High-latitude ionospheric response to co-rotating interaction region- and coronal mass ejection-driven geomagnetic storms revealed by GPS tomography and ionosondes

Abstract

Positive ionospheric anomalies induced in the polar cap region by co-rotating interaction region (CIR)-and coronal mass ejection (CME)-driven geomagnetic storms are analysed using four-dimensional tomographic reconstructions of the ionospheric plasma density based on measurements of the total electron content along ray paths of GPS signals. The results of GPS tomography are compared with ground-based observations of F region plasma density by digital ionosondes located in the Canadian Arctic. It is demonstrated that CIR-and CME-driven storms can produce large-scale polar cap anomalies of similar morphology in the form of the tongue of ionization (TOI) that appears on the poleward edge of the mid-latitude dayside storm-enhanced densities in positive ionospheric storms. The CIR-driven event of 14-16 October 2002 was able to produce ionospheric anomalies (TOI) comparable to those produced by the CME-driven storms of greater Dst magnitude. From the comparison of tomographic reconstructions and ionosonde data with solar wind measurements, it appears that the formation of largescale polar cap anomalies is controlled by the orientation of the interplanetary magnetic field (IMF) with the TOI forming during the periods of extended southward IMF under conditions of high solar wind velocity.

Ionospheric forecasts for the European region for space weather applications

“…In contrast, HSSs or CIRs seem to be not effectively captured by SWIF's present formulations. Such interplanetary structures usually drive the development of storm events of moderate intensity (e.g., Richardson & Cane 2012;Echer et al 2013) that are still able to produce significant ionospheric disturbances as they are described here, but also reported by others (e.g., Pokhotelov et al 2010;Tsurutani et al 2014). Such events are often ''missed'' by SWIF's ADA.…”

“…Taking into account the high warning ability of SWIF alert algorithm under the occurrence of intense storm events and the poorer performance for ionospheric disturbances that follow the occurrence of moderate storm events, it sounds reasonable to conclude that in practice SWIF alert criteria were designed to effectively anticipate the ionospheric storm time effects that occur under specific interplanetary conditions, e.g., cloud ICMEs and/or associated sheaths. In contrast, HSSs and probable CIRs, which are able to drive geomagnetic storms of moderate intensity followed by significant ionospheric disturbances (e.g., Pokhotelov et al 2010;Tsurutani et al 2014), are probably not effectively captured by the present criteria. Future analysis of the interplanetary conditions during such events is required to further support the argument and drive a more sophisticated formulation of SWIF's criteria.…”

Statistical characterization of ionosphere anomalies and their relationship to space weather events

“…Alternatively, an unsupervised detection approach relies primarily on the relative frequency of occurrence of normal conditions to distinguish them from abnormal conditions. The assumption that quiet conditions are a more common occurrence is implicit in many studies (see for examples, Tsurutani et al 2004;Pokhotelov et al 2010;Burns et al 2012;Tsurutani et al 2012). In developing an unsupervised classification scheme for ionosphere anomalies, we can attempt to establish possible correlations between ionosphere anomalies and externally driven space weather anomalies by examining the coincidence of occurrence of the two types of anomalies.…”

“…There is an abundance of research efforts focused on identifying and explaining the effects of space environment disturbances on the ionosphere (Fagundes et al 2008;Pokhotelov et al 2010;Lee et al 2011;Burns et al 2012;Tsurutani et al 2012). The identification of anomalous ionospheric features is often made within the context of a known space weather event, as well as by comparing ionospheric observations immediately following the event to preceding ''quiet'' period data.…”

Geospace effects of high-speed solar wind streams

“…Using networks of GPS receivers and tomographic inversion, the dynamics of the ionospheric 'tongue-of-ionization' are shown by Pokhotelov et al (2010) to be controlled by the orientation of the interplanetary magnetic field; they suggest that most CIR-driven events may not produce a persistent tongue of ionization owing to the oscillatory behaviour of the interplanetary magnetic field during such events. The system-wide coupling from Sun to atmosphere is highlighted by Mlynczak et al (2010), who report short-term periodicities in the radiative cooling of the Earth's thermosphere by monitoring of nitric oxide emissions; the cooling is shown to arise not from solar ultraviolet radiation, but from coupling of the solar wind to the thermosphere.…”