imaging the energetic particle penetration from the

IMAGING THE ENERGETIC PARTICLE PENETRATION FROM THESUBSTORM INJECTION REGION UP TO THE PLASMAPAUSE

I.B. Ievenko, S.G. ParnikovYu. G. Shafer Institute of Cosmophysical Research and Aeronomy, Yakutsk, 677980 Russia,

e-mail: [email protected]

Abstract. The analysis results of dynamics of diffuse aurora and mid-latitude red arc in the 557.7 and630.0 nm emissions at the Yakutsk meridian (CGM: 58ºN, 200ºE) during the isolated substorm onFebruary 13, 2013 are presented. The Van Allen Probe (A) satellite has detected the onset ofdispersionless substorm injection near the center of the substorm activization at the magnetic meridianat 0059 MLT in the orbit apogee at L = 6.4. The ground all-sky imager has registered the equatorwardand eastward extension of DA and the occurrence of SAR arc in the 0200-0425 MLT sector. We believethat the dynamics of DA and SAR arc maps the overlap of hot plasma with the outer plasmasphere as aresult of electric drift from the substorm injection region.

1. IntroductionThe stable auroral red (SAR) arcs are the consequence of interaction of the outer plasmasphere

(plasmapause) with energetic ions of the ring current during the magnetic storms (Cole, 1965, 1970; Kozyra etal, 1997). The diffuse aurora (DA) is caused by the low-energy electron precipitation from the near-earth plasmasheet. According to the mechanism of SAR arc generation proposed by Cole (1965, 1970), red arcs appearduring the main phase of a magnetic storm in the development process of auroral disturbance. Cole supposedthat energy transfer from the ring current to the thermal plasma in the outer plasmasphere takes place atall times of a storm. The Cole generalization was in a good agreement with the results of SAR arc observationsavailable at that time. Subsequently, after the theoretical work of Cornwall et al. (1971), it were established thatSAR arcs are formed during the storm recovery phase.

The photometric observations of the DA and SAR arc dynamics in the 557.7 and 630.0 nm emissions at theYakutsk meridian (199 E geomagnetic longitude) during substorms have been presented in details by Ievenko(1994, 1999). These studies indicate that the SAR arc appears and/or brightening during the substorm expansionphase. The SAR arc formation begins in the equatorward boundary region of DA. In the case of prolongedsubstorm activity, a SAR arc separates from DA and moves equatorward (Ievenko et al, 2004; Ievenko et al,2008). In this work we analyze the observation of DA and SAR arc dynamics at the Yakutsk meridian during theisolated substorm injection on February 13, 2013 detected with the Van Allen Probe (A) satellite near the orbitapogee with L = 6.4.

2. Methods of ObservationThe observation of DA and SAR arcs in the 630.0 and 557.7 nm [OI] emissions was carried out using the

digital meridian-scanning photometer (MSP) and the all-sky imager (ASI). The registration of the 427.8 nm and630.0 nm emissions intensity in the magnetic zenith was registered with the four channel photometer. In orderto analyze, the MSP and ASI data are presented in this work as isophots of the surface brightness of the 557,7and 630,0 nm emissions in Rayleighs (R) in a projection to the Earth's surface for the luminosity heights of 110(DA) and 450 (SAR arc) km, respectively (keograms and images). To determine time intervals when themagnetospheric convection is enhanced, the measurement data of the interplanetary magnetic field (IMF) andthe solar wind (SW) speed from the ACE spacecraft were used. The location of center of the substorm expansiononset was identified using magnetograms at the low-latitude stations.

3. Results of ObservationFig.1 shows the dynamics of the DA and occurrence of SAR arc during the isolated substorm on February

13, 2013. The simultaneous increase of the density and Ey dawn-dusk of solar wind was manifested in thebrightening of DA on the northern horizon. After the onset of substorm expansion at 1849 UT the equatorwardextension of DA occurs and the SAR arc in the 630 nm emission appears. The red arc is separated from the DAand moves equatorward through the observation station zenith in the morning MLT sector. During the negativeEy a rapid decay of DA and SAR arc is observed.

Proceedings of the 10th Intl Conf. “Problems of Geocosmos” (Oct 6-10, 2014, St. Petersburg, Russia)

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Fig.2 shows the longitudinal distribution of magnetic field disturbances during the substorm on February 13,2013 at the magnetic meridians of 156ºE, 178ºE and 202ºE. The isolated substorm with the onset of expansionphase at 1849 UT was clearly revealed in the variations of magnetic field after the MLT midnight. The sign andamplitude of the X and Y component variations indicate to the position of the activization center in the vicinitythe magnetic Irkutsk meridian with the onset of substorm expansion at 0140 MLT.

Fig. 3 shows the energetic electron flux measured with the ECT HOPE instrument aboard Van Allen Probe(A) satellite during the isolated substorm on February 13, 2013. At the onset of substorm expansion the satellitewas located near the apogee with the GSM X = -5.1, Y = -1.8, Z = -1.9 R E at the magnetic meridian at 0059MLT. The dispersionless injection of electrons with the energies 10-51 keV started at ~ 1846 UT. The frontduration of injection was ~ 4 min. The injection was registered near the center of the substorm activization onset.For the indicated five-minute 1 and 2 intervals the average spectra of fluxes of electrons, ions H + and O+ beforeand after the substorm injection have been calculated.

Fig. 1 Changes in the solar wind and the subauroralluminosity dynamics on February 13, 2013(a)- the electric field (EY) and density (Np) of the solarwind with the dТ shift time; (b) and (c) meridian-scanningphotometer data as keograms in the 557.7 and 630.0 nmemissions for the luminosity heights of 110 and 450 km,respectively. Z is a zenith of observation station.

Fig. 2 Mid-latitude magnetic disturbances duringthe substorm expansion phase on February 13, 2013Magnetograms of mid-latitude stations at magneticmeridians of 156ºE (a), 178ºE (b) and 202ºE (c). On themagnetograms MLT of the substorm expansion onset isindicated.


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Fig. 4 shows the dependences of the average fluxes on the energy before (F1) and after (F2) the onset ofsubstorm injection and the ratio F2 / F1 for the electrons, ions H+ and O+. During the injection there was asignificant increase of electron fluxes with energies of 6-51 keV with a maximum at 12 keV (in 47 times) as wellas the growth of fluxes of the over thermal electrons (in 2.3 times). In the spectrum of protons the injection wasmanifested both in the increase of fluxes in 2 times in the energy range 30-50 keV and in the decrease of fluxesfor the low-energy particles (in 2-5 times). During the injection the fluxes of O+ ions were increased by a factorof 2.2 in the energy range of 1-10 keV. The thermal ion flux was also increased in 2-3 times.

The set of all-sky images in the 630.0 nm emission during the SAR arc formation on February 13, 2013 ispresented in Fig. 5. The all-sky imager registered the manifestation of substorm injection in the 630.0 nmemission at the Yakutsk meridian in the interval of 0200-0425 MLT At first, the equatorward and eastwardextension of DA took place. The maximum intensity of 1.6 kR was observed in the spots of weak DA. Further,the formation of broad SAR arc at the geomagnetic latitude of ~ 60ºN on the equatorial boundary of DA began.The red arc moved up to the station zenith. The width and intensity of arc are significantly greater in the easternpart of the sky up to the horizon.

Fig. 6 shows the set of all-sky images in the 557.7 nm emission with the frame time as in Fig. 5. In thisemission only the weak DA dynamics with the maximum of intensity of 2.8 kR is mapped. As a result of theequatorward and eastward extension the boundary of DA reached the latitude of 60-59ºN. On the basis ofobservations the radial and azimuthal movement velocities of energetic plasma in the inner magnetosphere havebeen determined.

Fig. 3 Observation of the substorm injection with VanAllen Probe (A) satellite on February 13, 2013a-the energetic electron flux measured with ECT HOPEinstrument; b- calculated L-parameter and MLT of thesatellite.

Fig. 4 Particle spectra measured aboard VanAllen Probe A satellite on February 13, 2013The dependences of average fluxes on the energybefore (F1) and after (F2) the onset of substorminjection and the ratio F2 / F1 for the electrons (a),ions H+ (b) and O+ (c). The standard error of meanare indicated on the spectra.


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ConclusionAs a result of complex analysis of the event of 13 February 2013 has been obtained the following:

● The center of region of the substorm expansion onset was located at the meridian about MLT midnight.● Van Allen Probe (A) registered the dispersionless injection of energetic electrons and ions near the center ofactive region on the GSM X = -5.1 RE.● At the Yakutsk meridian ASI registered the equatorward and eastward extension of DA and the occurrence ofinhomogeneous SAR arc in longitude.● We believe that the dynamics of DA and SAR arc maps the overlap of hot plasma with the outer plasmasphereas a result of the electric drift from the substorm injection region.● The observed DA extension velocities can be explained by a drift of hot plasma in the substorm electric fieldwith EAzimuth = 1.76 and ERadial = 0.98- 1.73 mV / m.

Acknowledgments. This work was supported by Program of Russian Foundation for Basic Research (projectno. 12-05-98523_p_vostok_a). The data on solar wind and IMF were obtained in the ACE Science Center(http://www.srl.caltech.edu/ACE/ASC/level2/index.html). Spin averaged ECT-HOPE science data with VanAllen Probe (A) spacecraft were obtained in CDAWeb (http://cdaweb.gsfc.nasa.gov/istp_public/). Thegeomagnetic data were provided by INTERMAGNET (www.intermagnet.org).

References

Cole, K.D. (1965), Stable auroral red arcs, sinks for energy of Dst Main phase. J.Geophys.Res. 70, 7, 1689-1706.

Fig. 5 All-sky images in the 630.0 nm emissionduring the SAR arc formation on February 13, 2013Geomagnetic coordinate are shown for h=250 km

Fig. 6 All-sky images in the 557.7 nm emissionduring the SAR arc formation on February 13, 2013Geomagnetic coordinate are shown for h=110 km.


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Cole, K.D. (1970), Magnetospheric processes leading to mid-latitude auroras. Annales de Geophysique. 26, 1,187-193.

Cornwall, J.M., Coroniti, F.V., Thorne, R.M. (1971), Unified theory of SAR arc formation at the plasmapause.J.Geophys.Res. 76, 19, 4428-4445.

Ievenko, I.B. (1994), Dynamics of diffuse aurora and SAR arc during substorm. Geomagnetism and Aeronomy.33, 5, 599-611, (In Russian, English translation).

Ievenko, I.B. (1999), Effects of magnetospheric activity on the plasmasphere as inferred from observations ofdiffuse aurora and SAR arc. Geomagnetism and Aeronomy.. 39, 6, 697-703, (In Russian, English translation).

Ievenko, I.B., Alexeyev, V.N., (2004), Effect of the Substorm and Storm on the SAR Arc Dynamics: AStatistical Analysis. Geomagnetism and Aeronomy. 44(5), 592-602 (In Russian, English translation).

Ievenko I.B., S.G. Parnikov, V.N. Alexeyev (2008), Relationship of the diffuse aurora and SAR arc dynamics tosubstorms and storms. Adv. Space Res., Vol. 41/8, 1252-1260, DOI: 10.1016/j.asr.2007.07.030.

Kozyra, J.U., A.F. Nagy, D.W. Slater (1997), High-altitude energy source(s) for stable auroral red arcs. Reviewsof Geophysics, 35, 2, 155-190.


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