Magnetospheric response of two types in PSc geomagnetic pulsations to interaction with interplanetary shock waves

Using the June 22, 2015 event as an example, we present new data confirming the presence of a precursor of the sudden magnetic impulse caused by a powerful interplanetary shock wave (ISW). The precursor in the form of a train of oscillations (broadband pulse) with a falling frequency in the range 0.25÷11 Hz with a duration of ~20 s, which had a spectral resonance structure, was recorded globally by a network of induction magnetometers at 18:33:27 UT. No significant phase delays of the signals were detected in four frequency bands at widely spaced observatories. It is suggested that the impulse can be excited in the Earth – ionosphere waveguide by a pulsed electric field which occurs in the ionosphere due to the short-term impact of ISW on the magnetosphere

Sub-oval proton aurora spots: Mapping relatively to the plasmapause

Sub-ovalprotonaurorasdiscoveredbytheIMAGEspacecraftcorrelatewithEMICwaves(geomagnetic pulsationsofthePc1range).Thismeansthatacommonsourceofthewavesandprotonprecipitationis the ion-cyclotron(IC)instabilitydevelopinginthevicinityoftheequatorialplane.Differentformsof the protonaurorasreflectdifferentregimesoftheICinstabilityanddifferentconditionsinthenear- Earth equatorialmagnetosphere.Tounderstandwhataretheconditionsforthegenerationofthesub- oval protonauroraonemaymaptheauroraontotheequatorialplaneandcomparetheprojectionwith someimportantmagnetosphericboundaries.Inthisreportwecomparetheprojectionofso-called ‘‘protonauroraspots’’withthelocationoftheplasmapause.Thelatterisdeterminedbythe plasmapauseformationmodelbasedonthequasi-interchangeinstabilitymechanism.Thecomparison showsthatoftentheprotonauroraspotsourceislocatedinthevicinityoftheplasmapauseorinthe cold plasmagradientinsidetheplasmapause.Insomeevents,theprotonauroraspotsmapwelloutside the plasmapause.WeassumethatinthelattercasetheICinstabilitydevelopswhenwestwarddrifting energeticprotonsinteractwiththecoldplasmathatwasearlierdetachedfromtheplasmasphere

Pi2 magnetic pulsations, auroral break-ups, and the substorm current wedge: A case study

The two-dimensional distribution of the characteristics of Pi2 magnetic pulsations observed by the Scandinavian Magnetometer Array (SMA) during the passage of a westward travelling surge on 11 November 1976 and during three sucessive auroral break-ups around magnetic midnight on 15 February 1977 have been studied in relation to the position of active aurora and the break-up current system. On both days the greatest Pi2 amplitudes were collocated with the region where the brightest auroras were observed. The sense of polarization of the horizontal disturbance vectors changed along longitudinal and meridional lines. The two-dimensional equivalent current system of the Pi2 pulsations resembled a circular current vortex around the location of the localized upward field-aligned currents and changed its direction from counterclockwise to clockwise and back to counterclockwise again within one Pi2 cycle. Our observations indicate that the generation of Pi2 pulsations is not directly connected to periodic fluctuations of the complete current system at substorm onset, but that the upward directed field-aligned currents at the western edge of this system play the most important role for the Pi2 generation.           ARK: https://n2t.net/ark:/88439/y071359 Permalink: https://geophysicsjournal.com/article/167 &nbsp