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Ursa Astronomical Association

Auroras seen through breaks in the clouds - 23.4.2023 at 23.30 - 23.4.2023 at 23.55 Tampere Observation number 115575

Visibility III / V

Kari A. Kuure, Tampereen Ursa

Northern lights through the clouds. The magnetic storm "exploded" around 20:00 when the CME cloud collided with the Earth's magnetic field. The storm index flowed downwards throughout the evening and reached a bottom reading of -228 nT at 21:06 UT time (00:06 Finnish time). The magnetometer of the measuring station in Kiruna reached a peak reading of -944 nT during the evening and remained at this level for a long time. Potsdam's ap index, on the other hand, reached a reading of 207, which does not happen very often. Even at the measuring station of the University of Tartu, a strong magnetic disturbance was measured during the evening. The Northern Hemisphere power calculated by the OVATION model reached a peak reading of 180 GW, which is also a very rare reading. The intensity of the magnetic storm was determined to be G4. The maximum value of the Bz component of the IMF field measured by satellite was around -25 nT around 21:00. However, the field turned northward after 11 p.m. and would only occasionally turn southward for short periods after that.

It was cloudy in Tampere, so the beautiful northern lights were not visible. However, the cloud cover was thin in the early evening despite its coverage, so the observatory's camera recordings left a hint of the events in the sky and the green aurora borealis could be heard through the cloud cover. Here are a few pictures, in order the second picture is from the east facing camera.

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Additional information
  • Aurora brightness
    • Very bright auroras
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