Articles | Volume 35, issue 3
Ann. Geophys., 35, 365–376, 2017
https://doi.org/10.5194/angeo-35-365-2017
Ann. Geophys., 35, 365–376, 2017
https://doi.org/10.5194/angeo-35-365-2017

Regular paper 08 Mar 2017

Regular paper | 08 Mar 2017

Non-triggered auroral substorms and long-period (1–4 mHz) geomagnetic and auroral luminosity pulsations in the polar cap

Nadezda Yagova1, Natalia Nosikova1,2, Lisa Baddeley3,4,5, Olga Kozyreva1, Dag A. Lorentzen3,4,5, Vyacheslav Pilipenko1,6, and Magnar G. Johnsen7 Nadezda Yagova et al.
  • 1Schmidt Institute of Physics of the Earth, Moscow, Russia
  • 2National Research Nuclear University “MEPhI”, Moscow, Russia
  • 3University Centre in Svalbard, Svalbard, Norway
  • 4Birkeland Centre for Space Science (BCSS), University of Bergen, Bergen, Norway
  • 5British Antarctic Survey, Cambridge, UK
  • 6Space Research Institute of the Russian Academy of Sciences, Moscow, Russia
  • 7Tromsø Geophysical Observatory, UiT – the Arctic University of Norway, Tromsø, Norway

Abstract. A study is undertaken into parameters of the polar auroral and geomagnetic pulsations in the frequency range 1–4 mHz (Pc5∕Pi3) during quiet geomagnetic intervals preceding auroral substorms and non-substorm background variations. Special attention is paid to substorms that occur under parameters of the interplanetary magnetic field (IMF) conditions typical for undisturbed days (non-triggered substorms). The spectral parameters of pulsations observed in auroral luminosity as measured by a meridian scanning photometer (Svalbard) in the polar cap and near the polar boundary of the auroral oval are studied and compared with those for the geomagnetic pulsations measured by the magnetometer network IMAGE in the same frequency range. It is found that Pc5∕Pi3 power spectral density (PSD) is higher during pre-substorm time intervals than for non-substorm days and that specific variations of pulsation parameters (substorm precursors) occur during the last 2–4 pre-substorm hours.

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Short summary
A substorm is a dramatic phenomenon in the near-Earth space that is visualized as an aurora. Mostly substorms are caused by changes in the solar wind, but some of them can develop without any evident trigger. Such substorms together with undisturbed days were investigated using magnetometer and photometer data from Svalbard. Substorm precursors, i.e., specific features in 1–4 mHz geomagnetic and auroral luminosity pulsations, have been found at high geomagnetic latitudes.