Response of the Polar Cusp and the Magnetotail to CIRs Studied

by a Multispacecraft Wavelet Analysis

Axel Korth1, Ezequiel Echer2, Fernando L. Guarnieri3, Q.-G. Zong4

1 Max-Planck-Institut für Sonnensystemforschung, Katlenburg-Lindau, Germany

2 Instituto Nacional de Pesquisas Espaciais, Sao Jose dos Campos, Brazil3 Universidade do Vale do Paraiba – UNIVAP/IP&D, Sao Jose dos Campos,

Brazil4 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 L1 point about 210 RE around the Earth-Sun line.

ClusterCluster consists of four S/C flying in a tetrahedron formation with an apogee of 19.6 RE (119000 km) and a perigee of 4.2 RE (19000 km).

GeotailGeotail has been in an elliptical 9 RE by 30 RE orbit since February 1995.

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, 2003. 3.

crossing.

heated plasmasheet (increase of electron and ion flux).

low density0.15 – 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 fieldcomponent 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 HSSEvent 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 1990-095.

Local Midnightat 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 cuspcrossing. The vertical red lines indicate theregion of interest, where we perform thewavelet 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 2002.

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

and25 minutes are observedin two panels. The power

significance for the Vx-component is much lower.

Cross-wavelet analysisfor ACE and Geotail on 11 January 2002.

Excellent conjunction between

ACE and Geotail. At time of Cluster cusp crossing Geotailwas 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 2002.

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 (2001-2003) 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 15-25 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-DrivenStorms (CIRs)

sun

fast wind

slow wind

Earth'sorbit

interface

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