Observations of the spatial structure of electron precipitation pulsations using an imaging riometer

Abstract

Abstract. Electron precipitation can be modulated by geomagnetic pulsation activity. This can be observed as pulsation of cosmic noise absorption as measured by riometers. Observations of such pulsations exhibiting field-line resonance and particle-driven characteristics using an imaging riometer are presented and the capability of the instrument to map their spatial structure is demonstrated. It is shown that for the events studied, the spatial variation of pulsation phase as measured by the riometer agrees with that inferred from ground-based magnetometers, whereas the spatial variation of pulsation amplitude may show a different structure. It is suggested that this is consistent with the mechanism proposed by Coroniti and Kennel (1970) where one would expect a fixed phase relationship between magnetic and absorption pulsations, but where the amplitude of the absorption pulsation can depend on several factors other than the amplitude of the magnetic pulsation.

GPS scintillation in the high arctic associated with an auroral arc

“…The Kilpisjärvi IRIS imaging riometer in northern Finland (69.05°N, 20.79°E) shows radio signal fading at 38 MHz and around the time of interest (0120–0130 UT) showed evidence of strong absorption. Further details about the imaging riometer can be found in the work of Senior and Honary [2003]. This fading at low frequencies is likely to be associated with absorption at D ‐region altitudes, which implies energetic particle precipitation causing low‐altitude ionization enhancements.…”

Enhancement and modulation of cosmic noise absorption in the afternoon sector at subauroral location (L = 5) during the recovery phase of 17 March 2015 geomagnetic storm

“…Sometimes, pulsations are also seen in the cosmic noise absorption (CNA) event. Senior and Honary [] have shown that electron precipitation as seen in CNA data has been modulated by geomagnetic pulsations. In that study, IRIS for CNA observation and IMAGE chain magnetometers for geomagnetic pulsation observation have been used, respectively.…”

On the origin of high m magnetospheric waves

“…These pulsations often appear in the measurements of relative ionospheric opacity meters (riometers) and are generally linked to the occurrence of standing magnetospheric Alfvén waves, known as field line resonances (FLR) [e.g., Spanswick et al , 2005]. This is not the sole source of these pulsations; Senior and Honary [2003] identified a westward propagating wave in the Imaging Riometer for Ionospheric Studies (IRIS), which they attributed to modulation via a drift or drift‐bounce resonant wave.…”