Conjugate ground and multisatellite observations of compression‐related EMIC Pc1 waves and associated proton precipitation

Abstract

[1] We present coordinated ground satellite observations of solar wind compressionrelated dayside electromagnetic ion cyclotron (EMIC) waves from 25 September 2005. On the ground, dayside structured EMIC wave activity was observed by the CARISMA and STEP magnetometer arrays for several hours during the period of maximum compression. The EMIC waves were also registered by the Cluster satellites for half an hour, as they consecutively crossed the conjugate equatorial plasmasphere on their perigee passes at L ∼ 5. Simultaneously, conjugate to Cluster, NOAA 17 passed through field lines supporting EMIC wave activity and registered a localized enhancement of precipitating protons with energies >30 keV. Our observations suggest that generation of the EMIC waves and consequent loss of energetic protons may last for several hours while the magnetosphere remains compressed. The EMIC waves were confined to the outer plasmasphere region, just inside the plasmapause. Analysis of lower-frequency Pc5 waves observed both by the Cluster electron drift instrument (EDI) and fluxgate magnetometer (FGM) instruments and by the ground magnetometers show that the repetitive structure of EMIC wave packets observed on the ground cannot be explained by the ultra low frequency (ULF) wave modulation theory. However, the EMIC wave repetition period on the ground was close to the estimated field-aligned Alfvénic travel time. For a short interval of time, there was some evidence that EMIC wave packet repetition period in the source region was half of that on the ground, which further suggests bidirectional propagation of wave packets.Citation: Usanova, M. E., et al. (2010), Conjugate ground and multisatellite observations of compression-related EMIC Pc1 waves and associated proton precipitation,

Fast modulations of pulsating proton aurora related to subpacket structures of Pc1 geomagnetic pulsations at subauroral latitudes

“…A portion of the scattered energetic ions falls into the upper atmospheric loss cone, and the ion precipitation can then be observed as a proton aurora [Frey et al, 2004;Yahnin et al, 2007]. They did not report many faster luminosity modulations of PPA that may be related to the subpacket structures of Pc1/EMIC waves observed with amplitude modulations [Usanova et al, 2010;Nakamura et al, 2015]. Isolated proton aurora can be displayed as an ionospheric projection of the location, duration, and evolution of the wave-particle interaction region in the magnetosphere .…”

“…The Pc1 pulsations on the ground become left-hand polarized in the vicinity of the ionospheric footprint connected to the magnetospheric source region by geomagnetic field lines [Kim et al, 2010;Nomura et al, 2011Nomura et al, , 2012. Also, EMIC waves are capable of scattering magnetospheric energetic ions (keV to 100 keV) [Erlandson and Ukhorskiy, 2001;Yahnina et al, 2003;Usanova et al, 2010]. The EMIC waves may play a crucial role in the loss of relativistic (MeV energy) electrons from the radiation belts via wave-particle interactions [e.g., Miyoshi et al, 2008;Rodger et al, 2008;Usanova et al, 2014].…”

Evolution of ring current ion energy spectra during the storm recovery phase: Implication for dominant ion loss processes

“…The ring current decay is caused by loss of energetic ions. Four loss processes have been proposed: charge exchange collisions with geocorona [e.g., Hamilton et al , 1988; Kistler et al , 1989; Fok et al , 1993; Noël , 1997; Jordanova et al , 1998], leakage into the magnetosheath [ Takahashi and Iyemori , 1989; Takahashi et al , 1990; Liemohn et al , 1999, 2001; Kozyra et al , 2002; Kozyra and Liemohn , 2003; Keika et al , 2005] across the dayside magnetopause [e.g., Sibeck et al , 1987] or/and along the dayside reconnected field lines [ Zong et al , 2001; Kasahara et al , 2008], precipitation into the upper atmosphere mainly due to strong pitch angle scattering by electromagnetic ion cyclotron (EMIC) waves [e.g., Jordanova et al , 1997, 2001; Kozyra et al , 1998; Usanova et al , 2010] or caused by the “chaotic” motion in the stretched magnetic field lines in the outer ring current [e.g., Sergeev et al , 1993], and Coulomb collisions with thermal plasmaspheric electrons [e.g., Fok et al , 1991, 1993, 1995, 1996; Jordanova et al , 1998]. It has been believed that the change exchange is a major loss process, while recent numerical modeling and data analyses suggest that the rapid decay of the ring current cannot be explained by charge exchange alone [ Fok et al , 1995; Kozyra et al , 1998, 2002; Chen et al , 1998, 1999; Liemohn et al , 1999, 2001; Kozyra and Liemohn , 2003; Daglis et al , 2003; Keika et al , 2006].…”

“…Ion precipitation due to pitch angle scattering caused by the ion “chaotic” motion is more efficient at higher energies. Ion precipitation due to interactions with EMIC waves is clear for energies with a few tens to hundreds of keV [e.g., Usanova et al , 2010]. The loss rate through Coulomb collisions decreases with increasing ion energy above 1 keV.…”

Energy–latitude dispersion patterns near the isotropy boundaries of energetic protons

“…During substorm, the J 0 /J 90 flux ratio increases up to ∼ 1, so it may obscure the true isotropy boundary formed by the CSS mechanism, especially during storm times and in the evening sector (Dubyagin et al, 2013). Another well-documented precipitation type is the intense detached proton precipitation regions (often appearing as spikes) on the IB equatorward side (Yahnin and Yahnina, 2007;Usanova et al, 2010). These localized precipitations are known to correlate with isolated hydrogen auroral emission patches, and they show a close relationship to the Pc1-range pulsations, which is evidence for the interaction with EMIC waves.…”