View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Embry-Riddle Aeronautical University Publications 11-2005 Coordinated Cluster/Double Star Observations of Dayside Reconnection Signatures M. W. Dunlop Rutherford Appleton Laboratory M. G. G. T. Taylor University College London J. A. Davies Rutherford Appleton Laboratory C. J. Owen University College London F. Pitout ESA/ESTEC See next page for additional authors Follow this and additional works at: https://commons.erau.edu/publication Part of the Astrophysics and Astronomy Commons Scholarly Commons Citation Dunlop, M. W., Taylor, M. G., Davies, J. A., Owen, C. J., Pitout, F., Fazakerley, A. N., Nykyri, K., & et al. (2005). Coordinated Cluster/Double Star Observations of Dayside Reconnection Signatures. Annales Geophysicae, 23(). https://doi.org/10.5194/angeo-23-2867-2005 This Article is brought to you for free and open access by Scholarly Commons. It has been accepted for inclusion in Publications by an authorized administrator of Scholarly Commons. For more information, please contact [email protected]. Authors M. W. Dunlop, M. G. G. T. Taylor, J. A. Davies, C. J. Owen, F. Pitout, A. N. Fazakerley, K. Nykyri, and et al. This article is available at Scholarly Commons: https://commons.erau.edu/publication/731 Annales Geophysicae, 23, 2867–2875, 2005 SRef-ID: 1432-0576/ag/2005-23-2867 Annales © European Geosciences Union 2005 Geophysicae Coordinated Cluster/Double Star observations of dayside reconnection signatures M. W. Dunlop1,2, M. G. G. T. Taylor3, J. A. Davies1, C. J. Owen3, F. Pitout4, A. N. Fazakerley3, Z. Pu5, H. Laakso4, Y. V. Bogdanova3, Q.-G. Zong6, C. Shen7, K. Nykyri2, B. Lavraud8, S. E. Milan9, T. D. Phan10, H. Reme` 11, C. P. Escoubet4, C. M. Carr2, P. Cargill2, M. Lockwood1, and B. Sonnerup12 1Space Science and Technology Department, Rutherford Appleton Laboratory, Chilton, Oxfordshire, OX11 0QX, UK 2The Blackett Laboratory, Imperial College London, London, SW7 2AZ, UK 3Mullard Space Science Laboratory, University College London, Dorking, Surrey, RH5 6NT, UK 4ESA/ESTEC, Keplerlaan 1, 2200 AG Noordwijk, The Netherlands 5School of Earth and Space Sciences, Peking University, Beijing 100871, China 6Centre for Space Physics, Boston University, Boston, Massachusetts, MA 02215, USA 7Centre for Space Science and Applied Research, Chinese Academy of Sciences, Beijing 100080, China 8Space Science and Applications, Los Alamos National Laboratory, Los Alamos, NM 87545, USA 9Department of Physics and Astronomy, University of Leicester, Leicester, LE1 7RH, UK 10Space Sciences Laboratory, University of California, Berkeley, California, CA 94720, USA 11Centre d’Etude Spatiale des Rayonnements, Toulouse Cedex 4, France 12Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire, NH 03755, USA Received: 17 February 2005 – Revised: 9 May 2005 – Accepted: 8 April 2005 – Published: 8 November 2005 Part of Special Issue “Double Star – First Results” Abstract. The recent launch of the equatorial spacecraft of Keywords. Space plasma physics (Magnetic reconnection) the Double Star mission, TC-1, has provided an unprece- – Magnetospheric physics (Magnetopause, cusp, arid bound- dented opportunity to monitor the southern hemisphere day- ary layers) – Radioscience (Instruments and techniques) side magnetopause boundary layer in conjunction with north- ern hemisphere observations by the quartet of Cluster space- craft. We present first results of one such situation where, on 6 April 2004, both Cluster and the Double Star TC-1 1 Introduction spacecraft were on outbound transits through the dawnside Reconnection of the Earth’s dayside magnetic field with the magnetosphere. The observations are consistent with ongo- interplanetary magnetic field (IMF) readily facilitates the ing reconnection on the dayside magnetopause, resulting in a transfer of momentum and energy from the solar wind into series of flux transfer events (FTEs) seen both at Cluster and the Earth’s magnetosphere. The process of plasma pene- TC-1, which appear to lie north and south of the reconnection tration through the magnetopause via reconnection was first line, respectively. In fact, the observed polarity and motion discussed by Dungey (1961), assuming a purely southward- of each FTE signature advocates the existence of an active directed IMF field which presents the optimal conditions for reconnection region consistently located between the posi- reconnection in the subsolar region. Different IMF orienta- tions of Cluster and TC-1, with Cluster observing northward tion and solar wind conditions give rise to varying rates of moving FTEs with +/− polarity, whereas TC-1 sees −/+ po- reconnection (Smith and Lockwood, 1996) as well as vari- larity FTEs. This assertion is further supported by the appli- ations in the location of the reconnection site (e.g. Crooker, cation of a model designed to track flux tube motion for the 1979; Gosling et al., 1991; Kessel et al., 1996). The mor- prevailing interplanetary conditions. The results from this phology and dynamics of this momentum and energy trans- model show, in addition, that the low-latitude FTE dynamics fer is still a very active area of space plasma research, in are sensitive to changes in convected upstream conditions. In particular the nature of flux transfer events (FTEs) (Russell particular, changing the interplanetary magnetic field (IMF) and Elphic, 1978). FTEs are considered to be the signatures clock angle in the model suggests that TC-1 should miss the of transient or bursty reconnection, with newly reconnected resulting FTEs more often than Cluster and this is borne out flux at the subsolar region convecting tailward in the form by the observations. of a tube-like structure threading the magnetopause (Russell Correspondence to: M. W. Dunlop and Elphic, 1978, 1979; Smith and Lockwood, 1996; Rijn- ([email protected]) beek et al., 1982, 1984). FTEs were originally characterised Figure Captions Fig 1. Cluster s/c1 and Double Star TC-1 tracks in GSM coordinates for the interval 03 to 08 UT on 6 April 2004. The Cluster orbit also shows two spacecraft configurations (scaled up by a factor x50). Each orbit has hour markers. Model field lines are shown for the projection into the X,Z plane and cuts through the bow shock and magnetopause are shown for the X,Y plane. For the X,Z plane field lines are drawn from the Tsyganenko ’89 model for guidance. Fig 2. Summary of the PEACE, HIA, and FGM measurements for the interval shown. The plots for PEACE and HIA are in the same format for Cluster 3 and TC-1 respectively in both cases and show spin and pitch angle averaged, differential energy flux. The FGM plots show data from all four cluster spacecraft (1-black, 2-red, 3-green, 4-magenta) and TC-1 (in blue). A number of the FTE signatures are indicated by arrows at the top of the plot. The FTE discussed in the text is indicated also by the vertical red line (timed at Cluster). The lagged, IMF clock angle, obtained from ACE data, is shown in the bottom panel. Fig 3. A multi spacecraft plot of the magnetic field in LMN (MVA) coordinates. The analysis of Cluster gives: [n=0.720 0.163 0.675, m=-0.379 -0.722 0.579, l=-0.582 0.672 0.458], λ=5 and TC-1 gives [n=0.233 -0.682 -0.694, m= -0.679 -0.625 0.385, l=0.696 -0.381 0.609] , λ=3 (components in GSM). Clear FTEs are observed at Cluster (all spacecraft) with +/- polarity. The FTEs at TC-1 are less clear, but most have -/+ (reverse) polarity. Fig 4. Results from the Cooling model. The Figure is projected in the YZ plane, looking earthward from the Sun. The concentric dotted circles represent the radius of the magnetopause at 5 RE intervals along the X direction, with the innermost circle representing X= 5 RE. The diamonds represent the position of the cusps for a magnetopause standoff distance of 9 RE. The triangle represents the position of Double Star and the square the position of Cluster at the time of the FTE in question. Pairs of open reconnected flux tubes are initiated along the merging line (dot-dashed), with the motion of each tube calculated for a total of 500 seconds, which is represented by the extent of the line, with the solid line representing flux tubes connected to the northern cusp, and the dashed lines connected to the southern cusp. The IMF orientation is indicated by an arrow in the upper right hand of the figure and the components are stated at the bottom of the plot. The location information pertains to the mid point of the merging line. Other parameters are discussed in the text. Figure 4a shows the results for parameters representing the FTE signature seen at Cluster ~5:20 UT and at TC-1 at ~5:18:50 UT. Figure 4b shows the effect of modifying the IMF clock angle which moves the region of FTE evolution such that one can envisage Double star to move out of this region under certain clock angle values. 2868 M. W. Dunlop et al.: Coordinated Cluster/Double Star observations of dayside reconnection signatures Fig 1 Fig. 1. Cluster s/c1 and Double Star TC-1 tracks in GSM coordinates for the interval 03:00 to 08:00 UT on 6 April 2004. The Cluster orbit also shows two spacecraft configurations (scaled up by a factor x50). Each orbit has hour markers. Model field lines are shown for the projection into the X,Z plane and cuts through the bow shock and magnetopause are shown for the X,Y plane. For the X,Z plane field lines are drawn from the Tsyganenko ’89 model for guidance. according to their bipolar oscillation in the magnetic field surements. The recent launch of the Double Star TC-1 space- component normal to the magnetopause, with subsequent craft into an equatorial orbit provides a unique opportunity studies (e.g.