Positive storm effects in the dayside polar ionospheric F-region observed by EISCAT and ESR during the magnetic storm of 15 May 1997

Abstract

Abstract. EISCAT/ESR radar data and in situ FAST and PO-LAR satellite observations are coordinately analyzed to investigate positive ionospheric storm effects in the dayside upper F-region in both the polar cap and the auroral oval during the magnetic storm of 15 May 1997. An ionization enhancement, lasting for about 2.5 h, appeared first over the EIS-CAT site around magnetic noon; about one hour later, a similar ionization enhancement was also seen over ESR. During the concerned time period ion energy spectra measured on board FAST show clearly continuous energy-latitude dispersion when the satellite passed by over the EISCAT latitude. This implies that EISCAT was located under the polar cusp region which was highly active, and expanded greatly equatorwards due to magnetopause reconnections during longlasting southward IMF. Simultaneously, soft particles of the magnetosheath precipitated into the F-region ionosphere and caused the positive storm effects over EISCAT. The coincident increase in electron temperature at EISCAT gives additional evidence for soft particle precipitation. Consistently, POLAR UV images show strong dayside aurora extending to as low as 62 • N magnetic latitude. The ionization enhancement over ESR, however, seems not to be caused by local particle precipitation, evidenced by a lack of enhanced electron temperature. The observed plasma convection velocity and data-fitted convection patterns by AMIE suggested that it is likely to be a polar patch originating from the cusp region and traveling to the ESR site.

Study of the ionosphere during a magnetospheric storm using data on the ground and in space

“…An increase of DfoF2 on all ionosondes of the chain can be seen from 09:00 UT. A cause of the DfoF2 increase on the northern ionosondes is particle precipitation during the substorm expansive phase as shown in Ma et al (2002). A similar effect on the middle latitude ionosondes, as discussed just above, can be an F2 layer lift due to electrical fields and southward winds (Buonsanto, 1999).…”

“…Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.asr.2010.08.013 Ma et al, 2002;Yeh et al, 1994). However, these investigations are not enough and many questions are still unanswered.…”

“…Existing ionospheric models and methods of radio wave propagation calculations are not always correct for disturbed periods at middle latitudes to say nothing of high latitudes. Considerable recent attention has been focused on the joint observations both from the Earth's surface and from the terrestrial space (Hunsucker and Hargreaves, 2003;Ma et al, 2002). This dual observational approach allows us to understand better some processes of the magnetosphere-ionosphere coupling.…”

Numerical simulation of ionization enhancement in the topside ionosphere of cusp foot-point region caused by low energy particle precipitation

“…Ma et al [6] concluded that ionization enhancement observed by the EISCAT radar might be probably caused by soft particles from the magnetosheath precipitating into the F-region ionosphere. The coincidence increase in electron temperature at the EISCAT gives additional evidence for soft particle precipitation.…”

“…During the strong magnetic storm of 15 May 1997, positive storm effects were observed by both the European Incoherent SCATter radar (EISCAT) and the ESR radars in the dayside ionospheric F-region, which was superposed on a negative effect background [6] . Ma et al [6] concluded that ionization enhancement observed by the EISCAT radar might be probably caused by soft particles from the magnetosheath precipitating into the F-region ionosphere.…”