Observations of GPS scintillation during an isolated auroral substorm

Abstract

This paper reports simultaneous observations of ionospheric scintillation during an auroral substorm that were made using an all-sky full-color digital single-lens reflex (DSLR) camera (ASC) and a Global Positioning System (GPS) ionospheric scintillation and total electron content monitor (GISTM) in Tromsø (69.60 N, 19.20 E), Norway. On the night of November 19, 2009, a small substorm occurred in northern Scandinavia. The ASC captured its temporal evolution from the beginning of the growth phase to the end of the recovery phase. The amplitude scintillation, as monitored by the S 4 index from the GISTM, did not increase in any substorm phase. By contrast, phase scintillation, as measured by the σ φ index, occurred when discrete auroral arcs appeared on the GPS signal path. In particular, the phase scintillation was significantly enhanced for a few minutes immediately after the onset of the expansion phase. During this period, bright and discrete auroral forms covered the entire sky, which implies that structured precipitation on the scale of a few kilometers to a few tens of kilometers dominated the electron density distribution in the E region. Such inhomogeneous ionization structures probably produced significant changes in the refractive index and eventually resulted in the enhancement of the phase scintillation.

The Behaviors of Ionospheric Scintillations Around Different Types of Nightside Auroral Boundaries Seen at the Chinese Yellow River Station, Svalbard

“…Hosokawa et al (2014) also suggested that strong phase scintillation in the nighttime auroral oval is mostly due to the large scale ionospheric irregularity generated due to the structured precipitation of particles on the scale of a few tens of meters to a few tens of kilometers. On the other hand Figures 3F,H confirms that the BBAE auroral emission is in the vicinity of strong phase scintillation, therefore, the BBAE is mostly due to the large scale ionospheric irregularity generated due to the energetic particle precipitation due to substorm, on the scale of few tens of meters to few tens of kilometers (Hosokawa et al, 2014).…”

“…The scintillation observations shown in Figures 1, 2 also confirm the ionospheric scintillation occurring at the different MLATs beyond the red line boundaries of the FBAE and BBAE. Based on the previous polar ionospheric scintillation studies (e.g., Hosokawa et al, 2014;Jin et al, 2014;van der Meeren et al, 2014van der Meeren et al, , 2015 and the references therein) we can say that the strong phase scintillations with almost weak amplitude scintillation shown in Figures 2C,D above the upper boundary of the BBAE maybe associated to the fast moving polar cap patches, which are beyond the field of view of the ASI deployed at the CYRS. The weak amplitude as well as weak phase scintillations, above the upper auroral emission boundary during the FBAE might have occurred mostly due to the background ionosphere.…”

“…(Zhang et al, 2017), but, if they appear only in 630.0 nm keogram ( Figure 1B), so called polar cap patches (e.g., Sato et al, 1998;Zhang et al, 2011Zhang et al, , 2013aZhang et al, ,b, 2016Hosokawa et al, 2012). Whenever, these structures meet the GNSS signals, they give rise to moderate amplitude and phase scintillation (Hosokawa et al, 2014), especially for polar cap hot patches (Zhang et al, 2017). The equatorward boundary of the nightside auroral (which is calculated using the sharp intensity gradients of auroral emission) oval is at ∼69 • MLAT (see in Figures 1A,B), but the scintillation data are available between 70 and 80 • MLAT only, due to which only the poleward boundary is visible on the scintillation maps.…”

“…The cusp region scintillations are long lasting as compared to the night time auroral scintillation. The scintillation generated in the cusp is associated with the ionospheric irregularity perturbation in the cusp region as well as cusp region particle precipitation, whereas, nighttime auroral oval scintillations are associated with the nightside energetic particle precipitation giving rise to auroral emissions (Prikryl et al, 2010(Prikryl et al, , 2011(Prikryl et al, , 2014Jiao et al, 2013;Kinrade et al, 2013;Hosokawa et al, 2014;Jin et al, 2014 and references therein). Inside the auroral oval there are some regions, where the amplitude scintillations are stronger as compared to the phase scintillations and they are supposed to be the regions having strong particle precipitations around the existing polar cap patches (Wang et al, 2016).…”

“…Charged particles from the solar wind and magnetosphere, mostly electrons and protons, precipitate in the upper atmosphere and dissipate their energy by generating the auroral emission. The nightside auroral events have been studied by many researchers since the last several decades and it has been found that in the auroral region, strong ionospheric scintillations are observed (Coker et al, 2004;Mitchell et al, 2005;De Franceschi et al, 2008;Hosokawa et al, 2014;Jin et al, 2014;van der Meeren et al, 2014van der Meeren et al, , 2015; and the references therein). Cusp region ionospheric irregularity dynamics which gives rise to pre-noon hour scintillation and cycle slips have been found to be associated with the polar cap patches during the solar minimum (Prikryl et al, 2010).…”