Response of the Polar Cusp and the Magnetotail to CIRs Studied by a Multispacecraft Wavelet Analysis Axel Korth 1, Ezequiel Echer 2, Fernando L. Guarnieri 3, Q.-G. Zong 4 1 Max-Planck-Institut für Sonnensystemforschung, Katlenburg-Lindau, Germany 2 Instituto Nacional de Pesquisas Espaciais, Sao Jose dos Campos, Brazil 3 Universidade do Vale do Paraiba – UNIVAP/IP&D, Sao Jose dos Campos, Brazil 4 Center for Atmospheric Research, University of Massachusetts, USA. International Living With A Star 2009, Ubatuba-SP, Brazil, October 04-09, 2009

Wavelet Analysis The response of the solar wind and the magneto- sphere (here: magnetotail and cusp) are studied and made visible with the wavelet and cross-wavelet analysis. The wavelet transform is a technique to analyze non-steady signals. The cross-wavelet spectrum gives the correlation as function of the frequency.

ACE (Advanced Composition Explorer) It is positioned at the L 1 point about 210 R E around the Earth-Sun line. Cluster Cluster consists of four S/C flying in a tetrahedron formation with an apogee of 19.6 R E ( km) and a perigee of 4.2 R E (19000 km). Geotail Geotail has been in an elliptical 9 R E by 30 R E orbit since February LANL (Los Alamos National Laboratory) Spacecraft at geosynchronous orbit.

Solar Wind Proton Velocity and Proton Density (ACE) for 4 Solar Rotations Recurrent high speed stream 19/20 September 2003

Overview Recurrent high speed stream event seen by Cluster, ACE, and on ground in September 2003.

Response of the plasma sheet during a high speed stream CIR event on September 19/20, crossing. heated plasma sheet (increase of electron and ion flux). low density 0.15 – 0.2 cm-3. thinning (stretching) and dipolarization of plasma sheet (Bx). Theta angle changes. Pressure much higher (~1nPa) and changing. ß = 1 in plasma sheet.

Wavelet Analysis of the IMF Bz (ACE) and of dBx (Cluster) during the CIR HSS Event on September 19-20, 2003 (3.Crossing). The paraboloidal curve is the cone of the influence region. The contour line indicates the confidence levels higher than 95 %. Continuous turbulence at about two hours for the solar wind magnetic field component Bz (left) and the tail dBx-component (right). The Bx-component gives the thinning (stretching) and dipolarisation of the plasma sheet.

Cross-Correlations between IMF Bz (ACE) and Plasma Sheet dBx and Energetic Electrons (Cluster) during the CIR HSS Event on Sept. 19/20, 2003 (3. Tail Crossing). Continuous and strong turbulence at two hours period for cross-correlations between solar wind Bz-component and tail dBx-component and tail energetic electrons.

Cross-Correlations between IMF Bz and SW Vx (ACE) and Plasma Sheet Density (Cluster) during the CIR HSS Event on September 19/20, 2003 (3. Tail Crossing). Continuous and strong turbulence at two hours period for cross-correlations between solar wind Bz-and tail density. No strong correlation between solar wind Vx-component and the tail H + density.

Cross-Wavelet Correlation between dBx in the Tail (Cluster) and Energetic Particles at Geosynchronous orbit (LANL SC) on Sept 19/20, 2003 (3. Tail Crossing). Strong turbulence at two and four hours period for cross-correlations between Cluster tail dBx and energetic electrons at geosynchronous orbit from spacecraft LANL Local Midnight at 2:25 UT

Solar wind speed (ACE data) for 5 Bartels rotations during Nov/2001-Apr/2002. Red circles show the periods of Cluster cusp crossings and the black arrow the cusp crossing studied Jan 11, 2002

ACE data and Dst- and Kp indices on 11 January 2002 Red vertical lines give the two periods of interest for ACE at L1. The Cluster measurements in the magnetospheric cusp are shifted by 40 minutes (blue arrow).

Overview of Cluster 1 measurements inside the cusp and before and after the cusp crossing. The vertical red lines indicate the region of interest, where we perform the wavelet analysis.

Wavelet data of the ACE interplanetary Bz and the Cluster cusp density on 11 January 2002 Bz data have no time shift (left); the Cluster density data have 40 minutes time shift. ACE Bz show strong periodicities, mainly in the southward direction. The hydrogen density in the cusp (Cluster) shows similar variations between 15 and 25 minutes.

Cross-wavelet analysis for ACE and Cluster on 11 January Data series of Bz-, Vx- and the cross product Ey from the ACE spacecraft and data of the density from the Cluster 1 s/c and the various cross-correlations Strong and significant periodicities between 15 and 25 minutes are observed in two panels. The power significance for the Vx- component is much lower.

Cross-wavelet analysis for ACE and Geotail on 11 January Excellent conjunction between ACE and Geotail. At time of Cluster cusp crossing Geotail was outside the Earth‘s bow shock. Clear strong periodicities between 15 and 25 minutes. Periodicities persist over a large region in the solar wind.

Cross-wavelet analysis for ACE and Cluster on 11 January Further cross-correlations between ACE Bz and Cluster thermal temperature, ACE Ey and Cluster thermal temperature, and ACE Bz and the flux of energetic electrons. All cross-correlations show strong periodicities between 15 and 25 minutes.

Conclusions In the declining phase of Solar Cycle 23 ( ) the magnetospheric response to CIR high speed solar wind streams is investigated. The response of the solar wind on the cusp and magnetotail are studied with ACE, Cluster, Geotail, and LANL S/C. With the technique of the cross-wavelet analysis, correlations of plasma parameters in the solar wind, in the magnetotail, and the cusp were found. Significant correlation between solar wind and magnetotail plasma parameters were found at periods of 2-3 hours. For the cusp, the most significant correlation was found at periods around minutes during CIR high speed streams. We conclude that the fast solar wind streams and their embedded large amplitude Alfvén waves have a direct influence on the recurrent substorm activity. We further conclude that the causative driver in the solar wind are prolonged periods of intermittently large negative IMF Bz, that can lead to heating of the plasma sheet and to substorm activity. For the cusp we may conclude that solar wind Alfvén waves affect the interior of the Earth’s cusp. Several mechanisms may be involved in this modulation and have to be studied in the future.

Outline Corotation Interaction Regions (CIRs) Wavelet Analysis Response of the magnetospheric tail during recurrent high speed streams. Effects in the polar cusp during recurrent high speed streams.

Peak Season for High- Speed-Stream-Driven Storms (CIRs) In the solar wind: - Corotation Interaction Regions (CIRs) are followed in time by high speed streams. - CIRs occur mainly during the declining phase of the solar cycle. - CIRS repeat every 27 days. - CIRs have a long duration (1-4 days even 1 week) In the magnetosphere: - CIRs produce strong electron radiation belt, hot magnetic plasma and spacecraft charging. CIRs

Recurrent (CIR) High Speed Streams and their Effects in the Earth’s Magnetotail.

Recurrent (CIR) High Speed Streams and their Effects in the Earth’s Cusp