SM22A-01 INVITED 

Multipoint Investigations of Magnetic Storms and Radiation Belts

* Singer, H J (howard.singer@noaa.gov), NOAA Space Environment Center, 325 Broadway, Boulder, CO 80305, United States Onsager, T G (terry.onsager@noaa.gov), NOAA Space Environment Center, 325 Broadway, Boulder, CO 80305, United States

Understanding the structure and dynamics of Earth's radiation belts, and their relation to magnetic storms and solar wind drivers, is a long-standing challenge with important scientific value and significant practical implications. From studying Earth's radiation belts, we can expand our knowledge about universal processes at work in other cosmic systems, and we can develop tools to forecast the evolution and response of the radiation environment that affects satellites and humans in space. While recent emphasis on this topic has resulted in new theories, models, and observations; there remain many outstanding questions and unresolved issues. The solution to many of the outstanding questions can only be achieved through multipoint measurements and coordinated modeling efforts. For example, the multipoint technique is critical for understanding whether or not particles in the outer radiation belts are energized by a radial diffusion process or local acceleration. The focus of this presentation will be to provide an overview of recent multipoint research on storms and radiation belts; discuss the outstanding achievements and remaining problems; and to describe future programs and opportunities dedicated to expand our knowledge and understanding of this challenging problem.

SM22A-02 

Development of Magnetospheric Current Systems During Storms: MHD and Event-Oriented Magnetic Field Modeling Approaches

* Ganushkina, N (Nataly.Ganushkina@fmi.fi), Finnish Meteorological Institute, P.O.Box 503, Helsinki, FIN-00101, Finland Liemohn, M (liemohn@umich.edu), University of Michigan, Space Research Building 2455 Hayward St., Ann Arbor, MI 48109-2143, United States Ilie, R (rilie@umich.edu), University of Michigan, Space Research Building 2455 Hayward St., Ann Arbor, MI 48109-2143, United States Kubyshkina, M (kubysh@geo.phys.spbu.ru), Institute of Physics, University of St.Petersburg, Petrodvoretz, 1, Ulyanovskaya, St.Petersburg, 198504, Russian Federation Ridley, A (ridley@umich.edu), University of Michigan, Space Research Building 2455 Hayward St., Ann Arbor, MI 48109-2143, United States

Geomagnetic storms cause significant changes in all magnetospheric current systems and therefore in magnetospheric magnetic field configuration. Two storms on September 22, 1999 and April 18, 2001 were modeled using two different approaches, namely, first-principles and event-oriented magnetic field modeling. As a first-principles approach, three components of the Space Weather Modeling Framework (SWMF) were used: the global magnetosphere (GM), inner magnetosphere (IM), and ionospheric electrodynamics (IE). The SWMF was driven by time-dependent solar wind and interplanetary magnetic fields. As event-oriented approach, the developed time-evolving model for the inner magnetosphere magnetic field which gives a global representation of the magnetic field evolution during specified time periods. The model is based on an empirical parametrization of magnetospheric current systems and use of in-situ magnetospheric measurements from GOES 8, GOES 10, Polar, Geotail and CLUSTER satellites and Dst measurements to define the intensity and location of these current systems for each time and location. Outputs from both approaches were then compared with in-situ measurements of magnetic field and Dst measurements. Although the SWMF is becoming capable of accurately conducting storm simulations, significant differences between the modeled and observed magnetic field and Dst index were found during those two storm events. We compare the global magnetic field topology determined by the event-oriented approach to the SWMF to attempt to elucidate a physical understanding of the SWMF inaccuracies during these time periods.

SM22A-03 

Investigation of space and ground low-frequency particle and field oscillations during the 23 March 2007 substorm

* Keiling, A (keiling@ssl.berkeley.edu), UC Berkeley, SSL, a, Berkeley, USA, Angelopoulos, V), UC Berkeley, SSL, a, Berkeley, USA, Larson, D), UC Berkeley, SSL, a, Berkeley, USA, McFadden, J), UC Berkeley, SSL, a, Berkeley, USA, Carlson, C), UC Berkeley, SSL, a, Berkeley, USA, Bonnell, J W), UC Berkeley, SSL, a, Berkeley, USA, Mozer, F), UC Berkeley, SSL, a, Berkeley, USA, Glassmeier, K), TU Braunschweig, a, Braunschweig, Germany, Auster, U), TU Braunschweig, a, Braunschweig, Germany, Roux, A), CETP, a, Paris, France, LeContel, O), CETP, a, Paris, France, Mende, S), UC Berkeley, SSL, a, Berkeley, USA, Frey, H), UC Berkeley, SSL, a, Berkeley, USA, Donovan, E), University of Calgary, a, Calgary, Canada, Mann, I), University of Alberta, a, Edmonton, Canada, Shiokawa, K), Nagoya Universiy, a, Nagoya, Japan, Yumoto, K), Kyushu University, a, Kyushu, Japan, Liu, W), LASP, a, Boulder, USA, Li, X), LASP, a, Boulder, USA, Parks, G), UC Berkeley, SSL, a, Berkeley, USA, Fillingim, M), UC Berkeley, SSL, a, Berkeley, USA, Lui, A), APL, a, Baltimore, USA,

We will report in-situ THEMIS and ground observations and analyses of various quantities at and after the onset of the 23 March 2007 substorm. The spacecraft were located in the Southern Hemisphere magnetotail between 8 and 12 RE (radial distance) while their local time meridians approximately mapped onto the 210MM magnetometer network. The following key results will be presented: (1) Alfven waves (circularly polarized) coincided with substorm-related energetic ion injections. (2) Strong ion outflow occurred on the same field lines as those carrying the Alfven waves and the ion injections. (3) Simultaneously, ground magnetometer recorded very large, long-period Pi2 (~135 sec) covering low- to high latitudes. (4) Periodic (~135 sec) energetic ion fluxes at THEMIS were temporally one-to-one correlated with the ground Pi2, both of which showing similar characteristics. Results of all five THEMIS spacecraft, THEMIS ground stations, and the 210MM ground stations will be included.

SM22A-04 

The Influence of Magnetospheric Substorms on SuperDARN Backscatter: a Statistical Assessment

* Wild, J A (j.wild@lancaster.ac.uk), Department of Communication Systems, Lancaster University, Infolab21, Lancaster, LA1 4WA, United Kingdom Grocott, A (a.grocott@ion.le.ac.uk), Department of Physics and Astronomy, University of Leicester, University Road, Leicester, LE1 7RH, United Kingdom

With the advent of NASA's THEMIS mission, worldwide scientific attention is focused upon the investigation of magnetospheric substorms. The SuperDARN array of high-frequency coherent-scatter ionospheric radars are certain to play a key role in upcoming space- and ground-based studies. However, the level of SuperDARN backscatter, crucial for the production of geophysical data products, has been reported to sometimes reduce in the vicinity of the substorm-associated auroral bulge. We have therefore investigated the impact of magnetospheric substorms upon SuperDARN radar backscatter during approximately 3000 substorms and find that the global level of scatter maximizes at about the time of substorm onset. In the nightside ionosphere, backscatter in the region poleward of ~70° magnetic latitude is reduced slightly, with radar echoes shifting to lower latitudes. An examination of the frequency-dependence of nightside backscatter evolution during substorms reveals that the higher frequency bands offer the best relative backscatter performance in the period immediately after substorm expansion phase onset. Detailed findings and recommendations for future SuperDARN operations will be presented.

SM22A-05 

Breakdown of the Frozen-in Condition in the Earth's Magnetotail

* Lui, A T (Tony.Lui@jhuapl.edu), JHU/APL, 11100 Johns Hopkins Rd, Laurel, MD 20723, United States Zheng, Y (YIhua.Zheng@jhuapl.edu), JHU/APL, 11100 Johns Hopkins Rd, Laurel, MD 20723, United States Reme, H (Henri.Reme@cesr.fr), CESR, 31028 Toulouse Cedex, Toulouse, 4, France Dunlop, M W (M.W.Dunlop@rl.ac.uk), RAL, Chilton, Didcot, OX11 0QX, United Kingdom Gustafsson, G (Georg.gustafsson@irfu.se), IRF, S-755, Uppsala, 91, Sweden Owen, C J (cjo@mssl.ucl.ac.uk), MSSL, University College London, Holmbury, RH5 6NT, United Kingdom

We investigate in detail the breakdown of the frozen-in condition detected by Cluster at the downstream distance of ~19 RE in the midnight sector of the magnetotail during a substorm expansion on 2001 August 22. It is found that the breakdown occurred (1) in a low density environment with moderate to large proton plasma flow and significant fluctuations in electric and magnetic fields, (2) in regions with predominantly dissipation but occasionally dynamo effect, and (3) at times simultaneously at two Cluster satellites separated by more than 1000 km in both X- and Z-directions. Evaluation of the terms in the generalized Ohm's law indicates that the anomalous resistivity contribution arising from field fluctuations during this event is the most significant, followed by the Hall, electron viscosity, and inertial contributions in descending order of importance. This result demonstrates for the first time from observations that anomalous resistivity from field fluctuations (implying kinetic instabilities) can play a substantial role in the breakdown of the frozen-in condition in the magnetotail during substorm expansions. Consideration of several observed features in the breakdown regions indicates that the breakdown occurs in a turbulent site resembling observed features found in current disruption and dipolarization sites.

SM22A-06 

Multi-Spacecraft and ground-based observations of substorm activations¡GTwo case studies

* Cao, X (octorcx@agu.org), Institute of Space Physics and Applied Technology, Peking University, Room N419, Physics Building, Peking University, No 5 Yiheyuan Road, Haidian District, Beijing, 100871, China Pu, Z (zypu@pku.edu.cn), Institute of Space Physics and Applied Technology, Peking University, Room N419, Physics Building, Peking University, No 5 Yiheyuan Road, Haidian District, Beijing, 100871, China Zhang, H (hui@pku.edu.cn), Institute of Space Physics and Applied Technology, Peking University, Room N419, Physics Building, Peking University, No 5 Yiheyuan Road, Haidian District, Beijing, 100871, China

Two case studies are performed based on Double Star TC1¡ACluster¡APolar¡AIMAGE¡ALANL geostationary satellites and ground-based Pi2 measurements. In both events an earthward flow is measured by Cluster ~8-10 minutes ahead of aurora breakup. About 1 to 3 minutes prior to the breakup, TC1 may or may not observe the flux pileup-related magnetic field compression. A couple of minutes after the breakup, either TC1 first detects plasmasheet expansion and then LANL satellites near the midnight measure energetic electron injections at the geostationary orbit, or vise versus. About 20 minutes (or more) later, Cluster and Polar observe plasmasheet expansion successively. It is seen that in addition to a sudden decrease of Bx, simultaneous jump of Bz, and reversal of By, plasmasheet expansion is also characterized by a sharp increase of temperature of thermal ions and electrons, with a higher value in T// than TƒÎ. A short-lived earthward flow produced by substorm acceleration commonly appears as well, which is distinguishable from the flows ahead of onsets. Substorm expansion onset is shown to begin in the near-Earth tail around X~ -(8-9) RE. The tailward progression speed of plasmasheet expansion and the earthward propagation speed of substorm injection are estimated ~ 82 km/s and ~25 km/s, respectively. Poleward expansion of auroral bulges in the ionosphere and tailward progression of substorm expansion (SCW) in the magnetotail are shown to be closely related. An initial dipolarization in the near-Earth may eventually evolve to enable disruption of the cross-tail current in a wide range of the magnetotail.

SM22A-07 

Multipoint observations of quasi-periodic substorms associated with ULF pulsations

* Lee, D (dylee@chungbuk.ac.kr), Chungbuk National University, 410 Sungbong-ro, Heungduk-gu, Cheongju, 361-763, Korea, Republic of Lyons, L (larry@atmos.ucla.edu), UCLA, Dept of Atmospheric Sciences, Los Angeles, CA 90095-1565, United States Zou, S (sha@atmos.ucla.edu), UCLA, Dept of Atmospheric Sciences, Los Angeles, CA 90095-1565, United States Kim, K (kckim@chungbuk.ac.kr), Chungbuk National University, 410 Sungbong-ro, Heungduk-gu, Cheongju, 361-763, Korea, Republic of Ruohoniemi, J M (Mike.Ruohoniemi@jhuapl.edu), JHU, Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, MD 20723-6099, United States Weygand, J M (jweygand@igpp.ucla.edu), UCLA, IGPP, Los Angeles, CA 90095-1565, United States

Using auroral images from the IMAGE WIC instrument, geomagnetic data from various ground stations, and geosynchronous particle data, we have identified six consecutive substorms separated by about 45 min to 1.6 hr on November 8, 2000. Most of these substorms are of small to medium size and occurred under a weakly northward IMF condition: IMF Bz was near zero to about +5 nT prior to each substorm. IMF By was also weak, being within about ¢®¨ú3 nT. Most interestingly, we have found that for most of the substorms, about 10-15 min period ULF pulsation begins to amplify prior to each onset and tends to decline near the time of onset. The pulsation features are clearly seen at auroral zone and some higher latitude stations of the CANOPUS magnetic network when they cover morning side MLT regions. Similar features are also seen in the GOES magnetic field observations in similar MLT regions. For the first two substorms, the IMAGE magnetic network stations were at postnoon MLT regions and indicated similar ULF pulsation features. The SuperDARN data show that for most of the substorms, the ionospheric convection within the polar cap shows high-amplitude oscillations with a period of about 15 min that tend to amplify prior to onset and to decline after the onset. Based on the results, we will discuss the possible association between substorm triggering and convection associated with large-amplitude ULF pulsations.

SM22A-08 

Space Technology 5 Multi-point Observations of Field-aligned Currents: Temporal Variability of Meso-Scale Structures

* Le, G (Guan.Le@nasa.gov), NASA Goddard Space Flight Center, Space Weather Laboratory, Code 674, NASA/GSFC, Greenbelt, MD 20771, Wang, Y (yongli.wang@nasa.gov), UMBC/GEST at Goddard Space Flight Center, Space Weather Laboratory, Code 674, NASA/GSFC, Greenbelt, MD 20771, Slavin, J A (James.A.Slavin@nasa.gov), NASA Goddard Space Flight Center, Heliophysics Science Division, Code 670, NASA/GSFC, Greenbelt, MD 20771, Strangeway, R J (strange@igpp.ucla.edu), UCLA, IGPP/UCLA, Los Angeles, CA 90095-1567,

Space Technology 5 (ST5) is a three micro-satellite constellation deployed into a 300 x 4500 km, dawn-dusk, sun-synchronous polar orbit from March 22 to June 21, 2006, for technology validations. In this paper, we present a study of the temporal variability of field-aligned currents using multi-point magnetic field measurements from ST5. The data demonstrate that maso-scale current structures are commonly embedded within large-scale field- aligned current sheets. The meso-scale current structures are very dynamic with highly variable current density and/or polarity in time scales of ~ 10 min. They exhibit large temporal variations during both quiet and disturbed times in such time scales. On the other hand, the data also shown that the time scales for the currents to be relatively stable are ~ 1 min for meso-scale currents and ~ 10 min for large scale current sheets. These temporal features are obviously associated with dynamic variations of their particle carriers (mainly electrons) as they respond to the variations of the parallel electric field in auroral acceleration region. The characteristic time scales for the temporal variability of meso-scale field-aligned currents are found to be consistent with those of auroral parallel electric field.

Author(s) (2007), Title, Eos Trans. AGU, 88(52), Fall Meet. Suppl., Abstract #####-##.