Mapping the sub-oval proton auroras into the magnetosphere A. G. Yahnin and T. A. Yahnina Polar Geophysical Institute, Apatity, Russia Plasma Physics in the Solar System, SRI, Moscow, 6-10 February 2012

2 proton H  collision charge exchange Lyman  photon N2N2 velocity excited neutral H emission H atom Courtesy of S. Mende The FUV SI12 instrument onboard the IMAGE spacecraft was capable to observe the “proton aurora” - the luminosity in the Doppler shifted Lyman H α line at nm. This emission is produced by precipitation of magnetospheric protons after charge exchange with atmospheric constituents. The Doppler shift is due to motion of the emitting neutral hydrogen. Proton aurora from the IMAGE spacecraft

3 After H. Frey, Rev. Geophys., 2007 Sub-oval proton spots Frey et al., JGR, 2004 Dayside sub-oval proton flashes Hubert et al., GRL, 2003 Zhang et al., JGR, 2003 Fuselier et al., JGR, 2004 Sub-oval proton arcs Immel et al., GRL, 2002 Burch et al., JGR, 2002 Spasojevic et al., JGR, 2004 Proton aurora from the IMAGE spacecraft

4 Day-side sub-oval proton flashes Yahnina et al., JGR, 2008 Popova et al., GA, 2010 Zhang et al., JGR, 2008 Sub-oval proton arcs Immel et al., GM, 2005 Yahnin et al., JGR, 2009 Spasojevic et al., GM, 2005 Yuan et al., GRL, 2010 Sub-oval proton spots Yahnin et al., JGR, 2007 Yahnina & Yahnin, GA, 2012 Relationship between sub-oval proton aurora and EMIC/Pc1 waves

5 Day-side sub-oval proton flashes Pc1 bursts or Pc1 Sub-oval proton arcs IPDP or Pc1 Relationship between sub-oval proton aurora and EMIC/Pc1 waves Sub-oval proton spots “Monochromatic” Pc1

6 Mapping the sub-oval proton aurora relatively to plasmapause Mapping into the magnetosphere is, in particular, important for understanding what is (are) the main parameter(s) controlling the regime of the IC instability development (hot proton anisotropy, hot proton density, and cold plasma density) in different conditions. As to cold plasma, direct comparisons of sub-oval aurora with plasmasphere are very scanty in spite of the IMAGE spacecraft carried a special instrument (EUV imager) to observe the cold plasma distribution.

7 Mapping the sub-oval proton aurora relatively to plasmapause We used the plasmapause model by V. Pierrard from Belgian Institute for Space Aeronomy; this model is available at In this model the plasmapause is suggested to form due to Lemaire’s physical mechanism based on interchange instability (e.g., Lemaire and Gringauz, 1998).

8 Pierrard & Lemaire, GRL, 2004 Pierrard & Cabrera, Ann. Geophys., 2005 Pierrard et al., JGR, 2007 Pierrard & Stegen, JGR, 2008 Mapping the sub-oval proton aurora relatively to plasmapause Numerical calculations based on the Lemaire’s theory and a Kp-dependent magnetospheric electric field model satisfactorily reproduce plasmapause observed with IMAGE EUV.

9 Event of 2 Sep Sept 2 Sept 3 Sept 11 of 13 considered events demonstrate that proton spots map into the vicinity of plasmapause (  L<0.5 R E ). This is one of “good” examples.

10 24 Jun 25 Jun 26 Jun Event of 25 June of 13 considered events demonstrate that proton spots map into the vicinity of plasmapause (  L<0.5 R E ). This is one of “good” examples.

11 Event of 17July Jul 17 Jul 18 Jul 11 of 13 considered events demonstrate that proton spots map into the vicinity of plasmapause (  L<0.5 R E ). This is one of “good” examples.

12 2 Aug 3 Aug 4 Aug Event of 3 Aug 2003 FUV 11 of 13 considered events demonstrate that proton spots map into the vicinity of plasmapause (  L<0.5 R E ). This is one of “good” examples.

13 25 Nov 26 Nov 27 Nov Frey et al., 2004 Event of 26 Nov 2001 “Bad” example: The spot maps well inside modeled plasmapause. However, EUV data show clear structure of the outer plasmasphere. Thus, location of the spot projection in this case is also consistent with the cold plasma gradient. FUV EUV

14 27 Feb 28 Feb 29 Feb “Bad” example: The spot maps well outside modeled plasmapause. Event of 28 Feb 2001

15 Conclusion Mapping of the proton aurora spots onto the equatorial plane shows that the source of the quasi-monochromatic EMIC emissions (Pc1) tends to occur at the cold plasma gradients. This agrees with the theoretical prediction that both low and very high values of the cold plasma density reduce the increment of the ion-cyclotron instability. Observations of proton aurora spots can be used as an indicator of the plasmapause location.

16 IMAGE 10 November 00:50 UT Night-to-morning side sub-oval proton aurora arc (Poster #96) NOAA-16

Night-side sub-oval proton aurora arc, LPEP and plasmapause

18 Thanks for your attention!