Abstract
The magnetosphere substorm plays a crucial role in the solar wind energy dissipation into the ionosphere. We report on the intensity of the high-latitude ionospheric irregularities during one of the largest storms of the current solar cycle—the St. Patrick’s Day storm of 17 March 2015. The database of more than 2500 ground-based Global Positioning System (GPS) receivers was used to estimate the irregularities occurrence and dynamics over the auroral region of the Northern Hemisphere. We analyze the dependence of the GPS-detected ionospheric irregularities on the auroral activity. The development and intensity of the high-latitude irregularities during this geomagnetic storm reveal a high correlation with the auroral hemispheric power and auroral electrojet indices (0.84 and 0.79, respectively). Besides the ionospheric irregularities caused by particle precipitation inside the polar cap region, evidences of other irregularities related to the storm enhanced density (SED), formed at mid-latitudes and its further transportation in the form of tongue of ionization (TOI) towards and across the polar cap, are presented. We highlight the importance accounting contribution of ionospheric irregularities not directly related with particle precipitation in overall irregularities distribution and intensity.
Highlights
The magnetosphere substorm plays a crucial role in the solar wind energy dissipation into the ionosphere
Distinguishing features of the model include an optimized solar wind–magnetosphere coupling function which predicts auroral power significantly better than Kp or other traditional parameters, the separation of aurora into categories, the inclusion of seasonal variations, and separate parameter fits for each bin of 0.5° magnetic latitude (MLAT) × 0.25 magnetic local time (MLT) (Newell et al 2014)
The daily Rate of TEC Index (ROTI) map (Fig. 3e) shows the ionospheric irregularities’ occurrence as an oval-shape region and in form of the radial structures oriented from the noon sector to near midnight one that can be related to the tongue of ionization (TOI) dynamics through the polar cap region
Summary
The ionospheric dynamics in the high-latitude region is driven by a coupling between the solar wind, the magnetosphere, and the ionosphere. The linkage of the high-latitude ionospheric irregularities, which produce the radio signal scintillation, to the GPS measurements is of special importance for several research activities One of these concerns the study of the physical processes in the polar region, needed to understand the fundamental aspects of the coupling between the solar wind and the Earth’s magnetosphere and ionosphere. To study the dynamics and intensity of the ionospheric irregularities at the high-latitude ionosphere, we construct polar ROTI maps with temporal resolution of 15 min. We calculate the Hemisphere ROTI index (HROTI) on the base of the 15 min ROTI maps This index represents the average level of the GPS fluctuation activity from the mid-latitudes towards the auroral region. The sudden storm commencement (SSC) was registered at ~0445 UT and there was a quick drop of the SYM-H index to the value of −226 nT, observed at ~2300 UT, with a couple of local minima of −93 and
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