Dr. Jonathan P. Eastwood - Research Interests

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Research interests:

I conduct research into the basic properties of collisionless plasmas, by analyzing spacecraft observations of such plasmas in space. I am particularly interested in understanding the physics of magnetic reconnection and collisionless shocks. This research is also of practical importance, because ultimately it helps us to understand and predict space weather. Space weather research is our effort to understand how the conditions in space near the Earth are affected by the Sun (Eastwood, Phil. Trans. R. Soc. A, 2008).

Magnetic reconnection

Although magnetic reconnection is a phenomenon with global consequences, it is ultimately controlled by the central 'diffusion region' where the magnetic field decouples from the plasma and reconnects. Since it is crucial for understanding reconnection as a whole, I have recently focused on understanding the physics of the diffusion region itself. This is most easily done using satellite observations, since it is difficult to produce collisionless plasmas in the laboratory. I have used data from the ESA Cluster mission and the NASA THEMIS mission to publish definitive experimental studies showing that collisionless reconnection is described by the Hall reconnection model, rather than models based on anomalous resistivity (e.g. Eastwood et al., J. Geophys Res., 2010; Phys. Rev. Lett., 2009;2010).

These fundamental results have been applied to the magnetosphere by showing that the ‘first light’ signals from reconnection propagate much faster to the ionosphere and aurora than previously thought, with implications for understanding the rapid onset of auroral activity during geomagnetic substorms (Shay et al., Phys. Rev. Lett., 2011). I also published the first evidence directly showing that multi-point reconnection occurs in the Earth’s magnetotail current sheet (Eastwood et al., Geophys. Res. Lett., 2005). More recently I have become interested in the nature of multi-point reconnection on the magnetopause and the formation of flux transfer events (e.g. Oieroset et al., Phys. Rev. Lett., 2011, Eastwood et al., J. Geophys. Res., 2012).

In studying solar reconnection, I have concentrated on 'Type III radio storms', which have been observed as a precursor of some coronal mass ejections. Using STEREO radio data I discovered that the individual reconnection events in solar type-III radio storms occur independently, corresponding to the system being in a state of self organized criticality (Eastwood et al., Astrophys. J. Lett., 2010).

My work on reconnection at Earth has led to new research examining its role at other planets, particularly Mars, but more recently Saturn. Based on my discovery of magnetic reconnection at Mars (Eastwood et al., Geophys. Res. Lett., 2008), it has been found that reconnection may enable the bulk escape of the atmosphere originally protected by mini-magnetospheres (Brain et al., Geophys. Res. Lett., 2010, Eastwood et al., Geophys. Res. Lett., 2012). It is crucial to understand how Mars' atmosphere and water were lost, since this controls how long Mars was wet after its dynamo ceased to operate. Atmospheric loss at Mars will be studied by the MAVEN spacecraft which will launch to Mars in a few years time.

At Saturn, we have recently found that the different solar wind conditions (the solar wind plasma beta) restrict where reconnection can operate, potentially making it more difficult for the solar wind to penetrate Saturn's magnetosphere (Masters et al., Geophys. Res. Lett., 2012).

Collisionless shocks

The Earth's bow shock is one of the best places to make in-situ observations of collisionless shocks. During my doctoral work I used the novel capabilities of Cluster to study the different types of low frequency waves that are generated by backstreaming ion beams in the foreshock region (e.g. Eastwood et al., Geophys. Res. Lett., 2002). These waves play a crucial role in shock acceleration mechanisms. During my postdoctoral research at Goddard, I completed studies showing that the compressive properties of these waves are caused by wave refraction in the inhomogenous foreshock (Eastwood et al., J. Geophys. Res., 2005). Since completing my PhD, I have maintained an interest in shock physics and more recently, I have studied the properties of Hot Flow Anomalies, an interesting kinetic effect that occurs when a solar wind discontinuity hits the bow shock causing a global disruption (Eastwood et al., Geophys. Res. Lett., 2008; Eastwood et al., J. Geophys. Res., 2011).

 

 

This page was last changed on 3 May 2012