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From 1893 to 1905, the values of the geomagnetic field recorded three times a day are available from the (Ogyalla magnetic observatory. We introduce these unique records, and at the same time, we provide an analysis of three noteworthy magnetic storms from this period, namely the events on 30 March 1894, 9 September 1898, and 31 October 1903. In addition to violent magnetic variations, remarkable auroras were observed in Central Europe during these events. The analysed events indicate that the source of the most intense, potentially dangerous geomagnetic disturbances can be the electric currents of the auroral oval or the field-aligned currents connected to the auroral oval. [ABSTRACT FROM AUTHOR]

An analysis of Bošković's early paper concerned with the polar light (aurora borealis) gives an insight into the validity of the mathematical method which the young Bošković applied to significant geophysical phenomena in order to comprehend their nature. Based on the given data, we have examined numerical results about the height of atmosphere and the heights of the auroras which were observed over Europe in 1726 and in 1737. In his text there is not a single mathematical formula. Following his instructions we have derived a formula which may be used to determine the distance of an aurora by observing it from one station. For the assumed aurora model, his method is applicable. We find that described ideas on the physical cause of aurora, conceived in a fluid coming from the sun, have elements of modern knowledge. [ABSTRACT FROM AUTHOR]

We investigate the association between temporalspatial structure of polar cap convection and auroral electrojet intensifications during a 5-h-long interval of strong forcing of the magnetosphere by an ICME/Magnetic cloud on 20 March 2001. We use data from coordinated ground-satellite observations in the 15:00-20:00MLT sector. We take advantage of the good latitudinal coverage in the polar cap and in the auroral zone of the IMAGE chain of ground magnetometers in Svalbard - Scandinavia - Russia and the stable magnetic field conditions in ICMEs. The electrojet events are characterized by a sequence of 10 min-long AL excursions to -1000/-1500 nT followed by poleward expansions and auroral streamers. These events are superimposed on a high disturbance level when the AL index remains around -500 nT for several hours. These signatures are different from those appearing in classical substorms, most notably the absence of a complete recovery phase when AL usually reaches above -100 nT. We concentrate on polar cap convection in both hemispheres (DMSP F13 data) in relation to the ICME By conditions, electrojet intensifications, and the global UV auroral configuration obtained from the IMAGE spacecraft. The temporal evolution of convection properties such as the cross-polar cap potential (CPCP) drop and flow channels at the dawn/dusk polar cap (PC) boundaries around the time of the electrojet events are investigated. This approach allows us to distinguish between dayside (magnetopause reconnection) and nightside (magnetotail reconnection) sources of the PC convection events within the context of the expanding-contracting model of high-latitude convection in the Dungey cycle. Inter-hemispheric symmetries/ asymmetries in the presence of newly-discovered convection channels at the dawn or dusk side PC boundaries are determined. [ABSTRACT FROM AUTHOR]