . [, also manuscript in preparation, 2013] found that although TCV events could be identified in ground magnetometer data up to 6 h before local noon, Pc 1 bursts associated with these TCV events were only observed within 3 h of local noon.…”

“…stations is not surprising, however, both because of their somewhat lower latitude, and because of their local time, roughly 4.5 h before local noon. A statistical study of TCV / Pc 1 burst events by Posch et al [2011Posch et al [ , also manuscript in preparation, 2013 found that although TCV events could be identified in ground magnetometer data up to 6 h before local noon, Pc 1 bursts associated with these TCV events were only observed within 3 h of local noon.…”

“…By correlating magnetopause displacements (detected by the AMPTE CCE satellite) and bursts at South Pole Station, Antarctica, Anderson et al [1996] observed that Pc 1 bursts can be stimulated by compressions of the dayside magnetosphere, and can have a source region that extends 1 to 2 h azimuthally and 1 to 2 R E radially earthward of the low-latitude boundary layer. A recent statistical study by Posch et al [2011] found that, of the long-period transient events observed in cusp-latitude ground data within AE 3 h of local noon in 2008-2009, roughly 25% were accompanied by nearly simultaneous Pc 1 wave bursts at the same or nearby stations.…”

“…A recent statistical study by Posch et al . [] found that, of the long‐period transient events observed in cusp‐latitude ground data within ± 3 h of local noon in 2008–2009, roughly 25% were accompanied by nearly simultaneous Pc 1 wave bursts at the same or nearby stations.…”

Conjugate observations of electromagnetic ion cyclotron waves associated with traveling convection vortex events

“…It has also been reported that compression of the magnetosphere due to transient phenomena can cause EMIC waves [e.g., Anderson et al, 1992;Anderson and Hamilton, 1993;Engebretson et al, 2002;Usanova et al, 2010Usanova et al, , 2012Cho et al, 2016;Park et al, 2016;Saikin et al, 2016]. TCV events, which are closely associated with compression and decompression of the magnetosphere due to sudden P d change, also contribute to generation of EMIC waves [e.g., Arnoldy et al, 1988Arnoldy et al, , 1996Engebretson et al, 2013;Posch et al, 2013]. This paper presents simultaneous observations of TCVs and EMIC waves in association with transient P d changes in the magnetosphere.…”