Extension of Magnetic Clouds in the Inner Heliosphere as observed from Multi-Spacecraft

ILWS Conference, October 5, 2009

Extension of Magnetic Clouds in the Inner

Heliosphere as observed from Multi-Spacecraft

Aline de LucasAlisson Dal LagoRainer Schwenn

Alicia L. Clúa de Gonzalez


Motivation

The main motivation of the possibility to observe magnetic clouds at multi-spacecraft and

estimate their longitudinal extent in the inner heliosphere.


The orbits of the Helios 1&2 solar probes in 1976The mission lasted from Dec. 1974 to March 1986

The Helios 1&2 solar probe mission

Helios had a complete set of particle and field instruments, no optical telescopes


Helios 1&2a stereo-mission!


He 1

He 1

He 2

He 2

77:28, He 2

77:29, He 1

Helios orbits in1977

A transient MC driven shock, seen from Helios 1&2270 apart in longitude


MC seen from Helios 1&2270 apart in longitude

shockshock MC MC

Shocks and MCs were detected by H1,2 and at the Earth

HSS


Observation near Earth

H2 and IMP-8 are separated by only 9 degrees and they observed similar features.

Shocks and MCs were detected by H1,2 and at the Earth

HSSshock

MC


MVA for the MC seen by H1,2 and

IMP-8

Bx*

By*

H1

H2

IMP-8

Despite of the different rotations patterns, the direction is the same.

Ambiguity of 180º


Small Separation and Different Magnetic Features


MVA for the MCs observed by H1 and H2 on DOY 75-76/1977

H1 H2

H1 and H2 are separated by less than 19º. Despite of this fact, the magnetic field rotation inside the MC is different

By*

Bx*


H2 and IMP-8 observation

H2 is 7º away from the Sun-Earth line.

2 days later


MVA technique applied to the MC

H2 IMP-8

H2 and IMP-8 have the same rotation direction. Clouds’ axes have different orientations.

Bx*

By*


Statistics of all „safe“ MCs involving Helios1 & Helios2, IMP8 and ISEE3

Multi-Spacecraft Observed MCs

MCs may extend to 900;


Shocks extend to larger distances compared to their drivers

De Lucas (2009)


Concluding Remarks• MCs showed to behave as well organized structures

when analyzed separately by the MVA technique;

• Some MCs showed different rotation and axial directions according to the measurements from different probes;

• Could it be that the technique is not accurate enough to analyze this type of structures in order to provide information about their shapes? Or could be that MCs are not completely connected like a long flux tube?

• MCs observed by Helios extended to smaller distances compared to the shock waves driven by ICMEs.


THANKS!



Minimum Variance Analysis (MVA)

MVA can tell us the direction of the rotation and the clouds’ orientation.

Source: Adapted from Goldstein (1993).

Documents

Extension of Magnetic Clouds in the Inner Heliosphere as observed from Multi-Spacecraft