The commissioning phase of Swarm satellites provided opportunities to acquire measurement during special acquisitions sessions. The Absolute Scalar Magnetometer (ASM) instrument of each satellite were operated in "burst mode": the recording frequency of the instruments were risen from the nominal 1 Hz to 250 Hz. A total of seven burst mode sessions, covering between 3 and 48 hours of continuous recording, were realized between December 2013 and February 2014. During that time, the local time of Swarm satellites orbits shifted from midnight-noon to post sunrise-post sunset. The last burst-mode session occurred during the recovery phase of a geomagnetic storm. Therefore ASM burst mode data allow to investigate both quiet and geomagnetic active periods. The analysis of burst mode data was focused on the phenomena that can be investigated only using this higher sampling rate, providing insight in the frequency band between few Hz to 125 Hz. From the analysis of the magnetic field data we could observe typical signals related to different geomagnetic phenomena, showing distinct features at low, mid and high latitude. We were able to detect fast magnetic field fluctuations with a typical pattern, associated with low-latitudes irregularities in the ionospheric plasma during the development of post-sunset plasma bubbles. We also present results of the analysis of short electromagnetic signals that were detected mostly in the mid-to-low latitudes evening sector, investigating their correlation with the occurrence of lightning on the ground. Over the high latitudes, we detected fast variations in the intensity of the magnetic field during the active periods and analyse their correlations with plasma irregularities.