Hemispheric asymmetry of ionospheric scintillations during the 2015 St Hemispheric asymmetry of ionospheric scintillations during the 2015 St. Patrick’s Day storm Giulia D’Angelo1, Mirko Piersanti2,3, Igino Coco4, Lucilla Alfonsi4, Luca Spogli4,5 1Dipartimento di Matematica e Fisica, Università degli Studi “Roma Tre”, Rome, Italy. 2Dipartimento di Scienze Fisiche e Chimiche, Università di L’Aquila, L’Aquila, Italy. 3Consorzio Area di Ricerca in Astrogeofisica, Università di L’Aquila, L’Aquila, Italy. 4Istituto Nazionale di Geofisica e Vulcanologia, Rome, Italy. 5SpacEarth Technology, Rome, Italy. giulia.dangelo@uniroma3.it

Direction of the IP shock normal in the GSE system ICME1 The 2015 St. Patrick’s day Storm GOES 15 (nT) IP shock parameters IP shock’s normal: latitude (GSE) 𝜃=68.4° IP shock’s normal longitude: (GSE) 𝜙=169.5° IP shock’s speed 𝑉 𝐼𝑃 =560 km/s IP shock’s impact point at magnetopause: 𝑋 𝑖𝑚 𝑝 𝐺𝑆𝐸 =14.2 𝑅 𝐸 𝑌 𝑖𝑚 𝑝 𝐺𝑆𝐸 =3.9 𝑅 𝐸   CF R T FAC INT X 1 0.8 10 Y 3 5 Z -0.8

The Ionospheric Response Conjugate sites EURC-DMC0 RESC-BTN0 NYA0-ZSGN   Location Station ID Owner Latitude Longitude CGLat CGLon Arctic Eureka EURC CHAIN 79.99 °N 274.10 °E 87.41 °N 342.32 °E Resolute Bay RESC 74.75 °N 265.00 °E 82.45 °N 326.10 °E Ny-Ålesund 0 NYA0 INGV 78.92 °N 11.98 °E 76.54 °N 108.79 °E Antarctica Concordia DomeC0 DMC0 75.10 °S 123.35 °E 88.02 °S 225.55 °E Baia Terranova BTN0 74.41 °S 164.10 °E -77.12 °S 274.75 °E Zhongshan ZSGN IGGCAS 69.37 °S 76.37 °E 75.59 °S 102.53 °E

The Ionospheric Response SWA SWB SWA UT Spectral Width≥200 m/s NORTH Phase Scint (SatX) SOUTH SWB SWA SWB UT UT

Remarks GOES 15 observations, when compared with a modified version of Tsyganenko and Sitnov model, are consistent with an anti-dipolarization of the magnetotail and with the rigid southward lowering of both magnetosphere tail lobes. This deformation may justify the hemispheric differences in the evolution of the ionospheric convection at high latitude. The anti-dipolarization of the magnetospheric field may justify the loss of conjugacy between EURC-DMC0, RESC-BTN0, and NYA0-ZSGN respectively. The anti-dipolarization of the magnetospheric field and the rigid lowering of the both tail lobes explains the hemispheric asymmetries in the scintillation intensity recorded by the selected polar stations at ground. The comparison between the spectral width and the phase scintillation index allows confirming the link between the GPS phase scintillation and the ionospheric plasma dynamics. Moreover, this comparison suggests that the ionospheric regions characterized by high spectral width values are more likely to be affected by scintillation. The Swarm electron density measurements, combined with the phase scintillation index lead us to speculate the cause-effect relationships between the presence of localized plasma irregularities and the scintillation.