Time Lags between Ionospheric Scintillation Detection and Geomagnetic Storms at Auroral Latitudes

Abstract:

As growing awareness in vulnerabilities of technological infrastructures to space weather, intense research interests have focused on understanding ionospheric irregularities and associated scintillations in the context of solar wind coupling to the Earth’s magnetosphere-ionosphere system. The plasma irregularities at high latitude are strongly controlled by the solar wind and interplanetary magnetic field (IMF) conditions. The control results from a temporal coupling sequence of energy flow from the solar wind and their dissipations in the magnetosphere. Manifestations of the coupling process appear in the ionosphere as precipitating particles, plasma convection, electric fields and filed-aligned currents. These forms of energy release trigger plasma instability processes in the polar ionosphere, generating a wide variety of plasma irregularities in auroral oval, cusp and polar cap regions. The generated irregularities give rise to scintillations of trans-ionospheric radio signals.

Ionospheric scintillation is a phenomenon of rapid fluctuations in the amplitude and phase of trans-ionospheric radio wave signals. In the case of Global Navigation Satellite System (GNSS), scintillation impacts acquisition and tracking processes in receivers, causing signal slips or even loss of lock, hence becoming major threats to GNSS applications. While the physical processes responsible for the scintillation-causing irregularities are not yet fully understood, predicting ionospheric scintillations is fairly challenging especially under extreme space weather conditions.

This study provides a new insight into lead times in predicting ionospheric scintillations under space weather. We focus on the time lag between ionospheric scintillation detection (ISD) at auroral latitudes and the time of storm sudden commencement (SSC) of ten geomagnetic storms in 2015. Our objective is to understand the time delay of ionospheric irregularity impacts on ground based GNSS receivers when the arrival of solar wind shock wave compressing the geomagnetic field. Results could be applied into scintillation forecast modelling of GNSS signals in future studies.

This study utilizes data collected from a total of 13 of GNSS scintillation monitoring receivers located in above 55-degree latitude in North America and Europe during the 10 geomagnetic storm events. Our analysis results indicate that the solar wind disturbances first detected by spacecrafts orbiting at Lagrange L1 point took 30-80 min to cause the disturbance in the geomagnetic field. The geomagnetic disturbances induced ionospheric plasma irregularities and ISD at each receiver. The time lag between the onset of SSC and the corresponding ISD varies between 10 and 770 min. The variation shows the time lag dependence on the storm onset time, receivers’ locations, earth orientation in space, IMF and geomagnetic conditions. A longer lag was observed by the receivers on the dayside at the time of SSC. Discussions are given to explain the cause of time lag, which is related to ionospheric irregularity production and transport processes at polar ionosphere in response to temporal sequence effects of solar wind coupling to magnetosphere and ionosphere.