Stormtime Dynamics of the Magnetosphere near Geosynchronous Altitudes

Transcription

1 Stormtime Dynamics of the Magnetosphere near Geosynchronous Altitudes William J. Burke 1, Meg A. Noah 2 and Jun Yang 2 4 November Boston College/ISR 2. University of Massachusetts, Lowell

2 Stormtime near Geosynchronous Altitudes Abstract This presentation offers a tentative synthesis of inner-magnetospheric dynamics during magnetic storms gained over more than 4+ years starting with the launch of Explorer 45. During this mission the ring current s nose structure, the dynamics of the zero-energy Alfvén boundary and their inter-connectedness were first identified. About 2 years later the CRRES satellite was launched into a geostationary transfer orbit with a sensor payload that monitored the variability of electric fields and kev ions and electrons in the ring current and inner plasma sheet. CRRES latter provided the first detections of penetration, shielded and over-shielded electric fields, severe inflation of the stormtime magnetosphere and glimpses of ion-conics reaching the equatorial plane. In the early 199s Los Alamos National Laboratory (LANL) investigators first identified a stormtime phenomenon they called sawtooth events (STEs) that occur almost simultaneously at all local times. We show that STEs: (1) mostly they occur during the main phases of storms in a relatively small range of Dst indices, (2) reflect massive decreases in magnetotail open flux and consequent plasmoid ejections, and (3) cannot occur during magnetic super storms. The Van Allen Probe mission consists of two identical spacecraft that were launched into CRRES-like orbits in August 212. A major advance over CRRES-era sensors is their monitoring mass compositions as well as energy and pitch-angle ion distributions. We consider the dynamical properties flux of O + ion conic distributions observed during the 1 June 213 storm s main phase.

3 Stormtimes near Geosynchronous Altitudes Presentation has four parts: Outline A brief review of 1 background concepts (1) Magnetic Storm Phases (2) The Dessler-Parker-Sckopke relation (3) The Burton-Russell-McPherron equation (4) Plasma sheet configurations during substorms (5) Cross polar cap potential ( PC ) (6) Ring-current nose structure (7) Zero-energy Alfvén boundary (ZEAB) (8) Saw tooth Events (STE) (9) Magnetospheric inflation (1) Ion beams and conics Case-study analysis of a magnetic storm with STEs Whys and wherefores of the STE climatology Case-study analysis O + ion conic injections during a magnetic storm

4 Sym H (nt) Stormtimes near Geosynchronous Altitudes Background Reminders 1. Magnetic Storm Phases 5 SSC Main 4. Plasma Sheet Configurations during Substorms -5 Initial Recovery 151:12 152: 152:12 153: 153:12 Day: UT Dessler-Parker-Sckopke Relation Dst * DB 2W B / 3W m W m J 3. Burton-Russell-McPherron Equation ddst * Dst * EI dt Hones, E. J. (1984 ), Plasma sheet behavior during substorms, in Magnetic Reconnection in Space and Laboratory Plasmas, AGU Monograph 3,

5 Stormtime near Geosynchronous Altitude (5) Cross Polar Cap Potential PC Heppner-Maynard Pattern V E B B 2 2 B B Cold ionospheric plasma drifts along equipotential lines. Faraday s equation B E t E dl B da t t M With a stormtime PC of 1 kv, in 1 s crosses the red line from the day towards the night side. PC is a measure of the rate at which magnetic flux M in Webers moves from the day to the night side across a line connecting the maximum and minimum potential.

6 Stormtime near Geosynchronous Altitude Lessons from Explorer 45 => S 3 Satellite: (7) ZEAB (6) Ring current nose-structure Ejiri, M. (1978), Trajectory traces of charged particles in the magnetosphere, J. Geophys. Res., 83, Smith, P. H., and R. A. Hoffman (1974), Direct observations in the dusk hours of the characteristics of the storm time ring current particles during the beginning of magnetic storms, J. Geophys. Res., 79,

7 Stormtimes near Geosynchronous Altitudes (8) Sawtooth Structures (STEs) Example from 18 April 22 Schematic representation T = full period Ts = stretching phase Td = dipolarization phase Example of STEs observed simultaneously by 5 LANL satellites distributed in local time around geosynchronous

8 Stormtimes near Geosynchronous Altitude (9) Magnetospheric Inflation during Superstorms CRRES discovery during June 1991 storm 6 April 2 31 March 21 Tsyganenko, N. A., H. J. Singer, and J. C. Kasper (23), Storm-time distortion of the inner magnetosphere: How severe can it get?, J. Geophys. Res., 18(A5), 129, doi:1.129/22ja988.

9 Stormtimes near Geosynchronous Altitude (1) Ion Beams and Conics Parallel acceleration Perpendicular heating gyro-resonant wave-article interactions Upward push by magnetic gradient force Role of downward E => pressure cooker effect Retterer, J. M. et al. (1987), Monte Carlo modeling of ionospheric oxygen acceleration by cyclotron resonance with broadband electrostatic turbulence, Phys. Rev Lett. 59,

10 Stormtime near Geosynchronous Altitude Lessons from CRRES: We considered two manifestations of low energy ions detected by the LEPA sensor on CRRES. During times of minor disturbance LEPA detected both field-aligned and omni-directional. Identified as signatures of conics and S/C charging events. During the 24 March 1991 storm CRRES detected sporadic fieldaligned ion fluxes coming from both ionospheres, but not simultaneously. Rubin, A. G., W. J. Burke, and D. A. Hardy (1995), Low-energy ion spectral peaks detected by CRRES in the plasma sheet, J. Geophys. Res., 1, 19,22-19,226.

11 Stormtimes near Geosynchronous Altitudes Lessons from CRRES: 24 March 1991 Storm Huang, C. Y., W. J. Burke, and C. S. Lin (25), Ion precipitation in the dawn sector during geomagnetic storms, J. Geophys. Res., 11, A11213, doi:1.129/25ja11116.

12 Stormtimes near Geosynchronous Altitude Lessons from LANL/GOES Latitude longitude distribution of LANL and GOES spacecraft in relation to the magnetic equator

13 Stormtimes near Geosynchronous Altitudes Lessons from LANL/GOES: March 22 Storm

14 Stormtimes near Geosynchronous Altitudes Lessons from LANL/GOES: March 22 Storm near time of the first STE LANL-1A near local midnight Both GOES satellites on dayside

15 Stormtimes near Geosynchronous Altitude Lessons from LANL/GOES: March 22 Storm near times of the second, third and fourth STEs GOES s/c on nightside observed three stretching- dipolarization sequences near times of STE onsets. Night/day onset difference at time of STE3 (C) versus (A) Reflects gradient-curvature drift of ~ 1 minute delay time. E B drifts way too slow Two pseudo breakup events marked by green triangles

16 Stormtimes near Geosynchronous Altitude Lessons from LANL/GOES: March 22 Storm Observed interplanetary drivers and geomagnetic responses raise two questions: (a) How does one reconcile Sym-H behavior after STE onsets with requirements of D-P-S relation? (b) Are STEs directly driven by variations in the solar wind or IMF?

17 Stormtimes near Geosynchronous Altitudes Lessons from LANL/GOES: March 22 Storm Tests of hypotheses that STEs are directly driven by: Solar wind pressure pulses Northward turnings of IMF B Z Conclusion: not supported by LANL / ACE data comparison. Chaosong Huang s critical open magnetic flux hypothesis.

18 Polar Cap Area (M-km 2 ) Open Flux (G-Wb) Stormtimes near Geosynchronous Altitudes Lessons from LANL/GOES: March 22 Storm Tests of Chaosong Huang s hypothesis: STEs can only occur after the quantity of open flux in the lobes of the magnetotail exceeds a critical level near 1 GWb For a magnetic dipole B(R,θ) = -B [2Cosθ r ˆ + Sinθ θ] ˆ E The open magnetic flux threading the polar cap is RE PC PC Colatitude PC ( PC ) B da 4 RE B C os Sin d 2 RE BSin PC The corresponding polar cap area is PC 2 2 PC ( PC ) 2 E 2 E (1 PC ) A R Sin d R Cos

19 Stormtimes near Geosynchronous Altitudes Lessons from LANL/GOES: March 22 Storm Estimated A PC using EUV data from the IMAGE satellite Highly elliptical orbit of IMAGE allows it to view northern high latitudes for about 8 consecutive hours. Distinguish auroral oval (strong emissions) from polar cap (strong emissions) Optical data show A PC rising above km 2 (dash line) before STE onsets then quickly falling below this level.

20 Stormtimes near Geosynchronous Altitudes STE Climatology Studied 535 storm, 111 STE sequences 438 individual teeth (5.4%) outside storms < T > = min Required: Two or more teeth At midnight and noon 3 hr LT Magnetic Storm Categories Weak: Moderate: Intense: Super Dst min > -5 nt -5 Dst min > -1 nt -1 Dst min > -25 nt Dst min > -25 nt Cai, X., J. C. Zhang, C. R. Clauer, and M. W. Liemohn (211), Relationship between sawtooth events and magnetic storms, J. Geophys. Res., 116, A728, doi:1.129/21ja1631.

21 Stormtimes near Geosynchronous Altitudes Three critical observations from Cai et al. (211): Generally isolated substorms that occur outside of storm periods produce clear ion-injection signatures on the nightside but weak to no flux changes on the dayside disruption. Often during storms that occur after long periods of geomagnetic quiet the first tooth in an STE sequence looks like effects of a isolated substorm. Clear STE signatures often absent in electron* fluxes and low energy (< 6 kev) ions. Methodology: Cai et al only listed storms in which they found events that met their criteria. We developed our own list of storms and examined all storms with special concentration on those NOT listed as manifesting STEs.

22 Sym-H (nt) PC (kv) B Y B Z (nt) N SW (cm -3 ) P SW (npa) V SW (km/s) Stormtimes near Geosynchronous Altitudes STE Climatology : 272:12 273: 273:12 274: Non-storm STEs on 29 3 September 21reported by Cai et al. (211)

23 Sym-H Stormtime near Geosynchronous Altitude STE Climatology : 112:6 112:12 112:18 113: 149: 149:6 149:12 149:18 15: Examples of a missed STEs (left) and a case in which the dayside magnetopause crossed geostationary altitudes (right).

24 Sym-H (nt) PC (kv) B Y B Z (nt) N SW (cm -3 ) P SW (npa) V SW (km/s) Stormtime near Geosynchronous Altitude STE Climatology: The April 2 Superstorm -4 97: 97:12 98: 98:12 99: Interplanetary drivers and geomagnetic responses on 6-7 April 22. PC and Sym-H min approached ~ 22 kv and -33 nt ~ 5 s to transfer 1M Wb from the dayside into the polar cap Huang, C. Y., and W. J. Burke, Transient sheets of field-aligned current observed by DMSP during the main phase of a magnetic storm, J. Geophys. Res., 19, A633, doi: 1.129/ 23JA167, 24.

25 Sym-H (nt) PC (kv) B Y B Z (nt) N SW (cm -3 ) P SW (NPa) V SW (km/s) Stormtimes near Geosynchronous Altitude STE Climatology: The November 23 Superstorm Interplanetary drivers and geomagnetic responses on 2 November PC and Sym-H min approached 2 1 ~ 25 kv and -5 nt : 324:6 324:12 324:18 325: ~ 4 s to transfer 1M Wb from the dayside into the polar cap

26 Sym-H (nt) Stormtimes near Geosynchronous Altitudes April 2 Superstorm :: 97:12: 98:: 98:12: 99:: No evidence of a main phase injection event

27 Sym-H (nt) PC (kv) B Y B Z (nt) N SW (cm -3 ) P SW (NPa) V SW (km/s) Stormtimes near Geosynchronous Altitude STE Climatology: The November 23 Superstorm Interplanetary drivers and geomagnetic responses on 2 November PC and Sym-H min approached 2 1 ~ 25 kv and -5 nt : 324:6 324:12 324:18 325: ~ 4 s to transfer 1M Wb from the dayside into the polar cap

28 Sym-H (nt) PC (kv) B Y B Z (nt) N SW (cm -3 ) P SW (NPa) V SW (km/s) Stormtimes near Geosynchronous Altitude STE Climatology: The November 23 Superstorm Interplanetary drivers and geomagnetic responses on 2 November PC and Sym-H min approached 2 1 ~ 25 kv and -5 nt : 324:6 324:12 324:18 325: ~ 4 s to transfer 1M Wb from the dayside into the polar cap

29 Sym-H (nt) Stormtimes near Geosynchronous Altitudes 2 November 23 Superstorm : 324:6 324:12 324:18 325:

30 Sym-H (nt) PC (kv) B Y B Z (nt) N SW (cm -3 ) P SW (NPa) V SW (km/s) Stormtimes near Geosynchronous Altitude STE Climatology: November 23 Superstorm Interplanetary drivers and geomagnetic responses on 2 November PC and Sym-H min approached 2 1 ~ 25 kv and -5 nt : 324:6 324:12 324:18 325: ~ 4 s to transfer 1M Wb from the dayside into the polar cap

31 Sym-H (nt) :: 97:12: 98:: 98:12: 99:: Figure 4. Energetic proton fluxes measured by geosynchronous satellites (top), LANL-97A (2 nd ), (3 rd ), and on 6-7 April 26. Traces in the in the 6th panel show inclination angles inferred from measurements by magnetometers on GOES 8 (purple) and GOES 1 (green). The Sym-H trace is repeated in the bottom panel for reference.

32 Sym-H (nt) : 324:6 324:12 324:18 325: Figure 6. Energetic proton fluxes measured by the geosynchronous satellites (top), LANL-97A (2 nd ), (3 rd ), and on 2 November (DOY 324) 23. Traces in the in the 6th panel give inclination angles inferred from measurements by magnetometers on GOES 1 (purple) and GOES 12 (yellow). The Sym-H index is repeated in the bottom panel for reference.

33 Stormtimes near Geosynchronous Altitudes O+ Ion Conics Lessons from the Van Allen Probes: 1 June 213 Storm 3 8 (a) km/s) 5 1 SW 6 2 V NSW (cm ) PSW (npa) 4 Interplanetary drivers and responses of geomagnetic indices. (nt) 2 BZ 3 1 (b) Since VAP launch 6 storms with Dstmin < 9 nt. Ion conics seen on 3 with nightside apogee. No signatures detected on dayside BY -1-2 AU AL (nt) (c) Nsw increase and SSC occur ~16:3 UT 31 May -1 Southward / northward turnings near 1:4 and 7:37 UT on 1 June -2 Sym H (nt) 5 Bottom panels show AU (red), AL (blue) and Sym-H (black) indices (d) 151:12 152: 152:12 Day: UT : 153:12

34 Energy (ev) Stormtime near Geosynchronous Altitude Nose Structure ZEAB VAP-B: O + VAP-A: O + VAP-A: p + Van Allen Probes: 1 June 213 Storm Apogee near 21.1 MLT with VAP-B leading by ~ 19 min. Nose structure near L = 4 in O + and p + fluxes ZEAB crossed near 1:5 UT, marked by transition between photo- and plasma sheet electron dominance. UT L MLT 1: VAP-A: e - 2: : : : : Quasi-periodic structuring of < 2 kev O + fluxes detected from 2: to 6: UT VAP A & B traces appear similar but they are not identical

35 D L (R E ) D MLT (hrs) AU AL (nt) O + Energy (ev) O+ Energy (ev) Stormtime near Geosynchronous Altitude Lessons from the Van Allen Probes: 1 June 213 Storm UT 2: L 4.86 MLT : : : : VAP-A VAP-B 1 Pitch-angle distributions of < 2 kev O+ ions are nonisotropic and originate in northern ionosphere. Associated with substorm expansion recovery cycles. Similar histories when VAP A & Bin are close spatial proximity : 3: 4: 5: 6:

36 Ions Electrons Stormtimes near Geosynchronous Altitudes Lessons from the Van Allen Probes: 1 June 213 Storm DMSP F B Xsat B ysat B Zsat 12 Mapping of VAP-A trajectory to northern ionosphere (red) at 1 hour intervals and compared with equatorward boundary of auroral electron precipitation sampled by DMSP F18 (yellow) and F 16 (green). UT MLat MLT 2: : : : : Fluxes of down-coming electrons and ions with 3 ev < E < 3 kev. B components in S/C coordinates

37 B Z (nt) j ( A / m 2 ) Stormtimes near Geosynchronous Altitude Lessons from the Van Allen Probes: 1 June 213 Storm 2 N E 1-1 Y B Z Z :4 3:5 3:6 3:7 3:8 3:9 (1) Magnetic perturbation: (2) Rotation angle: (3) Ampère s law: B B B Z Ysat Zsat 1 cos BZsat 37 / BZ 1 1 BZ 1 d BZ j B Y Vsat Cos dt

38 Stormtimes near Geosynchronous Altitudes Summary and Conclusions: The reported studies concentrated on the phenomenology and causality of STEs and the presence of O + ions in the ring. The hypothesis of Chaosong Huang that large quantities of magnetic flux occurs during STE events was confirmed. This is consistent with anomalous behavior found in Sym-H traces near the times of STEs indicating that large plasmoids were ejected from the magnetosphere. Inflation of the inner magnetosphere by the ring current during superstorms is consistent with the absence of substorm triggering. VAP detections of O + ion conic signatures during the main phase of magnetic storms provides a plausible explanation of O+ presence in the nose structure of the ring current.