Storm Time EMIC Waves Observed by Swarm&amp;#160;and Van Allen Probe Satellites

Yangfan He,Shuying Ma,Saikin Anthony,Lund Eric,Lühr Hermann,Hui Wang,Kistler Lynn

doi:10.5194/egusphere-egu21-1156

Abstract

&lt;p&gt;The temporal and spatial evolution of electromagnetic ion cyclotron (EMIC) waves during&lt;br&gt;the magnetic storm of 21&amp;#8211;29 June 2015 was investigated using high-resolution magnetic field observations&lt;br&gt;from Swarm constellation in the ionosphere and Van Allen Probes in the magnetosphere. Magnetospheric&lt;br&gt;EMIC waves had a maximum occurrence frequency in the afternoon sector and shifted equatorward during&lt;br&gt;the expansion phase and poleward during the recovery phase. However, ionospheric waves in subauroral&lt;br&gt;regions occurred more frequently in the nighttime than during the day and exhibited less obvious&lt;br&gt;latitudinal movements. During the main phase, dayside EMIC waves occurred in both the ionosphere&lt;br&gt;and magnetosphere in response to the dramatic increase in the solar wind dynamic pressure. Waves were&lt;br&gt;absent in the magnetosphere and ionosphere around the minimum SYM-H. During the early recovery&lt;br&gt;phase, He&lt;sup&gt;+ &lt;/sup&gt;band EMIC waves were observed in the ionosphere and magnetosphere. During the late&lt;br&gt;recovery phase, H&lt;sup&gt;+&lt;/sup&gt; band EMIC waves emerged in response to enhanced earthward convection during&lt;br&gt;substorms in the premidnight sector. The occurrence of EMIC waves in the noon sector was affected by&lt;br&gt;the intensity of substorm activity. Both ionospheric wave frequency and power were higher in the summer&lt;br&gt;hemisphere than in the winter hemisphere. Waves were confined to an MLT interval of less than 5 hr with a&lt;br&gt;duration of less than 186 min from coordinated observations. The results could provide additional insights&lt;br&gt;into the spatial characteristics and propagation features of EMIC waves during storm periods&lt;/p&gt;

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