Coordinated Radar, Optical and Satellite Analysis of Plasma Sheet- Subauroral Ionospheric Coupling via Meso Scale Channels PI: Toshi Nishimura (UCLA/BU) Co-I: Larry Lyons (UCLA) Student: Beatriz Gallardo (UCLA, now postdoc) Collaborator: Evgeny Mishin (AFRL) AFOSR FA9550-15-1-0179 09/01/2015–08/31/2018 SAPS forma*on [Goldstein et al., 2005] SAPS: Subauroral polarizaon streams The source is the region-2 FACs driven by the ring current. The electric field is pronounced due to the low ionosphere conductance. SAID: Subauroral ion driBs SAPS with ~1 deg latude width Importance of SAPS research Key M-I coupling feature that involves ac-ve ionosphere feedback Density irregulari-es and radio signal scin-llaon Plasma upflow Enhanced neutral wind [Mishin and Blaunstein, 2008] SAPS and par*cle boundary reversal The electron precipitaon boundary is equatorward of the proton boundary when SAID occurs. Large flow fluctuaons associated with SAID. Proton Electron Proton Electron [Lyons and Williams, 1984] Purpose of this study • What is the condition to create SAID vs. latitudinally wide SAPS? • How do SAPS connect to auroral dynamics? • What does drive the subauroral arc? • How does the subauroral ionosphere evolve during SAPS? THM 2008-3-26 event THEMIS ASI SuperDARN NOAA DMSP DMSP SuperDARN NOAA Imagers CHAMP CHAMP THEMIS satellite Armature astronomer’s photo THEMIS all-sky imager data of the same event 0613 UT Substorm expansion phase onset 0730 UT Near the beginning of the recovery phase Arc started to emerge just equatorward of the diffuse auroral oval (~21 MLT). Extended azimuthally. Substructures propagang duskward. 0810 UT DMSP crossings 0900 UT The substorm ended. Arc disappeared Duskside subauroral arc photographed by armature astronomers North North Photos in courtesy of D. Anderson and C. Hall, near Anchorage, AK The red-green mixed color is quite different from the green diffuse aurora in the oval. Is this aurora? Proton aurora? SAR arc? Or a new aurora feature? What is the mechanism to create this arc? What can we learn from this about SAPS/SAID? DMSP satellites Earlier orbit Arc conjuncon Arc conjuncon • SoB precipitaon equatorward of plasma sheet electron precipitaon (à Electron aurora) • Proton precipitaon poleward of electron precipitaon (à Not proton aurora) • Subauroral ion dri adjacent to soB precipitaon, narrower than usual SAPS • Weak upward and downward FACs SuperDARN radars Before the subauroral arc formaon Wide westward flow (SAPS) Usual flow paern in the duskside subauroral ionosphere Before the arc During the subauroral arc formaon Narrow and faster flow (SAID) The arc is located just poleward of the flow channel. During the arc à The flow (or collisional heang) is not the cause of the arc. NOAA satellites Trapped Precip. Trapped protons are equatorward of electrons, but the separaon became smaller. Why can electrons penetrate as deep as protons? à Aurora and in-situ measurements DMSP and CHAMP satellites CHAMP sunward wind What is the magnetospheric driver of the subauroral arc? • The substorm surge and streamer near midnight à Subauroral proton aurora • The westward traveling surge propagates far from midnight. • The auroral streamers (injecons) also shi duskward à Subauroral arc • Deeper electron injec-on in the premidnight sector makes the flow thinner? Surge/ Surge/ streamer streamer Proton aurora Surge/ streamer Arc Arc • The substorm surge and streamer near midnight à Subauroral proton aurora • The westward traveling surge propagates far from midnight. • The auroral streamers (injecons) also shi duskward à Subauroral arc à Injec*on far from midnight makes the flow thinner? THEMIS satellites TH-C TH-E TH-A ⊥ (-8, 4 RE) (-10, 6 RE) (-10, 15 RE) Par-cle injec-on and auroral streamer locaons indeed shiB duskward (22 -> 20 h MLT) as the substorm evolves in -me. Coming back to the single par*cle viewpoint Proton Electron Injec-ons far to the dusk will create an electron-dominated region at premidnight. Tes*ng the idea by Rice Convec*on Model Movie in courtesy of Jian Yang at Rice U Le: Injec-on at 24 MLT Usual ~2 RE thickness SAPS flow channel in the ring current Right: Injec-on at 21 MLT Narrower SAPS (~1 RE) Follow the classical Region-2 FAC physics but the electron injec-on closer to the Earth makes the flow channel narrower and more intense. Summary We presented a case study of SAPS/SAID and duskside subauroral thin arc using mul--instrument conjunc-on (THEMIS satellites, THEMIS ASI, DMSP, SuperDARN and colored photos). The arc is associated with low-energy (~<100 eV) electron precipitaon and thus an auroral arc. This explains the color of the arc (primarily red mixed with green) in contrast to the green diffuse aurora in the auroral oval (~1-10 keV). The arc is adjacent to a la*tudinally narrow channel of flow (SAID). The arc can be used as an op-cal manifestaon of SAID. As opposed to a typical precipitaon boundary configuraon (ion precipitaon extends equatorward of electrons), electron precipitaon extends more equatorward of ions. The arc forms aer the substorm surge reached far duskward from midnight. These suggest that electron injec-on reaching deeper the premidnight inner magnetosphere than usual creates the arc and narrower SAPS. Selected papers Published • Zou, Y., Y. Nishimura, L. R. Lyons, E. F. Donovan, K. Shiokawa, J. M. Ruohoniemi, K. A. McWilliams, and N. Nishitani (2015), Polar cap precursor of nightside auroral oval intensificaons using polar cap arcs, J. Geophys. Res. Space Physics, 120, 10,698–10,711. • Nishimura, Y., and L. R. Lyons (2016), Localized reconnec-on in the magnetotail driven by lobe flow channels: Global MHD simulaon, J. Geophys. Res. Space Physics, 121, 1327–1338. • Lyons, L., Y. Nishimura, Y. Zou (2016), Unsolved Problems: Meso-Scale Polar Cap Flow Channels' Structure, Propagaon, and effects on Space Weather disturbances, J. Geophys. Res., 121, 3347–3352. • Kikuchi, T., K. K. Hashimoto, I. Tomizawa, Y. Ebihara, Y. Nishimura, T. Araki, A. Shinbori, B. Veenadhari, T. Tanaka, and T. Nagatsuma (2016), Response of the incompressible ionosphere to the compression of the magnetosphere during the geomagne-c sudden commencements, J. Geophys. Res. Space Physics, 121, 1536–1556. • Lyons, L. R., B. Gallardo-Lacourt, S. Zou, J. M. Weygand, Y. Nishimura, et al. (2016), The 17 March 2013 storm: Synergy of observaons related to electric field modes and their ionospheric and magnetospheric Effects, J. Geophys. Res. Space Physics, 121, 10,880–10,897. • Han, D.-S., H. Hietala, X.-C. Chen, Y. Nishimura, L. R. Lyons, J.-J. Liu, H.-q. Hu, and H.-G. Yang (2017), Observaonal proper-es of dayside throat aurora and implicaons on the possible generaon mechanisms, J. Geophys. Res. Space Physics, 122, 1853–1870 (Cover figure of JGR Feb 2017 issue) Submied • Gallardo-Lacourt B., Y. Nishimura, L. Lyons, E. Mishin, et al., Influence of auroral streamers on rapid evolu-on of ionospheric SAPS flows, J. Geophys. Res. Other acvies Student educaon: Bea Gallardo-Lacourt • Morris Neiburger Award, UCLA, November 2015 • Ph.D. Degree, September 2016 • Brian Bosart Award, UCLA, November 2016 Ongoing and future works: • Publish a paper on the ongoing work • Determine the ionospheric density and scin-llaon response—GPS and ISR • Find a student/postdoc • Complete the grant transfer from UCLA to BU backup Different event but with THEMIS in conjugate to the arc DMSP-16 9:40 UT TH-C moonlight Arc 10:25 THEMIS-C’s footprint crossed the arc. DMSP-16 measured similar features to the 2008-3-26 event. THEMIS-C detected a localized enhancement of duskward flow = Magnetospheric counterpart of SAID Narrow separaon between electron and ion inner boundaries (0.1 RE) as opposed to a typical separaon (~1 RE) Broad-band waves extend above the proton gyro frequency. Lower-hybrid waves or kine-c Alfven waves due to driBing cold ions? fLHR Waves scaering low-energy electrons fH and creang the arc? fLHR fH .